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Topband: 160m receive performance

To: <topband@contesting.com>
Subject: Topband: 160m receive performance
From: herbs at vitelcom.net (Herbert Schoenbohm)
Date: Fri Jun 27 09:44:18 2003

David Knepper wrote:

>The best receiver, in my opinion, continues to be the 75A-4.  OK, now let'er
>rip!
>
David,

I would tend to agree with you although I have not tried a Yaesu FT-1000 
series nor done any A/B comparisons.  The 75A4 in the 60's was certainly 
the best there was on top band.  By using single conversion it avoided 
some problems that were inherent in more modern radios to follow.  The 
idea of PBT by shifting the signal around the pass band with a strap 
rocking the PTO was unique. Of course the 500 Hz or 250 hz Collins 
filters were works of art.  (No pun intended.) With the filters one 
could literally create a deep tunnel effect dropping unwanted signals 
disappearing into the crevasse while retaining the weak signal 
resolution on a ledge.  This worked especially well with a 250 to 350 
cps CW note. The only drawback on top band that I recall was that the 
dial tune backward on 160 and that you tuned to PTO to the left to go 
lower in frequency.


 I have been looking for an 75A-4 primarily for nostalgia purposes.  ( 
Most of my youth I lived 25 miles from the plant and later went to work 
Collins, although as a sales rep in the broadcast division.)

I just checked e-Bay and found the following:  There is a 75A-4 
available but the bids are presently at $1076! Recently a 75A1 went for 
$550, a 75A2 for $659, and a 51J4 for $600. A 75A-4 noise blanker alone 
is over $300. The only bargain was a 75A3 that sold for $332.

 I think since they are becoming collector's items and over 50 years 
old, if you can find one at a hamfest, buy it.  If you decide you don't 
want it some day I will gladly cover the cost and provide a  2 week 
vacation at a B&B in the VI with a 160 meter station.

I have wished that some solid state copy of this receiver would be 
manufactured today as the schematic, apart from the PTO, is simple and 
straight forward. Good filters are available although the plug in 
mechanical are very expensive.  Maybe the closest thing available today 
is the Elcraft K-2 but I am waiting for Earl's (K6SE) comparative report 
if he can find a 75A-4 to try on the west coast.

73

Herb Schoenbohm, KV4FZ

Just a thought.

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