+++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "Gerhard, OE3ZK" , Subject: RE: [Elecraft] K2 SSB behaviour ? Date: Thu, 21 Mar 2002 11:41:33 -0800 > I'm a little bit puzzled with the SSB behavior of the K2! It > looks like it > needs different audio drive levels on the different bands to have the > bargraph indication going up to the actual CW power level. I also barely > see an > ALC indication using SSbA 3/SSbC 2:1. I have 8 watts CW into a > dummy load on > all bands > but SSB power out and ALC is much different indicated on some bands (i.e. > 10m). This seems to be dependent with the audio frequency also. A > high tone > whistle acts different on some bands as a low tone Ahhhhh. I just use the > bargraph indication for these observations. > > Is this a ALC problem ??? > Gerhard Kmet That's perfectly normal operation Gerhard. The ALC adjusts the audio level to produce the requested RF power output as measured at the antenna terminal. The overall r-f gain of the transmitter is different for different bands, tending to be lowest on 10 meters. So on those bands, like 10 meters, where the transmitter r-f strip overall gain is lowest, more audio is needed to drive the transmitter to full output. This shows up as LESS ALC action on those bands. On other bands like 40 or 80 meters where there is a LOT of gain in the r-f stages of the transmitter, you will see the ALC kicking higher, since it must turn down the audio level more in order to avoid excessive r-f output. It's very common to see just one bar of ALC action, barely, on 10 meters and see several bars of ALC on 40 or 80 meters. Of course, you should see full r-f output on all bands if your mic has enough output. The r-f bargraph display is 'peak reading' so it will show you what the actual peak SSB output is, while many external power meters are average reading and show a much lower r-f output depending upon the audio waveform. Ron AC7AC K2 # 1289 ++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'COLIN WHITMORE'" , "'Elecraft'" Subject: RE: [Elecraft] K2 - No SSB Output (long) Date: Thu, 19 Sep 2002 11:02:12 -0700 Hi Colin: The first test of SSB output is to hook up a dummy load to the K2 and look at the RF output indication on the bar graph rather than your external meter. Most external watt meters are the "averaging" type. The internal K2 circuit is a "peak reading" meter. Set your POWER control to 10 and be sure your menu setting for SSBA is "2" (gives you full gain from the mic). Transmit and watch the K2 bargraph while talking into the mic. It should flicker across, just hitting 10 on some voice peaks. Most of the time the audio will bounce between 5 and 7 on the bargraph scale (with the compression off - SSbC 1-1).=20 If it hits 10, you are getting all the RF out the K2 is capable of generating. The only way to increase your talk power now is to add compression (SSbC 2-1 to 4-1) or add an amplifier or a better antenna. Keep in mind that a signal that is very loud in CW can be "barely audible" in SSB. That's because of the difference in bandwidth between a CW and SSB signal. Your RF is concentrated in a bandwidth of about 50 Hz (depending upon your keying speed) in CW and it is spread out over 2000 Hz on SSB.=20 Check the output on various bands. If you are going to have low output on any band (assuming your K2 can make at least 10 watts CW on all bands) most likely it will be on 10 meters. The gain of the RF strip in the K2 transmitter is lowest on this band, so it requires the most drive from the audio circuits. If you like, you can now add your external wattmeter and see what it does. It will likely wiggle very LOW on the scale. The Human voice has a very low average-to-peak power ratio, and your averaging wattmeter will show this. That's why compression is so popular in SSB rigs. It kills the "natural" sound of the voice, but it really brings up the "talk power" by reducing the amplitude of the voice peaks thereby bringing up the "average" power quite a bit.=20 If your output is low as shown on the K2 bargraph, first check your mic connections. Be sure you have voltage getting to the electret element of the mic.=20 Ron AC7AC K2 # 1289 +++++++++++++++++ From: "COLIN WHITMORE" To: "Gary Surrency" Cc: "Elecraft" , "Zoerb, Ron" Date: Fri, 20 Sep 2002 13:04:44 -0600 Subject: [Elecraft] RE: K2 - No SSB Output - Follow up He shoots! He scores!!! =20 Ok, traced the problem. (Thanks Gary - Elecraft, Ron - AC7AC, & Ron - KI=D8= II) Turns out the toroid transformer T2 was wired backwards (1 in 3, 2 in= 4 and vice versa). I guess you could say that it was acting as a step-DO= WN transformer. Well that was a real bone-head move. Who knows how I mana= ged that, I'm usually over cautious when it comes to those transformer wi= rings. =20 =20 Anywho, I'm dimming the lights here in Denver now, with that RAW 10 WATTS= of awesome power ;-) =20 Thanks again. =20 Cheers, Colin N=D8YGY +++++++++++++++++++