[Test-Equipment] GR 1800A VTVM

[Richard Knoppow]

----- Original Message ----- 
From: "Dale H. Cook" <radiotest at plymouthcolony.net>
To: <test-equipment at mailman.qth.net>
Sent: Wednesday, December 18, 2013 8:16 AM
Subject: Re: [Test-Equipment] GR 1800A VTVM


> At 11:02 PM 12/17/2013, Richard Knoppow wrote:
>
>>... which is threaded in the center for the outer shell of 
>>a type 874 coaxial connector.
>
> The GR Type 1800-A predates the Type 874 connector series, 
> whose center conductor is a four-part genderless design 
> which is essentially a miniaturized version of its outer 
> conductor.
>
> The first option for the Type 1800-A probe is as a Type 
> 274-M plug, which is a double banana plug.
>
> The second option fits the probe as a Type 774 plug, which 
> is essentially a shielded banana plug. The Type 774 was 
> the standard RF connector on GR instruments of the '30s 
> and '40s, including the Type 916-A and 916-AL 
> Radio-Frequency Bridges, the Type 821-A Twin-T Impedance 
> Measuring Circuit, and the Type 805-C Standard Signal 
> Generator. After the Type 874 was introduced the later 
> production of some instruments that originally used the 
> Type 774 was converted to the Type 874. I have seen 
> instruments that were manufactured with a Type 774 jack 
> that had been field-converted to later RF connectors 
> including SO-239 and BNC. Many years ago an article in one 
> of the amateur radio mags (I think it was CQ) on the 821-A 
> described how to home-brew a connector to mate with the 
> Type 774s on the Twin-T.
>
> Dale H. Cook, GR / HP Collector, Roanoke/Lynchburg, VA
> http://plymouthcolony.net/starcity/radios/radtop.html
>
     Thanks Dale, I had forgotten that the 1800A also came 
with an adaptor for the 774 even though I have part of an 
adaptor.  774 connectors are pretty rare now and adaptors 
for 874 connectors even rarer. There are slightly different 
fittings in the compartment on the top of the 1800 case to 
accomodate the different parts.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com