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Author Topic: What is this UHF Interference??  (Read 2850 times)
K9DRX
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Posts: 12




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« on: February 28, 2003, 11:35:57 AM »

Hello to everyone... I need some help here..
Please listen to this interference by clicking the link below..
http://www.geocities.com/trirychewi/uhfinter.wav

This humming interference interrupts various regions of the UHF band and tends to move it's peak around slightly at times.  At this moment it is hanging around 435.025-435.125,  460.650-460.700,  455.025-455.075, just to name a few.  It also has been known to make it's way into the local wastewater treatment plant's repeater which has an output of 453.950.  As you can see, it totally eliminates my ability to do any type of satellite work.  

My experience, based on the frequency range and type of sound would say it's a cable TV leak.  However, the local cable company has been in the area twice and they claim it is not there's.  Best I can pinpoint for location is in about 1/4 mile radius area.  Whatever it is, it has the ability to interfere badly in that 1/4 mile radius range.  I am in a relatively rural area with about 8 homes total within 1 mile.

Does anyone have any ideas?
Thanks in advance!
Mike - K9DRX
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K9DRX
Member

Posts: 12




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« Reply #1 on: February 28, 2003, 11:46:02 AM »

I'm sorry everyone!
The correct link to the sound is:
http://www.geocities.com/trirychewi/uhfinter.html

Mike - K9DRX
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WJ5MH
Member

Posts: 21


WWW

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« Reply #2 on: March 02, 2003, 07:25:14 PM »

I coupled the cable through a cap to my recever and I heard the following with the receiver in AM mode:

Audio 431.74
Video 433.25

Audio 437.75
Video 439.25

Audio 443.75
Video 445.24

Audio 449.75
Video 451.25

451.25 +/- What sounded like high speed digital data coming through cable.

Audio 455.75
Video 457.25

The video sounds much like what you're hearing, but not quite.  Of course, it changes with the picture being displayed.  You don't have a TV broadcast transmitter site near you, do you?  I don't think you're hearing cable leakage.

You're going to have to dig into this one...  Nothing like a good challenge.

73,
Joe ( WJ5MH )
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WA4PTZ
Member

Posts: 528




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« Reply #3 on: March 03, 2003, 05:37:29 AM »

Sounds like you need to do some serious DF'ing and
locate the source of this emmission. With all of the
remote and range extending TV/VCR/Stereo/Telephone/
computer gadgets it could get interesting.
Locating the source may be a good way to get some
answers. UHF DF antennas are very easy and cheap to
build an attenuator can be made from a high ohms
value pot. 50k 100k but what's in the junk box may
also work fine. Experimenting is what we do.
73 - Tim  
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WJ5MH
Member

Posts: 21


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« Reply #4 on: March 07, 2003, 07:00:04 PM »

Maybe???

"FCC cites RV owners in RFI complaint: The FCC has told an Oregon couple
to stop using its Winegard amplified television antenna (Model
Sensar/Roadstar) on their recreational vehicle "until the condition
causing harmful interference has been corrected." The FCC contacted Jimmy
and Jan Bowen of Gresham, Oregon, following a February 3, RFI complaint
from an Amateur Radio operator to the FCC Portland office. The
interference was reported on 447.375 MHz. An FCC agent investigating the
allegation tracked the interfering signal to the Bowen's RV in Portland.
The FCC cited Part 15 rules and noted that certain Winegard antenna
amplifiers "have been the source of radio frequency interference in a
number of cases." Due to the complaints, Winegard
<http://www.winegard.com> has agreed to replace defective units at no
charge. The FCC advised the couple to contact Winegard to make necessary
arrangements."
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KA0MR
Member

Posts: 221




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« Reply #5 on: April 03, 2003, 07:07:27 AM »

Guys don't overlook your router or any network hardware in your house if you have a network going on at your home. I found this out by quite accident while chasing interference around the countryside brought me right back to my house and to my Linksys 4 port Router.
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KE4RWS
Member

Posts: 113




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« Reply #6 on: April 23, 2003, 06:37:59 AM »

Good point on the router. I also have the Linksys 4-port router, and I experience various interference as well. It took me quite a while to nail it down but a home network can cause lots of interference!
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K9DRX
Member

Posts: 12




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« Reply #7 on: April 23, 2003, 12:59:25 PM »

I have one of these but I powered it down and mine doesn't seem to be the source.  Could a router or modem that is up to 1000 feet or more away from me cause this?  I still haven't been able to figure out what it is.  I have two homes that didn't reply to mail or phone calls about television amplifiers.  This could still be the culprit as well.  It just bothers me very much that things are allowed to be manufactured and sold when they cause problems like this.  I have a house full of quality electronic items and not one problem, but people 1/4 mile away from me are causing me to pull my hair out!!
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WA1RKA
Member

Posts: 25




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« Reply #8 on: April 27, 2003, 10:57:48 PM »

Hi,
Another potential source of trouble are the new wireless weather instruments that operate in the 433Mhz range and while they are only supposed to have a range of 200 feet a sensitive receiver could be hearing them.

73
John
wa1rka
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VE3EGA
Member

Posts: 12




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« Reply #9 on: June 10, 2003, 10:42:47 AM »

Hi,

A few of other things to check for:

1. Carbon Monoxide Detectors (eg Ambulance Garage) some use a microprocessor that generates RF hash at UHF! Anything else with a MIcro in it!

2. FAX Machines - mostly VHF RFI

3. Graphic Cards with TV Tuner.

4. Paging Transmitters, Infant Monitors?

Good Hunting

73 Terry
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