[Hallicrafters] Phil's SX-71 mods (was) RE: Sloper and SX-71 (was) Re: An AM antenna

[jackiv at juno.com]

Happy Thursday to all.
There was an article on how to soup up the SX-71 some time ago. I hope
that the author
is reading the mail.
Basically it was to replace the ant and rf coils on band one with
universal replacements 
which have slugs to tune the low end (600 kc) so as to track the
oscillator stage.
These coils will mout in the same place as the old, non slug tuned coils
withthe slug adjusting screw on the chassis top.
This mod increased the sentitivity a bunch and did help with some images.
It may be more sensitive to overload on strong signals.
BUT the overall will be very good.  These coils are avaiable from Antique
Electronic Supply 
in Tempe AZ. .A change in the front end rf amp to a lower noise tube and
corresponding cathode resistor may also be in order.
Jack
 
On Mon, 3 May 2004 08:48:05 -0700 "RJB" <rjb at lynden.com> writes:
> Phil
> thanks for the response. I saw your article "Soup up your SX-71" in 
> which
> you mentioned some mods to the 2nd IF. Two questions, if i may
> 
> 1 - what exactly did you do to the cathode connection on this tube 
> (6SK7
> IIRC)?? The cathode resistor is (i think) 1K, going to a switched 
> set of
> resistors, presumably to keep gain constant from band to band. Did 
> you
> replace this with 270ohm to ground??
> 
> 2 - what mods did you make to the screen supply?
> 
> 3 - Did you ever check your electrode voltages?? mine are all over 
> the map,
> even after replacing all resistors and all tubular caps :(
> 
> 4 - Have you had your SX-71 repainted?? Mine works well, but is 
> ugly. (if it
> had engraved lettering i would do it myself :-)
> 
> thanks in advance for any help
> 
> Bob
> 
> -----Original Message-----
> From: Philip Atchley [mailto:beaconeer at elite.net]
> Sent: Monday, May 03, 2004 8:27 AM
> To: rjb at lynden.com
> Cc: hallicrafters at mailman.qth.net
> Subject: Sloper and SX-71 (was) Re: An AM antenna
> 
> 
> Bill, Bob et al,
> I too have used the Alpha Delta DX-B (60 footer) sloper antenna for 
> a
> number.....
> 
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