[Boatanchors] BC-639 Military Receiver

[eldim at att.net]

Hello Fellow BA'ers,
I just coundn't help but share a few thoughts on the BC-639 VHF AM Receiver.  Wonderful old receiver that did a swell job for it's era.  The Germans threatened to shut ours down at Rhein Main AB on the outskirts of Frankfurt am Main due to splatter from our matching BC-640 Transmitter.  We also complained that they were bleeding over on our Receivers.  It seemed that they had switched all their vintage 100 KHz BW VHF gear over to the new improved (new generation) 25 KHz BW receivers, Transmitters, and Transceivers.  We, the Americans on the other hand were still waiting for IT&T to bring in the 50 KHz BW "RIVET SWITCH" equipment which, was long over due, due to factory problems getting the Receiver specs in line with new Bandwidth regulations. I've owned the receivers from time to time, but never have seen a complete transmitter on the surplus market.  We had several in the Phillippines at Wallace Air Station, two units when I was in SAC RBS, and  a pair at AVIANO AB, Italy, and Rhein Main AB, Germany.  The Air Force had them on one VHF Freq for Commercial Aviation and another for the VHF Emergency Guard Freq 121.5 MHz better known as "DOG".  I don't know how they arrived at that name, other than it was an easy way to distinguish the VHF Emergency from the UHF Emergency of 243.0 MHz.  By the way, the Receiver Spec bandwidth was 155,000 Hz if I recall correctly.  So you can see how much wasted spectrum there was with those old receivers.  You can easily fit 4 seperate 25 khZ Channels by the new standards.  I haven't kept up with the technology, but there was once a rumor that they were working on 12.5 KHz Channel Spacing.  A fact in point, is that this was the radio that I made my FIRST 2 METER CONTACT on in the mid-sixties from our excess MARS BC-639A Receiver and BC-640 Transmitter.  I don't recall if they ever issued a 'FIRST DAY COMMEMORATIVE' for that historic event from our RADAR BOMB SCORING (RBS) site in Oronogo, Missouri.  :<) LONG LIVE HAPPY MEMORIES of  REAL BOATANCHORS from a bygone era. 
73,
Glen Galati, KA7BOJ, ex WB0AXK, DL4GG, HL9WA,  MARS: AFB0AXK.......

p.s.  What were those transmitter tubes used in the BC-640?  The ones with the Grid side pin and the Plate pin on top, and they had a BEAUTIFUL brilliant "white glow' wish filament voltage applied. I want to say, "2C40-A".......

-------------- Original message from WA5CAB at cs.com: -------------- 


> Joe, 
> 
> That modification is covered in T.O. 16-40BC639-22 dated 30 April 1948. 
> Receivers so modified became BC-639-AM or BC-639-BM. Copy of the T.O. $5.00 
> shipped CONUS. Includes extra copy of modified schematic to glue into cover. 
> 
> In a message dated 1/23/2006 7:18:38 PM Central Standard Time, w5jdy at cox.net 
> writes: 
> > Hello again,from w5jdy in Okla. I have completed restoration (all caps 
> > and 
> > realignment) of an old BC-639 Military AM Receiver. It tunes from 100mc to 
> > 155mc It is working quite well with about 1 microvolt sensitivity but there 
> > is a lot of noise Not in the radio but with the antenna connected. I saw a 
> > BC-639 Radio many years ago that had a 6H6 noise limiter built in it. It was 
> > under the chassis,it was original and came from the military that way. I 
> > would like to find a schematic of that model radio. I will build a noise 
> > limiter in the one I have. Kind of stupid aint it?. The one I saw was 
> > exactly the same as the BC-639 I have and had the schematic with the noise 
> > limiter in the cover. Just re-inventing the wheel in Okla. Joe 
> > w5jdy at cox.net Thanks for your time. 
> 
> Robert Downs - Houston 
> (Web Store) 
> MVPA 9480 
> (Primary email) 
> (Backup email) 
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