Maybe ? not so dumb a question

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Maybe ? not so dumb a question

Postby roblegion » Sat Aug 05, 2017 5:23 pm

Listening in on the marine frequencies using RTL SDR, I get MASSIVE interference up to about 156.3 MHz, by massive I mean totally blown out it comes and go's almost as if someone was sat outside transmitting a million watts.

I have read that this can be caused by Sky broadband routers but I have even tried running the laptop on battery and turning off the power to the whole house!

Any ideas guys and gals?

Thanks.

Rob.
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Re: Maybe ? not so dumb a question

Postby Alfie » Sat Aug 05, 2017 7:20 pm

Are you plugging your sdr directly into the pc? if so that causes a lot of interference. if you use a usb extender cable it will cut down a lot of that interference.
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Re: Maybe ? not so dumb a question

Postby m0lsx » Sat Aug 05, 2017 9:01 pm

roblegion wrote: I have even tried running the laptop on battery and turning off the power to the whole house!


It's always a good starting point, but it does not preclude your homes wiring system form being the cause of your issue. As despite what some of the liars who sell powerline devices say, they do radiate beyond your home. So unless you also isolate your electrical system, power line systems you could still be getting mains borne problems in your home, even after switching the mains off.
And do not assume that it's only electrical items in your own home that can cause QRM (man made interference) Electrical items many yards away from your home can ruin your day with with unwanted radiated signals too.
Street lights, solar panel inverters, alarms systems, led light bulbs, LED TV's all sorts.
It can take a fair amount of time to track down a signal.
Buy a database from Kimmy JS19 via http://ukscanningdirectory.co.uk/
Or do Google search of this forum via https://www.google.com/cse/home?cx=partner-pub-6291336405621919:2662881632
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Re: Maybe ? not so dumb a question

Postby FreqFreak » Sat Aug 05, 2017 9:41 pm

Use a USB extension lead, wrap some of it around a ferrite rod, and make sure you use an external aerial. Works for me.
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Re: Maybe ? not so dumb a question

Postby JGR » Sat Aug 05, 2017 10:00 pm

You could also be subject to overload from paging systems and they broadcast with very high power. Some are in and around the area that you mention.
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Re: Maybe ? not so dumb a question

Postby roblegion » Sun Aug 06, 2017 6:36 pm

Many thanks.
I will try a ferrite tomorrow, but as I said in original post, it comes and goes, will try my marine set at home tomos and see what happens with the same set up.

Thanks again.
Rob.
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Re: Maybe ? not so dumb a question

Postby roblegion » Sun Aug 06, 2017 6:46 pm

Sorry for the add on, I have recently moved to a really c£"p location, the house and gardens are great, but I have a major (10+KV) line within 100m, also disgustingly bright street lights to the front and side. I have already made approaches to the local council, as I am also an amateur astronomer, Telescope use from my new home is a joke, I might just as well give I up.
I don't think the QRM is coming from the HV line as I assume that would be constant.

If I had an hair, I would be tearing it out.
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Re: Maybe ? not so dumb a question

Postby lars » Mon Aug 07, 2017 9:14 am

Some locations, including my neighbourhood, are just crap for radio. An awful lot of domestic stuff generates interference, but I have the additional hazard of a main railway line at the bottom of my garden. My only solution is to play radio in a field some way from any buildings. This seems to work, but it's a bit of a nuisance. I can also do some things from my car. I gave up trying to make any kind of radio work in my house a long time ago.
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Re: Maybe ? not so dumb a question

Postby G4RMT » Mon Aug 07, 2017 9:52 am

The data and pager services near me mean the SDR system I have appears to be FULL of rubbish - silent carriers, loads of nasty spikes - but all these are regular. Series of exactly even spaced spikes are generated in the SDR device because it's trying to be sensitive over a huge range, and be dirt cheap. There simply is no filtering, no screening, and the USB cable or direct connection allows all the rubbish generated in the computer to re-enter. Add the overloading effect of the strong pager/data signals and it's a wonder it works at all. They're great for seeing that is out there, but even a basic cheap scanner peforms better. Using a USB extension, and wrapping some turns around a big torroid will help reduce the noise, but my computer the SDR is connected to has 7 cheap switch mode PSUs connected, and each one adds to the crud on the system
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Re: Maybe ? not so dumb a question

Postby roblegion » Mon Aug 07, 2017 3:15 pm

Many thanks for all your replies.
I will take it one step at a time, the pager frequencies worry me as I am less than a mile from the counties main hospital and probably surrounded by doctors and surgeons, who may have pagers.
I thought pagers may have died a death with mobile telephones, but I know my friend who is in the fire service still carries one.
I still can't get my head around the way it comes and goes, I don't mean it's OK for 20 mins and then firestorm, but like every 10-30 seconds, there is no set pulse time it's very random, if it were pulsing I would suspect some sort of electro mechanical device but it's totally random.

73's guys I'll keep trying.
Regards.
Rob.
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