Hi Myles, The microphone is the stock Elecraft hand mic. There is nothing betwen the microphone and the rig. I'm home now and doing some more tests and noticed something odd.
Upon initial keydown in SSB with the amp on and the K3 set to 50w, I'll get a forward reading on the wattmeter anywhere between 10-17w with no audio going into the mic. After about a two seconds the forward power will drop to about .5 watt. With mic gain set to 0, this problem doesn't occur. Turning it up to 14 or 15, the alarm still trips but not so often. Turning the gain back down to 3 or 4 and the problem occurs with much greater frequency. There's something going on the minute I key the mic that's looping into the audio circuitry. Turning the gain down makes the problem worse until I reach 0 gain. I also just found something very interesting. If I set the gain to 4 and the K3 to 50w, I can make the alarm trip. Dropping the K3's output to the point that I no longer am using the KPA3 (around 12w where the relay clicks), I can no longer recreate the issue. Cranking back the power so the KPA3 is used, the problem returns. James K2QI On Tue, Jul 14, 2009 at 6:41 PM, myles landstein <myles.landst...@gmail.com>wrote: > silly question can you describe your microphone set up are you using > a stock mic? > going thru anything between the mic and the rig ? > > if you key up on ssb and have the mic gain all the way down and say > (25-80-100w) does it still occur? > > > > wonder if you might have a ground loop or some other type of feedback > entering via the 'audio' chain > > > On Jul 14, 2009, at 6:26 PM, K2QI wrote: > > Hi Jim, > Thanks for the reply. I have not noticed any power fluctuations or > increases in reflected power during the alarm event. > > Antenna system is a Tarheel 100A screwdriver mounted on a tripod on my > balcony. The balcony is about 40 feet away from the station. The antenna > is fed with good quality Times Microwave LMR-400UF. The last 20 feet of it > were wound into a common mode choke using 4" PVC. The antenna does not > have > a very good radial system; about 10 strands of 20g wire cut to about 12 > feet > in length. I do have a 66' length counterpoise but have not laid it yet > due > to the size restrictions of the balcony (5' x 12'). The antenna's control > cable was also decoupled via a ferrite choke. > > Again, 1100w constant carrier doesn't cause this problem. Only keying up > when the K3 is in a sideband mode. Keying up with drive power from the K3 > at 100w or 50w doesn't make too much of a difference; the alarm will trip > at > random times. Dropping the drive power to about 12 watts seems to prevent > the alarm from tripping. > > This phenomenon does not happen if the amp is off line. > The wattmeter is one of MFJ's new digital/analog deals. It's the MFJ-828. > > Please clarify the K3 pin 1 issue; I do not have my assembly manual in > front > of me. > > 73 de James K2QI > > > > > On Tue, Jul 14, 2009 at 5:43 PM, Jim Brown <j...@audiosystemsgroup.com > >wrote: > > > On Tue, 14 Jul 2009 13:44:00 -0400, K2QI wrote: > > > I am curious though; your previous email mentioned rectification of audio > > in > > the wattmeter, feedline or antenna. > > > As noted, one or more good common mode chokes are in order. You mentioned > > the > > lack of a station ground. That is a lightning safety issue, but NOT a > > solution > > to RFI. > > > You didn't mention what your antenna system is, or how far it is from the > > rig. > > > The important question is, is this only RFI to the wattmeter, or is > > something > > else going on, like a spur or harmonic? Have a ham nearby listen for > spurs > > (or > > take the antenna off another radio and listen for spurs). > > > Is this an outboard wattmeter, or something built into the power amp? If > > outboard, my first move would be to replace the fancy wattmeter with a > > Bird, > > and look for fluctuations indicating increased reflected power. If you > > don't > > see any, I would blame the meter. If you DO still see the fluctuations, I > > would > > look at the K3 and the power amp. The K3 does have some pin 1 issues. > > Ferrite > > chokes would help with that. > > > http://audiosystemsgroup.com/RFI-Ham.pdf > > > 73, > > > Jim Brown K9YC > > > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:Elecraft@mailman.qth.net <Elecraft@mailman.qth.net> > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net <Elecraft@mailman.qth.net> > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > > Myles Landstein > myles.landst...@gmail.com > please note my new email address > dti will soon be eliminated , gmail is my new home update your dir > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
