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The long distance comms solution

Lightspeed posted the decision on the forum earlier today so there has already been some discussion about the next stages. Just to keep everyone updated I’m posting his decision here as well.

Looking at the feedback on this site and the results of the poll on possibility of using CB radio as Our primary long range network comms tool in a post SHTF world it is clear that we are insufficient in number for CB to be workable.

This means that PMR446 will be even less good as a long range communication tool.

I wanted to give CB the best possible try, as its inexpensive, setting up would have been fairly simple and a number of us already with strong knowledge and experience would accelerate the get-go . As a group we need to instigate a fast hands on training and systems testing, again the existing knowledge base would have been a big advantage. But I fear that with such a small number of declared active stations, the negative experience of assembling all of the recommended kit, hoisting up an antennas and then being met on the allotted day and time with nothing more than stubborn background hiss and not a glimmer of another prepper, will kill the whole idea of a viable comms network for a much larger number of us ……. That’s bad enough. But imagine the consequence of a supposed network that failed entirely the very first time we tried to use it in a post SHTF world?. If we’d mustered several hundred motivated individuals, a CB based solution might have been viable. With just the enthusiastic band of ten or so of us its a useless cause . Worse than useless if you believe Timelord’s perception the need for redundancy in the system to be reasonable and accurate, which I do. Going exclusively down the CB route in such small numbers is a waste of time, resource and effort, for it can only end in failure.

Parameters we are working with are that the solution must be inexpensive, not too complex and, because of our smallish number of geographically dispersed active stations, be capable of long term operation, delivering messages over hundreds of miles point to point. The solution must also be such that we as a prepper community can test and experiment with it straight away, pre-SHTF in order that we can hone our skills and adapt our stations for the best mix of performance and Opsec. Again training and testing, repeated and ongoing training and testing, are imperative and urgent.There is only one viable solution to this requirement, and that is Ham radio. I know this will be a disappointment to those of us who are already on CB and I know that there is an argument that by turning up the power we can achieve greater range with CB. But power is going to be a critically scarce recourses in a post SHTF world, I cannot see that any of us will be able to squander it when there are better solutions available. We need to make this decision with our heads, not our hearts.

With a just a few stations, each of them must be capable of long range. The range needed needs to be up to 300 miles or so, not intercontinental. It must be achievable day and night at all stages of the 11 year solar cycle. It must be achievable using simple and low power transmitters. The solution must preserve the OPSEC of the station location.

We’ve covered this elsewhere, but most point to point ( eg not repeater linked) radio transmitting systems and techniques fall into two distinct areas: Groundwave 0 to 20ish miles, and long distance 1000+miles. This is not the same as 0-1000 miles coverage. Over-simplifying the and restating this to illustrate the issue, Groundwave transmissions stop at around 20 miles, and long distance techniques start to be received at 1000 miles. Over the intervening 21 miles to 999 miles nothing is reachable.

A radio operating technique called Near Vertical Incident Skywave (NVIS) was developed by the Military precisely to meet the need to communicate between Zero and up to 300 miles range. A number of Ham radio enthusiast are active in this technique as well and a fairly large Ham radio resource is available to support our potential activity here.

Frequencies to be used for NVIS are critical: 40 meter (7Mhz) band works during daylight hours and the 80 meter (3.5Mhz) band by night . These are both Ham allocated frequency bands.
This is not just theory. My own station log records successful communication between Surrey and North Yorks, and Surrey and Cornwall using just a few watts of power.

Timelord has already voiced a very valid opinion about use of Morse code. Morse (or CW = Continuous Wave) is the most robust communications solution for NVIS too, although the NVIS technique will also support voice communication using Single Side Band (SSB). The advantages of using Morse are that the equipment has substantially better range than SSB, is less complex, more robust, consumes less power, is more user fixable, and costs less in financial terms.

NVIS transmissions on these frequencies and using these techniques will reach into the deepest of valleys and have greatest penetration of vegetation (will work well in forested locations). These transmissions will be receivable using SSB/CW capable Shortwave receivers, or even Shortwave AM receivers equipped with an inexpensive external device called a Beat Frequency Oscillator ( BFO) which will allow them to interpret the SSB /CW signals.

Antennas are the big issue with such stations. Good news is that they can be simple low tech wire construction, and that they only need to be mounted 6 to 15ft from the ground. BUT, they are long antennas. The daylight antenna 7Mhz is approx 20m = 66ft long, and the Night time antenna for 3.5Mhz twice this length. Depending on your location, this length does not have to be in a straight line, but should be pretty much parallel to the ground. Installing alongside the top of fences around the perimeter of a domestic garden sould be a viable solution.

So, are PMR 446, VHF, UHF and CB short range solutions redundant?

Absolutely no. PMR446, VHF, UHF and CB transceivers remain vital items of equipment that should be in every prepper’s kit.
Both the Ham technology described above, and these short range solutions are going to be important. Critically we must survive any SHTF transition stage first. In all thinking, start locally and work outward. If we do not command the comms ground under your feet we will never command the ground beyond it. This is where short range highly portable solutions are imperative.

In an emergency you and your family might be forced to move in a mass evacuation with large crowds. How will you know where your family is? How will you keep them together? How will you find one who is lost? How will you and your family be able to do things that others can’t? Quick, effective, close-in intelligence and reconnaissance will allow you to keep your heads while others are losing theirs.

These short range solutions operate at much higher frequencies than the NVIS systems discussed above. The physics of building transceivers for higher frequencies mean that efficient antenna sizes are hugely reduced, permitting true hand-held operation.
We have already discussed this equipment in some depth and those discussions are still valid.

For anyone intending to get licensed, however, there are additional benefits that can be had immediately. Comms testing on the Ham VHF and UHF can be undertaken without attracting the negative attentions of authorities.

Conclusion and some questions:

Currently there is no organized survivor radio comms network in the UK. This weakens our survival prospects. Bug Out Bag and others have argued elsewhere, it is probably not viable to survive in the long term as an individual, we need to group together for mutual support and protection.

As a smallish group of radio comms enabled preppers we should be considering both Short range tactical solutions AND longer range solutions, and that means Ham gear.

A nationwide coverage communications system is entirely viable using NVIS techniques on Ham frequenies. Far more well equipped stations will be reachable when we look at the Ham community, but how many of those Hams will survive a SHTF event is questionable. If we want a stand alone network, with redundancy, we will probably need a dozen or so well placed stations.

A network using NVIS for trunk communications connected to PMR/UHF/VHF/CB via “local” hubs for delivery of messages to “localized” survivors is technically possible. But why would the people who have gone to the trouble of setting up the long range NVIS systems be prepared to risk their own OPSEC, consume valuable power, and wear out their equipment do to support others? Assisting in this way is somewhat like sharing your food caches with those who did not make any preparation pre-event. As far as is possible we ALL need to be capable of both types of comms to some extent. And post event we will have to use these comms capabilities with great care and prudence.

Following on we need some details for what we need to buy and so we moved on to the next stage.

1) Started a thread to list and discuss NVIS capable equipment

It will cover:

1. Transmitter & Receiver or Transceivers that cover 80m and 40m bands, with minimum of say 2 watts power output and capable of CW transmission. Ideally transceivers should have VFO ( Variable Frequency oscillator) controll this will allow the unit to be tuned to find quiet frequencies. Tranceivers that are Crysal controlled are effectively fixed frequency, and so are much less flexible.

2. A device called an BALUN or and UNUN that will assist in making simple antennas usable

3. A device called an Antenna Tuning Unit (ATU) which will assist in making transmission possible on antennas that are not perfectly resonant to the transmitted frequency

4. An SWR meter that will function on 80m and 40m to work in conjunction with items 2 & 3 displaying the degree to which the antenna is matched to the transmitter.

5. Wire for antennas

6. Insulators for antennas

7. Paracord / nylon rope to rig antennas

8. Coaxial cable (this will be 50ohm cable for almost all modern transmitters)

9. Appropriate coaxial plugs to mach the transmitter, BALUN, ATU, SWR Meter. Most likely PL259 type.

10. Possibly ladder line feed wire: 300 Ohm or 450 Ohm this stuff is very low loss when used correctly, but considerably more visible than standard black coaxial cable.

11. Power supply cables and connectors

12. Power supplies and charging systems, most likely 12v

2.) Protocols.

First stage will be to get operating licenses, in so getting, basic operating protocols will be taught.

After this live trials can begin and secondary protocols can be developed to deal withthe real life issues encountered.

Basic protocols like choosing a frequency will only be possible once the participants confirm which quiet frequencies exist in their areas. All too often agreed frequences are clear in one place but have huge s9 interference in others. Pre SHTF we will have to deal with this. Post shtf it will prob be grid down so we can expect mush less noise to deal with.

8 comments to The long distance comms solution

  • Kenneth Eames

    SD, Cost would probably be a problem for me and of course, I would have mountains to contend with. The cost would be the bigger problem. I do have a 1,000 foot hill which might allow contact along the Irish sea and the Hebrides. Kenneth Eames.

  • Lightspeed

    Hi Kenneth, The NVIS technique has been found to be very good at getting signals over mountains and into deep valleys as the radio waves are being bounced of the atmouspher almost overhead.

    I need to do some research and experimenting to see if very low power transmitters can work in this way. If yes then there are a number of very low cost simple kits that would be viable.

    I’ll post a reply to you here once I’ve found out.

    Cheers

    LS

  • fred

    Short wave is surely fine. Or is that ignorant?

    • Lightspeed

      Hi Fred,

      Yes, shortwave is what we’re looking at, but different frequencies for different uses.

      My reply to KennethIta was about minimum transmit power required.

      So far I’ve not found any reference of NVIS being operable bleow 1.5w

  • Kenneth Eames

    Thank you Lightspeed. I await further info when available. I would certainly like to make kits, I would probably learn a lot more about radio this way. Kenneth Eames.

  • Lightspeed

    Hi Kenneth,

    I’m making a fairly substantial waterproof man-pack to allow me to coninue opeating my radio geat in the field. O

    nce complete, I’ll conduct my own ultra low power NVIS experiments to see what’s achievable. This may take a few months to complete, but I’ll let you know the results as soon as I have something meaningful to report.

    Best regards

    LS

  • I’m and “ex” IT Engineer with an on-going, avid interest in communications – you might want to consider the Clansman gear that is readily available. It’s relatively cheap and can cover virtually every frequency that would be required and of course is MOD spec.

  • Lightspeed

    Update to Kenneth

    1/2 watt to 3watt Shortwave radios now tested and operational in a friends and family network here.

    We are able to communicate over a geographic diameter of around 100 miles with fairly good reliability.

    Cost of transceivers is between £2.50 (1/2 watt Pixie Kit) and £30 (3 – 7watt built-up and cased Suoer Rockmite) Check e-bay for availability….use the search term QRP and it’ll find loads to choose from.

    Power supply is 12v

    Antennas are simple end fed wires, fed via a home brewed matching circuit. Cost of antenna system is around £23.00. If anyone wants such an antenna please PM me on the Forum.

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