Shared Frequencies

[FNG]

Yesterday I popped into Peterborough Sibson to get some fuel. Apparently empty circuit, lots of circuit r/t. Was my lookout really so bad that I couldn't see all of these people? It took me a moment to realise that most of the transmissions on the a/g frequency were from or to Blackbushe. I don't recall seeing the shared frequency mentioned in the published guide which I checked before I set off. Bourn has this problem as well, although I can't remember who it shares its frequency with. It's OK if people remember to say "Sibson" or whatever it is at the beginning of each transmission, but often they don't.
Where else does this occur? I gather that frequencies are in short supply, but couldn't overlaps between airfields close enough to hear each other be avoided? Are all of the frequencies in use really needed by those who've got them? I can think of places that have ATIS, GND, TWR and APP, but no radar, whilst other much bigger places get by without the GND and sometimes without the APP.

PS Sibson is well worth a visit if you haven't tried it: Very pleasant field, friendly welcome, and entertaining sight of entirely bonkers Ukrainian para-jump ship (called something like a Turbulentia). When it departs it thinks it's a Lightning on an intercept (with added blokes in stretchy suits dangling their feet out of the back door). When it returns a few minutes later (minus stretchy suits), it thinks it's a Stuka. When it lands and turns on its reverse thrusters it thinks it's a helicopter. Worth the landing fee just to watch that.

[ 06 August 2001: Message edited by: FNG ]

[Rallye Driver]

Stapleford has a shared frequency with Nottingham, and sometimes we can pick up their airborne radio calls. It seems to depend very much on the atmospheric conditions, although altitude must also be a factor.

I've also picked up other radio traffic inbound to Bourn. The first time it happened it was quite confusing as they were referring to runway directions which were completely different from what I was expecting and I though I had the wrong frequency.

The most bizarre occurrence was when I was flying to Earls Colne in a club C152 which didn't have the .25 steps on the frequencies. Having tried 122.4 without success I switched to 122.45 overhead Witham and got a reply from Goodwood. It's their frequency, but it was a good 75nm away as the crow flies, so it shows how far away you can pick up interference in the right conditions.

I assume (never assume anything!) the ground based station doesn't pick up the same interference, so if you happen to talk across a transmission it doesn't matter. But it is rather off-putting if you're trying to make a circuit call and can't work out whether the chatter is local traffic or not. :confused:

It's just one of the things that makes flying 'interesting'.

RD

[matspart3]

Dundee, Battersea & Gloucester share 122.90MHz. Although there's an obviuos geographical split, we do regularly get interference.

[JuicyLucy]

Waddington and Yoevilton share 127.35 - and very confusing it can be with both units giving RIS/RAS and talking to MIL a/c on UHF which we cant hear anyway !
Listen carefully I will say this only once..... :rolleyes:

[Yogi-Bear]

Whilst VHF is normally 'line of sight' and so shared freqs. sufficiently far apart shouldn't interact, during periods of atmospheric high pressure, 'tunneling' can occur. Thus VHF mimics AM or HF reflective propagation and carries further. We don't want 8.33kZ spacing in GA do we? Because if we moan too much, that'll be the answer. :eek:

[Squadgy]

At the airfield I provide FIS at we share with two other airfields. A while back we has a Mayday relayed by an aircraft in our circuit - Fire crew went to Full Emergency, and the incident was at an airfield about 140 miles away !! :rolleyes: :rolleyes:

[Wee Weasley Welshman]

Its a complete pain the backside and its not even necessary - there are plenty of alternative freqs in the spectrum if you dig around.

Only on Sunday I was over Welshpool (albeit at 30-odd thousand) and I called them on 123.25 just to say Hi as an ex-instructor there. It was real nice until Pembleshem or some similar sounding airfield asked me to shut up as I was interfering with their tower freq!

Roll on digital radio I say.

WWW

[Courtman]

I was inbound to Amsterdam (in a light single) the other day at 0330z working the approach frequency and had breakthrough from traffic leaving the EDN - I assume this to be Edinburgh traffic. Heard two different flights too, and I was only at 4000ft over Holland... Breakthrough can be right confusing at times...

[Spoonbill]

Our masters the CAA say, that each airfields frequency has a protected range, use the frequency outside that range, and you're on your own, so they say.
Unfortunately, they forgot to tell the weather man, who creates high pressure systems, which are conducive to sending VHF signals to ranges unheard of by us mere mortals.
The real pain in the ass is when the likes of Wee Weasily calls at high level, just to say hi, which is just irresponsible.
We share our tower frequency with an airport in Germany, which has the same runway configuration. Frequently, aircraft will call estimating at ----, for the ILS runway --, and we have ATIS information --.
Although we were not expecting the aircraft, in the early days, we commenced overdue action because all those features on that day were identical to our runway in use and ATIS letter.
The only way around it is, if you're not convinced of exactly who you're talking to, ask, and ask again.

[Wee Weasley Welshman]

Well hell - a quick hello ain't going to kill anyone.

Keep flying fun!

WWW

[You want it when?]

WWW - Agreed GA is supposed to fun, I presume that you listened out initially to confirm that you were not treading on anyone's transmission? Going off topic a bit here though and you a moderator shame on you.

[SteveR]

The only time I've heard interference (so far) is at Headcorn, but they're interfered with by a French field. Does anybody know which field it is? It'd be nice to know.

Steve R

[Wee Weasley Welshman]

Yeah, 'course I listened out for about 2mins before saying Hi. It was a crappy day for GA and nothing was heard. I flew from Welshpool for years and never got any breakthrough - I thought it didn't share the freq with anyone else. You live and learn.

Shame on me indeed. I'll be off to polish my halo now then...

WWW

[A and C]

Guys 8.33 is on the way ! eurocontrol are acording to "flight" talking about bringing 8.33 below FL240 as we speak.
Sounds like the answer to the problem to me.

[BEagle]

Welshpool Radio is an information service, not an ATC Tower frequency. My recollection is that one should NOT transmit on such frequencies outside 10nm/3000' (preferably 1000') from the site. For someone to call at over 10 times this altitude is, perhaps unsurprisingly, virtually inviting other users to complain!

'Saying hello', whilst well-intended, might well cause rather more important transmissions to be blocked!

So there. Right, WWW, write out a hundred times: "Llanfairpwyllgwyngyllgogerychwndrobwyllllantisiliogogogoch is a long way from Welshpool!"

Spelling mistake.....very probably too many vowels, look you!

[LowNSlow]

Looks OK to me BEagle except the LLLL could be a bit suspect :D

The field I fly from shares a freq with LGW ground (don't ask).

Southampton seems to share a freq with most of Northern France :eek:

[Wee Weasley Welshman]

Hmm, 10 miles 3000' - hadn't heard of that restriction and it certainly was/isn't an SOP there - not to say you aren't entirely correct BEagle.

I don't wish to give an impression of accepting gash r/t here - I was a complete r/t Nazi in Jerez and rightly so. But my action undoubtably lifted the spirits of half a dozen bored FI's sat watching the rain in the crewroom wondering how they were going to make it into the airlines - then up crackles me who was sat in that same crew room two years ago. Great morale boost.

Having listened to the freq for a good 2 mins there was no activity whatsoever heard and my transmissions were deliberately kept <3secs so any genuine caller had a chance to but in.

If you are going to do it then that is probably a sensible approach.

That said I agree in general that its not a good idea and if everyone did it every time they flew over somewhere they used to work then the whole thing would become a shambles.

WWW

[Squadgy]

BEagle, when you say Welshpool is an information service, that isn't the case. It's an Air/Ground radio station. They don't have qualified FISOs (callsign 'Information'), and can't provide any form of air traffic service unlike 'Information', with is a full FIS

[BEagle]

Squadgy - absolutely right. I meant to say a non-ATC service, A/G (ie 'Radio') is certainly correct. The restrictions I learned in my Air Law joy days applied to Tower, Approach and the 10 mile/3000 ft one applied to 'information'- and, I suppose, to 'Radio' sites.

Thanks for the clarification.

WWW - your happy-chatty calls whilst well-intentioned could one day interfere with serious transmissions. The Aeronautical Radio Service is NOT CB Radio!!

[Wee Weasley Welshman]

Indeed.

WWW

[Final 3 Greens]

A few years ago I was in the club office doing the paperwork after a flight when a very polite Scandinavian gentleman called asking for clearance to FL310 or similar!

As I had an A/G licence I called him back and explained who we were - he was very surprised as he thought he was talking to London Mil - never did find out whether it was breakthrough or just a wrong selection.

[Spoonbill]

Something to bear in mind folks,despite listening out before making your call from the air, it's highly likely that you will not hear transmissions from aircraft which are on the ground. Especially so the higher you are.
Irritatingly, the person in the tower and all other aircraft in the air will hear what you have to say, and in doing so, you interfere with ground transmissions.

[Dan Dare]

From the air pilot GEN 3.4.3 Para 2.2 (a) & (b)...
http://www.ais.org.uk/uk_aip/pdf/gen/10304.pdf

"In the case of TWR, AFIS and A/G facilities, communications on these frequencies should be restricted as far as possible to heights uo to 1000 ft in the immediate vicinity of the aerodrome concerned and in any event within 10 nm and 3000 ft."

The official line is a tad unreallistic and show the limitations of frequency allocation. As an ATCO I always appreciate a brief hello from a frendly voice when things are quiet in bad wx (just don't disturb the crossword/countdown/cards etc)

[EGTE]

The ILS on runway 26 at Exeter was/is on the same frequency of the ILS at Cherbourg. Several aviators approaching Exeter from the east have drifted out into Lyme Bay as a consequence. Disturbingly, many did not recognise the Cherbourg "ident" and, had a radar service not been available at Exeter, may have arived either in France or the briney!

[BIGJ91]

The airfield on the same frequency as Bourn is Popham and I think we pick them up more often than the opposite. I did once have a very superior sounding Bourn operator telling me I was on the wrong frequency and would I kindly leave their frequency NOW- till I pointed out that I was calling downwind for 26 and 129.8 WAS Popham's frequency. He went terribly quiet- can't think why :-)
The worst one down our way is IofW Sandown that has the French Frequence Club (Unicom effectively) 123.5 as its A/G given where Sandown is situated this is unfortunate to say the least.