FW: [Elecraft] Attenuation at narrow bandwidths NOT!
Do overs! What I really proved is that the AGC circuit works really well. Nobody spotted the error in my Setup, I.E., AGC OFF not specified. I just reran the test with AGC off. Results are still excellent, but not as perfect as I reported yesterday. Bandwidth Setting Peak 0.00 -41 0.10 -35 0.20 -34 0.30 -31 0.40 -30 0.50 -29 0.60 -29 0.70 -29 0.80 -30 0.90 -31 1.00 -30 1.25 -32 1.50 -32 1.75 -33 2.00 -34 2.25 -32 2.49 -33 OP1 -36 My perception of "No Attenuation" comes from my standard practice of cycling between 0.90, 0.50 and 0.20 (-31, -29 and -34 respectively) plus the AGC working made me think it was flatter than it is. However, 5db isn't too bad if the S9+ interfering signal disappears. Dan / WG4S / K2 #2456 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Dan Barker Sent: Thursday, December 09, 2004 8:25 AM To: Elecraft Subject: [Elecraft] Attenuation at narrow bandwidths NOT! Don, you got me thinking. Why would you say something like that? My K2 filters are EXCELLENT! But, I decided to test it out to prove my belief. Test Setup: Freq 7.040. Mode CW Normal. Set FL4 width to 0.00 (FL4 has the BFO for a "reasonable" left skirt. I didn't want to change frequency, just bandwidth. Broadband noise source on ANT2, Antenna selector to ANT2. Spectrogram on Fixed Audio Out (top of AF pot). Peak Hold on, wait for the graph to "fill in". Measure the peak, and the amplitude of the -6db points for bandwidth calculation. Note: BWs above 1,200 hz have significant ripple (not unexpected). However these bandwidths are not particularly useful to me. I measured the peak as above, and measured the -6db points on the far right hump. The ripple is at most 10db, but I'd measure the -6db point of the next hump. Not that it matters anyhow at 2.49! I imagine anyone wanting really wide CW reception is going to use OP1 anyway. Repeat measurements with FL4 bandwidth 0.10 (or more) higher. After 2.49, use OP1. Finally, return FL4 bw to operating BW, in my case, 0.20. Verify trace is still centered on my sidetone (it was). Raw data available at ftp://ftp.visioncomm.com/k2filter.xls, anonymous, your email address, bin, get. As these numbers appear to powerfully demonstrate the extremely excellent job done by the designers, I'll be happy to compare notes with any K2 owner with less stellar performance. EVERY K2s filter plots should look this good. I'm not sure what to compare tho, to find a discrepancy. Wayne? Eric? Ideas?. As I normally S&P with the 0.90, and work heavy QRM at 0.20, the ZERO db attenuation is what I notice. If I lose AF volume with FL4, then I AM OFF FREQ. It's not my filter. Dan Barker / WG4S / K2 #2456 Summary: Bandwidth -6db Bandwidth Setting Peak Measured 0.00 -43109 0.10 -43133 0.20 -43158 0.30 -42178 0.40 -42200 0.50 -42231 0.60 -42263 0.70 -42292 0.80 -42352 0.90 -43421 1.00 -42450 1.25 -43663 1.50 -43897 1.75 -42 1231 2.00 -43 1574 2.25 -44 1894 2.49 -45 2103 OP1 -47 1784 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Attenuation at narrow bandwidths NOT!
> -Original Message- > From: W3FPR - Don Wilhelm [mailto:[EMAIL PROTECTED] > Sent: Tuesday, December 07, 2004 3:50 PM > To: Dan Barker > Subject: Re: Discrete Passband Tuning Revisited > > > Dan, > > I must disagree - you must have a very good K2 CW filter - don't change it. I won't. > > There ARE K2s that have signifigant attentuation at bandwidths more narrow > than 200 Hz. One of mine is good to 150 Hz and the other is good only to > 180 Hz. I have built and worked on many K2s, and they are all a bit > different in the filter attenuation aspect - depends on the precise crystal > mix, component tolerances, construction techniques, etc. > Interesting, let's see. See below. > 73, > Don W3FPR Don, you got me thinking. Why would you say something like that? My K2 filters are EXCELLENT! But, I decided to test it out to prove my belief. Test Setup: Freq 7.040. Mode CW Normal. Set FL4 width to 0.00 (FL4 has the BFO for a "reasonable" left skirt. I didn't want to change frequency, just bandwidth. Broadband noise source on ANT2, Antenna selector to ANT2. Spectrogram on Fixed Audio Out (top of AF pot). Peak Hold on, wait for the graph to "fill in". Measure the peak, and the amplitude of the -6db points for bandwidth calculation. Note: BWs above 1,200 hz have significant ripple (not unexpected). However these bandwidths are not particularly useful to me. I measured the peak as above, and measured the -6db points on the far right hump. The ripple is at most 10db, but I'd measure the -6db point of the next hump. Not that it matters anyhow at 2.49! I imagine anyone wanting really wide CW reception is going to use OP1 anyway. Repeat measurements with FL4 bandwidth 0.10 (or more) higher. After 2.49, use OP1. Finally, return FL4 bw to operating BW, in my case, 0.20. Verify trace is still centered on my sidetone (it was). Raw data available at ftp://ftp.visioncomm.com/k2filter.xls, anonymous, your email address, bin, get. As these numbers appear to powerfully demonstrate the extremely excellent job done by the designers, I'll be happy to compare notes with any K2 owner with less stellar performance. EVERY K2s filter plots should look this good. I'm not sure what to compare tho, to find a discrepancy. Wayne? Eric? Ideas?. As I normally S&P with the 0.90, and work heavy QRM at 0.20, the ZERO db attenuation is what I notice. If I lose AF volume with FL4, then I AM OFF FREQ. It's not my filter. Dan Barker / WG4S / K2 #2456 Summary: Bandwidth -6db Bandwidth Setting Peak Measured 0.00 -43109 0.10 -43133 0.20 -43158 0.30 -42178 0.40 -42200 0.50 -42231 0.60 -42263 0.70 -42292 0.80 -42352 0.90 -43421 1.00 -42450 1.25 -43663 1.50 -43897 1.75 -42 1231 2.00 -43 1574 2.25 -44 1894 2.49 -45 2103 OP1 -47 1784 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
