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Author Topic: intermod weirdness  (Read 2218 times)

Offline IQ_imbalance

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intermod weirdness
« on: November 19, 2017, 2205 UTC »
So I'm sitting here monitoring the 43m band for this evening's entertainment....everything is nice and quiet until BLAM.  I see a carrier pop up on 6935kHz which rapidly develops into severe intermod (local AM station, sounds like).  It lasted a couple of minutes, and then died down to a barely visible carrier signal.  I didn't touch a thing....

LOG/NE-SW unterminated BOG/DJ-130/800Mhz Yagi
Central MD

Offline ChrisSmolinski

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Re: intermod weirdness
« Reply #1 on: November 19, 2017, 2326 UTC »
Most likely overloading. It's possible a transient strong signal appeared that caused the overload. Could even have been a nearby transmitter like a CB, etc.
Chris Smolinski
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Offline skeezix

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Re: intermod weirdness
« Reply #2 on: November 20, 2017, 0143 UTC »
I get some minor intermod on my ALA-1530S+ from MW. When listening to HF, I put in a high pass filter that blocks MW & below.

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Offline Josh

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Re: intermod weirdness
« Reply #3 on: November 20, 2017, 1601 UTC »
There was something going on in the idunnosphere yesterday. Around 1520 eastern I was tooling down the highway listening to 1450 and noted a weak echo, but it wasn't an echo, it was pre echo of the actual signal. First came the weak sig then a few ms later came the actual broadcast of the same words. I wondered if there was another cochannel sta running money talk but no, there was some funky delayed mixing going on. The sig on 1450 isn't strong enough to encourage imd and there aren't any am stas within several miles so I attributed it up to sum freaky mode splittin up in tha d laya, yo. It cleared up a few mins later. I suppose something like this could enhance mw stations and put some imd on receivers tuned to hf.
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Offline Pigmeat

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Re: intermod weirdness
« Reply #4 on: November 20, 2017, 2249 UTC »
I was noticing some weirdness with some of the local 24/7 one lungers that are normally reliable day and night late yesterday evening. They were being swamped by distant stations normally inaudible or barely so, with echoing as Josh described.

Once the "Coast to Coast AM" came on with many running the feed of that it became apparent that there was real lag in feeds of "C to C" going out to it's affiliates.

There was a massive could front with heavy wind that moved across most of the eastern 2/3's of the Lower 48 from Thursday to early Sunday. I wonder if the wind knocked their downlink antennas out of whack?

On RW's comment, my house sits on a corner lot with a four way stop sign at the back of the property. On one side of intersection there is a pull off where the city cops hide to nab speeders. When they key up to announce they're heading after someone, it does the same thing to my radios. A CB'er yapping into modified rig and running a power amp is worse. You might as well give up until you hear the last of their vehicle pulling off into the distance.


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