[Hammarlund] [National] [Boatanchors] Collins 3.1 KC filterquestion

[Richard Knoppow]

----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>; "National 
Radio Equipment" <national at mailman.qth.net>; 
<kgordon2006 at frontier.com>
Cc: "National Radio Equipment" <national at mailman.qth.net>; 
<Hammarlund at mailman.qth.net>
Sent: Thursday, September 13, 2012 11:24 AM
Subject: Re: [National] [Hammarlund] [Boatanchors] Collins 
3.1 KC filterquestion


>
> ----- Original Message ----- 
> From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
> To: <kgordon2006 at frontier.com>
> Cc: "National Radio Equipment" <national at mailman.qth.net>; 
> <Hammarlund at mailman.qth.net>
> Sent: Thursday, September 13, 2012 1:36 PM
> Subject: Re: [National] [Hammarlund] [Boatanchors] Collins 
> 3.1 KC filterquestion
>
>
>>
>> ----- 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
>
>
> The SP-200 IF is 465 KHz and predated and was out of 
> production before Collins mechanical filter release by 
> several years. The only early Hammarlund interest was in 
> the Zenith design.
>
> Post WW2 adaptors were only available for the SP-400, 
> HRO-60, and later the NC-400 which was not a Collins built 
> assembly.
>
> Carl
> KM1H
>
>
     You are right, the IF frequency is different. 465Khz 
was obsolete by the time these adaptors were made and AFAIK 
no mechanical filters were made for it.


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