++++++++++++++++++++++++++++++ Date: Fri, 4 May 2001 12:27:35 -0500 From: "Joe Wittmer" Subject: [Elecraft] IMD Mod - AFC Level Hi Group, I performed the IMD on my SSB adapter yesturday. I am very pleased... I do have a cockpit question regarding the ALC meter. When I adjust AF IN level to the K2, I see only a bar indication at the rightmost LED. To adjust the level I increase the AF IN until I see the LED flash then stop. Is this the correct procedure for setting AF IN? And, Is the display I am seeing normal? I was thinking I should see a display similar to the RF display where the display increased left to right. Thanks a bunch. 73 Joe KB9SIZ Bement, Illinois SN 1921 +++++++++++++++++++++++++++++++ Date: Fri, 4 May 2001 11:32:56 -0700 From: "Ron D'Eau Claire" Subject: RE: [Elecraft] IMD Mod - AFC Level Joe KB9SIZ asked: "question regarding the ALC meter. When I adjust AF IN level to the K2, I see only a bar indication at the rightmost LED. To adjust the level I increase the AF IN until I see the LED flash then stop.... Is this the correct procedure for setting AF IN?... And, Is the display I am seeing normal?" This is the normal display. There is an explanation in the manual that the r-f and signal strength readings on the bar graph go left to right and the ALC reads the OPPOSITE direction - RIGHT to LEFT - so you can tell very quickly that you have the display in ALC mode... (NOTE FROM ED... Above paragraph corrected based on follow on entries..) When a bar on the right end blinks, the ALC is holding down the audio gain to prevent over-driving the balanced modulator, so you have plenty of audio coming in at that point. The number of bars you see for a given audio input will vary according to the band, usually being less on 10 meters. That's because the gain of the r-f amplifiers in the transmitter varies with the different bands, and it takes more audio input to drive the K2 to a full 10 watts on some bands. Usually 10 meters is the band where the overall r-f gain is least. That is, if you transmit in CW with the r-f POWER control full clockwise, 10 meters is the band where most ops find they have the lowest maximum r-f output. So if you have enough audio to drive your K2 to 10 watts on 10 meters and see a bar flicker on the right in ALC, you will likely notice that two or even three bars flicker in ALC on other bands where the gain of the transmitter amplifiers is greater - such as 40 meters. That means that the ALC is acting normally and turning the audio down further to keep the maximum PEP output at 10 watts. Of course, you should always limit your r-f output to 10 watts maximum running SSB voice to avoid excessive distortion. Elecraft says that the IMD specification is only good at 10 watts PEP and below, even on those bands where the K2 can put out more power in CW. Also, you need to limit your SSB power if you are running a 'high duty cycle' mode such as PSK-31 to avoid overheating the finals. The 10 watt PEP specification assumes voice transmission in which the average power level is far below the 10 watt level. I believe the recommended maximum output for PSK 31 and similar modes is 5 watts PEP output. Another point about the 'proper audio level' if you are running PSK. With PSK is better to avoid having the ALC act at all. The ALC adds a little distortion to the signal. Many ops set their POWER control to 10 watts, then adjust the audio input to show 5 watts PEP on the r-f output meter. The ALC display should show no bars at all, indicating that the audio level is well below that at which the ALC will begin operating. Of course, that means that you have to reset your audio level if you change bands too. Ron AC7AC K2 # 1289 ++++++++++++++++++++++++++++++++++++++++++ Date: Sat, 5 May 2001 09:41:39 -0500 From: "Ed Juge/NM" Subject: Re: [Elecraft] IMD Mod - AFC Level ALC is supposed to read right to left. Like Ron, however, I never see more than one bar. Asked Gary Surrency about this and he said it is normal... not to worry about it, but to use the RF indication instead. 73... Ed, W5EJ ++++++++++++++++++++++++++++++++++++++++ Date: Mon, 28 Jan 2002 09:16:12 -0800 From: Eric Swartz WA6HHQ - Elecraft Organization: EleCraft To: "Julian, G4ILO" Cc: Elecraft List Subject: Re: [[Elecraft] Digipan not available...] >From our shipping status page: All KSB2s shipped after Sept 5, 2001 include the KI6WX PSK31 IMD mods. (Only part value changes were required.) 73, Eric "Julian, G4ILO" wrote: > > I would advise doing the SSB board mod that allows you to use the ALC to > limit the output power, +++++++++++++++++