56506Re: [softrock40] Low pass filters
- Jul 4, 2011Hi Chuck,
The external LP filters are needed with the multi-band version of the RXTX Ensemble to reduce the second harmonic of the lowest band by about four dB or so. This results in all spurious outputs being at least -43 dB down.
Tony Parks kb9yig@... http://www.kb9yig.com
On Mon, 2011-07-04 at 12:12 +0000, Chuck wrote:
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?
- << Previous post in topic Next post in topic >>