[ARC5] Selectivity improvement in BC-639

[D C _Mac_ Macdonald]

I used a BC-639 and modified SCR-522 transmitter on 2m AM from 1962 through 1966.  An AM pre-amp made the 639 quite usable.  I still have the 522 in rack in the garage but sold the 639 about 3 or 4 years ago. They were reasonably stable considering the bandwidth.  FAA used the 639s in fixed applications into the 60s IIRC. They were often paired with the BC-640 xmtrs with split-site installations.
 
* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* k2gkk hotmail com * 
* Oklahoma City, OK * 
* USAF & FAA (Ret.) * 
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> From: kgordon2006 at frontier.com
> To: Arc5 at mailman.qth.net
> Date: Mon, 2 Jun 2014 09:08:19 -0700
> Subject: Re: [ARC5] Selectivity improvement in BC-639
> 
> On 2 Jun 2014 at 7:31, D. Platt wrote:
> 
> > Tangential to this conversation, I'm looking at how to lower the 
> > coupling of the IF transformers within the BC-639( ) receivers.
> 
> Jeep: I am very curious why you would consider doing that to that receiver? It 
> covers 100 to 156 MHz, and as I recall, is not particularly sensitive in that 
> range, nor very stable either.
> 
> Are folks beginning to use that thing for some serious 2 meter AM work or 
> something?
> 
> >  The IFs 
> > in those are documented to be over-coupled to provide for a wide 
> > bandwidth.
> 
> Indeed! They are very broad. I forget exactly how broad but I think it was 
> something like 30 KHz.
> 
> Keep us informed. This is interesting.
> 
> Ken W7EKB