Scanning Low-Band VHF

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BravoHotelAlpha
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Scanning Low-Band VHF

Post by BravoHotelAlpha » 19 Jul 2018, 15:49

I've always found it difficult to receive low-band VHF particularly well (I include CB and the 66 - 88mhz band in this). I'm looking for how I could improve reception - I currently only have a mobile magnetic antenna which serves me very well, but would a wide-band Scanking in the loft improve on this to be worth the effort?

The main service I monitor is using low-band VHF at 84mhz but I'm only receiving bits and pieces. I'm about three miles away from their station but have difficult picking up local activity, I end up receiving a lot of activity from other stations that are on a repeater network which is interlinked with a UHF high site.

Any ideas appreciated.

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radiosification
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Re: Scanning Low-Band VHF

Post by radiosification » 22 Jul 2018, 10:07

If there's a specific small range of frequencies you want to hear well, then you could consider making an antenna that is suited to those frequencies. A half wave dipole will be easy to make and should work well, if you have enough space for one.
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Mitch
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Re: Scanning Low-Band VHF

Post by Mitch » 22 Jul 2018, 13:14

A home made dipole as suggested above would be easier and cheaper, it'd be aboout 6 feet end to end. Another option might be an FM radio beam if it's from mainly one direction, something like this, it wouldn't be so good for other frequencies though.
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Mikel
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Re: Scanning Low-Band VHF

Post by Mikel » 23 Jul 2018, 09:00

Unfortunately in recent years, man made noise on Low band has become so bad that even commercial operators are experiencing difficulties.

The RSGB VHF Manager John Regnault G4SWX, produced a report that notes Ofcom have increased the noise floor criteria used to calculate coverage areas for Low Band VHF from -104dBm to -92dBm.

This means you now need 150 watts to achieve the coverage once obtained with a 10 watt transmitter. This report was produced in 2016, so the situation may be even worse now!

This means that for my part of the world, that is hardly the most rf polluted part of the country i'm sure, low band monitoring has become a frustrating experience to the extent that I have largely given up on it.

I don't know what part of the world (UK?) the OP is in but obviously the 'noise' problem may be contributing to reception difficulties and if a specific transmitter site is of particular interest then maybe some kind of directional antenna such as a yagi or log periodic may warrant some some consideration.

BravoHotelAlpha
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Re: Scanning Low-Band VHF

Post by BravoHotelAlpha » 23 Jul 2018, 14:01

Mikel wrote:
23 Jul 2018, 09:00
Unfortunately in recent years, man made noise on Low band has become so bad that even commercial operators are experiencing difficulties.

The RSGB VHF Manager John Regnault G4SWX, produced a report that notes Ofcom have increased the noise floor criteria used to calculate coverage areas for Low Band VHF from -104dBm to -92dBm.

This means you now need 150 watts to achieve the coverage once obtained with a 10 watt transmitter. This report was produced in 2016, so the situation may be even worse now!

This means that for my part of the world, that is hardly the most rf polluted part of the country i'm sure, low band monitoring has become a frustrating experience to the extent that I have largely given up on it.

I don't know what part of the world (UK?) the OP is in but obviously the 'noise' problem may be contributing to reception difficulties and if a specific transmitter site is of particular interest then maybe some kind of directional antenna such as a yagi or log periodic may warrant some some consideration.
This is interesting, as I seem to get a lot of blank carriers and other noise. I've close to a hundred frequencies locked out due to this factor alone. However there is no interference on the service I monitor.

I like the idea of a directional antenna that would presumably work well given I now where the service's antenna is located and would limit some of the noise.

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