What could cause transmission interference in audio devices?
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I did another funky antenna project,? used simple 14 gauge wire I've made a 20m dipole with a 1:1 800W common mode choke.? I hung the dipole vertically and run the coax near 90 degree horizontally from the feed point.? Due to the tree height there is a little J hook at the bottom to avoid having that end drag on the ground.? The worst SWR I'm getting is 3.0 (measured on the coax end to the HF-Auto using an antenna analyzer) so it shouldn't be to bad for the HF-Auto to tune.? I also use LMR-400 to keep losses low due to the SWR.
The antenna did great, even got some DX across the Atlantic and into Brazil using SSB at about 400W.? However, my neighbor and my daughter can hear me transmitting with that high power though in their audio system.? Not sure about my neighbors setup but my daughter is using her head phones on the laptop and can hear me talking although it's impossible to understand what I say.? Interesting tidbit is that she doesn't get the interference when her laptop is disconnected from the mains power (i.e. running on battery).? She only can hear the interference when running higher power.? At 100W it seems to be either not there or to weak to notice.? I'm running the LA-1K on 120V.? Adding three FT240-43 ferrite toroids with 4 wraps on the power cable of the LA-1K didn't make a difference. Neither did using 240V with the LA-1K. I don't think it's the LA-1K that causing the interference but I would like to know what could cause that. While this specific antenna is very temporary, I'm hoping to setup a similar antenna because I really enjoyed it's performance.? Claus (AE0S) BTW, I'm also using a horizontal 40m non-optimal dipole feed with ladder line that doesn't cause any interference at high power. |
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Hello Klaus, ?? There's a pretty strong field around a dipole out to about twice the diameter of the antenna.? I don't know how far it is from the house, but within a few wavelengths of the antenna it's bound to create interference to modern devices which are very sensitive to RFI.? I wouldn't think the amplifier is the problem here.? Dennis N0SP On 10/3/2021 at 11:31 AM, "Claus (AE0S)" <claus-groupsio@...> wrote:
I did another funky antenna project,? used simple 14 gauge wire I've made a 20m dipole with a 1:1 800W common mode choke.? I hung the dipole vertically and run the coax near 90 degree horizontally from the feed point.? Due to the tree height there is a little J hook at the bottom to avoid having that end drag on the ground.? The worst SWR I'm getting is 3.0 (measured on the coax end to the HF-Auto using an antenna analyzer) so it shouldn't be to bad for the HF-Auto to tune.? I also use LMR-400 to keep losses low due to the SWR. |
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On Sun, Oct 3, 2021 at 01:31 PM, Claus (AE0S) wrote:
1:1 800W common mode choke... Interesting tidbit is that she doesn't get the interference when her laptop is disconnected from the mains power (i.e. running on battery). ...Adding three FT240-43 ferrite toroids with 4 wraps on the power cable of the LA-1K didn't make a difference. Maybe try a different CMC with higher choking impedance and/or?some ferrite toroids wrapped around the power cord to the laptop which might help if common mode current is involved. I had an attic dipole that set off some CO detectors at the last QTH (mine and my neighbors, in a condo). Luckily another brand mitigated the problem to a large extent. They also had no interference on battery but only when plugged in to AC. It's probably difficult to tell if a 'radiated' or 'conducted' issue.?It could be that the only solution might be moving the antenna (which may not be possible) or trying a different type of antenna. These things can sure be frustrating to solve. ? -- 73, Norm/KC1BMD |
Norm - KC1BMD