[Milsurplus] PRC-47

[David Ross]

H.O. & the gang -

"H. O. Tyler" wrote:
> 
> I am working on getting a PRC-47 modified and on the air.  I have noticed a
> delay on turn-on and think it is the filament warm-up of the front end
> tubes.  The turn-on time is about 5-6 seconds. I have not fired up the Tx
> yet and is the time delay on push to talk about the same ?  Also I am look
> for a source of data on the tube line-up in the PRC-47:  5907, 7761, 7905
> and PL-177.
> 

  The receive delay at initial turn-on is the warmup time for the two
peanut tubes in the RF TRANSLATOR module.  Their filaments are on
whenever the radio is on -  they see +28VDC B+ in receive and about
+150VDC B+ in transmit mode.  Both these peanut tubes are soldered in - 
no sockets.

  Both the 7905 PA driver and the PL177 PA tube are instant heating,
they get filament power only while transmitting -  you'll see maybe one
second delay for these two to heat up  (you'll get used to it quick - 
just think of it as if you were waiting for a dynamotor to spin up...).

  The PRC-47 is a fine radio, but I would sure like to find out why they
did not design it with better PA tube cooling.  The "1 minute on - nine
minutes off" transmit duty cycle is tough to live with...

73, have fun with it
Dave Ross    N7EPI    ross@hypertools.com