Resolving the Clandestine Radio Question

Continuing on from this original question from Keypounder, several close answers were posted, and generally the logic was in the right direction. That being said, here’s the correct answer:

“You are the lead station operator in the Resistance receiving station
mentioned in the first question.  You have received the message sent by
the operator in the capital at 1 pm local time in the first example on
160 meters and must now forward the vital information received to
Resistance HQ via HF radio.  Once you transmit this message, you will
immediately relocate to another predetermined location you have selected.

Assume the following:

-your station is located at approximately 65 degrees West and 10 degrees
North;
-Resistance HQ is located somewhere in the Intermountain Western united
States, New Mexico to Montana, Eastern Oregon to the Western Dakotas;
-Resistance HQ has receive capability 24/7/365 and will be waiting to
copy your message during whatever window you have told them to listen on
whatever frequency segment(s) you have specified;
-The message from the capital of Slobovia consists of 25 each 5 letter
encrypted groups.  You will re-encrypt the message prior to
retransmission using a OTP, but there will still be a minimum of 125
random letters to transmit;
-You are required to use any of the ITU region 1 authorized amateur
radio frequencies and modes from 1.8 to 29.7 mHz;
-You will have been onsite for at least a week prior to receiving the
message from the capital of Slobovia, and will have access to a small
house nearby the station site, but are forbidden to set up equipment at
the house;
-You are required to complete the transmission to HQ in less than 20
seconds, and to evacuate the transmit site in less than 15 minutes after
completing the transmission leaving no material behind.  You have 4
dedicated helpers with no electronics or radio training available;
-You have a compact 4wd crew cab pickup truck for transport, and
everything, your crew included, must fit into the truck.  No radio
equipment may be visible from outside the vehicle;
-Assume the ground is level farmland with very rich loamy soil planted
in low-growing crops or grass, with tall trees (>50′ high) at the field
boundaries with steel t-post electric fences around each field, and that
the field lines run north-south/east-west.  Further assume that each
field section is 8 hectares in area square. The surrounding general area
is agricultural, both crops and stock.”

Questions-

What frequency segment and time will you select to minimize DF
likelihood and maximize the chance that HQ will acknowledge it?  What
will your alternate(s) frequencies be, and under what circumstance will
you use them?

>Keypounder sez>  OK.  this is about a 6,000 kilometer short path, which
means about 2 hops.  One will be hitting the ionosphere about 1500 km
away, over the Carribean.  The next will hit the ionosphere somewhere
over the central US.  You could do this easily on either 40 or 80 meters
at night, but 40 and 80 meter antennas are big, and it is hard to get
them high enough off the ground to get good low angle propagation.  For
longer haul comms, we need to be looking at 10 mHz and up.  The higher
the frequency, the easier the contact as long as the band is open.  At
this time of the year and at this stage in the solar cycle, what are the
FoF2 readings over the south central and central USA?

Checking the Austin TX, Boulder CO and Idaho Falls ionosonde data, we
find that the FoF2 around local noon is between 5 and 6 mHz.  Puerto
Rico or Florida will give me a pretty good idea of what can be expected
for the first bounce;  these readings are around 6mHz, too.  The rule of
thumb is that the MUF will be around 3x the FoF2, so the maximum useable
frequency is going to be somewhere around 15 to 18 mhz, barring solar
activity.  For this purpose, we want to use as little power as possible,
which means as high a frequency as possible, but no higher than
propagation will allow.

I would expect that 20 meters (14 mHz)would be open for this path, and
maybe 17 meters, at about 1 pm in Colorado, or about 2000 Zulu;  we
still have good ionization over the Caribean at that time, so my
frequency band choice is 20 meters primary, with a backup of 17 and 15
meters if there is solar activity, in the digital portion of the 20
meter band.  (14.060 to 14.080)

Q>What antenna(s) systems will you use for transmitting this message?
How high will they be placed?  How will you orient and erect them and
take them down to minimize possibility of observation? Explain in
detail, including specifics of antenna and transmission line.

>Keypounder sez>  So, we need a directional antenna that is relatively
narrow in transmit mode, low profile, easy to take down quickly,
unidirectional with reasonable gain and a good front to back/side ratio.
Ideally this would be something that does not look like an antenna at
all.  My choice would be a terminated Vee-beam fed with window line; a
secondary choice would be a long wire. Reasons include:
– easy to fabricate in the field;
– forgiving of layout and construction errors;
– can be made using common electrical fence materials;
– When properly configured, capable of high front to back and side
ratios with reasonable gain.
-Easy to install in the field, and very quick to take down.

The feedpoint would be strung from the tallest tree I could get a rope
into on the south side of one of the plots with the least visibility
from the road or other houses.  An 8 hectare plot is about 20 acres, or
around 880,000 sq ft; this is about 900+ feet on a side, so I could use
up to 900′ legs.

If you look at an azimuthal map centered on the specified location in
Venezuela (see http://ns6t.net/azimuth/code/azimuth.fcgi) you will see
that the ‘intermountain west’ runs from about 305 degrees to about 328
degrees true bearing from 10 d N/65 d W.    This means that your antenna
should not have a 1/2 power beamwidth pattern any tighter than 23
degrees. Realistically, 30 or 35 degrees 1/2 power beamwidth is probably
a good idea to allow for inaccuracies in pointing, and the center line
direction should be about 315.5 degrees true bearing.

Classic amateur radio designs are intended to cover the maximum azimuth
possible with the maximum gain. From the Wire Antenna book, vol 1, page
5-2 figure 3, we see that a 23 degree 1/2 power primary lobe requires a
leg length of 3 wavelengths with an angle between the two legs of the
antenna of 60 degrees.

However, although the gain is decent, it is very broad in azimuth, with
lots of relatively high powered lobes off the sides and rear.  Once
again, the difference between amateur radio requirements, and resistance
operator requirements becomes apparent.  For OUR use, a better solution
would be to spend some time with EZNEC and look for a vee-beam solution
that provides reasonable gain with fewer sidelobes and better front to
back and sides to reduce the probability of being DFed.

EZNEC shows that a pair of 370′ long wires, feedpoint up 50′ high, with
500 ohm resistors to ground at the lower ends, and those ends separated
by 130 feet, an included angle of ~21  degrees, gives only about 4 to 5
db of gain, but much more importantly yields a very well defined beam
with side and back lobes down well over 20 db and a half-power beam
width of about 38 degrees.

Now, we need to figure out how to use a magnetic compass to set the
antenna legs. Magnetic bearing = True bearing – magnetic declination;
we consult the declination maps shown at
https://maps.ngdc.noaa.gov/viewers/historical_declination/  and find
that the declination is about -12.3 degrees.  To be really sure, since
the local declination can vary considerably, one could check the compass
bearings against various stars, but this will do especially since your
antenna has ample beamwidth. So, true bearing for the center of the vee
beam is 315.5 degrees -(-12.3) =~ 329 degrees to the centerline. Add 11
degrees for one leg and subtract 11 degrees for the other;  the ground
rods should be driven 360 feet from the feed point and at a bearing of
340 and 318 degrees respectively.

I’d use high strength aluminum electric fence wire for this antenna.
(When my transmission was complete, I’d re-roll the antenna wire onto
the rolls it came off and throw it in the back of the truck with the
rest of my electric fencing materials, insulators and such.) Ideally,
I’d use 450  ohm ladder line and a tuner, but I could use 14 gage
landscape wire for a feedline.  Lay this out with two of your helpers,
and drive ground rods at the terminus of each leg.  Attach the 20 watt
500 ohm carbon resistors to the each of the lower ends of the wire and
the ground rod.

Q-What mode will you use for transmitting the message?  If digital,
which specific mode and why?

I’d use PSK 250, because of the high transfer rate and low power
requirements; 20 watts will do nicely.

Q-Before you leave for Venezuela, you will be given an opportunity  to
study data available through NOAA on radio propagation.  Which ionosonde
stations will you study, and why?

As stated above, I’d study the ionosonde data from Florida and Puerto
Rico, as being indicative of the first ionospheric reflection
conditions, and the ionosonde data from Texas and Colorado for the second.

Q- What will your cover story be if you are stopped by Venezuelan security
forces?

We’re just on our way to install some more electric fence!

Q-What are three non-radio related personal essentials that you should
bring with you? (arms of any sort are not on this list.)

Insect repellent;
water disinfection tablets;
a good hat!

And that’s my answer, NC Scout!

A long wire would be another antenna possibility, as it also uses only
one pick point.  Everything else starts to look too much like an
antenna.  With this setup, you can leave the wire down on the ground
until the minute before you want to transmit, then pull it up into the
air, transmit, then drop it again and roll up the wire.
Yagi or quad antennas look like exactly what they are.

And there you have it. Where the Technical meets the Tactical, right were we want to be.

Open Sources- 14 FEB 2017

RT-DAPL.jpg

RT: ‘Veterans’ return to Standing Rock

CNN: Veterans unite for second ‘deployment’ against Dakota Access Pipeline

So while the ‘Liberty’ movement was still trying to figure out just how the Bundys got infiltrated while learning how not to get things done, your Marxist counterparts were faring better. And none payed any attention at all.

This ‘protest’ is a classical manifestation of Marx- the marginalized, phony-proletariat ‘scapegoat’ vs. the Bourgeois oil company. At its heart, this is all the ‘environmentalist’ movement is, has been, or ever will be. It’s not about the environment- it’s about overthrowing the existing order. What’s significant is that these ‘Veterans’ are returning with spring coming, and we know that to some degree, there are folks with some level of military training involved in the emerging antifa movement. They’re armed with sour outlooks from two wars run amok and likely a healthy dose of VA prescribed antidepressants and Marx-thought from the local University. Because what else would you do? Think on that one. If you think all vets are gun totin’ chaw spittin good ol boys waving MAGA flags, you got another thing coming.

All of this is going to have a major flashpoint, and right now the Left smells serious blood and are gaining momentum with the downing of LTG Flynn. Think about what might happen when Prof. Raul X meets disgruntled ex-Joe.

Situational Awareness and Wargaming Your AO

The most important questions you should be asking right now are not the hypothetical or abstract simply naming ‘SHTF!’, rather, it needs to be rationally rooted in the MOST LIKELY and MOST DEADLY courses of action. In a meeting over the weekend, discussing the growing local antifa movement and (somewhat) wargaming/red cell-ing capabilities, the emergency services communications systems were brought up (because it is me, after all). Think on that one for a second.

Just merely saying ‘well, when the S-hits the fan, I’ll do this‘ doesn’t cut it. For starters, its ridiculously lazy. It takes absolutely no work to come to that conclusion, and the answer usually is just to buy another widget from your favorite online vendor. These views are  adjacent to the ‘mental militia‘ that normally follows, about imaginary acts of bravado and ‘saving the Union from the clutches of the commies!‘. Calm down there Audie Murphy Jr…with your tricked out AR that you can’t zero. A smarter position to take would be to put into context what actually is possible in your AO, and what targets of value could come under attack. ‘But that’s the Police’s job!’…so is fighting off the Reds but that’s not stopping you from buying more stuff.

Looking back in a historical context, contemporary lessons from outside our borders might give a better view. Boko Haram, a name you all should be familiar with, has followed a historical pattern of violence not quite unlike what we are seeing the genesis of currently. It began in 2002 as a social movement among ‘repressed’ muslims in northern Nigeria. The real goal was growth of the Caliphate, but near term, it was ‘social equality for muslims’. Eventually, after organizing years of riots and small scale civil unrest, the group killed their original leader and broke 105 of their buddies out of prison. IS did the same in Iraq prior to seizing Fallujah and Ramadi. Immediately they began attacking infrastructure, in part to cause disruption of services and in part to discredit the government’s ability to protect and provide. Critical to this was the communications infrastructure- mass coordinated attacks against the cell phone network and government radio repeater systems- forcing the Nigerian government to first protect those before it could tend to the people under attack. And Nigeria is a country that is still quite rural in the North- imagine the magnified effect on a people spoiled by instant information access.

Let’s take a step back from the cell network and focus on something really more important- public service communications. Over time, the systems have evolved from a simple low band VHF affair to sophisticated digital networks out of the need for maximum bandwidth and additional over-the-air security. But there is a tradeoff. Both Project-16 (analog trunked systems being phased out) and Project-25 (digital trunked systems now in Phase II) require a networked series of repeaters to function and is not usually able to be troubleshot in the field. If those were to come under attack, what is plan B? Do you know? Do the end users know? What are the actual frequencies they work on (this is why just entering your zip code on a home patrol scanner, while convenient, is a bad thing)? Why should you care? Because if you’re a regular scanner junkie, notice things getting worse in your area socially, and then public service frequencies begin to act strange, there might just be something larger at work. This stuff doesn’t happen overnight.

In our discussion this very issue came up for a particular area of serious concern, identifying the weak points and potential backup plan (Remember PACE??? Primary, Alternate,Contingency, Emergency? Yep, still important) all the way down to the role Amateur repeaters would play (They would be the E…a distant E, but still an E). This is where knowing a bit about about all communications systems (or networking with folks who do) beyond the theoretical end comes in handy. It just so happens the area in question has a history of building public sector hardened systems, and many of the engineers are also avid radio amateurs. Having access to simple and well-built equipment is a plus, and having a group who knows their ass from a hole in the ground is a plus as well. Of course, you won’t know any of this if you’re of the ‘I got mine…screw you‘ attitude a lot of preppers advocate, even if you do get that ham license and go back home.

Building independent, resilient communities are paramount, as well as the strongest survivalist plan, but its important to recognize that threats are more than just simplistic catch phrases. You still live in the real world, not that lustful libertariatopia, and are subject to the ramifications of threats external to you. I take people at their word- and the Left’s core, the ‘instant gratification‘ groomed social justice warriors, a manifestation of all of the fingers that threaten Western Sovereignty- are the future of their movement. They see no benefit to the current order and through willful ignorance find solace amid revolutionary ideals whose only logical end is violence. I believe them. And instead of useless projecting, caterwauling and naysaying, one should be asking serious questions about what they’re capable of pulling off. I bet some folks in Nigeria today wished they had done a bit more in retrospect.

 

New from Yaesu

ft-65.jpgUninspired, Baofeng-looking HTs. Two of them, to be exact. A 2m only and a dual band model, that (at least from what they say) are rugged. Well, who knows. No wideband RX is an issue for me, and the styling makes me think they outsourced production to the same place that builds Wouxons. Maybe I’m wrong.

That being said, this is yet another (at least in my opinion) a big misstep by Yaesu. The 991, 891, and now these are all steps in the wrong direction, at the cost of the great radios they replaced (or are replacing). The VX-3R has been discontinued, signaling that Yaesu likely has plans to retire many other older models, including the venerable FT-60 and one of my top pics for a general purpose Survivalist radio, the VX-6R.

Having general purpose RX capability is a huge asset in a handheld package, really setting the Yaesu models apart from their cheap imitations and making the price of admission definitely much more than worth it. Listening to everything from SW to Airband to all our two way needs are worth it. If you’ve been on the fence about stepping up in quality, gaining much in capability as well as durability, do not wait.

Beverages for Listening, I

This is a re-print of Keypounder’s article on Beverage Antennas that originally appeared in Sparks31’s Signal-3 in the same issue my article on Afghanistan was published. In my assessment, its a very well written introduction to not just what Beverages do and why they are important, but how to build them. He very generously allowed it to be re-posted here. Use it!

My Sunday School teacher always taught us that it was better to give than to receive, but when I got into amateur radio as a teenager, I quickly learned that receiving and listening are much more important than transmitting. If you can’t hear them, you can’t work ‘em! I was also taught that the key to successful listening was having good antennas; good receivers were important, but good antennas were essential. On the upper HF bands, say 20 meters (14 mHz) and up, this is relatively easy; get a good dipole or longwire 35 or 40 feet up and you’re set.

But the lower HF bands are different, because of the size of the antennas required, the low effective height of the antennas, and the physics involved in propagation on the lower HF (40 and 80 meters); the Medium Frequency bands, (160 and the AM broadcast bands) much more so. One consequence of these factors is that most low-band transmitting antennas emit primarily high-angle RF. This in turn means the following:

  • low-band transmitting antennas disproportionately pick up high angle atmospheric noise;

  • Low-band transmitting antennas put most of their RF into higher angle paths, with a much smaller proportion of the transmitted energy going into the low angle RF needed for long haul communication.

  • Low band signals do not usually propagate as well as upper HF does when the upper HF bands are open. 160, in particular, is noted for odd ducting propagation modes, but in general the greater signal attenuation and greater difficulty in propagation on the low bands make low band operation more difficult. Long-haul signals received on transmit antennas challenge the limits of modern receiver technology.

Well,” I can imagine some readers saying, “Why operate on the low bands, especially in the summer, anyway? They’re fine for NVIS, but if I want to talk to the opposite coast or overseas, I’ll get on (upper HF band of choice) and work them with no trouble!”

It is true that when the upper bands are open, you can work the world on a few watts. Some time back, I made a transcontinental contact using a wire beam antenna hung from two trees on 10 meters, using SSB and 8 watts. My signal report was 10 db over S9; the operator on the other end was surprised when he was told what sort of setup I was using. When the propagation is good, and the bands are open, upper HF is very efficient. In the context of a hobby, waiting for good conditions is fine. But when your safety and well-being, or that of your family and friends, requires being able to provide communications at need, you may not be able to wait, and this is where operating on the low bands becomes important.

We’ve passed the peak of Solar Cycle 24, and we are headed back down to the bottom of the sunspot cycle; mediocre as the peak of SC24 was, in just a few years even 20 meters is likely to be dead except during broad daylight, and possibly dead even then. Cycle 24 is now confirmed as one of the lowest in over a hundred years, and 25 may be lower still. During the bottom of Cycle 24 and the buildup to the peak of Cycle 25, the low bands will be the backbone for night-time reliable long haul communication, 40 and 80 meters especially.

If you are serious about being able to communicate effectively locally, regionally and internationally under all conditions, then the low bands have much to offer, if you have the knowledge and skill to use them. So, what factors contribute to successful low band operation?

Even though my first operating experience was on 80 and 40 meters, it took me a while to notice that all the really successful operators on the lower HF bands (160, 80 and 40 meters, or 1.8, 3.5 and 7 mHz) all had one thing in common; they all had listening antennas. We’ve discussed the issues with using transmitting antennas for reception on the low bands; why are listening antennas so important? Why spend the time and go to the bother of putting up a listening antenna when you already have an antenna?

Because, especially on the lower HF bands, the requirements for hearing a signal, for receiving, are different from the capabilities of most common transmitting antennas. As mentioned above, the lower bands are noisier, both from atmospherics and man-made noise, and what makes the difference when listening is the ability to improve the signal to noise (S/N) ratio. Most modern receivers have plenty of gain, so signal strength is not as big an issue.

S/N defines how well you can pick out the signal that you want to hear. Whether the received signal is weak or very loud, what really matters is how much louder it is than the noise. It is not at all unusual for the base noise level on a nice summer evening on my elevated 80 meter dipole to be a steady S9 or even 10 db over that, with static crashes peaking at 20 to 40 db over S9. In order to be readable, the signal, even a CW signal, has to be louder than that. This is where the listening antenna comes in.

In many ways, listening antenna requirements are the opposite of everything one wants in a good transmit antenna. Good listening antennas are low to the ground, to minimize noise pickup, and they are directional, to reduce both noise and unwanted signal levels. If you can reduce the noise your receiver hears by 40 or 50 db, even if the signal you want is reduced by 20 db, the net gain in S/N is 30 db, which makes it easy copy. That is why the good operators spend days and weeks setting up listening antenna arrays; they WORK.

There are all sorts of listening antennas to try, but in the context of grid-down long distance communications, one stands out. I suggest you consider the Beverage, and specifically the Beverage On the Ground, or BOG antenna. No, I am not talking about spilled beer, but about a long wire antenna, lying on or just above the ground, named after its inventor, Harold Beverage. I’ll have some links for those who are interested in doing more research in the bibliography for this article.

If you are like many people, (including many licensed radio operators!) you have to be asking yourself, “Is this guy joking? An antenna ON THE GROUND? Nah!” No joke, it really works, and it is amazingly inexpensive, quick and low profile. All you need is about 100′ or more of almost any kind of insulated wire, a simple transformer, a ground rod and enough coax to connect to your receiver. This simple directional antenna, which can fit virtually unseen onto a modest suburban lot, will allow you to pull in distant low frequency AM broadcast stations, signals from ham operators and shortwave broadcast stations on frequencies up to 10 mHz or so, despite the summer time noise.

Being able to reliably receive news and information from around the world in the aftermath of a grid down event is a huge advantage. The very first Beverage I ever deployed, built for a friend from a book, took about 3 hours from a standing start to complete and on the air, including a trip to Home Depot for materials, and the performance was amazing. My buddy was able to copy stations using the BOG that he could not hear through the noise on his transmit antenna, a ¼ wave vertical.

So, what do I need for a Beverage On the Ground?

A simple Beverage on the ground requires the following-

-100′ to 150‘ of insulated wire (doesn’t need to be all one piece or even all the same size, but joints should be insulated);

-Ground rod(s) or ground radials, or both;

-A simple impendance transformer;

-enough coax or other transmission line to run from the antenna wire to the receiver;

-misc tools and connectors.

(A detailed material and equipment list follows the text of this article.)

Question from a Reader, II

Hello

I’ve been following your blog since it started and is a fantastic read.
I’ve also been following sparks blog when he had his own wordpress site.
I’ve also jumped into amrron corps last year and have been active in
that along with getting my general license.

I’ve followed your advice on uhf for squad comms. I have been able to
acquire 4 EF Johnson 5100’s. They have P25 capability along with
DES/AES, and a freq range of 380-470, so I can use all of 70cm, bubble
pack radios, and I have a GMRS license. I do understand the FCC’s rules
on encryption and digital use on GMRS/FRS so I wont get into that.

I have no experience as far a DFing and foot print size of the radios.
Will running narrow band p25 at 1 watt leave as big a footprint as
analog at 1 watt if I were on an extended walk?

Also, not relying on anyone else’s infrastructure, I had considered
setting up my own DTMF activated repeater for UHF use only to be used by
myself/group for our area. Is this a good idea, or should I stick to
NVIS if I need to reach our main living area and I’m out of range for 5
watts UHF?

Thanks for your time

SB

Sxxx,

Thanks for reading Brother. You have a bullet-proof setup with those EFJs. For your active footprint, I would say that you have it covered. While a ground unit could DF your signal, it’d be awfully damn tough to first get a bearing then decode it, if that group/unit is new to the area. As for bubba, forget it.

To your question regarding the GMRS repeater vs. NVIS, it really depends on how far you’re actually looking to cover. NVIS is normally a regional thing, and the repeater is definitely more reliable for community networking as we pass into the solar minimum.

You’ve definitely paid attention to what we’ve been saying, and I think its awesome. Many, many thanks for reading, and God bless you.

NC Scout

Beverages for Listening, II

Contained is the second half of the article, due to the overall length limitations of wordpress.

Wire-

For my simple BOG antennas, I use 14 gage THHN house wire, which is sturdy and double insulated, and comes in a variety of colors. If you want the antenna to stand out, use bright red or orange; I usually prefer the brown wire which blends in nicely with the ground. If you are piecing wire together, make sure the connections are soldered tight and that they are fully and completely waterproof.

Ground rods-

I take an 5/8 diameter 8‘ ground rod and cut it in half; this gives me two ground rods for about $12. If your soil is not rocky, you can use copper pipe for a ground rod, reinforced with a wooden dowel at the top to reduce mushrooming, and if budget is a particular concern, scrounged 1/2“ galvanized pipe will work too, especially with a couple of bare copper wires looped through the pipe and up the outside. If really stretched, a piece of rebar would probably work, too, although I have not tried it.

Enhancing the conductivity of the ground is a good idea; Epsom salt (magnesium sulfate) solution is the ‘school answer,’ and it works very well although I would not use it with a few feet of any concrete structure, but urine works too, and so does plain water. If you use urine, keep in mind that if you are moving around you’ll be handling the box and the ground rod, so remember the restroom sign- “We aim to please- we hope you aim too, please!”

Impedance transformer-

transformer.pngThe impedance of a BOG antenna runs from about 200 to 300 ohms, depending on soil type, height above ground, and other factors; you’ll need to find an approximate match between the antenna impedance and the transmission line you are using. If you are using 75 ohm RG6 television coax, as many do, then an impedance ratio of about 3 or 4 to 1 is about right. This is what one looks like; I use a 73 mix binocular toroid (Fair-Rite p/n 2873000202) with 24 gage teflon and 26 gage enameled wire. You can buy these from Mouser or Allied very inexpensively; I get a couple dozen at a time and they cost 50 cents apiece in bulk. A group buy will save money over one-at-a-time, or you might find them at a hamfest. For less than a dollar you can make a good BOG transformer.


Some folks directly connect the coax to the antenna and ground, but there are a couple of issues with this approach. One is that doing that couples the outside of your coax to the antenna and enables your coax to become part of the receiving array, eliminating the directional ability of the Beverage and increasing reception of unwanted signals and noise. The other is that the significant mismatch in impedance will reduce the already low signal level still further, and may make your beverage a bit ‘deaf’. It can and has been done, but such shortcuts do significantly impair the perrformance of the BOG. Better to make a transformer, even a field expedient out of a nut or a small piece of pipe.

trans2.pngDon’t get too panicked about making a transformer or impedance matching. If you don’t know what impedance coax you have, then do this: put three turns of insulated wire through both holes of the binocular core and leave 4“to 6“ legs. This is the primary, and hooks to the coax, one side to ground and one side to the center conductor or hot lead. Then run 5 turns of wire through both holes of the binocular core and leave 4-6 inch legs. This is the secondary and one leg goes to the Beverage wire terminal and one goes to the ground clamp. If I had to make a BOG from field expedient materials, I’d use a chunk of Cat 5 or Cat 6 cable for wire, and a steel hex nut for a transformer core. As good as my ferrite binocular toroid? No, but it will work.

It is a good idea to weather proof the transformer assembly and the connections to the antenna and the coax; here is how I do it.

I spent about $6 for the box, $2.50 for the SO-239 connector, about $3.50 for the two zinc ground clamps, and about $2 for the brass nuts and bolts from Home Depot. I put the SO-239 on the bottom of the box (3/4“ hole with 9/64” for the brass attachment bolts) , the ground clamps on the back (1/4“ holes) and I pick a side for the Beverage wire terminal (3/16“ hole) Here is another view –

trans3.png

As a field expedient one could do well with a cottage cheese container or any sort of plastic container sealed with tape or silicone sealant.

One needs transmission line to go from the transformer at the end of the BOG to the receiver; typically this is RG58 or RG6 coax, but you can use twisted pair line or even 16 gage insulated landscape wire which has an impedance of around 125 ohms; if you do this, then adjust the transformation ratio accordingly when winding your transformers. I ran across a 500‘ roll of new old stock RG6 for $20 at a ham-fest recently and this cheap coax works just fine for short term use. Longer term, the flooded quad shielded coax sold by DX Engineering and others is a better bet, as mice and other vermin apparently don’t like the taste of the goo that fills the coax.

RG6 is bigger and heavier than RG58, so if weight is an issue, use RG58. If you scrounge around you can often find perfectly good used coax being pulled out of a remodeled home; if you ask the electrician he may simply give it to you. Home Depot sells a 500‘ roll for $50, or 10 cents a foot. If you are on a typical suburban lot, you probably won’t need more than 100‘ of coax; another opportunity for a group buy.

When using coax, I use coax connectors to join things together, as this makes it easy to disassemble and relocate the antenna system; RG59 adapters for solder connected pl-259 (common VHF connectors) work well for RG6, and RG58 adapters are readily available commercially. These are probably cheaper for lower volume operators to do, but you do need to solder the connections, which may take time and if you haven’t done it, you are likely to ruin some cable and connectors learning how. I messed up my share of connectors learning how, but after over 40 years in radio and electronics I can do a good soldered PL-259. (A quick tutorial- the secret is being able to apply LOTS of heat very quickly and precisely to avoid melting the insulation of the cable and the connector. Silver plating helps, and so does Teflon insulation…)

These days, though, I don’t solder most of my connectors. I make a lot of cables and antennas, so I bought the required commercial crimping tools, and I mostly use crimp-on connectors for my cables as they are much quicker to produce, especially with the commercial coax prep tools available for RG-8, RG-6 and the smaller cables. You may have somebody local to you that has these tools and can make your cable up for you, or you can buy commercially made coax assemblies from dealers. Any PL-259/SO-239 connector/connection is NOT waterproof, so I waterproof these connectors and their connections with a combination of liquid electrical tape, Coax seal (moldable rubber tape) and regular hand wound electrical tape.

So, you have your BOG wire, your transformer box, your ground rod, and your coax with appropriate connectors. Drive the ground rod, attach the Beverage box to the rod with the ground clamps, attach the wire to the box and stretch it in the desired direction, and attach the coax and run it to your receiver input. Waterproof your connections if they are going to be there for more than overnight. Don’t get too hung up on maintaining a perfectly straight antenna; minor zigs and zags make no difference, and some up and down in the wire run doesn’t much matter either.

Compare the signal with what you hear on an elevated dipole or vertical transmitting antenna. Be prepared to be amazed at what you hear, and DON’T hear! You will hear broadcast band stations in your chosen direction that you cannot otherwise hear, day or night; you will hear 150, 80 and 40 meter amateur signals that were otherwise unreadable; and you will be able to pick up shortwave news broadcasts that have information you will never hear on the mainstream media. What you won’t hear is about 6-9 S-units of noise, and that is the best part. Comms UP! Enjoy your Beverage!

73, Keypounder.

Material list Cost

100-150 feet of insulated wire $7 to $15

4“ x 4“ x 2“ insulated PVC electrical box $6

1 ea #10-24 2“ brass bolt

3 ea #10-24 brass nuts

4 ea #10 brass washers

( the #10 hardware makes up the Beverage wire attachment point)

2 ea #6-32 3/4“ brass machine screws

3 each #6-32 brass nuts

4 ea #6-32 brass washers $2 or less net in bulk

(the #6 hardware holds the SO-239 socket to the PVC box)

1 SO-239 socket (recommend silver plated with Teflon insulator)

2 each PL-259 VHF plugs with adaptors $6 net

2 zinc ground clamps $4

50-150‘ of RG6 coax cable $5 to $15

Misc electrical tape and liquid tape, allow $5

Ground rod $0-$12

Tools-

Multimeter (check coax and beverage box for connectivity)

Soldering iron (100 watt plus recommended for PL-259 connectors)

60-40 electronic solder (DO NOT use acid core, get rosin core flux solder)

Drill bits- 9/64 for the #6, 3/16“ for the #10, 1/4“ for the ground clamps.

Reloading reamer to widen the hole to 3/4“ for the SO-239 mount.

Screwdrivers and nut drivers for the screws and nuts (Leatherman tool works)

Pocket knife or coax prep tool.

Bibliography-

Low Band Dxing” 5th Edition by ON4UN, John DeVoldevere.

Chapter 7 is on listening antennas, and section 7.2 is all about Beverage

antennas. The BOG section is 7.2.12, page 7-84.

The ARRL Antenna Book” 13th Edition. If you are interested in antennas, this is a must-have reference. If you are buying a used copy, make SURE that you get the CD-rom that comes with it; EZNEC and much good added information is on there.

Web links of note-

http://www.antennasbyn6lf.com/2015/04/nec-modeling-of-wire-close-to-andor-buried-in-soil.html (Rudy Severns, N6LF, has done some very good work on antenna research and design; his whole site is of interest to any antenna afficianado)

http://www.qsl.net/wb5ude/bog/

http://www.qsl.net/k1fz/bogantennanotes/

Keypounder sends-

“You are the lead station operator in the Resistance receiving station
mentioned in the first question.  You have received the message sent by
the operator in the capital at 1 pm local time in the first example on
160 meters and must now forward the vital information received to
Resistance HQ via HF radio.  Once you transmit this message, you will
immediately relocate to another predetermined location you have selected.

Assume the following:

-your station is located at approximately 65 degrees West and 10 degrees
North;
-Resistance HQ is located somewhere in the Intermountain Western united
States, New Mexico to Montana, Eastern Oregon to the Western Dakotas;
-Resistance HQ has receive capability 24/7/365 and will be waiting to
copy your message during whatever window you have told them to listen on
whatever frequency segment(s) you have specified;
-The message from the capital of Venezuela consists of 25 each 5 letter
encrypted groups.  You will re-encrypt the message prior to
retransmission using a OTP, but there will still be a minimum of 125
random letters to transmit;
-You are required to use any of the ITU region 1 authorized amateur
radio frequencies and modes from 1.8 to 29.7 mHz;
-You will have been onsite for at least a week prior to receiving the
message from the capital of Venezuela, and will have access to a small
house nearby the station site, but are forbidden to set up equipment at
the house;
-You are required to complete the transmission to HQ in less than 20
seconds, and to evacuate the transmit site in less than 15 minutes after
completing the transmission leaving no material behind.  You have 4
dedicated helpers with no electronics or radio training available;
-You have a compact 4wd crew cab pickup truck for transport, and
everything, your crew included, must fit into the truck.  No radio
equipment may be visible from outside the vehicle;
-Assume the ground is level farmland with very rich loamy soil planted
in low-growing crops or grass, with tall trees (>50′ high) at the field
boundaries with steel t-post electric fences around each field, and that
the field lines run north-south/east-west.  Further assume that each
field section is 8 hectares in area square. The surrounding general area
is agricultural, both crops and stock.”

Questions-

What frequency segment and time will you select to minimize DF
likelihood and maximize the chance that HQ will acknowledge it?  What
will your alternate(s) frequencies be, and under what circumstance will
you use them?

What antenna(s) systems will you use for transmitting this message?
How high will they be placed?  How will you orient and erect them and
take them down to minimize possibility of observation? Explain in
detail, including specifics of antenna and transmission line.

What mode will you use for transmitting the message?  If digital,
which specific mode and why?

Before you leave for Venezuela, you will be given an opportunity  to
study data available through NOAA on radio propagation.  Which ionosonde
stations will you study, and why?

What will your cover story be if you are stopped by Venezuelan security
forces?

Thoughts?