[Hammarlund] [Boatanchors] Collins 3.1 KC filter question

[Kenneth G. Gordon]

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