Ancient arcania-Petticoat Junction

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boteman
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Joined: Tue Nov 30, 2004 2:20 pm
What radios do you own?: AudioMate 360

Ancient arcania-Petticoat Junction

Post by boteman »

I just watched the fifth episode of Petticoat Junction "Is There a Doctor in the Roundhouse" where the C&FW Railroad president gathers his corporate buddies to repair the Cannonball throttle that he broke in his exuberance running the train.

One of them has set up a makeshift radio in the rear car to order parts from headquarters. The "radio" is an original Motorola Quik Call tube-type encoder (2+2 style with the big brass reeds) with the two rows of black buttons to select the tone pairs and the VU meter in the middle. I used to have one of those that I bought at a hamfest for $5 bucks in the early 1980s. I even had the preset box hooked to it which had better be grounded to the encoder chassis or you got a proper shock!

The encoder is sitting on a "Flying Wedge" BBB tube consolette or whatever they called it back in the stone ages and they're talking into a Motrac lollipop desktop mic. The stuff looks brand new and Motorola didn't even get a product placement out of it. I'm laughing my ass off when that scene came on because half the tone select buttons are pushed in and the only way to release them is to power up the encoder and hit the release button to trigger the solenoid.

Anyway, just a neat little tidbit from the early days of the Big M.
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d119
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Re: Ancient arcania-Petticoat Junction

Post by d119 »

I have one of those encoders at home, along with several of the decoder boxes. The encoder needs new capacitors installed as the timing and audio is completely haywire in it...
KE7JFF
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Re: Ancient arcania-Petticoat Junction

Post by KE7JFF »

I've been watching the A-Team lately on netflix and whoever Stephen J. Cannell has as prop person must be a twisted radio guy. He has the police using Motorola equipment of course, but then when the team uses a radio, its either a CB radio or a ham HF rig made to look like a VHF/UHF base station! Of course my favorite is when they used a ham HF rig as a receiver to listen to a FM bug.
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WA6OXN
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What radios do you own?: Saber, Astro Saber, Micor, Mot

Re: Ancient arcania-Petticoat Junction

Post by WA6OXN »

i just realized I could follow this whole thread and remember working on this stuff back in the day.

Geez I'm getting old...

btw I used to watch Petticoat Junction on a b/w TV ;)
JeffFireRadio
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Re: Ancient arcania-Petticoat Junction

Post by JeffFireRadio »

Me, too. Then, ironically, we got a color TV...a Quasar...by Motorola. Thanks Mr. Galvin. What didn't M make?
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boteman
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Re: Ancient arcania-Petticoat Junction

Post by boteman »

JeffFireRadio wrote:Me, too. Then, ironically, we got a color TV...a Quasar...by Motorola. Thanks Mr. Galvin. What didn't M make?
With "Works in a drawer!"

Remember Steve McGarrett asking "Patch me through to HPD" and holding down his red PTT button on his Motrac mic during the whole conversation. I never knew they made Motracs in full duplex! I used have a Modcom console that I pieced together over the years and it did have patch capabilities, but it was a kludge to set up properly.
RFguy
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Re: Ancient arcania-Petticoat Junction

Post by RFguy »

JeffFireRadio wrote:Me, too. Then, ironically, we got a color TV...a Quasar...by Motorola. Thanks Mr. Galvin. What didn't M make?
http://www.youtube.com/watch?v=jlk9-NGMrDQ
AL7OC
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Re: Ancient arcania-Petticoat Junction

Post by AL7OC »

I wouldn't mind having a QC1 encoder to restore. They used to be common as dirt in fire stations years ago. Our encoders had CZ through PZ reeds in them, and if I recall correctly, a few tubes. The usual story - the stuff that we pitched years ago as junk now has some nostalgic value. Although they're a pain to work on, some of the old electro-mechanical equipment was quite elegant in design. I remember also that sometimes we had problems with false-tripping in the reed decoders. Don't remember if it was related to timing, or the phase inversion not damping the reeds?
Pierre

AL7OC
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boteman
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Re: Ancient arcania-Petticoat Junction

Post by boteman »

AL7OC wrote:I wouldn't mind having a QC1 encoder to restore. They used to be common as dirt in fire stations years ago. Our encoders had CZ through PZ reeds in them, and if I recall correctly, a few tubes. The usual story - the stuff that we pitched years ago as junk now has some nostalgic value. Although they're a pain to work on, some of the old electro-mechanical equipment was quite elegant in design. I remember also that sometimes we had problems with false-tripping in the reed decoders. Don't remember if it was related to timing, or the phase inversion not damping the reeds?
They had one oscillator tube per reed, plus a couple others for audio amplification.

The timing had to be considered when setting up the encoder, most importantly the gap between the first pulse and the second pulse to give the first pair of reeds a chance to quench before they blasted the second tones. There was no reverse burst as there was with PL tones.

I know of several fire departments that used a common tone in each fire station with the other half of the pair determining if it alerted fire suppression or EMS. If the tone pairs and gap timing weren't chosen judiciously, they might end up with the first pair of reeds still vibrating when it started the second pair which wound up alerting the whole station. I know the reed frequencies were chosen to minimize harmonics and "crosstalk" between reeds in the same series.

The digital stuff works better and provides a lot more possibilities, but the 2+2 tone pairs sounded really cool, especially the Z-series like you had.
AL7OC
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Re: Ancient arcania-Petticoat Junction

Post by AL7OC »

It's been over 30 years since I got into the guts of one. The last one was while I was working at Harris. We had a customer that needed to interface one to an HF radio. I think that it was being used as a SELCALL unit for aircaft. I also think it had a vu meter on the front panel, but it's been a long time... They were also Z tones, but the letter assignments were different for aviation SELCALL. We hooked the encoder to an HP signal generator set to a low level and set off the our buddy volunteer FF's pager across the bench from us. It took him a day to figure out what was going on. Boys will be boys...

The county used M+N for a group call where, if I remember, you had to select M&N on the bottom row and manually press the group call button for 5-6 seconds. The group call set off the CD sirens, whilst the individual calls where some combination of M+t1 on the first row and N+t2 on the second. The timing was critical, and every now and then, some monitor would false trip on group call because the M reed wouldn't fully quench before the N in the second group started. Bigger districts had two station monitors - one for the CD siren, and another set to a different group call scheme for the district. The tone outs took longer for QC1, but the advantage was the unique sound each combination had. You knew which district was getting toned, and whether it was for fire or EMS, long before the announcement. The human ear can discriminate the tone combinations well.

One slow day, we figured out the tone relationships in the Z series tones where some non-integer number was the root, and each tone frequency was that number to the N-th power. We found the root by taking the log of each frequency and studying the relationship of the log number. A and B series had a different root number. The root number was close to one, and worked out to several decimal places. Like I said, it had to be a slow day...

Reeds were of the same vintage technology as mechanical SSB filters. Back then, you didn't have the Q factor necessary in electronic circuits, but you could get it in a resonant mechanical device. Reed technology sounds clunky, but I think that it was an elegant solution at the time.

PL
Pierre

AL7OC
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