Fun With R.F.



Over the years there have been many escapades and more than a little mischief involving radio, and the mysteries of R.F. in general. This article attempts to document them as best as I can remember......


One of the earliest forays into the strange and unpredictable nature of RF occurred in 1973. Back then, we found out that touching 2 walkie-talkie antennas to one of the rails of a railroad track at different locations did not make the signal any stronger to each other. We had been walking in opposite directions along the tracks one day with our 100 mW W-T's, checking our range. When we started getting out of range of one another, we decided to try touching the antennas to the tracks, with the hope that it would "connect" our antennas together like a big wire. But alas, it didn't work that way. Not long after that, we also found out that creek water is no more conductive when we "dipped" our antennas in the water while trying to improve our signals.


The next lesson took place in early 1974, when we learned that a Radio Shack "Colinear" 5/8th wave antenna could be burned out with a little over 400 watts.  Steve had become a bit lazy. Formerly used to running a 3 element beam antenna, Steve had recently switched to a Radio Shack 5/8th wave ground plane after getting tired of having to frequently turn his beam. While the convenience of not having to turn an antenna was advantageous for Steve's local talking, the one thing that he didn't count on was the ground plane's matching network. His former beam had no matching network, and was fed directly with coax cable so, consequently, it could take quite a few watts.  On the ground plane however, there was a matching network which transformed the impedance of the 5/8th wave radiator to 50 ohms for connection to the coax.  In the case of the Radio Shack antenna, this network was comprised of little more than a printed circuit board with a helical coil etched into it.  Usually, this matching network wasn't much of an issue, except for a slight increase in SWR whenever it rained.  But common sense should also tell you that this matching network would not take much power.  But like many other events which are viewed from hindsight, it's much easier to realize it after it happens.  Steve had also recently acquired a Palomar Skipper 300 amplifier (Which we nick-named "Chrome Dome") in need of a little T.L.C..  After replacing blown rectifier diodes and installing a fresh set of tubes, he soon had a new toy to play with.  Smitten with the rush that having a bit of extra wattage can give you, it didn't take long before Steve ended up on Channel 4, home of the resident "big radio" guys, ready to prove to them once and for all, that he could play in the yard with the big dogs.  Steve's radio at the time was a Cobra 135, and he had his new Palomar toy fired up as well. The Channel 4 guys didn't think too highly of Steve and would always needle him and poke fun at his feeble attempts to be included in the inner circle with the big boys, and they weren't about to give him the satisfaction of acknowledging his much stronger signal even now.  Having not gotten the reception he had hoped for, Steve soon became angry and started cranking the power up more and more. At one point when he unkeyed, the noise level in his receiver was suddenly much lower.  One of the Channel 4 guys came back with a similarly reduced signal, asking; "where'd ya go buddy", looking for Steve. A quick check of the SWR showed over a 20:1. Steve called me on the phone at that point, and I rode up to his house to give him a hand. When we climbed up on the roof and approached the antenna, we could smell burned circuit material. We took down the antenna, and Steve then gave it to me for helping him take it down. I later drilled out the rivets on the bottom of the antenna, and removed the charred remains of what once was the matching network. I made a display piece out of it as a reminder of what not to do with this type of antenna.  I ended up using the aluminum from the antenna to make a 1/4 wave antenna which I used for a short time in late '74, and then dipoles for myself and my next door neighbor, Spud. 


Later on in 1974, Big Al would find out that his Cobra Cam 89 base station made a pretty good remote control garage door opener.  It started not long after he had obtained his base setup, thanks to some very accommodating parents (Boy was I jealous of that!). He had been happily talking away, with a signal that was much stronger than what he used to put out with his old Midland 1 watt walkie-talkie.  Everything seemed fine in his neighborhood at first.  But at some point someone noticed that a neighbor's garage door was going up and down, seemingly at random.  Back in the 70's, most garage door openers were not yet on UHF and did not have sophisticated digital security codes. This left them vulnerable to overload from strong local CB signals. Big Al did some testing and determined that every time he talked on Channel 11, our home channel, he made the garage door move (The door opener was probably using class "C" Channel "11a" 27.095). At this point, I don't think the neighbor knew why the door was acting funny, and it's a good thing too, since a day or so later the door stopped in the middle of its travel about halfway down, and stayed that way. Eventually it was fixed and I assume that a new opener was installed, as the problem never came back. But this situation was a harbinger for things to come, as serious RFI interference issues would soon rear their ugly heads as we all upgraded from walkie-talkies to full power radios with gain antennas..


Sometimes when someone has an advanced knowledge of radio theory, it can be tempting to use it for mischievous or malicious purposes.  One of Steve's favorite pass times in the early 70's, was to drop a CB or ham radio, which was modified to cover the RC channels, into his car and head out to the local radio controlled airplane flying field.  Radio controlled airplanes use low power transmitters to control the various functions which allow the plane to fly. Of course, it isn't hard to figure out that if your radio control's signal gets overrun by a much stronger signal, that you lose the ability to control your airplane.  One of the most popular places to fly R.C. airplanes in our area was here in the Valley Forge historical park.  Both individuals and clubs would regularly show up there to show off their latest projects and take a turn or two at flying.  Most of the fliers used colored flags to indicate which frequencies they operated on so as to minimize co-channel interference while they flew.  There are a few different frequency bands open for radio control.  Hams can use a portion of 6 meters. There is also a 72-76 Mhz segment as well. And, of course, the 6 channels on the 27 Mhz class "C" segment. Today, the greatest majority of non-ham fliers use 72-76 Mhz, as 27 Mhz has become far too interference prone.  But back in the early 70's there were still a good many people operating there.  This fact is what provided the avenue for Steve's warped enjoyment.  Usually he would park in a place where he could overlook the flying field from a short distance. When he saw a plane flying by, he would dial through the 27 Mhz R.C. channels until he heard the signal. He would then fire up something in the neighborhood of 50 or 60 watts and dead key his transmitter. This was more than enough to overpower the less normally than 1 watt transmitters that the R.C. pilots used. Once jammed, the plane would often continue flying straight or, in some cases, would suddenly bank sharply. Steve would key and unkey just long enough to scare the bejesus out of the R.C. pilot, who would then frantically try to bring his "malfunctioning" plane back in without crashing it.  Sometimes, when Steve was in a particularly foul mood, he'd make one crash.  At the time, I thought it was funny in a sadistic sort of way, but knowing now the time and money that some of these guys have invested in this sport, it sickens me to think of how many planes Steve's antics may have ruined.


In 1975, just for fun, I lit up a large string of Christmas lights with the power of my Contex 75 watt amplifier. I don't know what the SWR was, but it did load up.  As a final and even more bizarre twist, the string actually radiated a fairly decent signal to the locals.  Nothing like having 200 little modulation indicators....


The years just kept on rolling on and by 1976, we found out that 50 watts run into an 18" loaded whip had enough current to give one's finger a nasty R.F. burn. We were tuning up LIM's mobile in anticipation of the Explorer Road Rally, when we discovered that the white plastic cap on top of the whip was starting to discolor. As LIM was trying to pull it off to see what had caused it, I inadvertently keyed the radio, and he let go of the antenna in a hurry. Having had a few R.F. burns in my life, I can attest that they are much more painful than simple heat-induced surface burns.  R.F. burns bore down below skin surface level and take a longer time to heal. Ouch!


In 1982, I found out that 500 watts out of my mobile would light up a neon bulb on the tip of another's mobile antenna, even brighter than they could, and from 50 feet away. The group of us from Channel 30, used to make a habit of meeting up in a local parking lot to hang out and shoot the B.S..  Naturally there was all sorts of radio stuff going on as well.  One night, I pulled in with my 1972 Ford truck, along with my newly acquired Golden Eagle 500 amp, and the fun started from there.  First there was the sound of my voice (along with an S8 signal!) coming over another's mobile radio. What was so special about this, you might ask? Well normally, it wouldn't be impressive, except for the fact that his radio was turned off. Then there was the 10 watts of reflected power that was shown on the wattmeter in the car next to me when I was keyed.  Mary Beth, one of the regulars, pulled in soon after that with her 102" whip topped with a neon bulb, which lit up when she transmitted.  She was afraid that my large signal would fry her radio, so she made it a point to park a little further way. But that still didn't stop me from lighting up her neon bulb anyway....


Later on, during a quick run to a local 7-11 (A convenience store), I was told that my voice could be heard coming through the video game that was situated against the window at the front of the store. Always one to take advantage of a situation for a few laughs, I came back later, while someone was playing the machine. Art was with me, and he went into the store to witness the effects. I watched the guy playing the machine, and when it became obvious that he had lost the game, I keyed and said "Man, you really suck!, wanna play again?" The guy gave the machine a double take and walked away. The next guy walked over and started playing. I soon keyed up again, and said something like "My baby sister could do better than you." The first guy was still there and the two guys started looking around the store to see what was going on. The only other people in the store were Art and the cashier, who were both at the counter. As the second guy ended his game, I keyed again and said "C'mon man, spend some more money. I've got a family to support here!". The two guys were now looking seriously for Alan Funt to pop out from behind the counter to tell them to smile for the Candid Camera, but it never happened. At this point, I was beside myself, and couldn't stop from laughing. I don't think those guys ever figured out what had happened.


We also found out that the local Burger King drive thru had no AGC in their remote drive-thru headphones. Sitting in the parking lot, adjacent to the drive thru pickup window, I could see the counter person filling orders and handing them out. While munching on my fries and just for kicks and grins, I turned on the amp, keyed the mike, and let out a whistle. I never saw someone pull a set of headphones off their head so fast...... Want to order your food before you get to the window? No problem, but it did confuse the counter person.


The last big R.F. experiment that I tried in 1982, was attempting to couple my signal, via RF ingress, into the audio feed to a commercial F.M. radio station transmitter. Radio station WIFI had its studios in Philadelphia, but the transmitter was located in East Norriton Township, about a mile from my house. The transmitter's signal played hell on the new homes which were situated in the immediate area. You could hear the station on all sorts of electrical devices, some of which were not designed to be radio receivers.  One night, I was mulling over the air about the possibility of getting close enough to the remote audio feeds to the transmitter to bleed into them and be heard over the F.M broadcast band.  Seemingly oblivious to the potential legal consequences which might result if this was actually successful, I set out to try my theory. The radio transmitter was located on a hill with a long narrow private drive leading up to it.  I figured that if I drove up underneath the building and the utility wires, and running my 500 watt amp, I'd be able to couple enough R.F. energy to bleed into them. This was late at night of course, but as soon as I got close to the road leading to the radio station transmitter, I saw a cop sitting in a nearby road, so I aborted my attempt. After trying it again a few more times and each time seeing another cop nearby, it occurred to me that the local cops had CB radios in their cars, as some of them even talked to us occasionally.  I guess they overheard my plan and were not happy about it, and were just waiting to bust me for trespassing.  Another reason to not divulge too many details over the radio.  I lost my nerve at that point and I never did find out if it was possible. The radio station soon changed hands, call signs, and moved the transmitter to a different location.


In 1995, I accidentally found out that it's not a good idea to run through a bank drive-thru while talking to someone with the amp on. Before the days of direct deposit, I used to get my paycheck on Friday and drive to my bank's branch close to work at lunch time to deposit the check. On this particular day, I was getting aggravated that the drive-thru was taking so long, but when it was finally my turn, the teller apologized to me stating that the computer system kept crashing. I didn't think anything of it at the time. The next week comes and I was again at the bank, and again I was talking, and once again there was a wait. Once again came an apology for "computer problems".  I though that this was a strange coincidence, so the next week I decided to test a theory. I went to the bank without using the radio. This time, everything seemed normal with no computer issues. After taking care of my bank business, I then pulled into the parking lot adjacent to the drive in. I fired up the amp and started transmitting, and not too long after, the line slowed down, and I could hear the teller's voice over the speaker telling someone that the computer had just crashed. Hmmm.... Coincidence? I think not......

By 1996 the local people had become totally obsessed with power.  10 years prior, having 500 watts in the car meant that you were the king of mobile power.  Now 500 watts was considered just a "driver".  Multi-alternator setups, and amps which ran into the multi-kilowatts, was becoming the norm.  But even guys with "wimpy" 500 watters like mine found out that while driving up the street in town at night you could set off burglar alarms with regularity.  Car alarms were equally susceptible. Then there were those sensor porch and yard lights, which would also respond to stray R.F.. Guys with a little more power could also cause certain traffic signals to stutter and eventually revert to flash mode. Even fluorescent lights were no match for the brute force of R.F..  Then there were the "you wash 'em" style car washes, which had the new style digital coin operated timers. One could put in 4 quarters, which bought about 3 or 4 minutes of time, jump back in the mobile and with the amp running, key up a few times and the minutes would increment upward. $1.00 for a ten minute leisurely car wash. Not bad!

Then there was a local known as Unit 1490 (Bill) Bill was an accomplished drag biker and engine builder, who also enjoyed dabbling in high power CBing. Being a personal friend of Dave, of "Dave Made" amplifiers, Bill had Dave build him a custom made tube A.C. amplifier, which was powered by two Leece Neville alternators. This setup, which he installed in an old 1970's vintage Chevy truck,  when he wound it up, could peg a Bird wattmeter with a 10KW slug in it.  One night, when he was fired up, a blue corona formed around his antenna, and you could hear the antenna's open air coils vibrating with modulation. If anyone approached the truck, the corona would leap out toward that person.  One of the guys in attendance managed to record the whole thing on video, but the sheer magnitude of the R.F. power was flaking out the video camera, putting in lines and removing all the color, even from 100 feet away. If I can find a copy of the video, I'll post it here.