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Author Topic: Nothing But Noise  (Read 355 times)
KB0BJL
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Posts: 3




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« on: January 11, 2008, 04:35:32 PM »

I recently got back into the Ham world and have antenna restrictions outside of my house.  So I have two HF antenna's in the attic over my garage.  It has alot of clearance space, so I have a Comet HVU-8 and a Tak-Tenna both in this space.  The HVU-8 has an SWR of 1.4:1 on 14Mhz and the Tak-Tenna has an SWR of 1.2:1 on 7Mhz (both  without a tuner).  The antenna's are both about 12 ft over the concrete of the garage.

My issue is that all I hear is noise.  At peak times I can work PSK-31, but only for a window of about 1 hour max.  When I do get open windows, I am getting stations about 1,000 miles from me.  (St. Louis to Florida, Georgia, and South.  Compared to no antenna (S0) I am getting noise at S8-9.  

Now some details of what I have tried...

1.  I was told that since my shack is on the second floor adjacent to the antenna's I needed an artificial ground.  I purchased an MFJ Art. Grd. and had no improvement.

2.  I needed a better tuner.  I purchased an MFJ-949E Deluxe Versa Tuner.  Though I can tune to a 1.1:1 SWR on all bands with the both antennas, I still only hear noise.

3.  I needed a better antenna, so I purchased the HVU-8.

As for the rest of the equipment, I have my older Kenwood TS-570S, Icom 706MkIIG, and a Icom 756ProIII.  All radios register the same noise level.  

So I think it is the antenna configuration, but I would like options.  I have thought about running a dipole around the siding on the back of the house 25 ft left and right and 20 ft down toward the ground.  Making a more square configurations, but having the feed point about 30 ft off the ground.  (The back of the house is a walk out basement.

Ok, lay it on me...

Thanks,
Rob
KB0BJL

 
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N3OX
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« Reply #1 on: January 11, 2008, 04:41:54 PM »

Rob,

You need to read this:

http://www.audiosystemsgroup.com/RFI-Ham.pdf

Your trouble is certainly noise pickup from stuff in the house.  

You have a long hard road ahead of you if you want to successfully run attic antennas and you have S9 noise.

Think hard about anything you could do to put a stealth antenna outdoors.  

You're also going to find that you have a hard time with transmitting efficiency after you can actually hear weak signals, but one thing at a time maybe.

73,
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
AC5UP
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Posts: 3835




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« Reply #2 on: January 11, 2008, 05:00:59 PM »

If you have aluminum siding or metal wall studs an indoor antenna won't cut it.

If not, the next step is to take your fav-o-rite battery operated AM radio out the the garage and tune it to a spot at the top of the band where you hear nothing but noise. Turn off all the breakers in the breaker box one by one and note if any have an effect on the noise level.

If one or more circuits are a noise source, figure out what's on that circuit and what can be done to put a muffler on it.

If you can turn off the entire house and still have the same noise level...

Move.
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K0RFD
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« Reply #3 on: January 11, 2008, 05:11:22 PM »

You have compromise antennas, and you have them mounted in a place that's guaranteed to pick up noise.

You have two choices:  Mount better antennas outside, or eliminate noise sources.

I'm sure you'll get plenty of suggestions for each one.
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KI6CFW
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« Reply #4 on: January 11, 2008, 11:41:16 PM »


As others have mentioned, antenna placement and/or something in the area generating noise.  

Also could be your power supply - what are you using for a power supply and are you using the same power supply with all radios?
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AC5UP
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« Reply #5 on: January 12, 2008, 04:43:58 AM »

Good comment on the noisy power supply. Easy way to check that is to unplug the antenna from the rig... If the noise is running anything above an S-1 with no antenna, it's internal.

BTW: I had a curious situation a few months back. Decided to start using the HT again and whenever I put it on the table next to the bed it wouldn't scan. Squelch opened up on noise. What's on the table? A phone and a battery operated 'atomic' clock.

The clock is the noise generator. Kinda' counter-intuitive to think that a clock with a 60 kHz RX inside would throw that much hash on 2 Meters, but it does...

A few years ago there was an article in one of the major Ham mags about an OM trying to track down a noise source that seemed to move around. Took a while, but he finally pegged it to his pager. Sometimes the pager was on his belt, sometimes not. Hence the difficulty in finding the culprit. Wink

 
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KB0BJL
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« Reply #6 on: January 12, 2008, 05:30:32 AM »

To the power supply question.  I was using an older Pyramid and thought that might be it so I purchased a new Icom PS-125 with the 756.
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N5RMS
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Posts: 37




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« Reply #7 on: January 12, 2008, 07:47:29 AM »

A low Swr is mainly an indication of a good match between your transmiter and antenna. A high SWR will not cause high noise. You can receive a lot of stations by just using a wire (24 inches or longer) stuck in the antenna port of the radio.  DO NOT TRANMIT when doing this.  

Sounds like you have a lot of locally generated noise.  Using a AM broadcast portable battery operated radio tuned to a vacant frequency may help you locate some of the noise.

A battery operated scanner tuned to the AM (not FM!!) aircraft freqs. (139.200mhz or so) can also be used. It will work a lot better with 3 element Yagi antenna (easy to make) to pin-point the noise source.  

Wall warts, (the little power pack that plugs into the wall), battery chargers, WIRELESS GARAGE DOOR OPENERS, flourescent lights, TV's, satellite receivers, light dimmers and AC powerlines can all generate noise.
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