[TMC] Odd plug-in on FFR receiver

[Roy Morgan]

Nick,

I used to own such a receiver.  One of my plug-ins had an octal socket on a little bracket installed where the normal (HC-6?) crystal is on normal plug-ins.  You can see that addition to the front panel in the photos.  The socket was meant for the small round crystal ovens such as are found in the R-390A 17 mc oscillator.  The added socket had 6.3 volt filament  power in addition to the connection to the oscillator circuit for the crystal.

I strongly suspect that the odd things seen in the photo are simply larger crystal ovens, quite likely more accurately controlled in temperature than the small round ones we are more familiar with.

Roy

> On Jun 15, 2019, at 2:46 PM, Nick England <navy.radio at gmail.com> wrote:
> 
Three of the FFR receivers (AN/FRR-49) have a very odd "something"
> 
> http://www.navy-radio.com/commsta/iceland/iceland-jd-1705-09.jpg

Roy Morgan
K1LKY since 1958
k1lky68 at gmail.com