[Hammarlund] ITT modified SP-600

[Richard Knoppow]

I found in my collection a schematic for a Northern Radio 
modified SP-600-JX with fewer modifications than indicated 
below.  This one has 6J6 tubes in place of the 6C4 used as 
the LO and BFO.  In the LO the two grids and plates are 
paralleled, in the BFO one grid and plate is used as the 
local BFO and the other grid is for an external BFO and goes 
to a connector on the back. The IFO uses half of a 12AU7 as 
the crystal oscillator and the other half as a buffer with a 
switch allowing either the use of a remote BFO for 
diversity.   The detector and audio circuits are identical 
to the standard receiver.  Evidently Northern Electric made 
a number of different modifications to the SP-600-JX. 
Hammarlund also made a modified version for diversity, the 
JX-17, which has a number of differences from the standard 
model.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com


----- Original Message ----- 
From: <mrharisn at hughes.net>
To: <Hammarlund at mailman.qth.net>
Sent: Sunday, August 31, 2014 11:44 AM
Subject: Re: [Hammarlund] ITT modified SP-600


> My apologies for jumping in here, but my understanding 
> also that these SP-600s were modified by Mackay Radio to 
> incorporate a third mixer with switchable 430 or 480 kc 
> injection, and driving a 25 kc 3rd IF output going to a 
> separate unit with two L-C bandpass filters, one for 22-25 
> kc, the other for 25-28 kc, each with its own detector. 
> This allowed independent sideband reception. T he antenna 
> input was changed to balanced feed and BFO/AGC provisions 
> were also added to allow diversity operation.
> ----- Original Message -----
>
> From: "Les Locklear" <leslocklear at hotmail.com>
> To: "Bob Camp" <kb8tq at n1k.org>, kgordon2006 at frontier.com
> Cc: Hammarlund at mailman.qth.net
> Sent: Friday, August 29, 2014 12:25:13 PM
> Subject: Re: [Hammarlund] ITT modified SP-600
>
> This was taken from the Hammarlund SP-600 models page:
>
> Another variant was the R-450/FRR-28. These were standard 
> Hammarlund JX
> receivers that were modified by Northern Radio; USN stock 
> no. F
> 16-Q-112117-200, contract number Nobsr-52132, 19 December, 
> 1950. These were
> designated SP-600-MX. Installed in a relay rack cabinet 
> with a LS-187/UR
> speaker, AM-615/UR amplifier detector, KY-79 keyer, 
> O-165/UR high stability
> oscillator, S-224/UR patch panel and an AN/URA-8 fsk 
> converter-comparator.
> The X-tal frequency control at the top r.h corner was 
> removed and covered
> with a Buships/Northern Radio order no. nameplate. 
> Northern Radio located in
> New York City made many modifications available for 
> SP-600's such as an IF
> gain control located where the dial lock was normally 
> located. This was a
> very common military modification.
>
> Les
>
> -----Original Message----- 
> From: Bob Camp
> Sent: Friday, August 29, 2014 12:20 PM
> To: kgordon2006 at frontier.com
> Cc: Hammarlund at mailman.qth.net
> Subject: Re: [Hammarlund] ITT modified SP-600
>
> Hi
>
> F.S. TELEG = Frequency Shift (Keying) Telegraphy. More 
> commonly known as
> FSK.
>
> Bob
>
> On Aug 29, 2014, at 12:17 PM, Kenneth G. Gordon 
> <kgordon2006 at frontier.com>
> wrote:
>
>> Well, the data-plate associated with the BFO says, "MOD 
>> FOR I.S.B. AND
>> F.S. TELEG."
>>
>> I know that ISB is Independent Side Band, but what, 
>> exactly, is F.S.
>> TELEG?
>> Some sort of RTTY, I would suppose.
>>
>> Anyway, it is very interesting, and the receiver looks to 
>> be in excellent
>> condition. I wish we knew fuller details of the mod.
>>
>> Price is way too much for me, though.
>>
>> Ken W7EKB