March 28, 2006 16:57
Subject: Page # 12, FAQ, Squeal In The Ham Radio On An 1800 GW
Squeal In The Ham Radio On An 1800 GW, Updated 3-28-2006
17 Mar 2006, Bob wrote:
I advised Jon of Kennedy Technology that right after I installed the unit, and the radio, I had a problem on 220 when the radio would "stutter" in transmit, when I had the PTT button depressed. Others said it suddenly sounded like the radio was being keyed and released quickly. This only happened on 220, 2 meter and 440 were ok, and it did not happen all the time. I tried checking connections, and although my 220 coax connector from the radio was loose, even after tightening it still persisted. I don't have the duplexer on 220, so knew that was not a problem. I just quit using the 220 band, since the 2 and 440 were fine.
At the last MS150, while going into the beach parking lot, I was talking on 2 meter, let go of the PTT button, and the radio would not release the transmit. I finally had to turn off the radio, then reset it. 440 was fine, and 220 was not attempted, but the problem persisted the rest of the day, anytime I used 2 meters. Since I use 440 most on the bike, I forgot about it for a while. Prior to this I had added an additional antenna mount for the handheld and GPS to be used later, nothing was put on the coax.
Several weeks ago while attempting to talk on the radio (440 MHz) on my morning commute to work, Mike KE6??? said he could not understand me and that there was some awful squeal on the signal.
After the Feb MARC meeting when I talked to you and Chuck, I started to get the help of a friend who is a communications specialist. He runs the shop for radio installation for the city of Pomona, was a tech for a number of years. I went out and got the ferrite donuts as well as some extra ground braid, which I added.
We noted that the squeal started within a few seconds of pressing the PTT button. We noted that as soon as a hand got close to the unused antenna mount on the rear rack, it got even worse. We completely removed the unused coax, squeal still there. We tried moving the power cable under the seat, and the coax in the trunk to separate them, no change. We tried moving the two Kennedy modules under the seat, to get them away from each other, with some change, not much. We tried putting one under the right frame rail, and the other under the left rail, no or little change. I put ferrite donuts on the leads that connected the two modules together, no change. Finally while playing with it, we noted that getting my hand even NEAR one of the modules would make a increase the squeal. I tried this over and over, noting as I got closer to it, the squeal got worse. We wrapped both modules in a couple layers of aluminum foil, and the problems seems to ALMOST go away. It seems to be gone on 2 meter and 220, but 440 still has a problem. Changing to low or medium power on the Kenwood TM742A does not seem to have any change in the squeal. I have not been able to recreate the "Stutter" on 220 that I had before.
It appears that Kennedy thinks everything is fine, so they are sending the units back to me. I will re-install the units so that I can at least get by GPS voice commands back, but unless I can find the real problem, 440 is not working.
Bob, I know you are doing all your own work, so you MAY have to bring your motorcycle over to the house so we can tear into the wiring under the shell and find out what exactly is the problem because no one else is having any of the problems that you are having. I know one thing for sure, we separate all the Kennedy Units as far away from all the other electronic gear on the motorcycle as we can. Placing it under the seat has never been done by us. This certainly may not be the problem either, but we have to start somewhere. Also, we will take one of our own Kenwood TM742A's that we know is working OK and plug it into you system. If the problem still persists, then we move on to the next step. Ray
Bob, thanks so much for the very well written and detailed information. Here is the bottom line, I would suggest that when you can find the time that you bring your motorcycle over to my house early some morning and we (Chuck and I) will tear it down (remove the shell) and take all the components out and see what you have done that is different from the way we do the installations here. It would be interesting to see what is up with this problem, since not one single one of the installations that we have done have any of these problems. I have a couple spare KW TM742A's over here and we could hook one of them up and see if the problem exits with a different radio, change the PTT button out and etc. I bet we could fix it.
Thinking about it, I would guess that you are not running the Comet 3D4M Coax on both the 220 antenna or the 2m/440 duplexer. Let me know the answer to that.
Don't get discouraged Bob, you are not the first to have had trouble and you won't be the last. I am absolutely sure it can be fixed, we just have to go back to square one.
73 Ray KD6FHN