Re: Best Gain Settings for 137 mhz reception


On 2017-09-13 10:35, doug wrote:
On 09/13/2017 06:40 AM, Ruben Navarro Huedo (EA5BZ) wrote:
Hello friends:

Thank's again for ALL your posts.
I'm learning a lot with this thread.
Today i have received the BCFM Notch filter and it is doing a GREAT Job.
Finally i bought RTL-SDR BCFM Filter.

One more question:
Where is the best place to install this filter?
My setup now is:
Antenna --> BCFM Filter --> LNA4ALL --> Coax --> Airspy R2

This evening i will test with NOAA's and Meteor M2.

Thank's again.
From the display, it seems to be doing its job. The FM station is 32 dB below your desired signal. Since the filter is a notch, it should have almost no attenuation in the desired band, and thus you have it
where it will do the most good.  --doug, WA2SAY
If the LNA4ALL is not being overloaded and the problem is simply AIRSPY saturation moving the filter after the LNA will purchase a modest noise figure improvement. If the LNA4ALL is generating IMD then the filter must go up front.

As a side point if the filter works placed after the LNA4ALL he can probably place it at the AIRSPY end of the coax. This will make it easier to take the filter out of the chain if he starts working on frequencies the BCFM stations are not a problem for the R820T.

{^_^} Joanne

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