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 Post subject: noise on 80, 40 and 20 trapped antenna
PostPosted: May Wed 18, 2016 11:34 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 291
Location: Mobile, AL USA
Why do I get s-7 white noise on all the bands with this . Antenna I replaced didn't have the noise.


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Wed 18, 2016 11:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3720
Location: Monterey California USA
Better supply more info. What did you have before? Noise is on all frequencies? Antenna is in the same location?

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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 12:13 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 291
Location: Mobile, AL USA
Sorry. I had a resonant 20 meter wire. New wire antenna is using the same fiber glass pole in the same location, but has buried everything into the noise. Screwed in my 40 meter antenna and have no trouble with it. This new one is a 20, 40 and 80 meter trapped wire antenna.


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 12:43 am 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 8072
Does it use the same feed line as the former (20 meter) antenna? If not check the new line for good shield/ground connections at the connectors and any exposed point. Sometimes you will end up with an antenna setup which is prone to conducting noise from the coax shield to the receiver and in these cases better grounding and/or shield chokes are often very helpful.

If you are using the same line then most likely it is the orientation of the antenna which is now coupling to a power line or other noise source. To some extent a lot of noise is vertically polarized so if the new antenna is vertically polarized then it will likely have greater noise pickup.

Another possibility is your prior antennas had issues/were highly sub-optimal and the new antenna has much greater signal pickup of everything including noise so do a quick comparison of this new antenna to your 40 meter on some off the air signals.

Rodger WQ9E


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 2:20 pm 
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Joined: Aug Fri 22, 2008 9:42 pm
Posts: 205
Location: Long Island, NY
Verticals are typically noisier than horizontal antennas. Since they are non-directional they pick up noise from all directions, which as Roger said is usually vertically polarized in itself. The vertical has a lower angle of radiation to allow reception of signals from greater distances, but has the noise issue.

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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 4:00 pm 
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Joined: Jul Sat 23, 2011 9:33 pm
Posts: 1016
Location: Long Beach Ms. USA 39560
Alternative option XXIV = someone next door just bought the wrong kind of appliance or TV.
(Above is not really a "smart remark").
Get out the transistor portable and check for local noise.
Good hunting,
Pat

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Unhappy tubes blush while unhappy power FETs scatter plastic


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 6:00 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 11025
Location: Santa Rosa, CA
Quote:
Why do I get s-7 white noise on all the bands with this . Antenna I replaced didn't have the noise.


I know it's a long shot, but could you have an open connection or broken wire in the feedline? Can you hear any signals, or just noise?

Rich


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 6:20 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 291
Location: Mobile, AL USA
-Yes. I can hear signals, but they are at or below the noise level.
-Yes, I am using the same coax, but I am connecting to about a foot of coax connected to the antenna.
-Note: The noise sounds similar to only having a connection to the center conductor of a radio's ant input....like not having a tight connect to ground.
-Wonder if I should do a continuity check between coax connector pins and the antenna legs?
-Again, switched to my 40 meter wire, and have no problems with noise.
-Just wonder if one of the arms is causing the problem.
-I do know the antenna is not resonant on any of the bands, but does that have any impact on the noise?


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 8:11 pm 
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Joined: Dec Mon 20, 2010 5:14 pm
Posts: 583
Location: Central Pennsylvania
Not sure from your description exactly what you have but it sounds like something is broken.

If you have a trap vertical you will need to connect the base of the vertical to a good rf ground system. i single ground rod driven into the ground is generally not sufficient for a - less than full length- vertical antenna.

Another possibility - and I am just guessing- could one or more of the resonant traps be defective, open or shorted?

High noise level and signals at the noise level could be caused if there was a major defect in the trap antenna such as an open or a short. Thus the signal level into the receiver front end would be weak and the receiver AGC would attempt to compensate by turning up the gain.

With that in mind it might be useful to do antenna A/B testing with the receiver set for fixed , manual gain. Connect your supposed good 40m wire antenna and set the manual gain for a convenient output level. Place an ac volt meter across the receiver output if you like.

Then without changing the receiver gain connect the trap antenna. If the noise level - and ac voltage- is noticeably less I would suspect the trap antenna lead in cable or an antenna defect of some kind.


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Thu 19, 2016 10:33 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 291
Location: Mobile, AL USA
I think you are right about a trap (s) having an open or short, and that the agc is compensating. Did the a/b test with the 40 meter antenna. Quiet on the 40 and noisy on the trap antenna.


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 Post subject: Re: noise on 80, 40 and 20 trapped antenna
PostPosted: May Fri 20, 2016 8:37 pm 
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Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2581
Location: Vincennes Indiana
If there's a break in a antenna wire strand and it corrodes, if there's enough rf around, like an ambc station nearby, it may be making rectified noise from that stations signal.


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