[R-390] 4kc filter position silent

[John]

There's a writeup on mechanical filter testing on my web page.
http://jlkolb.cts.com/site/MFtest.htm

Needs a stable RF generator and wide dynamic range voltmeter for the 
filter frequency.  Of course, a spectrum analyzer with tracking 
generator works well also.  Receiver S meter and switchable attenuator 
could be used for measurement.

The trick is to know the input and output impedance of the filter, and 
properly match it to the test equipment.  For R-390A filters, it's 100 
Kohms and around 120 pF.

John  KK6IL

On 3/17/2017 6:25 PM, Frank Hughes wrote:
> Hi,
>
> Trying to locate the trouble w/ my R-390A 4kc filter.
>

> Frank
> KJ4OLL
>
>
> PS: I even knew how to test these, out of circuit, at one time.
>
> Why can I remember what a 1950’s TV commercial “LSMFT” stands for, but
> can’t recall exactly what the setup was I used to test these stoopit
> mechanical filters????
>
> https://www.youtube.com/watch?v=3R3ja4WYjCc&t=17s