[R-390] Filter Options II

[Bob Camp]

Hi

They sold a *lot* of those IF decks with filters on them. A lot of people bought "more than one" for spares. I certainly did. I have absolutely no idea what shape the filters are in. I'll dig into them when I loose a filter….

Bob

On Feb 18, 2013, at 9:17 AM, djed1 at aol.com wrote:

> 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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