Dear group,
Regarding this issue I had described in a previous email, I wrote: >The "zipper" or "motorboat noise" occurs when tuning around 4.9-5.5 MHz or 4900-5500 KHz. It is >most noticeable when the sub receiver is turned on, the sub volume is up, and tuning steps are >set to fine. The noise ONLY occurs when I turn a VFO knob or filter knob. If I do not touch >any knob, the noise does not occur. It does not matter if VFO A or VFO B knob is used, or >whether or not they are linked. > >So think of it like this: when I am in that band area, if I continuously turn a VFO knob, I will >hear the motorboat noise until I stop turning the knob. > >If I pass that particular frequency area, the noise disappears completely. > >And another email of mine describing the issue: > >As for my motorboating issue, this is not something that you hear if you just let the receiver >sit at 5.000.000. Instead, the noise only appears when you turn any VFO or filter knob... if >you turn the VFO knob quickly enough, then it sounds like a motorboat. > >This happens from approximately 4.899.91 to 5.302.35 > >What's really weird though is that if I happen to come across a broadcast station anywhere >between those frequencies, then the motorboating noise will stop until I pass the station. >After that noise picks up again... it's as if the receivers don't know what to do with >themselves when there's no signal received between those frequencies, and they decide to inject >noise until another station pops up, or you reach the end of this particular frequency area. >Now if I stop turning the VFO, then no noise... just band static. Well, it looks like I've narrowed down whatever was going on with my K3. It seems this issue only manifests itself between 4.8-5.3 KHz with the peak of EMI noise around 5.00 KHz, AND only when the sub receiver is utilizing the same antenna input as the main receiver. If both receivers are set to ANT1 or ANT2, I can hear this EMI generated as I spin the VFO's. I also noticed that when tuning around, this EMI noise will peak the S-meter around S-7. However, if the sub receiver uses an antenna input other than what the main receiver is set to (or vice-versa), then there is no EMI noise. Again, this issue only occurs when both sub receiver and main receiver are set to use the same antenna input! I came across this discovery after exhausting all other possibilities. I spent several hours tonight doing the following: 1. Recalibrate synthesizers 2. Calibrate oscillator by zero-beating to WWV 3. Physically swap synthesizer positions 4. Check and adjust all TMP cables 5. Check all knobs and circuit boards in the face plate 6. Check oscillator board and crystal 7. Check all screws on main board and chassis Could there possibly be a problem with EMI isolation in my KAT3 tuner board when both receivers use the same antenna input? I inspected it physically, and everything is assembled according to the instructions. Can anyone here recreate this issue? Could my antenna tuner module be defective? I've already sent my findings via email to Elecraft tech support, but I'm hoping anyone here on the reflector can provide some input or solutions to try. It would be nice to find a way to isolate or eliminate this noise when using both receivers on a single antenna input. 73, James KC2UEE ______________________________________________________________ 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
