7

One of the fine folks from MMRCG identified this as model R-1484/PRR-15


6

It is the thickness of the crystal that primarily determines its operating frequency. When crystals are manufactured, they are gradually ground down in a special fixture. The operator monitors the process by keeping a shortwave radio nearby, which picks up the electrical noise created by the stress of the grinding action on the crystals, which is relatively ...


5

Out of left field - If function is the only cause and fashion isn't an issue, use a couple of black cotton socks. On my headphones the plastic outer pieces are removeable. I cut the ends off two socks, slid them over the phones and my wife sewed them in place. Comfortable, although the seams do show a little. I don't care! Cost nothing and works fine!


5

didn't do it, but back in the day stumbled across this, and thought it might be on-topic. EDIT: inserted original text below. To: Multiple recipients of list From: carreiro@netcom.com (Paul Carreiro) Subject: Help in FT-243 Grinding Greetings fellow boatanchorites! I need help from all the BA gurus out there practiced in the mysterious ...


3

Developing this comment of W2ASC (above): But, given the fact that radials are effective even when buried in a few inches of soil, my assumption was (and still is) that whatever difference exists between the two insulation types is - for all practical purposes - negligible. So, my question is probably a bit academic. I still believe my initial assumption was ...


3

You might be able to use this mechanical drawing, from the ARRL's monthly QST magazine for August 1974, to determine whether the available units are appropriate to your needs:


3

Audiophiles like to replace those plastic and foam earpads with a velour product such as this: If red doesn't suit you, there are other choices. There are several vendors for this type of product, with Brainwavz Audio as one example.


3

The connector is called an "HN" type connector. It has a 3/4-20 thread and it is usable up to 4 GHz. The Amphenol data on it is available here.


3

Is it more due to legal reasons (such as frequency allocation) or to technical reasons? Both. And the dominant reason is, as always, cost. I'll illustrate in RX first: Now, radios like these work by mixing the RF signal down – in this case, usually to a fixed IF (intermediate frequency), from which the actual demodulator (AM, FM, digital...) generates the ...


2

It's a crypto interface and crew terminal from a military radio system. It isn't useful on its own, and a lot of equipment of this nature is not legal for civilians to buy or sell. That said, this isn't the first time I've seen that exact terminal pop up in ham radio forums, so I suspect it's a model not covered by current control policies, though I can't ...


2

I can second the comments about bon-ami. Way back 2/3 of the way through the last century, we also used some of the super fine abrasives used for the later stages of grinding amateur telescope mirrors. Try Googling "Amateur Telescope Making Supplies" and "Telescope Mirror Blanks" for suppliers. - W6HPA


2

I only scanned that whole quote. I have my father's W9EHS SK, FT crystal grinding equipment. It has two special grinding compounds and the two plates. One of the plates has a rosette-like shaped indent that helps guide the blank in the figure 8 pattern. There is a special FT holder that allowed easy insertion and removal. At times, the edges had to be ...


2

To directly answer your question, the exact-replacement material would be open-celled polyurethane foam with a density of about 2.0 lb/ft^3 (30 kg/m^3). This can be found at just about any foam outlet store. Alternatives: It does not have to be polyurethane but I have found polyurethane to be far more durable than other foams. The density can be ...


2

Here's some information on GRA-39 Radio Set Control, TA-1 Telephone Set and Chinese 251A Radio Set. http://www.prc68.com/I/GRA39.shtml https://www.prc68.com/I/TA1.shtml http://chinesemilitaryradio.blogspot.com/2008/10/silicon-two-watt-short-wave-transceiver.html


2

The construction does not look appropriate for military service. Coast guard, Civil Aviation, emergency services or industry looks more likely. Photographs of the interior may yield more clues. A fixed squelch control may be a clue this was designed for VHF or UHF. It was not common to totally enclose radio equipment without ventilation so this may only ...


1

Thanks for joining us on Ham.SE! Insulation on wires will affect performance if they are part of the antenna's system of resonance. Just as with coaxial cable, adding insulation to a wire decreases the speed at which electromagnetic effects propagate: $$\lambda=\frac{vc}{f}$$ where $v$ is the velocity factor of the insulation and is less than or equal to ...


1

Looks like a male SC connector and the dimensions seem in the ballpark too. I found this via a "Microwave Coaxial Connectors" PDF which describes it as: SC (OSSC) - The SC coaxial connector is a medium size, older type constant 50 Ω impedance. It is larger than the BNC, but about the same as Type N. It has a frequency range of 0-11 GHz. This matches ...


Only top voted, non community-wiki answers of a minimum length are eligible