[Hammarlund] [Boatanchors] Collins 3.1 KC filter question

[Richard Knoppow]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
Cc: <Hammarlund at mailman.qth.net>; "National Radio Equipment" 
<national at mailman.qth.net>
Sent: Thursday, September 13, 2012 10:08 AM
Subject: Re: [Hammarlund] [Boatanchors] Collins 3.1 KC 
filter question


> On 13 Sep 2012 at 8:52, Richard Knoppow wrote:
>
>> Good Morning All,
>>
>> Collins made a filter for Hammarlund which is designated
>> "MFA-3 3.1 KC filter". Does anyone know which piece of
>> Hammarlund equipment this was for? Google was not my 
>> friend
>> in this inquiry.
>
> I have seen advertisments, and examples for sale on eBay, 
> of such filters which were made
> for Hammarlund receivers, HRO receivers, and for others.
>
> I cannot now remember which companies offered those for 
> sale, but I am reasonably certain
> Collins was one of the companies involved.
>
> These were complete units containing a Collins filter and 
> two tubes. The unit was mounted
> on an octal socket so that all that was required was to 
> unplug the 1st 455 KHz IF tube, and
> plug this in place of the tube. No other changes were made 
> to the receiver.
>
> Those very few I have seen on eBay went for prices 
> comparable to that for an entire receiver.
>
> I also have an article from a GE Ham News detailing 
> exactly how to make those units. I
> suspect that this GE Ham News article preceded the 
> offering by Collins and others.
>
> Go here:
>
> http://www.w7ekb.com/glowbugs/rx/receivers.htm
>
> then scroll down to 5) Packaged Selectivity.
>
> There are a number of PDFs offered there: one is the 
> complete article, the others are
> individual pages since the complete article consists of a 
> quite-large file and would take some
> time to download without a high-speed internet connection.
>
> Ken Gordon W7EKB

      The difference may have been in the plug.  The SP-600 
uses 6BA6 tubes in the IF which are 7-pin miniatures while 
the SP-400 and 200 and the HRO use octal-based tubes. There 
are probably other differences to account for mechanical 
clearances.


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