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Author Topic: "Chuffing" sounds on VHF  (Read 553 times)
K0AX
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Posts: 19




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« on: June 29, 2009, 08:57:50 AM »

I have several HTs of various brands and enjoy using all of them.  Each of them will, from time to time, receive rapid "chuffing" noises.  The sounds are like squelch tails but faster, often the same number of "chuffs."  Last night on the receive frequency of a local 2m repeater I was hearing groups of exactly 8 chuffs in about 2 seconds.  Then the channel would be quiet for a time and then the 8 chuffs would sound again. It did't seem to trigger the repeater and the sounds are too quick and regular to be from somebody keying a PTT switch.  These things are fairly common. Anybody know what they are?

Ken
K0WKM
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NJ2E
Member

Posts: 35




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« Reply #1 on: June 29, 2009, 10:00:28 AM »

Hello Ken, No being there, makes a diagnosis hard. But, my first thought is that the squelch is set a the lowest setting to silence the radio. Thus any local noise or weak signal opens the squelch. Even a temp change could effect a component and thus the squelch setting. Try increasing the squelch setting slightly. If the radio allows different squelch types (carrier or audio vs. noise)try that too. Regards and 73s, Don NJ2E
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WA3SKN
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Posts: 5484




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« Reply #2 on: June 29, 2009, 12:44:33 PM »

Sounds like an interference problem.  Have you tried to locate it with an old AM set?  That old ferrite bar antenna has some directionality in it you can put to use.

-Mike.
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GW0DIV
Member

Posts: 122




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« Reply #3 on: June 29, 2009, 02:42:23 PM »

Do you have pager transmitters near 2m? They sometimes break through at this QTH, but I can see their masts from my house. They're on around 150 - 155Mhz and are usually atleast 60 over 9.

Rhys
GW0DIV
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N6EY
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Posts: 107


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« Reply #4 on: June 29, 2009, 10:38:56 PM »

It's difficut to say. If it occurs consistently on several different radios, then I will toss out a guess and suggest intermod from somewhere in the area.  It's possible that a couple of transmitters are mixing in one or the other's finals to radiae a product.

Other causes can be leaky cable tv amps or cables and mast mounted TV preamps that have gone bad.

R/
Jason N6EY
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________________________________
73,
Jason N6EY
________________________________
K0AX
Member

Posts: 19




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« Reply #5 on: June 30, 2009, 08:37:01 AM »

Thanks to all who replied.  I'm guessing it's intermodulation.  Might be from my own cable TV stuff. Now that you folks mentioned it, it is worse in the living room where all the TV stuff is.  Also, I live in a fairly dense urban area and who knows what kind of RF sources abound.

I'm heading out to the New Mexico mountains later this week.  I'll play with the HTs out there in the middle of nowhere and see if I can hear the same thing.

It's all good! If Ham radio worked perfectly all the time, it would be about as interesting as cell phones.

73
Ken K0WKM
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K5YF
Member

Posts: 77




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« Reply #6 on: June 30, 2009, 09:09:56 PM »

Could be (in no particular order):
Computer hard drive... cable boxes have them too.
Computer wireless
Nearby cell phone
Wired computer network
Powerline & transformer noise
BOPL
aurora
microwave oven
HT batteries going dead
CATV
DSL
2m band opening
intermodulation
malicious interference
plasma tv
automotive ignition noise
brain scanner implanted by aliens
electric fence
lightening
rx desense by strong or nearby tx
the rare and exotic chuffing gerble

I wouldn't worry about it too much unless it makes that repeater, location, or band unusable.

-Brandon
-K5YF
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