+++++++++++++++++ From: "Don Brown" To: , "Jim W7RY" Cc: "Elecraft" Subject: Re: [Elecraft] K2/100 Flat topping on 30m? Date: Thu, 31 Oct 2002 07:15:54 -0600 Hi I don't know if this is your problem but I had this come up in the KPA100= field test to the one I built. If R26 is set too low 30 meters would dra= w a lot of current at high outputs. I was getting up around 25-30 amps at= 100 watts out. Other bands were not as high this only affected 30 meters= . If this is the case you may be overloading your power supply and the vo= ltage is dropping. Have you monitored the supply while transmitting to se= e if it is well regulated. The R26 problem was due to setting the power c= alibration at 5 watts rather than 50 or 100 watts. When setting the calib= ration that low it is easy to be off by a fair amount at 100 watts. R26 s= ets the ALC feedback so it can cause strange reactions if not calibrated = properly. Don Brown KD5NDB =20 ----- Original Message ----- From: kc4kgu at ENTERZONE.NET Sent: Wednesday, October 30, 2002 11:51 PM To: Jim W7RY Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] K2/100 Flat topping on 30m? On Wed, 30 Oct 2002, Jim W7RY wrote: > Is it possible you are getting RF feedback into the radio from the ante= nna ? > And only on that band due to antenna problems ? > =20 > Or is this test shown into a dummy load ? > =20 > Thanks and this is an interesting one! > 73 > Jim W7RY The test is into a dummy load. Given the way I'm testing (Saying "Helllllllllllloooooooooooooooo" into the microphone), it wouldn't be legal for me to test with an antenna. 73 de John - KC4KGU K2/100 #2490 +++++++++++++++ Date: Thu, 31 Oct 2002 08:50:37 -0500 (EST) From: kc4kgu at ENTERZONE.NET To: Don Brown Cc: kc4kgu at ENTERZONE.NET, Jim W7RY , Elecraft Subject: Re: [Elecraft] K2/100 Flat topping on 30m? On Thu, 31 Oct 2002, Don Brown wrote: > Hi > -- snip -- > When setting the calibration that low it is easy > to be off by a fair amount at 100 watts. R26 sets the ALC feedback so > it can cause strange reactions if not calibrated properly. > > Don Brown > KD5NDB > Don, I'd lean towards this not being a calibration issue. After I finished the KPA100, when I was seing ALC problems with SSB on _all_ bands, I sent the rig to Gary who found that the problem was a 1/2 installed PSK mod on the KSB2. (Don't ask me. I installed the resisters and caps that were supplied and they fit what the manual said.) Anyway, Gary also aligned the rig, set up the filters, etc. I will take a look today though and see what I can find. I'm wondering if you can provide me a point of reference? What is your R26 set to? (measured between which two points?) Thanks, 73 de John - KC4KGU K2/100 #2490 +++++++++++++++ From: "Don Brown" To: Cc: "Jim W7RY" , "Elecraft" Subject: Re: [Elecraft] K2/100 Flat topping on 30m? Date: Thu, 31 Oct 2002 08:23:39 -0600 Hi One more thing you may want to try. Wayne mentioned adding a ground strap= from the shield to one of the screws on the SO239 connector may be neede= d to suppress oscillation in some cases. Just install a terminal lug at t= he connector and solder a short wire from the shield to the lug. It may n= ot help but it is easy to try. I will make the measurements on R26 you re= quested. I have 3 K2/100 in house at this time so I can get the values on= all of them. I will measure the resistance from end to the wiper and the= ALC voltage at the wiper at 100 watts if you think this will help Don Brown KD5NDB +++++++++++++++++ Date: Thu, 31 Oct 2002 14:54:31 +0000 To: elecraft at mailman.qth.net From: peter barville Subject: [Elecraft] Re K2/100 Flat Topping on 30m On Thu, 31 Oct 2002, Don Brown wrote: -- snip -- > When setting the calibration that low it is easy > to be off by a fair amount at 100 watts. R26 sets the ALC feedback so > it can cause strange reactions if not calibrated properly. > > Don Brown > KD5NDB I don't think the calibration of R26 can be the issue here, otherwise the problem would be noticeable on all bands, and not just 30m (see my *original* post). However, if the low pass filter is tending to filter out some of the desired 30m RF (ie the filter is rolling off too low in frequency), then the PA would have to draw more current in order to produce the same amount of RF. This could well explain why you were seeing excessive current drain specifically on 30m, and why I (and perhaps others?) see evidence of the rig flat topping on 30m at power levels well below 100 watts. I'd be interested to know if others can set up a two tone test on 30m and look at the output on a monitor 'scope. -- 72, peter g3xjs ++++++++++++++++ Date: Thu, 31 Oct 2002 13:11:37 -0800 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: kc4kgu at ENTERZONE.NET Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] K2/100 Flat topping on 30m? Hi John, We just checked several K2/100s here and several at one of our Builders for Hire's QTH and do not see any SSB flat topping at 100w on 30M. Its possible that your K2 or KPA100 30M LPF is rolling off too quickly, which would require excessive drive and current drain from the K2 or KPA100. This could happen if there was an extra turn on one of the LPF toroids or if there was a wrong capacitor value (or bad cap) in the LPF. Also, are you making these tests with the compressor off? If you can't find an obvious source for your problem, lets have you send it at our cost to Gary ( support at elecraft.com ) and we will dig into it and get it resolved. (We love mysteries :*) We will also post here on the Elecraft list what we find. 73, Eric WA6HHQ ================================== ++++++++++++++++ Date: Thu, 31 Oct 2002 16:24:32 -0500 (EST) From: kc4kgu at ENTERZONE.NET To: Eric Swartz WA6HHQ - Elecraft Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] K2/100 Flat topping on 30m? On Thu, 31 Oct 2002, Eric Swartz WA6HHQ - Elecraft wrote: > Hi John, > > We just checked several K2/100s here and several at one of our Builders for > Hire's QTH and do not see any SSB flat topping at 100w on 30M. Its possible > that your K2 or KPA100 30M LPF is rolling off too quickly, which would > require excessive drive and current drain from the K2 or KPA100. This could > happen if there was an extra turn on one of the LPF toroids or if there was > a wrong capacitor value (or bad cap) in the LPF. OK. I'll take a look and make sure everything is kosher. Gary just had the rig a couple months ago and with exception of opening the thing up to install the new firmware for the FT KAT100 and then going through just now to carefully do a CAL FIL using the new Spectrogram, there hasn't been anything done to the rig. It has been operated of course but, no mods, etc. > > Also, are you making these tests with the compressor off? > No. The compressor was on. I just tested with the compressor off and while not as extreme (compressor obviously works) it still flat tops. > If you can't find an obvious source for your problem, lets have you send it > at our cost to Gary ( support at elecraft.com ) and we will dig into it and get > it resolved. (We love mysteries :*) > > We will also post here on the Elecraft list what we find. And man do I seem to be good at breaking...er...finding things. >;-) I hope we can figure out what may be causing this without having to resort to a cross country trip for the rig. Note: I'm not the only person exhibiting this. I didn't even know my rig did it until I looked at 30m SSB because someone else had posted a question to the list regarding it. Anyway, thanks. As always, Elecraft is tops! 73 de John - KC4KGU K2/100 #2490 +++++++++++++++++ Date: Tue, 05 Nov 2002 15:10:34 -0800 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: peter barville Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] On the trail of 30m flat topping Hi Peter, Could you try spreading the turns on the toroids in your 30M LPF while watching the SWR with your Autek analyzer? If they are wound too closely together it might be possible that the filter is rolling off too quickly. 73, Eric WA6HHQ ------- peter barville wrote: You may recall that a week or so ago I reported that my K2/100 flat tops (at about 65-70 watts), but ONLY on 30m. One or two others reported similar findings, but K2/100's tested by Elecraft were okay. I had a couple of hours spare today and decided to investigate further. A prime suspect, of course, is the LPF. A visual inspection of the 40/30m LPF (on the PA board) reveals that L4, L5 and L6 each has the correct number of turns (on the correct toroid). It also reveals that the C3x capacitors are correct - according to their markings, and I do tend to check component values with a meter before installation. So, nothing obviously wrong there. I also checked that the LPF's were switching as they should. Finally, I decided to look at the swr of the 40/30m LPF by using my Autek RF1 Antenna Analyser. I terminated the PA output with a 50 ohm dummy load, and fed the Autek into the input of the PA board. With the PA board powered, but disabled in the menu, I was able to switch LPF's by changing bands on the K2. I think the results may give a clue as to why the rig is flat topping on 30m: MHz Indicated SWR 7.05 1.2 7.80 1.1 8.00 1.1 8.40 1.1 8.80 1.2 9.10 1.3 9.60 1.4 10.00 1.5 10.20 1.6 10.30 1.7 10.40 1.8 10.59 1.9 10.65 2.0 > I suspect these figures suggest that the filter *is* rolling off too low > in frequency. Maybe removing a turn from one (or more) of L4/5/6 would > help? > > I would be grateful if Team Elecraft could comment, and also let me know > what value inductance L4 and L5/6 should be? It would be fairly easy to > remove them from the board to check their values, and possibly remove a > turn. > -- > 72, peter g3xjs ++++++++++++++++