[Hammarlund] {Collins} more on Collins Filter for Hammarlund

Sat Sep 15 10:27:11 EDT 2012

All,

Rodger WQ9E found a 1955 August Radio and Television News which which featured the filter in question.  They were available in .8, 1.2, 3.1 and 6.0 Kc and for the SP-600.

Thank you all for your help.

Brian Harris, WA5UEK
cell 214-763-5977
email cosmophone at yahoo.com

________________________________
 From: susy <jonesjames at imonmail.com>
To: A R <raf_3 at msn.com>; Richard Knoppow <dickburk at ix.netcom.com>; Brian Harris <cosmophone at yahoo.com>; Collins Collectors Association <COLLINS at LISTSERVE.COM>; Hammarlund <hammarlund at mailman.qth.net> 
Sent: Saturday, September 15, 2012 9:15 AM
Subject: Re: {Collins} more on Collins Filter for Hammarlund

There were quite a number of "filter adapters"/filter conversion kits with 353/354 model numbers.

One was recently sold on ebay that was a 1.2 kHz unit (MFA-2) and was said to be for the SP-600.

I have never seen anything on any of the SP-600 sites that mentioned the adapters.  There have been some filter conversion articles for some of the Hammarlund receivers, but none ever mentioned the adapter.

Nothing mentioned in any of the listings for any of the military units, although there were some contracts that were considered to be CIA that may have used the adapters, but I suppose we will never know for sure.

The adapters had model numbers such as 353A12, so I assume the last digits were the bandwidth indicators.  I found:  05, 08,1, 12, 14, 15, 31 and 60. Looks as though once you plugged in the adapter, you were limited to that bandwidth until you plugged in a different adapter.  Seems like that might not be to good for hams, but would be great if you had a rack with a bunch of receivers.

There was an adapter for the HRO-60, but I think it was National not Collins.  There was also a Mackay adapter for the SP-600.

More investigation needed on this one!

73
Jim w0nkn

-----Original Message----- From: A R
Sent: Saturday, September 15, 2012 3:05 AM
To: Richard Knoppow ; Brian Harris ; Collins Collectors Association ; Hammarlund
Subject: Re: {Collins} more on Collins Filter for Hammarlund

The 9003 is a remote-cutoff pentode, and an understandable choice if the original stage is AGC-controlled. The Collins plug-in filter adapters were generally designed to replace the 1st IF tube, with the original control features (including AGC if used in the original stage design), and enough gain to compensate for the mechanical filter attenuation or loss. To the best of my recollection, the Hammarlund commercial (ham/swl) receivers used tube sockets without chassis "wells" for bayonet shields, as the commercial receivers used slip-on tube shields, and only the mil receivers used bayonet tube shields. Brian's filter adapter has an extension on the male chassis plug pins that suggests it's designed to accommodate the depth of a tube socket well originally intended for a bayonet shield. My guess is that the filter adapter is for a mil-design Hammarlund outfitted with 7-pin and 9-pin miniatures........like the SP-600. Just an educated guess.......no
 guarantees.

Allen-----W7GIF

----- Original Message -----  From: Richard Knoppow<mailto:dickburk at ix.netcom.com>
To: Brian Harris<mailto:cosmophone at yahoo.com> ; Collins Collectors Association<mailto:COLLINS at LISTSERVE.COM> ; Hammarlund<mailto:hammarlund at mailman.qth.net>
Sent: Friday, September 14, 2012 11:52 PM
Subject: Re: {Collins} more on Collins Filter for Hammarlund

      The choice of tubes is curious. Both are sharp cut off
pentodes designed for VHF use.  I wonder why they were used
here instead of some more conventional type such as a 6BA6.
While Collins applies AVC to the 6AK5's in both the 51J and
75A receivers its not really meant for it.  I don't have
complete data on the 9003, probably on the web somewhere.
Collins mostly knew what they were doing so I suppose there
was a good reason for this.

--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com<mailto:dickburk at ix.netcom.com>

----- Original Message -----  From: "Brian Harris" <cosmophone at yahoo.com<mailto:cosmophone at yahoo.com>>
To: "Collins Collectors Association"
<COLLINS at LISTSERVE.COM<mailto:COLLINS at LISTSERVE.COM>>; "Hammarlund"
<hammarlund at mailman.qth.net<mailto:hammarlund at mailman.qth.net>>
Sent: Friday, September 14, 2012 6:30 PM
Subject: {Collins} more on Collins Filter for Hammarlund

I've learned a little more about the mysterious Collins-made
3.1Kc filter for a yet-to-be-determined Hammarlund piece
which is no doubt a receiver. It uses a 6AK5 and a 9003,
which is silkscreened near the tubes. The Collins part
number is 522 9032 014. The Hammarlund part number is MFA-3.
The unit plugs into a 7 pin miniature tube socket. I've
uploaded a picture of the filter at
http://www.myhamshack.com/WA5UEK/<http://www.myhamshack.com/WA5UEK/>. I would very much like to
determine what receiver this was meant for.

Brian Harris
cell 214-763-5977
email cosmophone at yahoo.com<mailto:cosmophone at yahoo.com>

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NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)

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