SOME NVIS DISCUSSION; From Sean T. Kelly, and Dennis Starks
     Special Event Reports, & War Time Photos/Films.
     From Ed Guzick, and Dennis Starks


NVIS; Some more web sites and even more questions:

     There's a drawing of the PRC-70 in the Army's on line FM 24-18.  Does anybody know anything about their use with the Atomic Demolitions Units (Engineers). 

Here's the    

There's a new book out on military history that has a few paragraphs on use of the PRC-74 by Rangers in Veit Nam.  There wasn't much there but they gave the impression that it wasn't a sure bet to be able to communicate every sked.

     Two more gifs of interest are FM 24-18 Figure M-14 and and 24180165.gif  The first one is titled Communications success with the AN/PRC-74 as a function of time of day and antenna type over a 12-mile path in low mountains, spring(sic) and summer(sic) 1963.  The thing claims that from 8 am to 1 pm you could just walk around with the rig on your back and talk over said 12 mile path.  I'd love to know what kind of antenna they were using on the other end of the path.

  Figure M-15 is titled Communications success as a function of range for the AN/PRC-74 in mountainous and varied terrain-including jungle in Thailand.  It depicts the same frequency used for the first graph, but with a 30% plus 20% or minus 10% success rate.  I'm guessing that the first graph is showing the results from a limited test, and the second from a more complete test.

     There are some more drawings and charts which you can get to by going first to the FM 24-18 appendex  There's one of the Shirley folded dipole for NVIS.  It looks like my UHF bowtie antenna flat on it's back and cut for HF.  That gave me the idea to put foil on the screen of the TV antenna, which dramatically improved reception (which had been driving me nuts for two years-damn rich people and their old-fashioned wind-powered sailboats).  There's also a table showing effective radiated power for several different antennas used for NVIS.

  (Let's see now, if I can boost the power of my PRC-47 to a kilowatt using built-in whip antenna, it'll work as well as my 1 watt HW-7 into a dipole, or as well as 100 watts into a dipole lying on the ground.  Better get a motorcycle helmet to shield from the RF...). is a graph showing relitive gain of various antenna types at all angles from the zeinith to the horizon.     When Dennis said he had some expirience with NVIS it really peaked my curiousity.  I enjoy listening to the emergency communications net on 75 meters here in the evening.  They check by city, so I can make a map showing locations of signals recieved as the net progresses.  This using the built in whip antenna of my shortwave from Radio Shack.  So Dennis, what's the scoop on NVIS? 

Anybody else into shooting bolts at the sky? ps:  FM 7-93 has an appendix on NVIS. It's online at the same site above.  Worth reading.

Sean T. Kelly     email is


 "Communications success with the AN/PRC-74 as a function of time of day and antenna type over a 12-mile path in low mountains, spring(sic) and summer(sic) 1963."

  The date of this material in conjunction with the PRC-74 would indicate that these were experiments being conducted, and the radio in question was most likely not the PRC-74, but it's commercial ancestor the Huges HC-161. Is it possible that these may have been the result of field trials of the radio itself? Interesting!

     A low mounted (in terms of wave length) standard dipole will produce near vertical radiation. The antenna you note that looks like a folded dipole is most likely terminated between it's ends with a non-inductive resistor and is much shorter(in terms of wave length), and has an extremely wide bandwidth as compared to a standard folded dipole. This minute, I can't recall the proper name for this antenna but a version of it has been available from Barker & Williamson for many years and is said to be in service by various military organizations world wide.

     The radios standard whip antenna will also work well for NVIS propagation, but not if kept vertical where it's radiation pattern will be at a low angle, it must be laid over producing a high angle of radiation. In it's vertical position it's best suited for ground wave communications through dense foliage up to 5 miles where there are no geographic obstructions. Or long range ground to air, or for long (Skywave) propogation at distances over 150 miles(and not under). One advantage of NVIS becomes apparent in adverse terrain where an NVIS signal can be bounced off the atmosphere sending a signal from one side of a mountain to the other.

     A simple case in point, a couple years ago while returning home from a friends house 90 miles distant(George WD0ALN) in hilly southern Missouri, I had a GRC-9 mounted between the front seats in my 1965 International Scout. We thought it would be neat to see how far I could get before communications were lost on 75 meters in the afternoon. The antenna used was an old Webster Band Spanner slightly modified with some mast extensions underneath the antenna proper, thus elevating the load surface producing a center loaded antenna. I was only able to talk to George for about five miles before losing contact. I then pulled the Scout over to the side of the highway, pulled the antenna down to a near horizontal position and tied it off. Our communications were then extended to near 20 miles. The antenna in the upright position produced a low angle of radiation which was good for ground wave only(in this application). Pulling it over to the horizontal plain produced a very high angle of radiation(due to it's proximity to ground) well suited for NVIS propagation. George and I repeated this experiment some months later when we were headed off into the wilds of eastern Kansas on a Search & Collect mission. This time the same antenna was used, but the radio was a PRC-47. Constant calls on 75 meters to our destination(about 150 miles) began when we left home that morning. At about 100miles contact was made, and Jim(W0RRL) was able to then talk us in, right to his door step. I might add that the PRC-47 was always on low power(20 watts).

     Even at a kilowatt your PRC-47 will not produce short range communications(other than ground wave) with it's vertical whip antenna, your 1 watt HW-7 on a low mounted dipole, will. For reliable communications at ranges up to 150 miles on say 75 meters, reverse wave propagation is used, I/E typical military frequency-to-time-of-day usage for long range communications would be 2-6mc for nighttime, and 8-12mc in the daytime. The opposite of this is used for NVIS propagation, so a 75meter net will operate very will during daylight hours. Remember, the object of NVIS propagation is to produce "reliable short to medium range communications"when other means are not suitable". Your emergency 75 meter net operates on this band under the premise that in an actual emergency VHF or UHF repeaters might not be left in operation.

     The reasoning for Navy's testing of NVIS propagation on the other hand is not same as that of the other services. Here the object was to provide secure inter-task force communications between ships being deployed, say an Aircraft Carrier, or Battleship task force, the maximum distance between ships being around 100 miles. It should be stressed, that properly orchestrated NVIS propagation bounces off the atmosphere only once.

     The advantage of such a practice was the inability of and adversary to use conventional Direction Finding techniques and equipment mounted in aircraft to locate said task force. Where it was possible for these same aircraft to easily locate a VHF or UHF signal out to 500 miles or more. To this end, in the late 1970's experiments were conducted which used a URT-23(1kw) transmitter modified with an attenuator pad mounted between the exciter and the power amplifier that resulted in a total output power of around one watt or less(ironic isn't it!). We called it LNFR(Limited Near Field Radiation), or something like that, memory is fading me in my old age. Low mounted horizontal wire antennas and reverse wave-propagation were used with limited RF output. The expected result was a signal that would radiate nearly strait up, bounce back to earth only once then dissipate. Thus providing the desired minimal area of coverage with nothing left over for the bad guy's to sniff out.

     While I cannot comment directly on the success of these experiments as I was a simple Radioman at the time tasked with the operation of those modified URT-23's. I can however relate a story which could very well be related. In 1977(or thereabouts) a task force centered around the Aircraft Carrier USS John F. Kennedy headed off in the Atlantic bound for the Mediterranean. Such movements are always kept very hush-hush for some reason(though everybody knows all about it anyway). Complete radio silence(EMCOM) was normally the practice on the trans-Atlantic leg of these trips, but on this occasion the low power URT-23's were left in operation. It was common practice for the Russians to send out a Bear Bomber modified as described above for direction finding and surveillance to locate these task forces bound for the Med. At about 3/4 way across the Atlantic, this Bear was thought to be way over due so the Captain(Jerry O Tuttle, a real dip shit) ordered six Tomcats into the air to go out and look for it, then escort it in so's to prevent it from otherwise just wondering into the Carrier's air space thus avoiding possible incident. Three days later all non-essential personnel were ordered onto the flight deck to provide a single finger salute for the Bear. Having been found by the Tomcats it was being escorted in so it could take it's pictures. Had our NVIS experiment worked?

     On a unrelated note, just prior to my arrival aboard "Big John" in late 1976, she had had her 10kw amplifiers removed due to the generally accepted idea that this much power was over-kill and unnecessary for long range communications.




Special Event Reports, & War Time Photos/Films, and the SCR-511(Pogo-Stick) which would tend to show Marine Corps use in early WW-II.

     History CH had one of the WWII documentaries going and managed to get a kwik glimpse of a "Horsey Talky" stuck in the sand during a Marine landing on some Island. The only thing about some of those shows is that they have been edited from a pile of footage and whats on the screen doesn't always match the story.   A friend said there were several shots of GIs carrying the radios in the documentary on the Italian campaign but I have not seen that one.

     Pretty darn good narrative Dennis! Have had similar things happen hauling boats, hardwood, trucks, and even radios. Going thru deepest LA in a dying VW Camper FULL of Mil BoatAnchor and realizing the Randall .45 got left home is a real workout for the adrenal gland. Couldn't stop for gas anywhere without a long down hill to pop start the thing. Poor old Westfalia was loaded shoulder deep back to front with TCS stuff including AC supply bunch of GRC-9 with pwr supplies, RBSs etc . Sure didn't want to have to walk away from the load in places where English was a second language.

Ed Zeranski  This is a private opinion or statement.

home email:

ed) the subject of the dubious origins of printed photos and films, as they were combined with captions, and subject matter, came up during our series "Mystery Radio, the SCR-511". They can still be valuable provided they are closely inspected by multiple authorities expert in varied fields. I/E closer inspection of the other equipment in the seen might prove far more valuable that the caption. In the case of the BC-745(Pogo-Stick) we had an Airborne trooper that was supposedly in the Mediterranean, but the presents of an M1A1 carbine showed that this was late war. The identification of such things as uniforms, knives, and other ancillary equipment also help correctly determine dates, places, and services.

     A photo in my library of Signal Corps origin has the caption that reads "Army Signalman disembarks ship for marine assault with Walkie Talkie on his back". The photo is actually of a Marine, and the "Walkie Talkie" is a TBY! So record those History Channel shows, and use you VCR to closer inspect the goings on in each clip.



As you know, one problem encountered when building an alternate power supply is how to turn it on/off. Mark's BC-611 idea (which I never saw) using an IC that operates by rapidly shaking it three times comes the closest as I would assume it required no hard wired connections to the transceiver. My guess would be he used a counter and a mercury switch?

I've thought about using various switches, relays or transistor circuits but I can't get around the hard wired connection and that's the rub!. I heard of a uA sensing IC switch but never came across one. However, it would probably need to be wired in. On a BC-611 there is little room for anything. I've used a small relay wired to operate off the filament voltage and my present method uses the existing antenna switch but requires 3 wires tacked onto the chassis. It works but there must be a better way. All my schemes revolve around using the filament voltage, however, I've yet to come up with a brilliant idea.

How to switch the converter without using hard wiring between the receiver and the supply? So far I do not have a solution. Any ideas?

Ed Guzick

ed)  Mark Gluch is currently off line due to AOL troubles, and a dead monitor, so he can't respond just now in regard to his BC-611 on/off  switching method. But it did use a mercury switch and an IC counter.

     Unlike most military radios that use a single switch contact, & ground leg switching of all their batteries to turn them on and off simultaneously, the BC-611 uses two tandem switch contacts to connect the heater & B+ batteries to their respective loads via the positive side of the batteries separately. When operation from an inverter and rechargeable battery is desired, this presents the peculiar problem of turning on two distinctive power supplies with a single switch yet still keeping them isolated. To compound this problem, a primary power source must be connected, & switched that provides both heater, and inverter power supplies, yet this same switch must pass both the voltage of the primary power source, and one of the secondary ones while also keeping them isolated. Of course, this is imposible, so we must contrive a method buy which one switch will control a second switch that will in turn serve our purpose.

     I don't know what your using as a primary power supply or it's voltage. If it is a design similar to, or the same as that I presented you are probably using four "D" cells in series for around 5 volts which makes an output of around 90 from the inverter.

     Try something along this line, I know you have a selection of tiny relays, some even 1.5 volt, use one of these with it's coil(and maybe a resistor) in series with the heater supply, place a small 6 volt light bulb in parallel with the seriesed relay-coil/resistor. The resultant current drain when the radio is switched on will close the relay turning on the inverter. The resistor will compensate for relay coil resistance, and the combination relay coil/resistor will provide a voltage drop for the heaters to operate from.

     The light bulb acts like a ballast tube to protect the tube heaters, and when full-on contributes to the voltage drop needed. When the radio is first turned on, the light bulb will glow brilliantly because of the low heater resistance, but as the radios heaters warm up, this glow will fade to near nothing as heater resistance goes up. Some experimentation will of coarse be required due to the various relay/light bulb combinations/availability, so it would be a good idea to calculate the  radio's full-on heater resistance so that a substitute load can be used preventing radio damage.

     Another approach would be to use a two transistor "flip-flop" circuit or even the current sensing methods you mention, but either system would still require the use of a small relay(dependant on current drain, and transistor size), and a ballast type heater voltage control circuit. So in the interest of minimum parts count(the relay coil is an integral part of the heater voltage control circuit thus serves a dual purpose), and simplicity the above might be the best way. Once you've hit upon the right relay-coil type, resistor, and light bulb combination, you might let us know about it. A possible commercial source for miniature low voltage relays might be those little DIP relays once available from (eeek) "Radio Shack", in 5, 6 and 12vdc versions.

     One final note, while the relay coil, dependant on it's resistance and current requirement, may be placed in parallel with a large wattage voltage dropping resistor(typically 5 watts or more), their sum resistance will be higher than that needed for the operation of the radio's heaters. It's the variable resistance of the light bulb placed in parallel with these that brings the total circuit resistance within the operational range of the radio's heaters. A light bulb must be selected as a companion to the power-resistor/relay-coil, that draws sufficient current when cold to allow the radio's heaters to slowly light up. If you are lucky enough to have a supply of 1.5 volt relays, the coil itself need not be a part of the heater/ballast circuit, it can simply be connected between the output of the circuit and ground, in this case only the power resistor, and light bulb form the ballast regulator circuit for the radio's heaters.
     All your ideas and input are eagerly sought on this subject.




Seeing as how Powerball in the USA is over $200 million this week, I thought today's joke was appropriate...
A guy named Joe finds himself in dire trouble. His business has gone bust and he's in serious financial trouble. He's so desperate he decides to ask God for help. He begins to pray... "God, please help me.  I've lost my business and if I don't get some money, I'm going to lose my house as well.  Please let me win the lotto." Lotto night comes and somebody else wins it. Joe again prays... "God, please let me win the lotto! I've lost my business, my house and I'm going to lose my car as well".  Lotto night comes and Joe still has no luck. Once again, he prays... "My God, why have you forsaken me?? I've lost my business, my house, and my car. My wife and children are starving. I don't often ask you for help and I have always been a good servant to you. PLEASE just let me win the lotto this one time so I can get my life back in order." Suddenly there is a blinding flash of light as the heavens open and Joe is confronted by the voice of God Himself: "Joe, meet Me halfway on this.  Buy a ticket."


A man who lived in a block of apartments thought it was raining and put his head out the window to check.  As he did so a glass eye fell into his hand. He looked up to see where it came from in time to see a young woman looking down.  "Is this yours?" he asked.  She said, "Yes, could you bring it up?" and the man agreed.  On arrival she was profuse in her thanks and offered the man a drink.  As she was very attractive he agreed.  Shortly afterwards she said, "I'm about to have dinner.  There's plenty; would you like to join me?"  He readily accepted her offer and both enjoyed a lovely meal.  As the evening was drawing to a close the lady said, "I've had a marvelous evening.  Would you like to stay the night?"  The man hesitated then said, "Do you act like this with every man you meet?"  "No," she replied, "only those who catch my eye."


An old Jewish woman took it upon herself to travel to Nepal to meet with this famous guru.  Her friends tried to dissuade her, saying that the trip was long and arduous, and with her varicose veins it could mean real trouble. They could not talk her out of it, however. So, she made her preparations and set out.  It began with a 36-hour flight on Air India with four stopovers, followed by 2 hours on a rickety propeller plane from WWI.  Then a ride on a cog railway.  Then a 2-day trek in a camel caravan over icy mountain paths.  She was half dead when she reached the guru's village.  There she learned that it would be perhaps ten days before she could have an audience with the guru because so many seekers had come to see him. She was also told that when she  entered the guru's tent, she would only be allowed to speak five words, 
since the guru was so busy. So, she rested and prepared, all the while trying to choose her five words carefully.  Finally, the day came.  Into the tent she went and seated herself on the hard stool facing the guru.  And then she leaned over and spoke:  "Enough already, Sheldon, come home."

The ambassador of a small African nation chanced to visit Russia, and was entertained by his opposite number, the Russian ambassador.   For three days, the African ambassador was wined, dined, and generally treated to the best hospitality that Russia had  to offer. On the final day of his visit, the Russian ambassador said "As your stay is coming to an end, it is time for you to play our traditional game, Russian roulette.  One of the six chambers of this gun is loaded - you spin the cylinder, point the gun at your head, and pull the trigger."  This phased the African slightly, but he was a proud man of a warrior people, and to show fear would be unthinkable.  Both men took their guns, spun, and pulled the triggers. <click> <click> Both chambers were empty, and both ambassadors breathed a sigh of relief. The African ambassador was much impressed with the courageous game, and thought hard about the subject before the Russian Ambassador was due to visit his country the next year. When the visit came, the African ambassador treated the Russian with all hospitality, until the final day of his stay.  Leading him to a private room in the palace, the African ambassador spoke "Now it is time for you to sample our game, African roulette".  So saying, he led the Russian into the room, the only occupants of which were six beautiful, naked women. The African ambassador said "These women are the most beautiful members of one of our tribes.  Any one of them will provide you with oral sex - take your pick". The Russian was not entirely averse to this idea, but he couldn't see the connection with Russian Roulette. He said "Well, ok, great, but where's the roulette part? Where's the danger?" With a big grin on his face, the African ambassador Answered, "One of them is a cannibal"


(The preceding was a product of the"Military Collector Group Post", an international email magazine dedicated to the preservation of history and the equipment that made it. Unlimited circulation of this material is authorized so long as the proper credits to the original authors, and publisher or this group are included. For more information conserning this group contact Dennis Starks at,