[R-390] Filter Options II

[Bob Camp]

Hi

One very real question is - do some batches of filters hold up better than others? 

The "stuff" turning into goo should be just as detrimental to a 16 KHz filter as to a 4 KHz filter. Neither one will last long hanging from the support wires. We have a lot of data that 4 KHz seems to fail much more often than the rest. I'm wondering if either they had a bad batch of 4 KHz filters or if they had to open them for re-tune more often than the rest. 

There may be a population of filters out there that will last a very long time. 

Bob


On Feb 18, 2013, at 9:57 AM, Cecil <chacuff at cableone.net> wrote:

> I would expect NOS filters to be about like NOS paper and electrolytic caps....to have aged just the same as an in service part...and possibly worse.  
> 
> Just my thoughts though...
> 
> Cecil
> 
> Sent from my iPad
> 
> On Feb 18, 2013, at 8:47 AM, Bob Camp <ham at kb8tq.com> wrote:
> 
>> 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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