Re: [Elecraft] K3: Would not it be nice...
To answer your last question, PA3AKE has published 3rd Order Dynamic Range data with both signals in the passband of the roofing filter of a homebrewed receiver's front end. You might like to look at his website. In my experience when working 40m SSB DX zero beat with a BC station's carrier, maintaining a large in- passband receiver dynamic range helps a lot. 73, Geoff GM4ESD Arie Kleingeld PA3A wrote on Wednesday, April 02, 2008 11:44 PM Would not it be nice... if someone measured the IMD dynamic range of the K3 with the interfering signals placed within the bandwidth of the first IF (roofing) filter? Or has that one already been published somewhere? Or is that impossible to measure? Arie PA3A ___ 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
RE: [Elecraft] K3: Would not it be nice...
For a graphic representation of Joe's point, check out the BDR section of my LP-PAN web page at http://www.telepostinc.com/LP-PAN.html I ran some tests of the K3/LP-PAN combo for very close in interference. The phase noise issue pointed out by Joe can be seen quite easily in the panoramic display. As you slide the interfering signal toward the wanted one, the noise sidebands of the interfering signal become higher than the noise floor, and eventually louder than the desired signal. In my test, I slid a very clean S9+63dB signal from an analog HP generator toward a 3uV desired signal, and the noise sidebands were just audible at a bit over 3 kHz spacing. With the interfering signal at S9+18dB, the sidebands could be heard at about 800 Hz spacing. With this strength of interference, the interfering signal had to be within about 200 Hz to wipe out the desired signal. This would be worse with a synthesized rig as the interference, of course, or a signal with modulation (even CW). At this signal level (just below the HAGC threshold), the K3's DSP dynamic range is high enough that AGC could be disabled, avoiding pumping. It's a moot point, however, since you're not likely to find interference this clean in practice, unless your neighbor has a xtal controlled QRP rig ;-) 73, Larry N8LP -- Message: 49 Date: Wed, 2 Apr 2008 22:29:33 -0400 From: Joe Subich, W4TV [EMAIL PROTECTED] Subject: RE: [Elecraft] K3: Would not it be nice... To: 'Arie Kleingeld PA3A' [EMAIL PROTECTED], elecraft@mailman.qth.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=US-ASCII Nobody makes 500 Hz IMD dynamic range measurements - they are meaningless but that is what it would take to get both interfering signals inside the passband of the 2.7 KHz roofing filter. Sherwood has made some very close in blocking dynamic range measurements but I do not know if he has released that data. The essence of the private e-mail is that even at 1 KHz the limiting factor in the K3 is not blocking but phase noise performance of the K3 and/or the interfering signal. The final analysis is that key clicks and phase noise from signals less than 1 KHz way would be more of a problem than either IMD or blocking. 73, ... Joe, W4TV ___ 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
RE: [Elecraft] K3: Would not it be nice...
For a graphic representation of Joe's point, check out the BDR section of my LP-PAN web page at http://www.telepostinc.com/LP-PAN.html The 5 KHz and 2 KHz examples with LP-Pan and PowerSDR are worst case for the K3 and would be equivalent to using the FM filter for all modes. Even at 2 KHz, the interfering carrier would be nearly 30 dB down the skirt of the 2.8 KHz/8 pole filter and any IMD between it and another signal even farther away would be down significantly (assuming the CW signal is centered). Phase noise, key clicks and transmitted IMD from other stations will be the limiting factor for receiver performance in the K3. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Phipps Sent: Thursday, April 03, 2008 9:15 AM To: elecraft@mailman.qth.net Subject: RE: [Elecraft] K3: Would not it be nice... For a graphic representation of Joe's point, check out the BDR section of my LP-PAN web page at http://www.telepostinc.com/LP-PAN.html I ran some tests of the K3/LP-PAN combo for very close in interference. The phase noise issue pointed out by Joe can be seen quite easily in the panoramic display. As you slide the interfering signal toward the wanted one, the noise sidebands of the interfering signal become higher than the noise floor, and eventually louder than the desired signal. In my test, I slid a very clean S9+63dB signal from an analog HP generator toward a 3uV desired signal, and the noise sidebands were just audible at a bit over 3 kHz spacing. With the interfering signal at S9+18dB, the sidebands could be heard at about 800 Hz spacing. With this strength of interference, the interfering signal had to be within about 200 Hz to wipe out the desired signal. This would be worse with a synthesized rig as the interference, of course, or a signal with modulation (even CW). At this signal level (just below the HAGC threshold), the K3's DSP dynamic range is high enough that AGC could be disabled, avoiding pumping. It's a moot point, however, since you're not likely to find interference this clean in practice, unless your neighbor has a xtal controlled QRP rig ;-) 73, Larry N8LP -- Message: 49 Date: Wed, 2 Apr 2008 22:29:33 -0400 From: Joe Subich, W4TV [EMAIL PROTECTED] Subject: RE: [Elecraft] K3: Would not it be nice... To: 'Arie Kleingeld PA3A' [EMAIL PROTECTED], elecraft@mailman.qth.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=US-ASCII Nobody makes 500 Hz IMD dynamic range measurements - they are meaningless but that is what it would take to get both interfering signals inside the passband of the 2.7 KHz roofing filter. Sherwood has made some very close in blocking dynamic range measurements but I do not know if he has released that data. The essence of the private e-mail is that even at 1 KHz the limiting factor in the K3 is not blocking but phase noise performance of the K3 and/or the interfering signal. The final analysis is that key clicks and phase noise from signals less than 1 KHz way would be more of a problem than either IMD or blocking. 73, ... Joe, W4TV ___ 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 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
Re: [Elecraft] K3: Would not it be nice...
The example wasn't meant to be K3 specific, but rather to graphically show the concept of why transmitted phase noise is such an important factor with close in interference. The overall BW in these examples is actually 192 kHz! Larry N8LP Joe Subich, W4TV wrote: For a graphic representation of Joe's point, check out the BDR section of my LP-PAN web page at http://www.telepostinc.com/LP-PAN.html The 5 KHz and 2 KHz examples with LP-Pan and PowerSDR are worst case for the K3 and would be equivalent to using the FM filter for all modes. Even at 2 KHz, the interfering carrier would be nearly 30 dB down the skirt of the 2.8 KHz/8 pole filter and any IMD between it and another signal even farther away would be down significantly (assuming the CW signal is centered). Phase noise, key clicks and transmitted IMD from other stations will be the limiting factor for receiver performance in the K3. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Phipps Sent: Thursday, April 03, 2008 9:15 AM To: elecraft@mailman.qth.net Subject: RE: [Elecraft] K3: Would not it be nice... For a graphic representation of Joe's point, check out the BDR section of my LP-PAN web page at http://www.telepostinc.com/LP-PAN.html I ran some tests of the K3/LP-PAN combo for very close in interference. The phase noise issue pointed out by Joe can be seen quite easily in the panoramic display. As you slide the interfering signal toward the wanted one, the noise sidebands of the interfering signal become higher than the noise floor, and eventually louder than the desired signal. In my test, I slid a very clean S9+63dB signal from an analog HP generator toward a 3uV desired signal, and the noise sidebands were just audible at a bit over 3 kHz spacing. With the interfering signal at S9+18dB, the sidebands could be heard at about 800 Hz spacing. With this strength of interference, the interfering signal had to be within about 200 Hz to wipe out the desired signal. This would be worse with a synthesized rig as the interference, of course, or a signal with modulation (even CW). At this signal level (just below the HAGC threshold), the K3's DSP dynamic range is high enough that AGC could be disabled, avoiding pumping. It's a moot point, however, since you're not likely to find interference this clean in practice, unless your neighbor has a xtal controlled QRP rig ;-) 73, Larry N8LP -- Message: 49 Date: Wed, 2 Apr 2008 22:29:33 -0400 From: Joe Subich, W4TV [EMAIL PROTECTED] Subject: RE: [Elecraft] K3: Would not it be nice... To: 'Arie Kleingeld PA3A' [EMAIL PROTECTED], elecraft@mailman.qth.net Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=US-ASCII Nobody makes 500 Hz IMD dynamic range measurements - they are meaningless but that is what it would take to get both interfering signals inside the passband of the 2.7 KHz roofing filter. Sherwood has made some very close in blocking dynamic range measurements but I do not know if he has released that data. The essence of the private e-mail is that even at 1 KHz the limiting factor in the K3 is not blocking but phase noise performance of the K3 and/or the interfering signal. The final analysis is that key clicks and phase noise from signals less than 1 KHz way would be more of a problem than either IMD or blocking. 73, ... Joe, W4TV ___ 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 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
RE: [Elecraft] K3: Would not it be nice...
Nobody makes 500 Hz IMD dynamic range measurements - they are meaningless but that is what it would take to get both interfering signals inside the passband of the 2.7 KHz roofing filter. Sherwood has made some very close in blocking dynamic range measurements but I do not know if he has released that data. The essence of the private e-mail is that even at 1 KHz the limiting factor in the K3 is not blocking but phase noise performance of the K3 and/or the interfering signal. The final analysis is that key clicks and phase noise from signals less than 1 KHz way would be more of a problem than either IMD or blocking. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Arie Kleingeld PA3A Sent: Wednesday, April 02, 2008 6:45 PM To: elecraft@mailman.qth.net Subject: [Elecraft] K3: Would not it be nice... Would not it be nice... if someone measured the IMD dynamic range of the K3 with the interfering signals placed within the bandwidth of the first IF (roofing) filter? Or has that one already been published somewhere? Or is that impossible to measure? Arie PA3A ___ 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 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
