56508Re: [softrock40] Re: Low pass filters
- Jul 4, 2011Chuck,
I was just trying to imagine a simple means of testing your filter design.
If you had a antenna analyzer and another softrock receiver you could emit from the analyzer (tune through the area of interest) and receive with the softrock and see the BP on the SR spectrum. I think that would work.
From: Chuck <chuck@...>
Sent: Monday, July 4, 2011 7:59 AM
Subject: [softrock40] Re: Low pass filtersJohn,
That is where I'm trying to get to. I was just looking at the builders notes to figure out how to go about it. The Elsie results were not what I expected so understanding what to expect from my own filter design is job one.
--- In firstname.lastname@example.org, JOHN GREUSEL <greusel@...> wrote:
> I could be wrong but I believe the correct approach is to put filters for all bands you're going to use after the amplifier (pennywhistle) I don't think the built in filters for 30 and 20 will be sufficient for adequate suppression after the amplifier. If you want to design and construct your own system why don't you put in a three position switch and have a new BP filter for each band? They're simple enough to create.
> From: Chuck <chuck@...>
> To: email@example.com
> Sent: Monday, July 4, 2011 7:12 AM
> Subject: [softrock40] Low pass filters
> Lately, I've been thinking about the low pass filters that Robby calls out in his section on external coonnections in the Ensemble RXTX builders notes. Since I built the 20/30/40 veersion I'll be interested in the 40m LPF. I just downloaded and installed Elsie, a very nice filter design program, and entered the values Robby cals out. I'm seeing around -11dB at 14MHz. I thought this was supposed to be -43dB from the fundemental of 7MHz. Have I found a bug in the design or, more likely, where have I gone wrong in my thinking?
> Thank you,
> Chuck Lippmeier
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