> Date: Sat, 16 Oct 2010 12:03:18 -0400 > From: K8JDC <k8...@sbcglobal.net> > To: drakelist@zerobeat.net > Subject: [Drakelist] TR-7 - More Info > Message-ID: <4cb9ccc6.7020...@sbcglobal.net> > Content-Type: text/plain; charset=ISO-8859-1; > format=flowed > > Some more data points: > > 1. I cannot get the radio to malfunction on a dummy > load. I have only > seen the problem on 40m when connected to the antenna which > is a 135-ft > doublet fed with ladder line. Tuner is a Tentec 238B > and the tuner is > right next to the TR-7. That leads me to wonder if > there's some RF from > the balanced line that is part of the problem. > > 2. I checked on 20m and don't see the problem on > either a dummy load or > my antenna which is a Steppir. Output power is > stable. > > 3. The TR-7 forward meter goes to zero when the > problem happens. > Reflected indicator goes max scale. So those readings > are the same as > my external meter. > > 4. I hooked up my Tentec Orion to the same > tuner/antenna and all is > well. No hint of anything wrong with the > antenna. Output power is > totally stable. > > 5. This problem happens on CW as well as SSB. I > have a toggle switch > wired to key the radio for tuning and it will put out full > power into > the antenna for a few seconds and then the reflected power > will go to > infinity. Power into the dummy load is fine. > > 6. I did notice at least once that the problem > occurred just as I > unkeyed in CW mode. So, just as I unkeyed, I saw the > reflected power > jump high. > > So, the above leads me to wonder about the transmit > relay. I wondered > if the contacts are somehow dirty but I don't see the > problem on the > dummy load so that leads me to wonder if the T/R relay is > somehow being > affected by some RF from the ladder line which is > nearby. It's not > easily possible to separate the radio and tuner any more > because of how > my desk is laid out. The ladder line comes out of the > tuner and goes to > the left to the outside world. The TR-7 sits just to > the right of the > tuner so the ladder line does not go behind the radio > although it's only > about 10 inches away from the T/R relay when it exits the > tuner. > > ?? > > Dave > K8JDC
I've not found a 135 ft antenna feed with ladder line to be ideal on 40 meters. It presents a high impedance/high RF voltage load to your tuner, increasing the RF field around the ladder line and probably causing RF feedback within your TR7. I'd attempt to lengthen the ladder line to find a combo that works better or better yet simply use another antenna on 40 mtrs. If you have enough room for 135 ft, you have enough room for a 66 ft coax feed dipole for 40. 73, Doug/WA1TUT _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
