Rick, Your no ground situation + high power is a recipe for RF problems. Try some 1/4 wave counterpoises connected to the rig ground. You can have multiple ones for different bands connected simultaneously. People who live on second and third floors have the same problem with long ground paths. Counterpoises help them sometimes.
Cheap and easy. Sounds like you need <10 db of improvement and these may be enough. 73 de Brian/K3KO --- In digitalradio@yahoogroups.com, Jose Amador <[EMAIL PROTECTED]> wrote: > > > Rick, > > Every wire "under the influence" of your radiating antenna can be a > feedback pickup path. > > Try to minimize currents, ferrites are your best friends. Use only > capacitors in shunt to ground > only after a choke to minimize currents. > > All the homebrew equipment I have built has an RF filter in the power > leads, L first and C after. > > I had to wind some ten turns of my speakers power cable on a mid size > toroidal ferrite core > (salvaged fom a defunct 100 W commercial radio) to quiet down the noises > of PSK31 and Olivia. > > In a course of a certain solid state high power broadcast transmitter I > learned that EVERYTHING > that enters the transmitter cabinet passes thru some ferrite core FIRST, > because every wire may > be a feedback path in the near field of the broadcast antenna. It even > provides some lightning > protection, inductors first, varistors after, in the incoming signal path. > > Hope this helps, > > Jose, CO2JA > > Rick escribió: > > > Antenna that gives me the main problem is an inverted vee dipole with > > apex at about 35 feet and ends at about 15 feet high. I have a > > Butternut vertical located about 150 out from the house that does not > > seem to cause any problems, but for close in (< 200 miles) the dipole > > is indispensable. It is of course throwing RF back to the shack as > > the apex is only 40 feet in horizontal distance to the base of the > > tower on the end of the garage. > > > > Everything is coax fed. I have tried "balanced" lines with tuners off > > and on over the years, but it is less convenient for routing and can > > be more of a problem with RF feedback too. I don't use any separate > > grounding and may have to try it as the main RF ingress seems to be > > the audio lines from the computer. > > > > If I disconnect from the computer (even leaving the DIN plug > > connected with the ferrite rod on that line which is a few feet long) > > it seems to clear up. It is only a foot of cable between the sound > > card and my 1:1 isolation transformers. I suspect that if I put a > > scope on the shield from the sound card I won't like what I see. > > > > It would be about 20 feet to run a ground to the outside SPG and I > > have also been skeptical that would help a lot. For some lightning > > protection, I disconnect my rigs from the antenna switch which > > grounds all unused feedlines, but of course, only through their > > shields, but at least it makes them common to each other. I admit > > that for 160/80 and maybe 40 meters, a 20 foot run is not too bad for > > "grounding." > > > > 73, > > > > Rick, KV9U > > > __________________________________________ > > Participe en Universidad 2008. > 11 al 15 de febrero del 2008. > Palacio de las Convenciones, Ciudad de la Habana, Cuba > http://www.universidad2008.cu >
