Radio Communications Systems During Crisis Situations (Frequencies)

What are the best frequencies to use?

• This section deals with long distance propagation via the ionosphere and does not apply to local line of sight/point to point communications. Except during an extreme solar storm line of sight comms should work with no issues. We're also talking reliable communications that are available 90% of the time or better.  Other bands may open up during atmospheric events but it varies too much to be considered reliable.
• The trick to choosing a frequency is to know which ones are going to work at certain times.  The times can be divided into day/night/twilight, solar minimum/maximum, all four seasons, and even location as in high latitudes (near the poles) mid latitude, and equatorial latitudes (near the equator). Even where (how far) you are trying to communicate with will dictate what the best frequency to use is.
• A combination of these factors will determine what the Lowest Usable Frequency (LUF) and Maximum Usable Frequency (MUF) will be for a given situation.  It can be quite complicated when taking in all the parameters that go into calculating the LUF/MUF needed to talk to another region on the earth.
• In general radio waves between the LUF and MUF reflect of the ionosphere. Radio waves below the LUF are absorbed by the ionosphere and radio waves above the MUF pass through the ionosphere into space. The trick is to know what the LUF and MUF are. But in a SHTF situation that information may not be available to you.  Even the parameters used to calculate the LUF and MUF won’t be available to you.  So how do we figure out what frequencies will work and what ones won’t?  We don’t want to waste precious battery power transmitting on useless frequencies.
• So how does all this frequency stuff work anyway?  The sun produces ultraviolet (UV) light and that UV light is captured/filtered/absorbed by the upper levels of the atmosphere or ionosphere.  The UV light hits the upper atmosphere and the atoms up there temporarily loose an electron and then recombine with that electron later. The separating and combining of electrons is a continual process as long as the UV light is present.  These free electrons are called ions, hence the name ionosphere. During the day (or more precisely on the sunlit side of the earth) the UV light forms more ions. During the night or on the shadow side of the earth there is no UV light so there are fewer ions. During periods of low solar activity the UV light levels are even lower and the density of free electrons is also low.  During periods of high solar activity the UV levels are quite high and the free electron density is high.  The more ions present in the atmosphere the higher the MUF will be.  Think of the ion density like a net, the more ions the smaller the openings in the net.  The smaller openings keep the higher frequencies (due to their smaller wavelength) from passing though into space and they bounce back to earth.
• As the UV light excites the atmosphere on the sunlit side of the earth the ions created separate into layers.  On the shadow side of the earth the few ions that are there combine into fewer layers.  The upper layers (F1 and F2) during the day make long distance communications possible on the higher HF frequencies. Again the more free ions the higher the MUF will be. During daylight hours the LUF is set by the lowest of the layers called the D layer (remember D for Day) that actually absorbs all the frequencies below the LUF.  So during the day ionosphere propagation of the low frequency waves is impossible, no matter how many watts of power you force into it.  After sunset the D layer quickly (thankfully) dissipates so long distance communications is now possible on the lower frequencies. The F1 and F2 layers combine into a single F layer.
• In the region of the atmosphere where the sunlit and shadow areas meet (twilight/sunset/sunrise on earth) there is a collapsed combination of all the layers and they form a little conduit.  This little conduit traps the radio waves and sends them all along the conduit bouncing them to the earth all along the way.  This little conduit is also called the grayline.  So what happens is anyone passing through the grayline can communicate with someone else that is also in the grayline at another location on earth. So communication is possible during sunrise on one side of the earth to somewhere during sunset on the other side of the earth.  So don’t rule out twilight hours for long distance communications.
• Also remember even after dark when the D layer dissipates, the LUF will be higher towards the west (sunlit areas) that to the east (areas already in the dark). This is because the D layer still exists for the areas in the daylight and will absorb the lower frequencies while the D layer is gone for the areas in the dark.  So when trying to talk to areas still in sunlight a higher band may be needed while talking to areas already in the dark maybe possible on a lower band.
• The peak for this solar cycle is from 2013 to 2016, a good 3 years of higher frequency band openings. Right now in 2011 we are about ¼ of the way to the peak.  The downslope of the solar cycle is usually less steep than the upslope which is a good thing. It means the peak will arrive sooner and linger longer.
• A few caveats I need to mention during solar maximum.  Once the sun really begins to pick up activity there can be solar storms from X-ray Flares or UV Coronal Mass Ejections (CME) that can wipe out all communications for a period of time, usually just a few hours but sometimes days. These storms can be heard as really loud white noise or static on the radio. 10 meters really gets noisy during a CME and you can actually hear the wave waver in intensity as the CME passes over the earth.  Also a large X-ray or CME burst can cause inducted power spikes on really long antennas.  This is what happens to our power grid during a solar storm.  Also these storms can wipe out satellite communications and even damage satellites because they are not protected by the earth’s electromagnetic field.
• So in saying all that we really haven’t discussed what frequencies to use when only to determine higher frequencies work better in the day and lower frequencies work better at night.
• Long Distance Comms (HF):
• During solar minimum 20 meters is about the highest frequency that can be used during the day and usually only with high reliable modes like CW and PSK.  During solar maximum up to 10 meter and even 6 meters can be used during the day and since it takes a little while for the ions to recombine 20 meters can be used for a while after dark. SSB voice can be used easily during solar maximum.
• At night during solar minimum the lower frequencies work well up to 40 meters. During solar maximum all the low frequencies through 20 meters work well even 10 meters in the early evening. Noise may wipe out 160 and 80 meters at times.  Electrical storms (lightning strikes) can cause very loud crashes of static, so be careful if you are wearing head phones and listening to the lower frequencies. It’s quite startling and painful.
• So you can see that the more viable bands are 40 and 20 meters. That’s why they are called workhorse bands. If you could only have two HF bands these would be the ones to have.  And these bands are where I’d invest more in my antennas.
• At a minimum these antennas should be at least ½ wavelength high to get the take-off angle below the critical takeoff angle so it will skip.  They do not need to be higher than 1 wavelength and trying to doing so will only use valuable resources that could be used elsewhere.
• Local Comms (HF):
• Using a Near Vertical Incidence Skywave (NVIS) antenna (covered under the Antennas section)
• I’d use 80 meters at night and 40 meters during the day.  During solar minimum 80 meters is not absorbed as much during the day. During solar max 80 meters is wiped out during the day. 40 meters is open at night most of the time. 
• To sum it all up:
• 80 meters and below work during the night.
• 40 meters and up work during the day. 15 and 10 meters need some solar activity to open up; dead during solar minimum for the most part and dead at night. The current solar peak is slated from 2013 to 2015.
• The more active the sun is (further into the solar max peak) the higher the frequencies we can use. Up to 6 meters is possible.
• Local point to point or line of sight communications are not affected by solar activity except during solar storms.
• Now the final part to this is what specific frequency should I transmit on?  
• Other than listening up and down the band for someone to talk to there are specific frequencies on each band call calling frequencies.  There are calling frequencies for different modes.  A good source can be found here. Once you establish a contact on the calling frequency you should move from that frequency to carry on the conversation.  
• During a crisis situation "networks" or nets are established on the bands to handle emergency traffic.  There are also established nets like the Maritime Mobile Service Network (MMSN)on the 20 meter band at 14.300MHz that run from 1600 to 0200 UTC or on 21.412MHz that run from 2200 to 2400 UTC. The MMSN is for ships that need to check in to give position reports or report emergencies. All kinds of Nets and their times and frequencies can be found here.

Radio Communications Systems During Crisis Situations (Antennas)

 This is part 5 in an ongoing series on radio communications during a crisis event.

What type(s) of antenna should I have?

• Antennas are the best and cheapest way to increase RF signal strength and they don’t require any more resource power to provide the amplification.  One can easily double, triple, and even quadruple the effective radiated power out of the antenna. So quite easily you can amplify those 5 watts of transmitter power into 20 watts at the antenna.  Remember the inverse square law where doubling the output power only increased received signal strength by 25%? By quadrupling the power we have increase receive signal strength by 50%. So the receiving end can hear us 50% better! 
•  How is this possible with no extra resource power consumption?  Quite simply by the way the antenna materials act with the RF energy.  A typical dipole antenna in free space radiates the energy equally in all directions.  Since the receiver’s short path is in only one direction that’s a lot of wasted energy going in all other directions where it’s not needed.  What if we could turn all that wasted energy in the direction of the receiver so they get ALL the radiated power from the antenna?  Well we sure can. 
• RF energy reacts with metal objects that reside in an area a certain distance (based on the frequency) from the main radiating element. If a longer (about 5%) element is placed to one side of the radiating element it tends to reflect the energy in the opposite direction. This element is called a reflector. If another element (5% shorter) is placed on the opposite side of the reflector it will tend to pull the RF energy in the same direction. More than one (incrementally) shorter element can be placed in the directed path further refining the RF energy into a well defined beam of energy. These elements are called directors.  The reflector and director elements are passive parasitic elements that are not directly connected to the radio coax antenna cable.  They do not require any power resource to accomplish the reflecting and directing of the RF energy.  They accomplish this task by their parasitic nature by robbing the RF energy pulling it toward them and thus in a specific direction.  If the reflector and director elements are all in the same plane then all the energy is concentrated into a beam.  The more directors the more concentrated the beam becomes though with diminishing returns. Because the RF energy is formed into a beam, these antennas are called beam antennas or Yagi antennas after the inventors Uda and Yagi.  The old TV antennas are also beam antennas but are of a different design. They are actually log periodic and have a wide frequency range and mainly used for receiving only. Amateur band antennas are not as wide a frequency range and usually limited to a large portion of the band they were designed for.
• The lower the radio frequency the longer the antenna elements and the higher the frequency of the radio wave the smaller the element lengths.  This makes constructing large element arrays at lower frequencies more difficult and expensive due to material costs and structural framing to hold all the elements in the same plane. However higher frequency antennas can support much larger element arrays again due to material costs and structural requirements.  This makes it easier and less costly to make a higher gain VHF or UHF antenna than to make a high gain HF antenna.  Typical element lengths are approximately half the wavelength. So an 80 meter element will be about 40 meters long, a 40 meter element will be about 20 meters long, a 20 meter element will be about 10 meters long and 10, 6, 2 and 70cm elements will be 5, 3, 1 meters and 35cm long respectively.  These element lengths are approximations and the true element length depends on the actual frequency being transmitted but it does give one an appreciation of how large an antenna can get for the lower HF bands.  Practically speaking, when building your own antenna out of scrounged parts after TSHTF, it would be difficult to build a gain antenna for 80 or 40 meters. For these bands a simple dipole is hard to beat cost and construction wise.  A 20 meter beam antenna might be practical and for 10 meters and higher it’s quite practical and even preferred over a simple dipole since the structure can now be supported by one supporting post rather than two for a dipole.  For the added cost in materials and ease of building it just doesn’t make sense to not use a beam gain antenna at the higher VHF/UHF frequencies.

How high should the antenna be?

• Antenna height is a much debated topic when it really shouldn’t be if you know all the factors about antenna height.  What I think usually happens is someone asks someone how high their antenna should be and the answer given is only one of many possible answers.  This then starts the heated discussions I’ve seen in forums and at Ham meets where each is arguing that their height is the best (and for their application it most probably is) but it won’t help the other guy that is trying to accomplish something different with their radio.
• So let’s start with a little theory and hopefully it will explain that the best antenna height depends on where you are trying to communicate to.
• Remember the question about which antenna should I use there was the isotropic di-pole antenna that radiated that precious RF energy equally in all directions and wasting it? And by putting parasitic elements in an array we could form the energy into a more compact beam and direct it at our receiver? Well we can do the same thing by bringing that isotropic di-pole down to earth and having the earth act as a parasitic element.  What this does (and I’ll try to explain this without a picture) is to squish the round sphere of energy so it no longer sends energy toward the ground or toward the sky but only out to the sides of the wire element. By directing the energy wasted in the air and ground we’ve almost doubled the energy going out the sides.  It’s not quite double as the beam width is still too wide and going in 2 directions.  I’ve never done the calculations myself but it has been calculated about 2dB gain (3dB gain is double power) can be had over an isotropic dipole. 
• If the dipole is set about ½ wavelength above ground the energy is concentrated into a beam that points at about 30 degrees (for simple math) into the air.  This angle is called the takeoff angle.  If we raise the antenna to 1 wavelength the beam splits into 2 separate beams the lower one at 15 degrees. As the antenna is raised the beam splits into more beams with tighter patterns and the angle of the lower beam is lower, about ½ the previous angle per wavelength in height. Now in between each beam is an area called a “null” area that will reduce the signal strength of any RF energy coming in at that angle. 
• These beams at different angles shoot into the sky and the beams that point higher will bounce at a less of an angle angle in the sky and land at a closer distance than the lower angled beams.  The lower angle beam thus can travel further distance across the ground in one bounce (hop).  Each hop chews up some signal strength so to talk long distances it’s best to do it in the fewest possible hops. 
• Now remember the nulls? The angle of these nulls will produce mini skip zones where the signal strength will be less at the distant receiving and could be so much less at a specific angle so the signal may not be heard. For an antenna at ½ wavelength with the one wide beam at 30 degrees there will be a significant initial skip zone then several progressively smaller skip zones because the bouncing beams will scatter a little causing the energy to spread out.  After several hops the skip zones will be minor however if for some reason the beam of energy is only received at a certain angle and the height of the receiving antenna is such that there is a null at that angle the signal will be weak or unreadable. 
• Set the transmit antenna at 1 wavelength and now there are 2 beams one that bounces closer and one that bounces further.  We now have 2 skip zones but after a few hops of beam spread they are greatly reduced because of the overlap.  Raise the antenna further and you have more beams, more nulls, but lower angles for longer hops.  The same happens for a beam antenna only the elevation patterns take on a more complex beam and null pattern with the lowest beam being the strongest and many smaller beams and quite wide nulls in places.
• So armed with this knowledge you can see why there might be some heated discussion going on about antenna height.  For one person talking to Europe his antenna height may be perfect but someone a little further away may not hear Europe very well.  And vice versa the guy that can hear Europe may not hear Japan but the guy that can’t hear Europe may hear Japan just fine.  If either one could change the antenna height then they could hear the other locations just fine also.
• So what’s the correct answer? Antenna height will need to be calculated for your transmitter location and receiver location.  Most people with simple setups put the antenna at ½ wavelength and leave it.  That’s what I did in Florida. Actually the antenna was at 20’, not quite ½ wavelength for 20 meters which is what I usually transmitted on. It was a bit of a “sky warmer”. Outside the initial skip zone I could talk all up the east coast on the first hop and all of Europe and some of Eastern Russia on the second hop.  Even though the wide beam pattern at only one angle may not be as strong as the more concentrated lower beam of a dipole at a higher elevation I had enough power for 2 hops and no receiving nulls. That was during solar minimum too.
• One important area we briefly mentioned, the initial skip zone, is a very important zone is a SHTF situation.  At HF frequencies it’s too wide to cover with line of sight VHF so there is this zone around us that we can’t hear, literally. From my receiver in NW Florida I could not hear Georgia, Alabama, Mississippi, Arkansas, Louisiana, and most of Florida.  Extend that circle around into the Gulf of New Mexico and that’s how much area around a receiver in the Midwest would not be able to hear. That’s almost half the country.  So what can we do to remedy that problem?
• Remember the dipole at ½ wavelength radiated the energy in beams off the side at about 30 degrees and when raised these beams multiplied and pointed lower in the air? If you do the opposite the beams actually point higher into the sky to where they become one beam pointing straight up and less RF energy is radiated at the lower angles.  The antenna at this height is horrible for long distance communications since the energy is pointing straight up and there is no skip.  This antenna is called a “cloud warmer” by some and meant in a bad way when trying to communicate long distance.  The term used for this antenna when used for its practical purpose is Near Vertical Incidence Skywave (NVIS) antenna.  Its practical purpose is for communicating to people located in the skip zone.  The energy is not so much reflected like a beam hopping over the Atlantic, but scattered in all directions (backscatter) filling in the skip zone void. A NVIS antenna is also great when you station is located in mountainous country and the takeoff angle of a higher antenna points right into the side of the mountain.
• So now knowing this much information it seems like you would need a of couple antennas to cover long distance and the skip zone.  That would be the best idea, a beam antenna at a calculated height to cover the long distance areas of interest and an NVIS dipole to cover the skip zone.  If that’s practical for you and you can afford to hang a HF beam higher than ½ wavelength then it may be your answer.  However for OPSEC reasons I’d not like to advertize I had communications to everyone who drove by. A wire strung between two poles is harder to see from a distance than a big HF beam on a tower.
• My choice STSHTF would be a single Off Center Fed (OCF) Di-Pole cut for the 80 meter band stretched between 2 masts 30-60ish feet off the ground and on a pulley system so the height of the dipole can be adjusted for long distance or skip zone communications.  The OCF dipole is a special dipole pole that is not fed in the center but off center a bit. By doing that the impedance match is now off by 4 and the antenna becomes unbalanced so to feed it with coax take a couple of extra components called BALUNS.  I’ll not get to technical on how the antenna works, but this antenna not only radiates well on 80 meters but also quite well on 40, 20 and 10 meters.  The radiation pattern is not quite the same as the standard dipole nor is the takeoff angle the same when transmitting on a frequency off the 80 meter band.  But taking all that into account this makes a wonderful single antenna that covers 4 HF bands.  You can cut the OCF for 160 meters but the wire is so long that it needs a center support as well. Now it becomes more expensive to support, needs more surface area to stretch out and more work involved to raise and lower it.  During SHTF situations my bet is communications will be concentrated on the 3 work horse bands, 80 (NVIS – local night comms), 40 meters (NVIS – local day comms) and 20 meters (30 to 60’ - long distance day comms), since simple antennas for these bands are easily deployed due to their smaller size and height requirements.
• One other antenna that I haven’t mentioned yet is the HF vertical.  If you have the time to prepare beforehand then a tall vertical makes a decent antenna also for long distance work.  They are more complicated, need a foundation and heavier materials to support it and many wires strung out underneath it for a ground counterpoise.  I don’t recommend this antenna if you are going to construct it ATSHTF. Also the vertical has a low take off angle making it a poor choice for local comms.
• So my final recommendations for SHTF antennas are:
• An 80 meter OCF dipole stretched between two poles or trees 33 or 66 feet in the air on a pulley system to raise or lower it. This will cover 80/40/20/10 and even 6 meters.  You will need 140 feet of available ground to stretch it out.
• A 20-15-10 meter triband yagi at 30ish feet.  You can also add  6 meter parasitic elements to add 6 meters to the antenna.
• A copper pipe (or whatever metal you can scrounge ATSHTF) J-Pole cut for each of your VHF bands.  Though one 2 meter J-Pole will work on 70cm quite well so if you only build one antenna build the 2 meter version. I only use the 2 meter version for my 2 meter/70cm dualband handheld. This is a line of sight antenna so the highest practical height you can get it the better. I'm at 20 feet supported by the roof apex on the end of the house. If you house is taller, then any height about 6 to 8 feet above your roof peak would be good. Using the building to support the mast eliminates the need to use guy wires. A cheap mast for light antenna work are 10 foot chain link fence top rails.  

What polarization should my antenna be? 

• Antenna polarization is how the electrical field of the electromagnet wave (RF energy) is in relation to the earth’s surface. If the electrical field is perpendicular to the earth then the polarization is considered vertical.  In demonstration, a person walking upright is vertical and a person lying down is horizontal. 
• In the RF communications world, horizontal polarization is used for long distance and vertical polarization is used for local line of sight communications. Some satellite communications use circular or cross polarization but that’s for a specific use. 
• Vertical antenna for HF bands can also use vertical polarization because once the beam reflects off the ionosphere it becomes more of a random pattern. More hops equals more randomization. 
• The biggest factor when communicating direct (no ionosphere) is that the antenna polarizations match.  If not the received RF energy will be reduced dramatically.  
• The venerable di-pole antenna is a horizontally polarized antenna while the sturdy J-Pole is vertically polarized. 
• To change the polarization of a beam antenna just rotate it so the elements point up/down for vertical or lay flat for horizontal polarization.   
• If you are using a beam antenna to work a distant repeater the antenna will need to be vertically polarized to match the repeater’s antenna. 
• If you are working SSB long distance then the beam antenna should be horizontally polarized and so should the distant end.
•  

What should I use to connect my radio to the antenna?

• Normally ordinary wire can't be used to connect  the radio to an antenna, unless you are using a long wire antenna that leads directly out of the antenna jack on the radio or an antenna tuner.  A long wire antenna is simply that, a long wire that is several wave lengths long and not an even multiple of any wavelength you want to listen too.  It is a receive antenna but can and has been used successfully as a QRP or low power antenna for CW (or any mode really).
• To connect the radio to any other sort of antenna means using either balanced ladder line or coaxial line.  Balanced ladder line has been used since the dawn of radio use and is well suited for any balanced antenna like the di-pole.  The problem with it is it involves very stringent installation methods and is therefore not easy to work with.  It is very low loss but unless you are very familiar with balanced line installation I will discount it as a viable means to connect to the antenna. Most modern radios will only have coaxial PL259 connectors and attaching ladder line will involve a separate piece of equipment to match the ladder line's 450 ohm impedance to the radio's 50 ohm.
• Coaxial cable is bar far the easiest to install and connect to your modern radio. It has a 50 ohm impedance so it matches the radio with no additional equipment.  If the antenna is also 50 ohms at the desired transmitter frequency then all should work well enough to radiate some signal off the antenna.  Coaxial cable is not without some drawbacks that must be discussed otherwise you could be wasting power.  Antenna impedance at the desired frequency is very important.  The antenna must be cut or trimmed to provide the best possible SWR. In a SHTF situation or a temporary  antenna installation a 3:1 SWR might be all that you can manage and it will work but at greatly reduced power.  First the impedance mismatch between the radio and antenna will lose power and most solid state rigs will automatically reduce output power if the SWR is 3:1 or greater.  Some solid state radios will not even transmit if the SWR is too high.  So it's best to try to get an SWR of less than 2:1 even in a temporary antenna installation.  For permanent installations SWR readings of less than 1.5:1 are good.  Don't spend too much time trying to get the SWR below 1.2:1. In most installations that's about as good as it's going to get.  Anything less than 2:1 is going to be OK.
• The reason the antenna SWR needs to be as low as possible is that any energy not radiated off the antenna due to impedance mismatch is sent back down the coax to the radio.  This is what is called reflected power and that power is sent right back to the transmitter and in severe cases will cause permanent damage to the transmitter.  This is why the transmitters automatically reduce output power in a high SWR situation so they don't blow themselves up.  If you use an antenna tuner between the radio and the antenna and the antenna mismatch is off the reflected power is absorbed by the tuner and not reflected back to the radio.  The antenna tuner does not have delicate solid state final transistor amplifiers to get damaged.  The antenna tuner always show 50 ohm impedance to the radio so the radio will never reduce power in a high SWR condition.  However the antenna mismatch will still cause power to be reflected back to the tuner so that power is lost.  But when using an antenna tuner the antenna reflected loss is not combined with a transmitter reduction loss so the overall loss is less.  Antenna tuners are good if you can not for what ever reason obtain a less than 3:1 SWR on the antenna.  If your antenna is well matched (less than 3:1) to the transmitter frequency then I'd take out the tuner and connect the radio directly to the antenna as the antenna tuner does rob some of the transmit power.
• Another important factor with coax cable is it's efficiency.  Coaxial cable is reactive to RF energy and as the frequency goes up the more resistant the coax is to the RF energy.  Some cheaper coaxial cables can reduce power as much as 6dB (for VHF frequencies, more for UHF) or 1/2 the transmitted power in 100 feet.  So if the coaxial run from the radio to the antenna is about 100ft, not an unrealistic length, then you have lost half your transmitter power.  The better coax cable with less impedance to high frequencies costs more but is an investment if you plan to operate on low power.  A 100ft piece of 3dB/100ft loss coax compared to a same length piece of 6dB/100ft loss means you can transmit at 5 W for 20hrs/100aH battery compared to 10W for 10hrs for the same effective radiated power (ERP).
• So in summary, get the best flexible low loss cable (UV resistant) that you can afford and it will be a good investment toward power savings in the end. Another option would be some super low loss 75ohm TV coax used for digital cable.  Even with the impedance mismatch the line loss is so low it makes up for it and the net gain is in the positive.  Good low loss TV coax should be readily available in SHTF conditions especially in urban settings.  Many Hams use 75 ohm coax connected to a dipole antenna (for HF not VHF+) and it works just fine for what they are using it for.

Radio Communications Systems During Crisis Situations (Power)

This is part 4 in an ongoing series on radio communications during a crisis event.

How much RF power do I need?

• As much as possible, but only use the least amount of power required to complete the communication.  There are reasons for both high power and low power.
• Low power conserves battery consumption and keeps the range of communications as short as possible when trying to maintain a low profile.
• High power is used to reach out longer distances when conditions form weak propagation but propagation is still possible. No amount of power will reach out long distances if the conditions for propagation are not favorable.
• During the best propagating conditions one can talk (voice) around the world on 5 watts or less using a gain antenna. Using a low power mode such as CW or PSK31 even milliwatts (less than a watt) is all that is required to communicate long distances.
• I know I previously said as much power as possible and sure that would be nice.  However it’s not practical to have all that power as the battery or power source requirements would not be feasible in SHTF conditions.  100 watts is the most feasible transmitter power running from a 12 volt system. That’s from a fully charged battery putting out 13.8 volts.  To get 200 watts of transmitter power the voltage requirements jump up to 85VAC for the ICOM IC 7700 ($7000 retail, almost 9 times the cost of the FT857D).  This radio now requires a generator to operate and dino fuel is scarce and expensive WTSHTF.  So how much better will 200 watts sound at the receiving end compared to 100 watts? Only about 25% better because of the inverse square law.  However depending on how noisy the conditions are at the time 25% might mean the difference between copying the communication before the transmitter batteries die and not hearing the transmission at all.  To use the full legal limit power of 1500 watts you’ll need a full house generator to supply the required power and the expensive power supplies to provide the amplifier the required power. Expensive equipment and expensive fuel consumption!  Instead of using transmitter or amplifier power to boost the transmitted signal which costs exponentially more money and consumes exponentially more resource power there is a better way to amplify the RF signal using an antenna. We’ll talk about antennas more later.

 What type of power sources should I use?

• Unless you have unlimited fuel and will be running generator power throughout the crisis you will need some sort of battery bank to run the radio equipment. If you stick to the radio types recommended here the most power you will require is from a 12 volt deep cycle battery bank for the mobile/base radios to AA or AAA batteries for the portable hand held radios.  The 12 volt batteries should be charged via solar or wind power through a charge controller so as not to over-charge and damage the batteries. The AA or AAA batteries should be rechargeable via direct solar charging from the solar panels or 12 volt battery bank and not through wall warts that use converted DC to AC/AC to DC voltage.  There is substantial waste converting the DC to AC and then AC back to DC to charge the batteries. 
• Save wasted power by not using 12 VDC rectified power supplies that run off of 120VAC. Again much needless energy waste happens in the conversion process.  Stick to direct battery power where the only losses are in charging the battery and cable resistance loss.  Speaking of power cables, they should be heavy enough for the 22A current draw when transmitting at 100 watts of power and I’d even go up a gauge in size to help reduce the power cable loss even more.  The min gauge is set for safety reasons but the cable will still be wasting energy which you can feel as the cable warms up.  Use the largest feasible wire (cost/ease of workability/available connectors) possible so as to conserve precious battery power.

How long can I expect to operate off one battery charge?

• A typical 12 volt lead acid battery is capable of taking a charge from a 14 volt (14.4 typical) bulk charge source before it starts to damage the battery.  At 13.4 volts (float charge) the rated output power of a typical mobile/base radio will be close to 100 watts. So while the charging source is applied to the battery your radio will be transmitting at or near 100%. Once the charging source is removed a fully charged battery will output about 12.7 volts. At this level your radio will produce about 92 watts. At 12.4 volts your battery is about 75% capacity and at this point it should be recharged.  If not then sulfur will build up on the plates and begin to shorten the life of the battery. At this level your radio will only be outputting about 90 watts. As the battery drains down to 12.2 volts the radio will only put out about 88 watts. At this point the battery is getting to 50% capacity.
   
• A 100Ah battery will run the radio in receive mode (squelch open mode 1A) for about 50 hours before it reaches 50% capacity.  However, for longer battery life (longevity) it is recommended not to run the batteries below 75%. So the most you can run off a 100Ah battery in receive mode is about 25 hours or one day.  If the radio was to transmit at full power (22A) the time to 75% capacity is now at just over 1 hour.  Reducing transmit power to 25 watts will get you about 4 hours of transmit time. 10 watts will get you 10 hours of transmit time. 5 watts of output power consumes about as much power as the radio in receive (squelch open) mode or about one day of operation or 25 hours.  I’ve used rounded numbers here for easy understandable math.  These are just rounded ball park figures to give you an idea on battery drain compared to output power. Remember 5 watts of power during the best propagation conditions will travel all around the world with the right antenna.

In the next series we'll discuss what antennas to use.

Radio Communications Systems During Crisis Situations (Radios)

This is part 3 in an ongoing series on radio communications during a crisis event.

What type(s) of radio should I have?

• Just like tools certain radio types work better than others in different situations.  You should use a hammer to pound nails rather than a shovel. It just works better.  Also different hammers work better at certain types of hammering jobs likewise different modes of operation work better in some circumstances than others.  You wouldn’t use a sledgehammer to drive a finish nail in a piece of skirting board.

• While it would be nice to have one of each radio system available plus spares it just isn’t feasible or cost efficient nor is it necessary in a crisis situation.
• Instead of having several radios it would be better to have an all mode/all bands (or at least the popular bands) radio and one spare. That will help keep your comm. gear footprint in check.  Older radio systems and some home built systems have a separate transmitter and receiver box.  I don’t recommend using the big sets that take up precious space. The reason I don’t recommend them is not only do they increase your comm. footprint, they are not readily portable, and consume more power than a single transmitter/receiver (transceiver) box.  When considering a comm. system for emergency crisis situations you’ll want a radio that is small yet puts put decent power (preferably adjustable output power) and one that uses minimal power consumption (especially in receive, squelch, or standby mode).  Most modern transceivers made today meet these requirements. Small is better for spare(s) storage and also for hiding your in-use equipment in case of visitors.  It’s quite hard to hide in plain sight separate large transmitter and receiver as together they would take up most of the top of the average sized dining table.  Also small is better for portability reasons in case you have to bug out.  Just unhook the antenna cable(s) and the power wire and shove the small radio in your BOB.

• If you can’t afford a new radio system and are forced to look on the used market, try to get an all mode all band radio that at least has 80, 40, 20, and 10 meters. Try for 6 meters and if possible 2 meters VHF also.  Having these bands available will cover most if not all your communications requirements.  Having 160 meter band is not critical and the problem will be the antenna size.  We’ll cover antenna sizes in a later session. Having 6 meters available is also nice but long haul communications may not be possible especially during periods of low solar activity.  If I were to skip a band it would be 6 meters since that band is not open for reliable communications all the time. In a crunch you’ll get by with just 40 and 20 meters in the HF bands.  You may find small 40 and 20 meter SSB/CW radios that were built from kits.  Since these aren’t commercial rigs you can probably get them for a song.  Being built from kits you may be able to stock up on some of the major components as spare parts and repair the radios if they ever fail. That's a viable option even if only for a spare radio.
• For the VHF bands a 2 meter FM radio will cover most of your local communications needs.  If the local repeater is powered by alternate power source (most are) all the better, it will greatly extend the communications range of a low power radio.  A UHF radio in the 70cm band is nice to have but not essential.  Dual band VHF/UHF radios are abundant but usually cost at least twice as much as a single band radio.  These radio packages come in mobile sized packages the size of a CB (or smaller) and hand held walkie-talkie types that range in size from an Altoids mint can to the size of a multi-function TV remote.  If I were to only get one VHF radio it would be the 2 meter FM 50 or 75 watt mobile if I was any distance from the local repeater or a smaller handheld in the 5 to 7 watt range if the local repeater is close by. With an external antenna such as a J-Pole (discussed later) handhelds go quite a distance. From my location I can hit the repeater about 80 miles away with the J-Pole at ground level. The repeater is on a high mountain (10,000ft) and in clear sight of my location so don’t expect that range between two radios at ground level. We’ll discuss antenna height in a bit.  A 2 meter all-mode would be better but there are none on the new radio market and on the used market they are scarce.
• You’re going to need a base station and as many portable radios (not necessarily amateur frequencies though) as you can muster or think you could possibly use.  The portable radios are indispensable for anyone working or traveling outside the protected areas.  While I recommend personnel travel in pairs (buddy system) it’s not always possible or warranted in certain times but having a means to communicate back to base in the event of an emergency goes a long ways in being prepared. 
• For local use around the community I highly recommend purchasing Part 15 (no license) devices such as Family Radio Service FRS or CB walkie-talkies. They are cheaper than amateur radio gear and don’t require a license to use.  They are usually low power so they are only good for up to a mile or so depending on terrain.  Don’t pay attention to the wild claims of 20 plus miles of range.  You might get that kind of range if both parties were standing on top of a mountain top with clear line of sight.  At ground level with trees and terrain obstacles your range will be much less.  Leaves and ground obstacles eat up a lot of RF energy at these frequencies. Also since these radios are to be used for short distance around your block communications, high power (or long range) radios are not required and will use up your batteries faster.  Keep the power levels low for this type of use and your battery life will be longer.  Remember FRS radios will not work with you Amateur radio so in addition to portable FRS radios you’ll also need a FRS radio for a base station.  There are modifications (illegal) that can be done to the radio so you can hook the base radio up to an external antenna.  This will extend the range of even the portable radios as the base station now has better ears and a better mouth. Another radio type is General Mobile Radio Service (GMRS). These radios require a license which extends to immediate family members but requires no test.  These radios can output up to 50 watts and can have external antennas.  They cost more that FRS radios but a base station with a high external antenna on flat ground will reach out 20 plus miles if needed.
• For more private/secure communications there are several choices.  However remember no radio frequency communications are secure unless some sort of encryption device is used.  Use obscure frequencies that are not normally used by the general populous. A marine VHF radio makes a good radio for inland communications so long as you are a fair distance from the coast and any major river transportation routes (Mississippi/Missouri rivers/Great Lakes).  Low power handhelds are good options, stay away from the high power radios used onboard ships unless they are capable of reduced power modes.  You don’t want your signals to go much further than around your retreat.  Commercial fleet radios are another good option for a SHTF radio.  These do require an FCC license to operate but when the worst of it is upon us that won’t matter.  Most fleet radios have programmed channels and only a few will be programmed. If you can try to get the programming software along with the radios so you can program your own frequencies.  The problem with fleet radios is they are higher powered and may not have the ability to reduce power.  Some radios, especially portable walkie-talkie types can operate on different voltage levels and this has the added feature of being able to increase or decrease the output power.  Check for a radio that has a wide operable voltage range.  To reduce the power of a 3 cell AA battery system, just remove one of the batteries and short the space where the battery was with some wire or metal (tinfoil wrapped in tape with the ends uncovered). You have now just reduced transmit power to 2/3 of what full power was and saved a battery in the process.  If more power is needed just put the 3^rd battery back in the radio.  No physical modifications. These systems are suited for around the retreat or convoy operations where low-power more secure communications are warranted.  GMRS radios are also a viable option as they are more expensive than FRS and may not be as popular in the community.  They are usually more powerful so make sure the power can be reduced.
• For handheld amateur VHF FM radios any model you can get your hands on is a good model; especially the newer ones.  Yes some will be better than others but for what you are going to use them for any model is going to do the job.  Features to look for on a handheld VHF FM radio are a removable antenna so you can connect an external antenna for better range, one that uses readily available batteries, AA or AAA. Stay away from proprietary battery packs as when they fail, and they will, you will have to rig some alternate power source and possibly damage the radio.  A lot of radios may also have a AA or AAA accessory pack that can be used in lieu of the proprietary battery pack, so pick one of those up also. Radios with a standby mode are great on conserving power consumption.  In standby mode the radio basically goes to sleep for a second or two, then wakes up and listens to the frequency it’s monitoring and if silent goes back to sleep.  This can cut power consumption by 2/3.  The radio will not scan frequencies in standby mode so it’s only a viable power saving method if you are monitoring one frequency. Another feature that could be useful is a cross band repeater. This will only be available on some of the higher end dual band radios.  Only one of your dual-band (2meter/70cm) hand held/mobile radios needs to have this capability.  What this allows is the ability for the radios on 2 meters to communicate with the radios on 70cm.  By having one radio with this capability set in repeater mode you have greatly widened your community/neighborhood communications system.  This radio will be set as a base radio and can’t be used by a person in this configuration. So make sure if you sacrifice a radio for this purpose you have another you can use for operations.
• If you are purchasing new and can spend about $1600 (for just the main radios, primary and spare), the base/mobile radio that I recommend is the YAESU - FT-857D. At about $800 each this radio is small, covers all the HF bands + VHF 6 meters and 2 meters and UHF 70 cm.  It is an all-mode radio and has the 3 main modes CW/SSB(LSB-USB)/FM that you will need to communicate. It also has AM and WFM in case you are in contact with a station with only those modes. Current consumption in squelch mode is 550mA (there is no standby mode), 1A in receive (squelch open), and 22A when transmitting at 100W.  You may not need 100W for most communications especially low power modes such as CW and PSK31.  More on required power and operating modes later.  The cost of this radio is about the same cost (or less) than if you bought 3 different radios on the used market to cover HF/VHF/UHF (good deals not withstanding). 
• The FT-857D is a fairly rugged design and will withstand some moderate abuse in a portable environment.  It is not advertized as MIL-SPEC but most reputable manufacturers these days do conform to some electronics construction specifications/standards. I wouldn’t subject the radio to copious amounts of water but a light splashing should not cause any problems especially away from the front panel. If you are going portable with a radio a water proof wrapper/sleeve is a must-have.
• There is the FT-857 model that is older and is exactly the same radio except the D model has the Digital Signal Processing (DSP) filter built in. The 857 (non D) model does not have DSP but it can be installed if you buy the module.  DSP is not required it just helps filter the signal you are trying to receive better.  If you find a deal on an older FT-857 (non D) model don’t hesitate to snatch it up.
• Also the FT-897 and 897D (DSP) models are the bigger brothers to the 857.  It is virtually the same guts in a different (much larger) package that allows installation of internal power supply (requires 120V AC) or battery pack(s) that operate the radio on reduced power (20W max). It’s receive and transmit power consumption is the same (1A/22A respectively) however the squelched power consumption is 50mA more (600mA) than the 857 model.  It costs about $130 more per radio and to me for a SHTF radio it’s not worth the extra cost. 
• However if the radio is to be used more for hobby/enjoyment in a fixed location (that's why I'm getting this model)  and the extra $130 is not a deal breaker, I recommend the 897D due to its larger face panel/display screen and larger knobs.  There are more buttons available on the front panel so less menu access is required to change the more common settings.  If a good deal can be found on a used model don’t hesitate to snatch it up either. 
• All four of these models also have a very useful feature called a spectrum scope. This allows one to visually see if a frequency has a signal on it without having to scan the entire band. A quick visual for a few seconds will reveal if anyone is transmitting or not.  This is a great feature to quickly scan all the bands for activity and thus reduce power consumption.  Most of the older used radios don’t have this feature and is a factor in considering whether to buy new or older used equipment. Some of the more expensive base style radios have a better spectrum scope with more resolution and can even display out to a computer monitor for easy viewing.  I’m not sure the added expense in equipment and power consumption is worth it though.
• Either one of these four radios will work just fine for the intended purposes and if you can find one on the used market for a few hundred bucks then grab any of them.
• Other manufacturers have similar models with similar features however an all-mode/all-band radio in this price range is not available. The closest one is the ICOM IC-7000 at $1240 each retail. The added features and specifications are better but the added cost and a whopping 1.2A (double the 897D) squelched mode power consumption don’t make it the best SHTF radio in my book. The transmit consumption on all the 12V 100W radios is about the same, it’s the squelch and receive consumption that will chew up your battery.  A more feature rich radio will cost more and chew up more power in idle mode.
• Since this section has a lot of material I’ll summarize here:
• What I'm going to have in my kit:
• New FT 897D with a used FT 857 or 857D for a spare or mobile rig. Still need to purchase.
• Icom 2100H 2 meter FM rig. Purchased 2004. Great solid reliable rig!
• Icom W32A 2 meter/70cm dualband portable. Another solid performer with dual band repeater mode.  This is my in the house scanner to monitor the local repeaters. Its a true dual band where I can scan both bands at the same time and hear both transmissions. Awesome. It's hooked to my copper J-Pole mounted at 20'.
• Older Kenwood TS180 HF 160 - 10 M 100 W. My HF backup backup. It's huge but it's already in the inventory. Great radio that's over 30 years old and still running strong! Don't buy one for SHTF preparedness but any radio you currently own keep or trade for 2 of another type you do need. I'd trade this in a heartbeat for two more 2 meter/70cm 5W+ dualband handhelds of any brand.
• Radio Shack 2 meter FM radio that works 50/50. I'll keep for spare or trade during SHTF times.
• Radios that you need (minimum):
•  One HF at least 80 through 10 meters. 40 and 20 meters are a must! 100W output power (the standard for base/mobile amateur radios) and capable of power reduction to at least 5 watts.
• One 2 meter VHF FM mobile (50 to 75Watt) with adjustable output power settings.
• 1 spare for each type (if you can afford it)
• Alternate radios that use obscure frequencies (marine bands/fleet radios etc) or low power GMRS radios for more secure personal communications.
• Radios that you may want to consider:
• HF/UHF/VHF all mode all band transceiver. (base station) Highly recommend the FT 857 or FT 897 (D or non D models) as they contain all you need in one package.
•  One 2 meter/70cm dualband VHF/UHF FM mobile (50 to 75Watt) with adjustable output power settings. (vehicle/mobile operations)
• Portable 2 meter/70cm VHF/UHF FM handheld w/ removable antenna the more watts the better. Adjustable power output even if by removing battery cells.  Standard AA or AAA battery packs or accessory packs.
• 1 Spare of each of the above or combination of different spares to cover all the band segments. Band coverage is more important that same brand spares.
• As many FRS and/or mobile/base/walkie talkie CB radios as you can afford for neighborhood/community communications (good barter items also). These can be picked up at yard sales for a few dollars.  Keep one base station CB with SSB capabilities for yourself as this can be used for long distance communications with a beam antenna.
• Remember it is important to store all unused radios with silica gel desiccant packs in sealed/grounded metal boxes that the radios will fit in. FRS and walkie talkie radios can be stored multiple to a box. Foam padding or bubble wrap will help absorb shock in the event a box is dropped. Do not store batteries in the same boxes as the radios! Make sure all batteries are removed from the radios before they are put in storage!
• If you can only buy one radio and have $800 in your budget get the FT-857D!

Stay tuned for the next post in the series in which I will discuss radio power.