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Ground radial length and TVI.

Discussion in 'General Technical Questions and Answers' started by K5BDH, May 1, 2010.

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  1. K5BDH

    K5BDH Ham Member QRZ Page

    I have been trying to narrow down the tvi issues I have with my ground mounted vertical. The antenna is 37' from my house and the radials consist of 21 at various lengths from 15' to 52' long, basically as long as I could make them to fit my 40x60' backyard. I have replaced all my coax with rg-213 and installed a balun designs (#1115) 1:1 isolator balun prior to my ldg z11pro which is installed in a ammobox for water proofing. My problem with interference on the tv's in the house is limited to only 15m (21.070) on both tv's and 20m (14.070) on the bedroom tv. My question is that of radial length and their possible effects on creating tvi. Could I be having problems due to a few radials being close to resonant length on these two bands, I'm pretty new to all of this and have been either replacing or rearranging things to overcome this issue without much improvement.

    As far as radio, im using a kenwood tx480sat and a max of 50watts output, most of the time I'm doing about half that. I also am using a Direct Tv dish.
     
    Last edited: May 1, 2010
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I doubt radial length has anything to do with it, assuming the radials are on the ground.

    I'm astonished you have "TVI" at all! I run a kilowatt or more with antennas pretty close and have no interference of any kind to anything, and we have 7 TVs in the house, often all running at once (kids!).

    What are you using to receive TV signals? Are these "OTA" signals, received with a TV antenna, or via cable, or satellite, or what?
     
  3. AG3Y

    AG3Y Guest

    You haven't told us what radio you are using ! And what power level!
     
  4. K5BDH

    K5BDH Ham Member QRZ Page

    Your correct the radials are on the ground and held in place by quite a few lawn staples.

    As far as power, im only running on digital modes so my power is around 25 watts and it usually doesnt take but about 2 secs of transmit till the XYL is hollering about the tv messing up. I cant imagine what the TV would do with a kilowatt going out. yikes.

    All my connections are new, properly sealed, etc. Just odd that it is only on 20 and for sure on 15m. I'm not sure if its just overloading the tv's on those two frequencies or what. I didnt see any difference at all when I placed the 1:1 isolator balun inline and dont have any issues with rf coming back into the house or shack.
     
  5. KA5S

    KA5S Subscriber QRZ Page

    I'd guess RF is getting into the DirectTV equipment via the antenna/LNA-to-decoder wiring, which will pick up your radiated RF pretty well. The problem MIGHT yield to a number of turns of that wiring around some ferrite cores. Alternatively, it could get into the decoder via the AC power wiring, which is a pretty good antenna as well.


    Cortland
    KA5S
     
  6. W8JI

    W8JI Ham Member QRZ Page

    This is virtually certain to be something in the TV system, and not the antenna or rig.

    Maybe DirectTV is as bad at getting RFI as it is giving it out? My neighbor's DirectTV bothers my receivers.

    Do you have this problem with a VCR or DVD or some other input besides DirectTV?
     
  7. AG3Y

    AG3Y Guest

    I used DirecTV for years, and never had a problem with RFI . My antenna was no more than 10 feet away from the DTV dish, which was mounted on a roof with the standard mast.

    If you are having interference problems with DirecTV, you should contact your installer. This should NOT be happening!
     
  8. K5BDH

    K5BDH Ham Member QRZ Page

    Used to have up a par end fedz 40 and 20m wire and didnt have any issues as long as both werent up at the same time. When they were both up then things started going goofy in the house.

    FWIW, 18m and 12 meters work grt and no issues with tvi etc, that whats sort of odd that only 20 and 15 mess it up.

    Problems also occur when I'm using the vcr but no issues when the dvd player part of it is selected and running. But I hear vcr's are notorious for having rf issues so I kind of just accepted that, or make sure to just use the DVD player side of it.

    The direct tv dish is on the roof on the back of the house and is 37' away from the antenna as well.



     
  9. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    I don't think it is your station either. You need to get a handful or chokes and start puttting them on the cables and power line close to the tvs' and the other devices. I recommend starting with one tv.

    Wrap as many turns as you can each choke. IF you wind on both sides make all the turns in the same direction.

    There is lots of info on the web about dealing with RFI.

    Good luck. Bill
     
  10. M0GVZ

    M0GVZ Ham Member QRZ Page

    So its Satellite TV? Sorry for sounding dumb about Direct TV but I'm from the UK. (Googles) Ah, it is Satellite TV. There is no way in hell that its anything to do with the HF antenna interfering with the Satellite TV signal nor the box.

    If it was the UK has everything to do with a rubbish TV that doesn't comply with EMC regulations (if it were in the UK) and as such has a front end susceptible to interference that it should be rejecting. In fact the RSGB EMC website states that older TVs and low rent flat panels are highly susceptible to TVI.
     
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