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Thread: RF Getting Into Neighbor's Sony Surround Sound Unit???

  1. #1

    Default RF Getting Into Neighbor's Sony Surround Sound Unit???

    So here’s my situation… The other day I was chatting with my neighbor who mentioned that he can hear my ham radio transmissions through his Sony STR-DH770 surround sound unit. Not wanting to cause any problems, I offered to help, and here are some facts I’ve found to date….
    1. The radio sounds/RFI (Radio Freq. Interference) come through all speakers; light and muffled, but there.
    2. My ham radio was tested here on 7.233 MHz.
    3. RFI was not significantly different from 800W down to 400W.
    4. The distance from the nearest part of my end-fed Zepp to the Sony unit is about 60 feet.
    5. The sounds are present only when his surround sound unit is ON.
    6. Given #5 I assumed the RFI (Radio Freq. Interference) was entering his unit directly, and was being sent to the speakers as it would any signal input.
    7. Even though I had the assumption outlined in #6, I placed Snap-On ferrite chokes on all speaker wires as they exited the main unit, placed a choke on the HDMI line to TV, plus did several wraps of the AC power cord, FIRE TV cable, and one other cable through a larger choke. All this had no effect.
    8. Also, just to prove the theory from #6, I removed one of the speakers from the ceiling, and placed two snap-on chokes with several wraps each of speaker wire near the speaker itself; no improvement.
    9. The Sony unit does not have a three prong AC, only a two prong cord. Understanding there’s a difference between RF ground and electrical ground, I grounded the unit’s case to the nearby electrical outlet ground; no improvement.
    10. I sent a support email to Sony asked for their thoughts…..I won’t hold my breath.
    11. Plans going forward include:
    a. Disconnecting all cables to the surround sound unit except speakers to further prove #6
    b. Consider a low-pass filter for my radio system, though most feel the low-pass filters in my radio (Kenwood TS-570D) should be sufficient
    c. Test at 100W
    d. Test using my mini-G5RV antenna which is an additional 20 feet away
    e. Investigate a means of “shielding” his unit which would work AND be acceptable from a cosmetic standpoint
    f. Test a .001 ceramic cap across the posts of one speaker.
    Any thoughts/ideas would be appreciated. Worst case scenario would be to voluntarily reduce power to 100W during any 7PM through evening transmissions.
    Thanks in advance! Mike, N3QIG

  2. #2
    Super Moderator 5B4AJB's Avatar
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    Did you try snap-on chokes on the AC input cable? sounds like the problem is on the power supply.

    A low pass filter straight on the back of the transceiver usually helps...

  3. #3

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    I have had only one case of RF getting into a neighbour's equipment. HF or VHF, low or high power, made no difference. So, like the OP, I said I'd get to the bottom of things. Just to amuse you, here's what I found.

    AM radio - no antenna at all.
    FM radio - "T" type ribbon antenna, hanging from the ceiling - only one wire connected to receiver
    TV - co-ax from TV set only had the inner core connected, braid not connected at either end. Up in the loft, the said inner conductor was connected to the boom of the TV antenna.

    Now, we live less than 2km from the transmitter for TV and FM radio, and it's line of sight. The TV will work just fine with no antenna at all plugged in, so it's perhaps no surprise that his lash up job worked!

    These issues were duly fixed for him, but although the RFI was reduced, it was still there. Chokes and HPFs were installed but the one thing that really worked on HF was a low pass filter installed as just described. On 2m, a band pass filter instead.

    Never heard a murmur from the neighbour after that.
    Current radios: VHF/UHF: 2 x Baofeng 2/70 Handhelds. VHF: Kenwood TR9130 2m multimode. HF: Kenwood TS930S-AT
    Home antennas planned: G5RV / G7FEK / end fed wire. 1/2 wave vertical for 10m. 6 element beam for 2m. Vertical collinear for 2/70
    Website for the 'day job': www.andrew-gilbert.com

  4. #4

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    I have had only one case of RF getting into a neighbour's equipment. HF or VHF, low or high power, made no difference. So, like the OP, I said I'd get to the bottom of things. Just to amuse you, here's what I found.

    AM radio - no antenna at all.
    FM radio - "T" type ribbon antenna, hanging from the ceiling - only one wire connected to receiver
    TV - co-ax from TV set only had the inner core connected, braid not connected at either end. Up in the loft, the said inner conductor was connected to the boom of the TV antenna.

    Now, we live less than 2km from the transmitter for TV and FM radio, and it's line of sight. The TV will work just fine with no antenna at all plugged in, so it's perhaps no surprise that his lash up job worked!

    These issues were duly fixed for him, but although the RFI was reduced, it was still there. Chokes and HPFs were installed but the one thing that really worked on HF was a low pass filter installed as just described. On 2m, a band pass filter instead.

    Never heard a murmur from the neighbour after that. Ironically, at a previous house, I had a long wire, triband HF beam, 10m vertical, 2m collinear and a large 2m beam. Never gave RFI to anyone!
    Current radios: VHF/UHF: 2 x Baofeng 2/70 Handhelds. VHF: Kenwood TR9130 2m multimode. HF: Kenwood TS930S-AT
    Home antennas planned: G5RV / G7FEK / end fed wire. 1/2 wave vertical for 10m. 6 element beam for 2m. Vertical collinear for 2/70
    Website for the 'day job': www.andrew-gilbert.com

  5. #5

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    I have had a few issues over the years with neighbors, the snap on ferrite and low pass filter took care of them all. Well, all except one, I had one neighbor that said I was getting into his phone line, even when my stuff was turned off... never found a solution for that one.

  6. #6

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    Put about 7 cores on your feedline. I have a suspicion that you are radiating from your coax and that is what is getting into his system. This happens a lot when an antenna is lossy and not near resonance. I chased the same problem at out TV station once with a nearby Ham getting into our remote site audio. He had a beam for 20/10 meters that had suffered damage, but not so much his tuner would not tune it. The spectrum analyzer showed spurious emissions up to 515 mhz and as low as 4 mhz. He replaced the antenna, problem solved. Just my $.02

  7. #7

    Join Date
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    Quote Originally Posted by Obed View Post
    I have had a few issues over the years with neighbors, the snap on ferrite and low pass filter took care of them all. Well, all except one, I had one neighbor that said I was getting into his phone line, even when my stuff was turned off... never found a solution for that one.
    I know what that’s like, obed... they usually start when they see our antennas. “What’s that (for)?” I just tell them it’s for AM BC, that I listen to talk radio. Or hide it as a St. Louis Fishpole, a rain gutter antenna, etc. Then I have to use all the filtering on my end (rfi chokes, noise cancellers, etc.) for their poorly built plasma tvs, square wave power inverters, solar arrays, power line arcing, etc. Yet we’re always presumed guilty. Go figure.

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