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deliberate qrm on 40m
https://www.hamradiodeals.co.uk/forums/viewtopic.php?f=57&t=36348
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Author:  m0jha [ Thu Oct 25, 2012 5:05 pm ]
Post subject:  deliberate qrm on 40m

anyone else noticed it ? the last few weeks i have noticed a lot of deliberate qrm and it seems more than 1 station doing it .. normally i hear it in the evenings around .030 . i was having a great ragchew before and it started so we ended up having to cut short before it got too bad although my 2 and the other guys 5w was getting over it but that's not the point ..

billy

Author:  G3OBU [ Thu Oct 25, 2012 5:39 pm ]
Post subject:  Re: deliberate qrm on 40m

.


I was on a WAB net this afternoon on 40, and people were tuning up on the frequency several times.

If I want to call in on an established QSO or Net, I drop down or up a bit to tune, but always tune into the Dummy load, then just peak the ATU, its easy so why do they do it ?? ... I guess its these rigs that you just hit a frequency and it all sorts itself out. I am a plate and load man these days !!!

Author:  ei9ju [ Thu Oct 25, 2012 5:58 pm ]
Post subject:  Re: deliberate qrm on 40m

I listened just there now and there's about a 10kc swathe of noise centered around 7.160

Edit; the 2nd shot (edit has actually placed the 2nd shot 1st) shows it's bandwidth better as that's a 12khz filter it more than covering.

Attachments:
40m interference 2 [800x600].jpg
40m interference 2 [800x600].jpg [ 87.07 KiB | Viewed 1144 times ]
40m interference [800x600].jpg
40m interference [800x600].jpg [ 88.28 KiB | Viewed 1146 times ]

Author:  m0jha [ Thu Oct 25, 2012 6:00 pm ]
Post subject:  Re: deliberate qrm on 40m

It's not just inconsiderate tuning john , it's deliberate key downs etc .. They are lurking around to start the crap when someone calls cq or turn up on a freq and try blocking you .. not heard much during the day but seems a problem in the evening ..

Someone was getting the finger the other week but i don't think it's this person doing it , a few saw their botts with him because they thought it was him , personally i couldn't say ..

I'm not proud but me and another guy sat for a good half hour and drove a guy off .028 a few week back , he had the brass neck to sit on .028 sending some data mode .. not proud of doing it but me and this other guy made a point , it was a battle of wills but i wasn't moving , nor did my comrade :) i have the respect to stay away from there little bit so they should do the same ..

Author:  m0jha [ Thu Oct 25, 2012 6:01 pm ]
Post subject:  Re: deliberate qrm on 40m

ei9ju wrote:
I listened just there now and there's about a 10kc swathe of noise centered around 7.160



Gerry , i meant the real bit of 40 mate, cw :) lordy lordy not been that high for years ...

wish i understood what the pic meant , i can sus out the freq , after that i'm lost :)

Author:  ei9ju [ Thu Oct 25, 2012 6:39 pm ]
Post subject:  Re: deliberate qrm on 40m

Billy look at both plots, one is the swathe of interference and the other is the same part of the band when there's no interference, on the lower shot you can clearly see the two SSB signals each about 3 khz wide the interference nearly covers.
The plot I pasted when i first replied with the 3khz filter in place focuses in on the interference and the closeness of the peaks suggests a radar type signal pulsating very fast, the interference noise is a loud buzzing sound.
One plot is sampling over 25khz and the other is sampling over 100khz but there both centered on more or less the same part of the band.

Attachments:
40m interference 2 [800x600].jpg
40m interference 2 [800x600].jpg [ 87.07 KiB | Viewed 1135 times ]
40m two signals. [800x600].jpg
40m two signals. [800x600].jpg [ 88.35 KiB | Viewed 1135 times ]

Author:  m0jha [ Thu Oct 25, 2012 6:53 pm ]
Post subject:  Re: deliberate qrm on 40m

Cheers Gerry , i presume that is some sort of pc based program you run your radio with HRD ?? ? forgive the ignorance i'm a simple chap with a bunch of AA cells and a 2n2222 tranny , 2 if i'm lucky ... :)

Author:  ei9ju [ Thu Oct 25, 2012 7:29 pm ]
Post subject:  Re: deliberate qrm on 40m

m0jha wrote:
Cheers Gerry , i presume that is some sort of pc based program you run your radio with HRD ?? ? forgive the ignorance i'm a simple chap with a bunch of AA cells and a 2n2222 tranny , 2 if i'm lucky ... :)


It's an SDR receiver a bit smaller than a VHS video tape completely independent from the rig. The amp I have has two inputs, i have the rig in one and the SDR in the other so if I want to change from one to the other I just select input 1 or 2.
There's smaller homebrew versions that would be up your alley and you'd have a ball with one in the CW section as with the software available you can really hone in on a weak signal and bring brickwall filtering into play.
Here's your part of the band, look at the smaller screen at how tight the filter is pulled in, listening to it you'd get the impression it was the only signal on the band, he's in QSO.

Attachments:
40cw billy [800x600].jpg
40cw billy [800x600].jpg [ 88.68 KiB | Viewed 1128 times ]

Author:  m0jha [ Thu Oct 25, 2012 7:37 pm ]
Post subject:  Re: deliberate qrm on 40m

is that smaller screen a snap shot of the bigger one just concentrating on that particular little bit of freq ?

Author:  ei9ju [ Thu Oct 25, 2012 7:41 pm ]
Post subject:  Re: deliberate qrm on 40m

m0jha wrote:
is that smaller screen a snap shot of the bigger one just concentrating on that particular little bit of freq ?


Yes.

Author:  ei9ju [ Thu Oct 25, 2012 7:51 pm ]
Post subject:  Re: deliberate qrm on 40m

Here's a more congested part of the band, the station within the filter may as well be the only signal on the band.
You should try and get one to play with, you'd have a ball with it.

Attachments:
40cw billy 2 [800x600].jpg
40cw billy 2 [800x600].jpg [ 88.25 KiB | Viewed 1118 times ]

Author:  2E0SDK [ Thu Oct 25, 2012 8:01 pm ]
Post subject:  Re: deliberate qrm on 40m

there was a station transmitting a single tone as if they were tuning up on 20m and 10m on wednesday morning / mid day as my mate was trying for a vk station i really don't see what they get out of it to be honest i know they was not tuning as it went on for servile minutes and was doing it deliberately .....

Author:  ei9ju [ Thu Oct 25, 2012 8:03 pm ]
Post subject:  Re: deliberate qrm on 40m

2E0SDK wrote:
there was a station transmitting a single tone as if they were tuning up on 20m and 10m on wednesday morning / mid day as my mate was trying for a vk station i really don't see what they get out of it to be honest i know they was not tuning as it went on for servile minutes and was doing it deliberately .....


Thank God for a good notch filter....now you hear it now you don't. :)

Author:  G0TSH [ Thu Oct 25, 2012 11:48 pm ]
Post subject:  Re: deliberate qrm on 40m

m0jha wrote:
anyone else noticed it ? the last few weeks i have noticed a lot of deliberate qrm and it seems more than 1 station doing it .. normally i hear it in the evenings around .030 . i was having a great ragchew before and it started so we ended up having to cut short before it got too bad although my 2 and the other guys 5w was getting over it but that's not the point ..

billy



Billly

There was a PA1 stn knobbing around a while ago on the bottom end of 40m maybe its him again, he sends the worst cw you have ever heard.

Keith G0TSH

Author:  m0jha [ Fri Oct 26, 2012 6:15 am ]
Post subject:  Re: deliberate qrm on 40m

yes i heard a few people state he was messing around , i'm sure there is more than one doing it though. OR i'm being targeted ,mind you i do have a tendancy to tell them to check the antenna is plugged in as they are having little impact to me so maybe i am :)

never mind if it starts getting too bad i will stick another AA cell in series and up the power :)

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