++++++++++++++++++ From: "Scott Martin" To: , Subject: RE: [Elecraft] K2: SSB FL1 OP1 weaker audio output Date: Sun, 18 Aug 2002 11:36:38 -0400 Was just about to post this very same question :) I'm seeing the same thing. Just completed #2794 with ssb and there is a 6-10 db difference in audio level between opt1 and the stock K2 filters when testing with a noise generator. I added the 2nd Xtal filter mod and the attenuation is even more noticeable now. I have to run opt1 with AF gain near max on weak ones. CW on the stock filters NEVER needs to go above 12-1 o'clock even on the weakest sigs. In fact, if I run too much AF gain on the stock filters, the audio will start to clip it's so hot. Is this normal? Scott -----Original Message----- From: elecraft-admin at mailman.qth.net [mailto:elecraft-admin at mailman.qth.net]On Behalf Of JimWMiller at aol.com Sent: Sunday, August 18, 2002 10:51 AM To: elecraft at mailman.qth.net Subject: [Elecraft] K2: SSB FL1 OP1 weaker audio output Good Morning, I've been testing the SSB board and have encountered a problem. I wonder if others have delt with the same issue. 1. The audio output of the SSB FL1 OP1 filters are much weaker than FL2, FL3, and FL4. 2. Also when listening to WWV or CHU, USB is louder (6 db) than LSB. Transmit seems OK and looks clean on oscilloscope, Talked with a lighthouse station yesterday and got 549 in LSB, but used FL2 for receive. Here's action taken so far: 1. Recalibrated to WWV. I'm at least within 20 Hz. 2. Read up and used Spectrogram software and adjusted BFO. It looks pretty good. No obvious problem. 3. Have *not* rechecked SSB hardware yet. Any ideas? Any one had a similar problem? 73 & Tnx in advance, Jim WA2UMP K2:2679 ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: , Subject: RE: [Elecraft] K2: SSB FL1 OP1 weaker audio output Date: Sun, 18 Aug 2002 09:59:26 -0700 It's easier to mis-read the spectrogram display than you might think. Or, I should say, then I might have thought from my personal experience. So, for a first troubleshooting step, I recommend setting the BFO frequencies to the values shown in the SSB module manual and see if things are better. Those frequencies might not be exactly optimum, but they are so close that most ops can set them there and never no any difference. In my manual (Rev B), the recommended frequencies for OPT1 FL1 are 4913.5 for the LSB and 4916.3 for the USB. Possibly your symptoms might be caused by a defective crystal (or bad solder joint to a crystal or too much solder flowed into the pad and it is shorting to the crystal case on the top of the board), but that ought to stand out like a "sore thumb" on Spectrogram as well. There will be a BIG difference in the "sound" of the USB vs. LSB until you install the "2nd Xfil Flattening Mod" described in the Elecraft Builder's resources. John, KI6WX,developed a variation on the mod that produces an even slightly flatter response. See Sverre's (LA3ZA) outstanding page of Elecraft rig mods at http://www.qsl.net/la3za/K2/mod.html, and scroll down to "Improved version of 2nd stage crystal filter mod". A point of possible future interest: This mod has NO effect on your transmit audio, only the received audio. The 2nd Xfil is a simple crystal filter at the OUTPUT of the i-f amplifier that is active only in receive. But it has enough tilt to cause a very obvious difference in the sound of the upper vs lower sideband when listening. Ron AC7AC K2 # 1289 +++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: , , Cc: Subject: RE: [Elecraft] K2: SSB FL1 OP1 weaker audio output Date: Sun, 18 Aug 2002 12:17:34 -0700 .. I have not done the mod to smooth out the SSB ripple and yes that will probably equalize the pitch but can't fix the poor gain. ... 73 Jim WA2UMP K2:2679 I don't recall that doing the 2nd Xfil flattening mod had any noticeable effect on the "loudness" of one sideband over the other. It was more a matter of one sideband sounding very "tinny" because the slope of the filter caused a sharply rising characteristic toward the higher frequencies on one sideband. The poor gain definitely sounds like something else. Ron AC7AC K2 #1289 +++++++++++++++++++ From: Unifiedtx at aol.com Date: Wed, 28 Aug 2002 15:36:24 EDT To: elecraft at mailman.qth.net Subject: [Elecraft] K2 Adjustments for Identical Sounding Sidebands 
At the risk of being redundant and passing along what others may already be 
doing, I am submitting the following for adjusting the FL1 BFO to get the 
bandpass the same for LSB and USB.  Once the passband looks good on one 
sideband using Spectrogram, I print the passband picture.  Without adjusting 
the audio amplitude on the K2 or computer, I shift the K2 to the other 
sideband and print another passband picture.  I then superimpose the two 
printouts, hold them up to the light and determine which way I want to move 
one of the sidebands in CALFIL (moving the BFO frequency control parameter).  
After making the adjustment I run another printout to see if the slopes 
coincide (are superimposed). I repeat the process until they do.  Keep in 
mind the sideband that is changed will result in the need to change the CW or 
CWRev BFO frequency contol parameter in FL1 since the CW and CWRev bandwidths 
are the same as the sidebands in OP1 (as recommended by Elecraft).  The 
changes are made at 7Mhz, AGC off, AF filter off, AF to EXT SPKR (not front 
headphone jack), and using a noise generator. These are the setup parameters 
recommended by John Grebenkemper.  On the air tests show that both sidebands 
sound identical.  Roy Morris  W4WFB  K2/100 #2225

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