[R-390] Filter Options II

[djed1 at aol.com]

Probably a lot of filters out there- I have a set of spare filters stashed away.  What I don 't know is whether they are deteriorating as they sit in the box.  My R-390A has been in my possession for 30 years and has  seen light use all that time.  I hope that the deterioration of the foam in the filters is somewhat related to the operating temperature.
Ed  W2EMN

 

 

 

-----Original Message-----
From: Bob Camp <ham at kb8tq.com>
To: r-390 at mailman.qth.net Group <r-390 at mailman.qth.net>
Sent: Sun, Feb 17, 2013 10:14 pm
Subject: Re: [R-390] Filter Options II


Hi

I keep coming back to another option:

How many IF modules are there still out there? The world was awash in them a 
while back. I have a suspicion there are many more out there than one might 
think.
 
Bob

On Feb 17, 2013, at 5:00 PM, Perry Sandeen <sandeenpa at yahoo.com> wrote:

> List,
> 
> Wrote: With the exception of watch crystals, the whole industry of sub 1 MHz 
crystals is pretty much a thing of the past. Yes, there are a couple of people 
who will make you this or that. You better have deep pockets to get them 
interested in whatever you need done. Yes, one of them is a buddy, but that only 
goes just so far.
> 
> Yea verily.
> 
> My take of the group’s replies is that:
> 
> 1. Crystal filters are out of the question unless one does and up 
converter/down converter to use some of the commercial filters used in the rice 
box radios.  Probably a real PITA.
> 
> 2.  While ceramic filters can be used, the supply is probably extremely 
limited, even worse that getting a original Collins replacement filter for the 
“A”.
> 
> 3.  Use the Lankford roofing filter mod and stick to a 6 KHz or less 
bandwidth. For a $100 or so it is probably the most cost/time effective 
solution.
> 
> 4.  Convert your “A” to a R-725 and selling your remaining good filters on 
epay to help offset the conversion cost.  Takes a lot of time and patience to 
convert the I.F. to 6 volt filaments. (Yes Tisha, I have 3 to do when I get 
a-round-to-it.)
> 
> 5.  Something microprocessor based would be too complex for the vast majority 
of us.
> 
> Regards,
> 
> Perrier
> 
> 
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