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Getting rid of RF in shack.

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  • #110
    K0YNE
    Participant

    Thanks woody. your suggestion about using 75 ohm coax to feed my ladder line from the tuner
    worked just fine. At least, no more rf in monitor and it seems easier to tune the 20 meter band
    now since i made the change. Woody suggested I hook up two lengths of 75 ohm coax, using the center
    conductor to one of the tuners balanced connections and then do the same on the remaining
    balanced connector. I must have used 15 to 20 feet on each connector. I twisted the shields together
    from both lines and grounded that shield to the tuner chassis. Then outside, i kept both cables together
    and bared both ends  and hooking up the center conductor of each cable to a balanced lead. I also
    twisted the shields together but on this end I did not ground them. My first attempt to tune up on
    20 meters, meant that i had to use new dial settings on the air variable capacitors, both the antenna
    and the transmitter tuning. And they seemed to tune smoother and less adjustments needed to be
    made to establish a 1 to 1 SWR. I then tried sending SSTV and did not notice any RF in the monitor
    at all. Another thing, was that i observed on the watt meter about 5 to 7 watts more than I normally
    read in the past… Thanks Woody    Paul k0yne 🙂

    #500
    wd0avl
    Participant

    I too, did the 75 ohm trick on my twin lead, referring to Paul's article, and the tip from Woody.  I on the other hand now have no rf in the shack, but I can't tune 10, 15, or 20 meter band at all, and it made it a lot touchier to tune 80, and 160 is almost impossible to tune.  So if anyone has any tips, I am open to all suggestions, otherwise, I am going to have to go back to my original twin lead wires that were so easy to tune on everything but the 10 and 15 meter band.    Steve WDØAVL

    #501
    KCØWA
    Participant

    Paul:  I'm glad that the tip worked for you…… I've used that one in the past and it has worked well.

    Steve:  Well, sometimes it doesn't work, as in your case….. Make sure you are well grounded on the tuner end and open at the antenna end regarding the shied……… You might try a shorter or longer length.  Maybe you just hit a length that has a really wierd rf voltage or current.  also try some different coax, there is nothing magical about 75 ohm. Try some 50 ohm.  I think if you play with it a while you can get it to work,,,,, Also borrow and try a different tuner……. You will just have to experiment with it…. In my shack, I run 300 ohm ladder line direct to the tuner, with no rf in the shack…….. Just lucky I gues…….. 73's      Woody

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