Scottish Information - Questions

[junction34]

I'm looking for some information on the service provided by Scottish Info on 119.875 in the South of Scotland.

Am I correct in understanding the service is provided from several radio sites all on the same frequency?

If so, what are the site locations and does each site have a slight frequency offset?

We've been having problems with the radio on our aircraft and although the radio has just been serviced by the manufacturer, we've still got very poor radio performance. There's no doubt in my mind the problem is with the aircraft - I think we've got breakthrough from the ignition system, and the antenna doesn't appear to have a very consistent radiating pattern.

Today for example, we had reasonable reception when flying away from the airfield transmitter, on other days it seems to work best with the other station is approx. 30 degrees either side of the nose. Hopefully by finding out the transmitter site locations I'll be able to get a better idea if the problem is the radiation pattern or if we're just not getting enough transmit power to the antenna.

The second question is if Scottish Info do have multiple radio sites, is there any triangulation capability like 121.5? If, for example, I'm faced with an emergency over the south of Scotland or north Irish Sea, would I be better to convey my position to Scottish Info or would a change to 121.5 be a better choice. The scenario that I'm thinking of would be an engine failure over water, which depending on altitude would give me between 30 sec and 5 minutes to try and make sure my position is known before depending on the PLB.

Thanks in advance, and if anybody has recommendations for a good radio engineer in the north of England or south / central Scotland I'd be grateful.

[BackPacker]

If you don't get a straight answer here, you might want to send fisbangwollop a PM. He (she?) works Scottish Info.

[flybymike]

He is indeed a "he"...

[Crash one]

I have recently been on a very informative visit to Scottish Centre Prestwick which was conducted by fisbangwollop & highly recommend it to all.
D&D, also in the same building, will welcome a practice PAN or training fix, they WANT you to call & become used to speaking to them.
fisbangwollop is the very man to tell you all about the system.

[fisbangwollop]

Ok guys I am here!!..:ok: Scottish info on 119.875 we use 3 tx/rx sites...one at Windy head on the Moray coast NW of Aberdeen, another on Craigowl Hill north of Dundee and the third on Lowther Hill NE of Dumfries......all these sites use a slight offset...unable to tell you what but will check with my tels guys tommorrow and report back....one thing though recently we had new equipment installed and I now find where as before we would get good 2way with aircraft in certain positions and height I find now this is not always the case and I believe this freq offset has something to do with that! especially if you are equi distance between 2 TX/RX site's i.e. St Abbs area. Also dont forget VHF radio is line of sight...theoretical range is 120nm at 12000ft but as most of you guys and gals :cool: operate at and below 3000ft the range can be very limited. If you want to test your radio out with me, send me a PM and i will give you the sector phone number so maybe we could do some tests one day. The noise you sometimes hear and assume is the a/c ignition could be caused by these offset frequencies (hetradyting!! unsure if that is the correct word as I am no radio expert)
As for auto triangulation no not possible on 119.975...Scottish D and D do have the facility on 121.5 but coverage is poor below 3000ft over the Scottish Highlands. The best thing in an emergency or Pan situation is if talking to me already (and yes please do I really dont bite!! :cool:) would be to advise me soonest, i will then ask you to squak 7700 assuming you have a transponder then every radar head that see's you will alarm SOS and at the very least help will soon be forthcoming with the aid of my military colleague's at Scottish D and D even though you are working me on 119.875.

Another problem certain pilots have told me is certain GPS sets in company with certain VHF radio's seem to interfere with the 119.875 freq in the aircraft....in a few cases the operators would rather use the GPS so therefore dont bother talking to Scottish..:(

OK well I hope I have cleared up a little of the mystique of my job but the best way for sure is one day come over and say hello ...:ok::ok::ok:

[junction34]

Thanks for the information fisbangwollop, it would seem that where we normally operate it would only be the Lowther Hill station we're working, and that would mean we were able to contact Scottish at a range of 60+ nautical miles - far further than I expected.

It also helps me with our radio issue as the one time we had a report of being unreadable we were almost directly nose-on to the radio station. This ties in with my previous experience. I think as we're only in range of one radio station it's not likely to be a radio frequency issue.

Thanks for the info on D&D coverage, do you know what the low level radar / auto-triangluation coverage is like around the north Irish Sea / Solway firth?

[fisbangwollop]

Hey J34...I have had a good chat with my tels guys this morning....it appears the Craigowlhill TX/RX site operates on the spot frequency of 119.875mhz, Lowther hill operates on an offset of -7.5khz and Windy head on an offset of + 7.5khz. This is done so that when I transmit from all 3 sites I dont just get a load of mush!!! Apparantley all aircraft recievers should have sufficient bandwidth to cope with recieving offset transmissions...that said I remember in my military days we could not talk to USAF F111 swing wing bombers if using multi channel TX/RX we had to select a single channel before their radios would recieve our transmissions. It apppears there are some certain types of radios on the market that have a poor band width capability..it would be interesting to know what radio you use and see if it is on the known list of offending radios. Another problem could be is the aspect your aircraft shows to the aerial site. Sometimes on certain tracks to and from the TX site your own aerial may be shielded from the TX site....altering your heading may indeed improve reception but of course not always practicle.

As for auto triang coverage over the north Irish sea/Solway as I said before the auto triang is a little old hat so dont worry too much there....providing you have a transponder and can squack in event of an emergency your 7700 code will be picked up very quickly and accurately from one of our many radar heads....Coverage over the Solway area is good as one of our main radars sits on high ground not too far away...that said at the moment it is off for long term maintainance as it has mode"s" equipment fitted. :ok::ok:

[flybymike]

Many thanks FBW. Interesting stuff. I did not know a lot, if indeed any, of it.

Would be interested to hear whether your "Tels" guys have any opinion or advice to offer on the recognised GPS interference on 119 frequencies. I find that particular problem quite a concern personally.

[junction34]

Thanks for taking the time to get the information, it's been very helpful - We've got a Narco Com 810+

The aircraft aspect is one major factor I'm looking at as radio performance is worst when the station is directly infront of the aircraft.

-j34-

[fisbangwollop]

J34...do we speak often??? I guess you operae from NS ??...I often speak to a PA28 operates most days from the island at 1500ft and lands Kirkbride...I have good comms with him all the way from departure at Andreas to landing at ZF...:ok::ok:

[fisbangwollop]

FBM....asked my tels guys today about the GPS problem but they didnt really have an answer...its a shame as I know more than 1 pilot one an Air Traffiker that cannot speak because of GPS interference on 119.875!!:(:(:(

[junction34]

Replied by PM!

[fisbangwollop]

J34....many thank, hopefully talk soon...:ok::ok::ok:

[Humaround]

We flew around Scotland in May last year, from Perth to Aberdeen to Kirkwall to Oban and back Sarf again. I fear we got a bit confused with Scot Inf. Is there just the one frequency?

I understood there were more than one, to be used as transmission conditions allow - can't remember the details now, but somewhere around Inverness we were invited the freecall Scot Inf, and then as reception deteriorated, we were given a different freq.

Sorry my memory about this isn't better, so I can't give more details. I do remember calling Scottish Mil at one point, got rather a perplexed response from them...

[Paul Bromley]

Great guys to have watching us across the water !

non intimidating and superbly helpful.

Thanks.

[TrafficPilot]

Apparantley all aircraft recievers should have sufficient bandwidth to cope with recieving offset transmissions...that said I remember in my military days we could not talk to USAF F111 swing wing bombers if using multi channel TX/RX we had to select a single channel before their radios would recieve our transmissions. It apppears there are some certain types of radios on the market that have a poor band width capability..it would be interesting to know what radio you use and see if it is on the known list of offending radios.

Rather than "poor bandwidth capability" I think it's more likely to be due to the radio having good filtering abilities to cut out transmissions from other frequencies near to your operating frequency. It probably "thinks" that the offset transmissions are rogue and tries to cut them out rather than letting them through clearly on your current frequency.

I have the same problem with the scanner I use to listen to ATIS/ATC before I leave for the airfield. On certain frequencies the controllers cut out/sound distorted unless you detune the scanner slightly (something you can't do on an aircraft comms set AFAIK)

Hope that made some sense:O

TrafficPilot

[fisbangwollop]

traffic pilot....as most ATC frequencys now use multi channel frequency's the need for greater bandwidth on the radio is paramount...especially now with the 8.33khz spacing freqs!!....yes I agree some radio's fitted have good filtering capabilities but it is indeed these radios now that are proving no use in communications with ATC..!!!!:D

[CJ Driver]

The best background source on offset carrier is AIC 72/2008, Pink 144, available in the usual way from the NATS AIS web site.

http://www.nats-uk.ead-it.com/aip/current/aic/pink/EG_Circ_2008_P_072_en.pdf

You do read all the AIC's don't you?

[fisbangwollop]

Of course we do and the Beano to!! :ok::ok:

[buggies]

We had directional problems on particular frequencies with a PA38 that we operated. It was (eventually) proven to be an unfortunate spacing between the aerial and the tail fin which caused signal cancellation. Moving the aerial a foot or so further away solved the problem.