163.775 & 163.825 blocking out VHF users

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Re: 163.775 & 163.825 blocking out VHF users

Postby G4RMT » Mon Nov 02, 2015 2:31 pm

The first thing to do is establish IF the licence conditions are being broken. As in, are the transmissions extending outwards from their centre frequency too far, or maybe they have large numbers of spurious outputs. Sadly, in many wide band receivers, there is no front end filtering, because the design is to make it sensitive over a very large range, and these strong data signals overload the input, create all kinds of phantom signals on frequencies where they really aren't and cause grief to listeners. I'd be surprised if these transmissions were not filtered with a band pass cavity or two at the site, and perhaps are not causing other license holders any grief at all. I guess you need to stick an analyser on them (like the RF Explorer series) and look at what is coming out - I'd bet you find a nice sharp peak at the carrier frequency and very little either side of it. Having one of these close to a frequency you want to listen on is never going to be nice. OFCOM will investigate interference issues from licensed users, but have very little interest in scanner enthusiasts. One of my repeaters when used in my van, wipes out Radio 2 - nowhere near it in frequency, but the van radio seems to have a front end like a barn door - and the UHF TX desenses the receiver. The repeater receiver, ignores it.

Could this be happening to you? If you look on an analyser and see numerous nasty spurious outputs, then OFCOM could well be interested in that - to save them effort when licensees complain, but if the analyser says it's clean - then the best you could do is insert a notch filter into your feeder to try to remove it and reduce the problem.
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Re: 163.775 & 163.825 blocking out VHF users

Postby milly » Mon Nov 02, 2015 6:07 pm

The system has been in use for 35 years now so good luck with making a case.
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Re: 163.775 & 163.825 blocking out VHF users

Postby SilverShadow » Tue Nov 24, 2015 10:02 pm

Davie Boy wrote:
In your area they may be using different frequencies as shown below.

163.7625 159.2625 Vodafone, VODAFONE DATA, UK WIDE
163.7750 159.2750 Vodafone, VODAFONE DATA, UK WIDE
163.7875 159.2875 Vodafone, VODAFONE DATA, UK WIDE
163.8000 159.3000 Vodafone, VODAFONE DATA, UK WIDE
163.8125 159.3125 Vodafone, VODAFONE DATA, UK WIDE
163.8250 159.3250 Vodafone, VODAFONE DATA, UK WIDE
163.8375 159.3375 Vodafone, VODAFONE DATA, UK WIDE


Checking my directory it is indeed listed as such... but a little different than yours...

163.7625 159.2625 VODAFONE PAKNET DATA, UK WIDE NATIONAL USAGE Fm KimmyJS19 Oct 2015
163.7750 159.2750 VODAFONE PAKNET DATA, UK WIDE NATIONAL USAGE FM KimmyJS19 Oct 2015
163.7875 159.2875 VODAFONE PAKNET DATA, UK WIDE NATIONAL USAGE FM KimmyJS19 Oct 2015
163.8000 159.3000 VODAFONE PAKNET DATA, UK WIDE NATIONAL USAGE FM KimmyJS19 Oct 2015
163.8125 159.3125 VODAFONE PAKNET DATA, UK WIDE NATIONAL USAGE FM KimmyJS19 Oct 2015
163.8250 159.3250 VODAFONE PAKNET DATA, UK WIDE NATIONAL USAGE FM KimmyJS19 Oct 2015
163.8375 159.3375 VODAFONE PAKNET DATA, UK WIDE NATIONAL USAGE FM KimmyJS19 Oct 2015
(http://ukscanningdirectory.co.uk/)


We updated those entries just before you got that copy. I've just sent you the latest version :walkietalkie:
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Re: 163.775 & 163.825 blocking out VHF users

Postby Davie Boy » Wed Nov 25, 2015 5:28 pm

Much appreciated :thumbup:
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Re: 163.775 & 163.825 blocking out VHF users

Postby scanhermit » Sat Nov 28, 2015 10:36 pm

I get a lot of crap between 163 and 164, but up here in North Yokshire, it's just those channels with the rest of high band being clear. Low band seems plagued by static though.
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Re: 163.775 & 163.825 blocking out VHF users

Postby JohnUK » Mon May 15, 2017 1:14 pm

THIS PROBLEM MAY SOON BE GOING AWAY :thumbup:

SEE viewtopic.php?f=21&t=5530

Heres hoping they knock both the 163 and 153 mhz systems off the air :thumbup:
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Re: 163.775 & 163.825 blocking out VHF users

Postby G4RMT » Mon May 15, 2017 6:11 pm

Might be worth mentioning that these signals are VERY strong, and simply swamp the front ends of receivers with no filtering - which covers most scanners and cheaper radios.I programmed up a cheap chinese radio and the nasty noises appear on many frequencies. My Kenwood, Icom and Motorola expensive business radios don't suffer on frequencies in the next band up.In many cases, these are powerful enough to receive here, half a mile away without an aerial. I don't think they really caused any signifiant interference, and are just very, very, strong.
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Re: 163.775 & 163.825 blocking out VHF users

Postby redman99 » Tue May 16, 2017 9:53 am

G4RMT wrote:Might be worth mentioning that these signals are VERY strong, and simply swamp the front ends of receivers with no filtering - which covers most scanners and cheaper radios.I programmed up a cheap chinese radio and the nasty noises appear on many frequencies. My Kenwood, Icom and Motorola expensive business radios don't suffer on frequencies in the next band up.In many cases, these are powerful enough to receive here, half a mile away without an aerial. I don't think they really caused any signifiant interference, and are just very, very, strong.
G4RMT is right.All radio scanners bar none are a compromise.
Due to compactness or cost limitations many have poor front end designs.
Fitting a notch filter before the radio can help.PAKNET signals are as said seriously stong.
Most PMR radio's can cope well, even a few channels away from PAKNET.
Find the WinRadio G315 ok too but not cheap.
Whistler TRX-2 BCD396T BCT15X CS-701 Plessey Vixen WinRadio G315 + other various old tat
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