#763

Episode 763
I got this from Murphy Surplus. I paid $28. When I got it there was no receive. I tracked it down to the LO and a bad Xtal. Replacing the crystal fixed it. It was designed for 47-57MHz FM 9.5kHz deviation. Runs with 6VDC supply.
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[@PapasDino]

From someone who actually used that POS receiver when I was a rifle platoon leader in the mid '70s; used it to talk to my squad leaders while I also carried a PRC-77 to talk to my company commander...this receiver clipped to your steel pot so your head was proverbially tilted to one side. The companion transmitter hooked, the RT-4 as I recall, onto your LCE (load carrying equipment) and you had to lean to the side to use it. It wasn't meant for stationary duty, you actually wore and used this thing while you were tramping thru the woods. Obviously only one frequency...had to take it to the commo shop to have it changed. Worst piece of comms gear I used in 26 years of active duty (ok Dino, tell us how you really feel!).

[@IMSAIGuy]

You definitely need one now. your XYL can talk to you using her 7300 while you are doing honey do projects.

[@gordselectronicshobby3853]

While I was employed in the Federal Civil Service for 20 years, I repaired and aligned these radios.

[@Bernesemtdog]

Any idea where one may be able to find an antenna and batteries for one? I purchased one recently I plan on getting set up to test my PRC-77 with.

[@gerrywoody4301]

Thanks for the memories mr imsai I was an army radio tech for 20 years and love to see this not old but my era stuff

[@vk2zay]

Odd that is has thermistors in the RF amplifier and LO biasing circuits, I guess it needed to be temperature compensated to meet the specs? The VHF amplifiers are common base to get the needed gain and low impedances for stability with the 2N987 which has an Ft of only around 50 MHz and a large Miller capacitance of about 12 pF. The squelch is a noise-squelch driven from the output of the 2nd IF limiter through an AM detector CR1. The collector load for the Q11 baseband noise amplifier is an inductor which is a bit weird, I can't tell if it is a 47 uH or 47 mH, mH would make more sense especially with the fairly large 220 nF emitter bypass. It is clearly intended to be an audio frequency amplifier with a high pass characteristic, the squelch is opened by a reduction in high frequency noise (i.e. a quieting) in the IF signal. It looks like it functions by cutting the bias to Q13.

[@barryfairwood2174]

That receiver was designed to be used with the PRT-4 transmitter. Normally it was used as a squad leaders radio set in a infantry platoon That radio replaced the PRC-6, Korean War vintage sub minature tube radio.

[@gordselectronicshobby3853]

When I was a Federal Civil Service Electronics Tech for the military, I repaired both the transmitter and receiver. Those were the days and I loved that job.

[@benjaminscherrey1124]

I must be old. Immediately recognized the test points for what they were. 😎 Nice hardware!

[@MrSparks54]

Very cool stuff. I had military radios in the past. A pair of URC-68 pilot emergency radios, they were pretty good on VHF Low band. Also had a pair of PRC-77 Vietnam era backpack radios, they were awesome, apparently a lot of preppers still use them.

[@johnwest7993]

What a cool mil radio! I've never seen that model before. I once had a couple of what I figured were WWII mil HT radios with tiny tubes. I never found ANY documentation for them.

[@chrisscott1547]

Germanium transistors. Note the thermistors and elaborate bias compensation networks. That was the only way to keep them working over a temperature range. About 1968 I had super-regen 27 MHz walkie talkies which would quit below 50 degrees. 50 MHz is an interesting band - probably the best for tactical use in mixed terrain.

[@Stellar12316]

Old super geek I have no idea. Most of what you said I own a set of these it you are amazing

[@craigtegeler4677]

The PRT-4 and PRR-9 worked together as an attempt at a simple, lightweight Squad radio, albeit one-way. First fielded in Vietnam by the U.S. Army in March 1967. Here's a good link: www.n6cc.com/prt-4-prr-9-squad-radios/ . I've seen this battery before. You could perhaps make up an inline Ni-Cad pack of 6 with an inline diode to drop the voltage down 6 volts and it probably behave okay, that is you're not going to put out the bucks. I'm trying to remember some of the other battery chemistries that were used back then such as Manganese and Cadmium???

[@drussell_]

That is a *_horn_* speaker, not a _ported_ speaker. The increasing diameter from the throat to the mouth of the horn provides an improved acoustical impedance match from the speaker driver to open air than the driver radiating directly, increasing the efficiency.

[@mikegLXIVMM]

Control unit for the Universal Soldier.

[@blargdarsky392]

Murphys Surplus in El Cajon? That shop is wild. I remember the crazy hair guy trying to sell me an old mammogram machine. Be sure to ask for the full tour.

[@GateKommand]

Thanks for another interesting video mate!

[@TeslaTales59]

Great presentation!

[@joeteejoetee]

How much current does it draw? It seems like it would run on a 6V solar module.

[@andytomm1]

Isn't it dated in the contract # 05 1967?

[@hanskoc3473]

Thank you for another interesting lecture. How did you obtain the HP device you have used, it's quite expensive one, about 3500 to 5000 $ in used condition now.

[@IMSAIGuy]

It will make you sick... There was a cell phone service company moving and the manager was told to clear out the building. Everything was going in the dumpster. I got two HP8921a analyzers for $100 😎

[@mmouse928]

Great video I have one and you gave me a good tip. Would you by any chance have a 1.647 MHz crystal, it would be for my codon radio to receive LSB.

[@Stellar12316]

More videos on these please

[@IMSAIGuy]

what would you be interested in. have you watched part 2?

[@Joseph-zq2mh]

Is this for functional like this connect to a like say EE8 or TA 43 field field? I’m a newb at all this communication stuff but I find it fascinating! Lol thanks in advance

[@Joseph-zq2mh]

Fully functional *

[@fnordhorn]

The radio is in 2 parts - you have the receiver - the 2nd unit is a transmitter that one would clip on the suspenders of the web gear at shoulder level... See www.greenradio.de/e_prr.htm about the PRT-4 & PRT-9

[@akepatinagaraju8564]

Sir 27 mhz linear bremi about plz

[@akepatinagaraju8564]

Sir linear bremi about plz

[@mmouse928]

Sorry it should read Codan radio

[@IMSAIGuy]

I don't think so, that is a odd frequency

[@mmouse928]

@@IMSAIGuy thank you I saw that you ad lots of crystal. Yes its very odd but the Codan radio come standard with only usb, and you need that crystal to be able to receive LSB. Thanks' again for looking.