[R-390] Mechanical filter substitute

[Jon Schlegel]

100k - Ugh.  Now that's just convenient!

At 12:18 PM 12/18/2007 -0500, you wrote:
>Hi
>
>The R-390A filters are high impedance. I don't remember the exact
>numbers, but > 100K ohms would not surprise me at all.
>
>Bob
>
>
>On Dec 18, 2007, at 12:09 PM, Jon Schlegel wrote:
>
>>Thanks for all the info guys,
>>
>>Bob C - I'll cobb in the 10k to see what happens.  BTW, Maybe Bob N.
>>should try using one of the Motorola Permakay filters.  Think I
>>still got a few around here somewhere...
>>
>>Also what are the in/out Zs of the mechanical filters.  If I want to
>>measure one what source/load should it be looking into?
>>
>>Jon
>>
>>
>>
>>At 09:23 AM 12/18/2007 -0600, you wrote:
>>>On Dec 18, 2007 9:14 AM, Bob Camp <ham at cq.nu> wrote:
>>>
>>> > Before you go to crazy - sling a 10K ohm resistor between input and
>>> > output directly on the filter.
>>>
>>>Good tip, Bob.   And it reminded me - at the Belevidere IL hamfest
>>>I saw a Collins 75A series receiver that had a homebrew "filter
>>>replacement" in it.  This was a small perf-board with a couple of
>>>chokes and capacitors which would obviously be for wideband AM but
>>>I thought it would be neat to give it a try.   Of course I forgot
>>>to go back and sketch the circuit!   Wonder if anyone knows about
>>>this and has the design details?
>>>
>>>73, Bob W9RAN
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>>
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