[R-390] Mechanical filter substitute

[Bob Camp]

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
>> _____________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/faq.htm
>> Post: mailto:R-390 at mailman.qth.net
>> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>
>
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>