Re: 23cm interference


Dave - G4RQI
 

I post this in case you find yourself with the same issue. This morning I think we identified the Mini DisplayPort to HDMI cable as the culprit. Placing a hand over the device reduced the noise and unplugging it eliminated the noise altogether. The device appears to produce a carrier on 1297.750 with sidebands spaced in multiples of 66Khz.


Is anyone using a DisplayPort to hdmi device without any issues. If so what make and model is it?

We have managed to reduce the signal strength by bypassing a KVM. Wurth clip on ferrite good to Ghz made no difference. COVID restrictions meant this was all done over the phone so not ideal.

David


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of David Redman <davidredmang4idr@...>
Sent: Saturday, December 12, 2020 9:15:55 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 23cm interference
 
Well done Dave
At least you have found it
Good luck resolving the issue

Dave
G4IDR

On Sat, 12 Dec 2020, 19:22 Dave - G4RQI, <io93ir@...> wrote:
Found it ! - a neighbour has his computer connected up to a KVM switch and when he connects his surface pro doc I get a S9+10 on 1297.750 with sidebands spaced in multiples of 66Khz across 23cm. He also has a power line adapter.

So far we’ve had 30 min on the phone trying to resolve it but with little success. I can’t be sure what is producing the strong carrier on 1297.750

The question is how to resolve it. Plug everything in to a SEK mains filter apart from the power line adapter? I don’t care about the 1297.750 carrier it’s the sidebands that are the issue. Anything else?

Unfortunately the same neighbour wiped me out on 4m when he bought some new (cheap) led lights. Fixed that with ferrite. I was so hoping it wasn’t going to be him...

David - G4RQI

From: David Warr <io93ir@...>
Sent: Saturday, December 12, 2020 6:28:12 PM
To: g3vpf@... <g3vpf@...>
Subject: Re: [UKMicrowaves] 23cm interference
 
Found it ! - a neighbour has his computer connected up to a KVM switch and when he connects his surface pro doc I get a S9+10 on 1297.750 with sidebands spaced in multiples of 66Khz across 23cm. He also has a power line adapter.

So far we’ve had 30 min on the phone trying to resolve it but with little success. I can’t be sure what is producing the strong carrier on 1297.750

The question is how to resolve it. Plug everything in to a SEK mains filter apart from the power line adapter? I don’t care about the 1297.750 carrier it’s the sidebands that are the issue. Anything else?

Unfortunately the same neighbour wiped me out on 4m when he bought some new (cheap) led lights. Fixed that with ferrite. I was so hoping it wasn’t going to be him...

David... G4RQI


From: David Warr <io93ir@...>
Sent: Wednesday, December 9, 2020 8:31:51 PM
To: g3vpf@... <g3vpf@...>
Subject: FW: [UKMicrowaves] 23cm interference
 

Hello Ed,

 

I was thinking of a second hand Panasonic Toughpad with an Intel Celeron. There’s quite a few for sale on ebay but I don’t know if the Celeron is up to it or not. I have a laptop but it doesn’t lend itself to wandering around with hence I was thinking of using a tablet.

 

I have looked to see what others are using but I was hoping the interference might just disappear. I considered reporting it to Ofcom as they sorted out a problem for Mel on 70cm a couple of years ago but we weren’t in the middle of a Pandemic back then.

 

David

Sent from Mail for Windows 10

 

From: Ed G3VPF
Sent: 08 December 2020 19:34
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 23cm interference

 

Dave

 

SDRPlay works fine with one of the cheap Windows-based tablets.

 

Ed G3VPF IO80RQ

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Dave - G4RQI <io93ir@...>
Sent: 08 December 2020 18:56
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 23cm interference

 

Hello John

 

I looked for the device either side of 432.580 and there’s nothing there. Tonight it’s particularly strong and noisy and is present as low as 1296.200. I’ve noticed that it drops in level sometimes but it’s always on the same heading. I could do with a portable analyser/SDR.

 

Anyone successfully connected an SDRplay to a tablet?

 

73 David

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Dave - G4RQI <io93ir@...>
Sent: Saturday, December 5, 2020 9:44:09 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 23cm interference

 

No but I will once the 70cm yagi goes up ready for Tuesday night... ta

 

David

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of g4bao <john@...>
Sent: Saturday, December 5, 2020 12:52:08 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 23cm interference

 

Have you looked for it on 432.58?

I have something similar here.
3rd harmonic of some sort of crappy licence free thingy.

73
John

 

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