[Hammarlund] Old Hammarlunds

[djed1 at aol.com]

I have both a BC-779 and a SP-400, so I'll offer my experiences.  It's been a couple of years, so some issues are a bit hazy.  I restored the BC-779 and was surprised at how bad it drifted- 75 KHz from a cold start at 20 MHz.  I finally found some TC caps, and put in two 10 pf in series.  This reduced the drift to about 50 KHz.  This is with the dust cover on- it may be significantly better in open air, but nowhere close to anecdotal numbers.
As for the SP-400, I got one that had TC caps installed, but I have no idea if they are original.  The radio had been worked on, so they may have been added.  I did get the original manual, and the schematic doesn't show any compensation.  I do remember that the SP-400 drift was much better than the BC-779 when on the bench- maybe 15 KHz.  But after I put it in the cabinet it wasn't much better than the BC-779.  
Just to show how the technology changed, my SP-600 drifted about 12 KHz from a cold start, and the R-390A drifted 0.4 KHz.
Ed  W2EMN

 


 

 

-----Original Message-----
From: Richard Knoppow <1oldlens1 at ix.netcom.com>
To: Carl <km1h at jeremy.mv.com>; kgordon2006 <kgordon2006 at frontier.com>; Hammarlund <Hammarlund at mailman.qth.net>
Sent: Mon, Apr 11, 2011 8:50 pm
Subject: Re: [Hammarlund] Old Hammarlunds




----- Original Message ----- 

From: "Carl" <km1h at jeremy.mv.com>

To: <kgordon2006 at frontier.com>; <Hammarlund at mailman.qth.net>

Sent: Monday, April 11, 2011 5:12 PM

Subject: Re: [Hammarlund] Old Hammarlunds





> Also realize that the one cap across the variable is there 

> for all bands.

> That means other values may be needed for the lower ranges 

> that have to be

> wired into the oscillator circuits.

>

> Later production SP-400's had TC but I dont have that 

> detail handy at the

> moment.

>

> Carl

>

    It would be interesting to know especially if the 

compensation was detailed in any schematics or even in parts 

lists. That would be a very good clue for adding it to older 

receivers. I doubt if H would have changed the tuning caps 

but the value of the fixed padders and trimmers might have 

been changed.





--

Richard Knoppow

Los Angeles

WB6KBL

dickburk at ix.netcom.com 



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