Author Topic: I'm Still Naive to Radio Frequencies  (Read 3135 times)

Bob Durnell

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Re: I'm Still Naive to Radio Frequencies
« Reply #20 on: March 22, 2014, 12:07:40 AM »
Here is an off topic but weird one for you along similar lines.  My pole barn/workshop sits about 100 feet behind my parents house. After we built it, we ran a phone wire underground from the house to the barn, so we could make calls from out there.   Any time you picked up the receiver (in the barn only, not the house) WOWO radio would play faintly, but clear as a bell over the phone receiver. This went on for over 20 years, until the phone line got tore up during a building addition, and due to cell phones, we didn't bother to put it back.  What in the heck could cause this?  :o ???

SemperVaporo

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Re: I'm Still Naive to Radio Frequencies
« Reply #21 on: March 22, 2014, 02:32:45 AM »
I have seen that happen too.
 
Way back when the Hayes 1200 Baud MODEM was "new", I had one at work on one of the three HP-1000 systems of which I was System Manager.  I bought one for my Atari 800XL computer at home and wrote a "Terminal" program to use on the Atari so I could call the Work computer and from it get to a test station in the factory so I could "fix it" when the technicians would get that one all messed up, and I would not have to go into work just to hit the reset button on the terminal (I gave up trying to explain over the phone how to do that!).  I could log-in remotely, reset the programs, and log-out in less than a minute.
 
Then I had a 2nd phone line put in at home just to use for data transmission and not tie up the original phone line so my wife would not miss any of her phone calls!  I wired the 2nd line in the house myself and installed a couple of 2 line phones so we could use that 2nd line for talking if we wanted to.  She could use the original line for all of her talking and I could be "on-line" on the computer as long as I wanted on the other line.
 
When I called my work computer the first time it printed the request for "Log-In:" and then inexplicably it would randomly add more characters to the screen... I would start typing "SYSTEM MANAGER" and the screen would show:
 
"Log-In: 2c4dDetg$35wSYS24mcw456EM &#234d MANA*@&U$GER298898j5cd"
 
Or some such gibberish.  The correct data got sent and I got logged in, but received data was always screwy with lots and lots of random characters.  A request to display the directory of a disk was a joke on the screen.  I was going bananas trying to figure out what was wrong with the HP-1000.
 
About that time, a corporate "inspector" came through the factory and went ballistic over this "Huge hole in the company computer systems.  These teenage hackers will get into these computers and then get to payroll and cause havoc!".  I tried to explain that at 1200 Baud, it would take thousands of years just to transmit password guesses to get into the HP-1000 computer and even if someone did get in, there was absolutely NO connection between it and the payroll computers 600 miles south at corporate headquarters.  All to no avail.
 
After much arguing and explaining, he finally accepted my proposal that when an incoming call arrived, and the user would enter an ID, then the system would hang up and call the user back at a pre-determined phone number.  I wrote the code and that night I called in to check it out.
 
When I called in, I got that gibberish, but, if I paid attention to my typing and not what was on the screen, I could get my ID entered and the phone would disconnect and then a few seconds later it would ring and the modem would answer and all worked like it was supposed to and I could complete the log-in and do anything I wanted to do.  And most importantly to me, no more gibberish in the call back connection!  Solved 2 problems!  Corporate was happy and I could get work done from home!
 
 
Then my wife complained that when she was using the 2nd line for talking, sometimes she would hear WMT radio on the phone, but the person she had called did not hear the radio station.  I experimented with the 2 phones, calling each other and no matter which one called the other, sometimes the music/talk show audio was louder than my own voice over the 2nd line phone; and ONLY on the 2nd line phone!
 
This explained why the MODEM printed garbage... MODEMs use 2 audio frequencies on the phone lines.  The MODEM that initiates the call uses one frequency to send data and listens for data on the other frequency.  The answering MODEM does the opposite; so the "CALLED" listens to the "CALLER" on one frequency and the "CALLED" talks to the "CALLER" on the other frequency (and vice versa)  When I would call out, the Radio station "noise" on the line was in the range of the "CALLED" MODEM's talking ("CALLER" listen frequency), and when the HP system would call back then the Radio station "noise" was not in the range of the listen frequency and thus didn't cause garbage characters to be displayed  The noise was not sent to the outside world because it was only on the "incoming" line of the phone.
 
That told me the problem was in the wiring I DID in my house!  I replaced the wires from the RJ-11 wall jacks to the MODEM and the phones but that didn't fix the problem, so I then started really tightening the screws on the inside of the RJ-11 wall jacks.  The one in the den fixed the problem.
 
Not necessarily a loose screw, but an "insufficiently tightened" one! ;)
 
 
Any mechanical connection in any wiring can get some corrosion in it and that can act like a "diode" (which in radio parlance is also known as a "detector") which will, in conjunction with the lengths of wire involved and some other molecular constructs in the poor connection tend to resonate at a particular radio frequency and "detect" any audio signal that happens to be impressed on the radio frequency that it is sensitive to.  Thus my phone line was "tuned to" WMT (AM 600KHz) and your phone was sensitive to WOWO (do you remember what frequency that was?)
 
We both had what one might call a "Crystal Radio Set" or maybe more correct, a 'Foxhole Radio" (soldiers would make a radio receiver with some wire, a safety pin, a razor blade and some headphones to listen to radio broadcasts while in a "foxhole"... the point of the safety pin touching the side of the razor blade ["Blue Blades" worked best] would form a diode to "detect" the AM radio signal).
 
Semper Vaporo
Charles T. McCullough
CMBY RY

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Bob Durnell

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Re: I'm Still Naive to Radio Frequencies
« Reply #22 on: March 22, 2014, 11:18:29 AM »
WOW, very interesting!  I only understood about half of it, but thanks for the education.  WOWO is AM 1190, at one time, (no longer) one of the nation's big 50,000 watt "blowtorch" clear channel stations.
« Last Edit: March 22, 2014, 03:18:45 PM by Bob Durnell »

indyspy

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Re: I'm Still Naive to Radio Frequencies
« Reply #23 on: March 22, 2014, 12:16:00 PM »
It's no birdie or image, it is being transmitted from the grove.
If in doubt, Notch it out!