7 votes

Can anyone identify this military radio?

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

Shaving Quartz Crystal for New Frequency

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 ...
5 votes

Suitable acoustic foam rubber for headphones?

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,...
  • 51
5 votes
Accepted

Shaving Quartz Crystal for New Frequency

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 ...
3 votes

Dielectric Constant of Insulation/RF Permeability

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 ...
  • 2,912
3 votes

Can't identify old Chinese(?) and American radio/telephone

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....
  • 737
3 votes

What are the parameters and necessary features of a Gunn diode oscillator cavity?

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:
  • 7,723
3 votes

Suitable acoustic foam rubber for headphones?

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, ...
  • 18.3k
3 votes
Accepted

Identify this “large TNC” coax connector

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.
  • 18.3k
3 votes
Accepted

How is the PRC-152 able to achieve such a wide frequency range?

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 ...
2 votes

I need help identifying what I believe is a military radio

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'...
  • 1,814
2 votes

Shaving Quartz Crystal for New Frequency

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 ...
2 votes

Shaving Quartz Crystal for New Frequency

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 ...
2 votes

Suitable acoustic foam rubber for headphones?

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 ...
  • 1,042
2 votes

What is this military radio?

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 ...
1 vote

Dielectric Constant of Insulation/RF Permeability

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 ...
  • 7,723
1 vote

Identify this “large TNC” coax connector

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 ...

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