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Noise on 2m


#1

I have recently sent the following email to the Editor of the VHF Column in Radcom. Has anyone else noticed this when out on hills?

Dear Norman

I have recently been getting back on 2m SSB. An early task was to construct a halo antenna for the car. This works well but I have been surprised at just how much noise one can hear driving round town. Although the level was worse than I would have expected, I was not surprised to hear some noise. What has really surprised me though is the level of noise I hear when out portable on hilltops.

A while ago I was on Shining Tor (IO83WG) and noticed that there was a pronounced peak in noise when I beamed towards Stockport/Manchester (over 14km away). Last night I was on a hill called Gun (IO83XD) and could not fail to notice the electrical noise when beaming towards Leek (again some kilometres away). This was not using some huge array either, in each case the antenna system was modest, as was the equipment.

Both these hills are some distance from habitation and I would have expected them to be “quiet”. It seems to me that weak signal DX is simply not possible anymore for the urban dweller and that even rurally based stations may be suffering (in some directions at least). This man made noise is surely the limiting factor on receive performance for most radio amateurs these days on 2m.

73

Richard
G3CWI


#2

In reply to G3CWI:

Today I activated G/WB009, Worcester Beacon. I used a simple dipole, and was surprised to find the 2m band very nearly as rich in birdies as it is in Brum! The most inconvenient one sits on the SSB calling channel, it was stronger on top of the Malverns than it is in my home shack, but there was a couple of dozen strong birdies between 144.200 and 144.400. Several FM channels were infested, too. Mind you, 2m is nothing compared to 6m!

At the current rate of increase of birdies (and yes, I get the broad band noise, too!) I reckon that within 5 years VHF will no longer be suitable for weak signal work, which is little short of tragic.

73

Brian G8ADD


#3

In reply to G3CWI:

This is a problem which plagues me in the (very) rural village in which I live. In the frequency range 144.030 to 144.375 I have a continuous and very directional collection of S9 plus crud. Broadband noise and computer clock birdies predominate but I also get what sounds like data signals from the TV/mobile phone mast, a Tetra microwave link, the telephone exchange, the fire station and the ambulance station. In addition there are unbelievable (and very unstable) signals from domestic oil tank remote monitoring systems on 70cm. All my VHF/UHF rigs have state-of-the-art front ends so the problem probably doesn’t lie there. Combine that with a qth at 350m surrounded by hills at 1100m and you know why I despair about any operating on my favourite bands.

At least when out on the hills (provided they are not fitted with those large mast type qrm generators)the noise levels are somewhat reduced but, as Richard says, the noise is quite significant still. The question is, apart from computer clocks and Broadband, are these other interfering sources in-band violations or poor screening (therefore poor RF design)?

73

Barry GM4TOE