Signal strength boosted Sun 17th?

[EyesToTheSkies]

Listening to 118.825 today, the signal strength from the controller seemed to double between 2 listening sessions, around 1 hour apart.

I doubt any atmospheric changes would've had any effect over such a short period, and there were no other local changes made between the two (pc on/off etc)

Is the signal now routed through an additional transmitter closer to me? (I'm 10 miles south of Stansted)

[RobertK]

Actually it would be possible for that to be caused by athmospheric changes.

I remember a situation last year when we could clearly hear naval vessels talking on VHF which were as far west as you can go in the Baltic - while we were as far east as possible in that "lake" on a vessel ourselves. :)

That situation came up quite suddenly and lasted for days.

Regards,

Robert

[Keef]

If the barometric pressure is high (1030 or more) then things start to happen at VHF. If it goes very high, the effect can be "interesting".

[threemiles]

I doubt any atmospheric changes would've had any effect over such a short period, and there were no other local changes made between the two (pc on/off etc)

Watch out for high pressure, temperature inversion with height and clear and calm weather and you will most likely experience a phanomena called ducting on VHF. When you tune in other transmitters in the direction of the one you heard you will most probably also notice an increase in signal strength. Range of ATIS and VOLMET stations even if unheard usually are a good inidicator for such conditions.

[SM4 Pirate]

Perhaps they changed to the secondary or tertiary transmitter site; which is closer to your location?

[EyesToTheSkies]

Thanks for all your replies.

The effect has subsided even though the pressure is 1030mb; I guess that the temperature inversion variable may not quite be playing ball at the moment.

ETTS.

[tired]

I experienced this effect when doing circuits for my PPL (more years ago than I'm going to admit in public :) ) in the circuit in Durban, South Africa one winter's morning (high pressure + an inversion, as described above) - we heard the tower in Abidjan, Ivory Coast which is 3000 nm away, on the other side of the continent!! Two transmissions, clear as a bell!

[MikeStanton]

Regarding signal deviation in strength, I listen to Thames Radar on 132.7 which I believe comes from Tatsfield near Biggin Hill, any way Aviation radio is AM, ampitude modulation i.e the louder a controller speaks the more power the transmitter will produce, sometimes just using a different microphone or terminal may make a difference..... some controllers are louder than others, there is a lady who occasionly works thames who is allways very loud!! ;)

[Airways B]

Not true, compression is used early on in the voice transmission process to even out any changes in volume produced by the controller. With a scanner on the ground, unless you are quite close to the transmitter, the signal you are receiving will not at times be nescessarily strong due to obstructions etc. Any atmospheric changes can increase the signal, as can reflections from aircraft.

[OwnNav]

Interesting stuff ref Tropospheric Ducting on here:-

http://www.dxinfocentre.com/tropo.html