[ARC5] GRC-109 or RR-2B

[Kenneth G. Gordon]

On 9 Jan 2014 at 10:12, Leslie Smith wrote:

>   G'day list readers.
>   Can any-one on this list  comment on the general capability of the
>   GRC-109, 3 band receiver, covering 3-6, 6-12 and 12-24 MHz.
>   This set is also known as RR-2B - a 6 "tube" superhet.  I have a copy
>   of the TM.

I have an AN/GRC-109 which I use on the air regularly. Over a period 
of several years, I worked 35 countries with it on 40 meters, crystal 
controlled, and I was using a low end-fed wire antenna too.

>   It uses the miniature "toobs", including the hard-to-get 1L6.

I found a fellow who makes a solid-state replacement for the 1L6 
which works much better than even a new 1L6 does. Although I have at 
least two NIB 1L6s, I MUCH perfer the SS replacement. The fellow 
builds them into minuature tubes so they simply plug in to the 1L6 
socket. For one thing, the 1L6 "pulls" frequency on strong signals 
and when keying the transmitter. The SS version doesn't do any of 
this. It is rock solid.

>   The selectivity appears to be broad (9 kHz at 6 dB "down").

Correct. Although I "sweep aligned" mine, it really is wide.

>   (Seems broad for a set with 2 I.F.'s at 455 kHz)

That can probably be improved by working on the IF transformers.

>  Sensitivity is quoted at 5uV. 

Although I have not tested mine, I think the actually sensitivity is 
better than that. I have no problem copying any one I need to. I DO 
use an external audio amp though: one of those small 9 V battery 
powered Radio Shack jobs. I also use a "beam filter" with mine, which 
makes a big difference. 

>   I have not been able to find a spec relating to stability.

In my opinion, the receiver is quite stable. Also, it is capable of 
being crystal controlled: there is a crystal socket with a built-in 
bypass switch mounted on the front panel.

However, due to the way the T-784 (or its TT equivalient) does "QSK" 
the receiver overloads easily. It has no AGC. Furthermore, again due 
to the QSK method, there is TERRIBLE "suck out" if you use the RX and 
TX on the same frequency. The transmitter's tuned circuits reduce the 
receiver input by 30db. In fact, the manual tells the operator to use 
a separate antenna for the RX if he must operate with RX and TX on 
the same frequency.

Normally, when those rigs were used by the Special Forces in 'Nam, 
the receivers were on a much different frequency from the 
transmitter.

Ken W7EKB