Hearing VHF Base Transmissions

[bailey_uk]

Hi folks, recently installed a new SSJ VHF antenna  for my Scanner, and well pleased with the reception, but unable to hear any ATC transmission, just aircraft.

I thought this would be the case, as I live a fair distance from any main airport.
If I turn the squelch right up, I can faintly hear some ATC transmissions on certain frequencies but definately not enough to make anything out. Is this a typical case of needing a pre amp?

I am unable to get my antenna any higher, as its already 10ft above the chimney, and used RG213u cable to my scanner. (14m).

Thanks

James

[WAL 2T]

James,

There is a possibility that a good quality masthead amplifier might help but I would be inclined to replace the feeder with Westflex, Ecoflex or similar low loss feeder if you were going to consider this measure. Don't bother with a preamp at the receive end of the feeder, you would be wasting your money.

hth
Chris

[bailey_uk]

Ok cheers Chris, I bought the RG213u with the impression it was the best for VHF, and Westflex would be overkill and possibly the same loss, but I take it its not?

By the receive end, do you mean the scanner end? So it best to have the preamp connected to the base of the antenna or near?

[WAL 2T]

You need your preamp at the top of the mast next to the antenna unfortunately. The loss in your coax will be pulling the valuable signal closer the noise floor and placing an amplifier inside the house near the receiver will just have the effect of amplifying the noise as well as the signal which is already barely audible.

RG213 is ok under normal circumstances in that part of the VHF spectrum but in your case where every db at the antenna socket of your receiver counts the difference between RG213 and  a lower loss cable might just be the difference between hearing a readable signal or struggling to hear it.

[dudbaker]

James

Your profile indicates you are in the Lake District.  How far from Great Dun Fell.  Try 125.475   126.6   and   128.675.  Also, 121.5 on that transmitter as well as some Mil UHF.

Dudley

[bailey_uk]

Thanks for the info guys, Yeh I have heard of Great Dun Fell, is it a repeater station?

The 125.475 was the one VHF frequency that I managed to receive the base station last night.

[WAL 2T]

Not repeaters in the strictest sense of the word but remote transmission/receiver locations. R/T for London, London Mil, Scottish, Shanwick and Manchester ACCs are all remotely operated from various hilltop sites around the UK. Great Dun Fell is closest to you of course. If you're near the coast you may be able to hear the Snaefell site on the IOM, key ones:

130.975 Scottish ACC Talla Low sector
133.050 Manchester ACC
282.125 London Mil

[dudbaker]

James

That frequency is also on Sneafell IOM.  If you are not getting 126.6 which is Volmet then may be you are getting Sneafell.  Try 133.05 for Manchester control.  These transmitters are sending from Swanwick, Manchester and Preswick

Dudley

[WAL 2T]

James,

Just wondering which ground stations you are hearing faintly, do you have the frequencies to hand? Might be worth considering a log periodic fixed in the direction of said station if feasible and you have room on your mast. LPs for VHF/UHF are relatively compact and efficient directional antennae widely used for commercial VHF applications. I've built a couple for 2m/70cm portable operation and they work very well indeed.

[bailey_uk]

126.6 seems to be there very faint, like you say VOLMET, like a continuous transmission,

Im pretty sure it was the 124.475, that I heard last night and it was Cessna 404 Titan, G-MIND, 400CAD, Requesting to Route via Dean Cross - Pole Hill and then onto Coventry at lowish level.

My house lies directly in the line of DCS and POL so looked out for it and saw it fly overhead.

Added the suggested frequencies and listening out.

[dudbaker]

Good

Now let us look at 126.6.  As it is transmitted from several sites it cannot be on the same frequency as other sites, as it will cause interference.  So try 5khz low and 5khz high to see if there is an improvement.  The system is called Climax. 

What ever happens you are now able to check radio and antenna system at any time because as you said it is continuous.

Try 118.775.  This is Manchester transmitted from Preston.  If you get this then there are 12 more.

Dudley

[dca]

Sticking with the theme of VHF transmissions a strange thing has happened to me recently. I'm located just to the south of LGW, great reception area with the Reigate, Ventnor & Warlingham transmitters within range. I also have a roof mounted antenna.
For some reason, I cannot now pick up the Swanick controllers for 126.07, 128.425 & 134.9 any longer- these used to be 3 of my strongest signals too. Even at full squelch open I hear no ATC now.
Does anyone know if the transmitter sites for these frequencies has been changed?

[bailey_uk]

Yep 118.775 is one of my favourites, appears to be the frequency used for slightly lower flights, around FL195 into Manchester from the north, flying over head my house.

(Irritating thing is that the lower flights as mentioned above seem be mainly the 'Jersy' call signs, which are the FlyBe DH8D's with no ADSB!

[bailey_uk]

Good

Now let us look at 126.6.  As it is transmitted from several sites it cannot be on the same frequency as other sites, as it will cause interference.  So try 5khz low and 5khz high to see if there is an improvement.  The system is called Climax. 
Dudley

Wow,. yes your right!

126.595 is coming through considerably stronger, however squelch is still needed!

[WAL 2T]

Yep 118.775 is one of my favourites, appears to be the frequency used for slightly lower flights, around FL195 into Manchester from the north, flying over head my house.

(Irritating thing is that the lower flights as mentioned above seem be mainly the 'Jersy' call signs, which are the FlyBe DH8D's with no ADSB!

Draw an imaginary box approximately North-South distance Honiley to Dean Cross then East - West DOLAS to LIFFY, that's Manchester ACC up to FL285