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Author Topic: What would cause more noise on just one 2m frequency?  (Read 271 times)

KK4GMU

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What would cause more noise on just one 2m frequency?
« on: August 04, 2022, 06:29:28 AM »

Note in the video that 145.330 has a lot more noise than any other 2m frequency.

What should I be looking for to overcome?

https://linksharing.samsungcloud.com/whbZ9sGb8auU
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IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

AB5CC

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Re: What would cause more noise on just one 2m frequency?
« Reply #1 on: August 04, 2022, 08:02:58 AM »

I have had this occur and it turned out to be an un-terminated Cable TV tap.  Lots of cable TV companies, if not all, use ham radio frequencies.  They can do this because it is a closed system.  A local cable technician said they can always tell when they have a "leaky" line because when I transmit on 2m at higher power, they start getting calls about channel 18 blanking out. 

Since they are operating in a closed system, they are required to fix the problem and avoid harmful interference to licensed services.  This may not be your problem, but it is a possibility to consider.

Kenneth, AB5CC
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WA3SKN

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Re: What would cause more noise on just one 2m frequency?
« Reply #2 on: August 04, 2022, 09:32:07 AM »

Since you are working with a broadband noise source I would recommend sweeping the frequencies in AM mode to locate the peak amplitude and not use FM mode.  Use the VFO instead of channels to locate the peak.

-Mike.

 
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KD2HCU

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Re: What would cause more noise on just one 2m frequency?
« Reply #3 on: August 04, 2022, 01:08:00 PM »

I had this problem on 145.210, and it was driving me crazy.  Turned out to be my computer monitor, shut the monitor and the noise stopped.
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N8AUC

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Re: What would cause more noise on just one 2m frequency?
« Reply #4 on: August 04, 2022, 03:28:57 PM »

I have had this occur and it turned out to be an un-terminated Cable TV tap.  Lots of cable TV companies, if not all, use ham radio frequencies.  They can do this because it is a closed system.  A local cable technician said they can always tell when they have a "leaky" line because when I transmit on 2m at higher power, they start getting calls about channel 18 blanking out. 

Since they are operating in a closed system, they are required to fix the problem and avoid harmful interference to licensed services.  This may not be your problem, but it is a possibility to consider.

Kenneth, AB5CC

Totally agree with AB5CC. Probably Cable TV leakage.
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AI5BC

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Re: What would cause more noise on just one 2m frequency?
« Reply #5 on: August 04, 2022, 04:37:20 PM »

What should I be looking for to overcome?

The source of the noise. Happy fox hunting.

Best place to start is with yourself. Turn the electricity off from your house. If the noise disappears, congrats, you found the noise. Something in your house.
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K0UA

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Re: What would cause more noise on just one 2m frequency?
« Reply #6 on: August 04, 2022, 05:04:21 PM »

Another vote for cable TV channel 18 leakage.  Could be some distance from your house.
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73  James K0UA

AA4PB

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Re: What would cause more noise on just one 2m frequency?
« Reply #7 on: August 05, 2022, 07:09:20 AM »

Cable leakage used to drive us crazy while driving around town. We even added a Tx PLL tone to the repeater output so we could use PLL to prevent the cable leakage from opening the squelch on our mobile receivers.
 
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Bob  AA4PB
Garrisonville, VA

KK4GMU

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Re: What would cause more noise on just one 2m frequency?
« Reply #8 on: August 05, 2022, 08:49:19 AM »

Well, this is strange.  I discovered that the cause of the elevated audio noise on that one frequency on my IC-7100 was due to the IF filter setting being set to 2 or 3.  The apparent audible noise level increases while the readability of the voice improves.  This was new info for me.  So whatever frequency I have the IF filter set at 2 or 3 will seem to have a higher audible noise floor but the actual S meter reading is lower.

Go figure.  Still learning this radio.
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IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot
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