Phenomenal VHF range!

[SmokingHole]

Today at 3000' approaching YTJU, heard a helicopter reporting overhead YESP on 126.7. Surprised, I looked up the GPS to find the exact distance to ESP was 360nm. I spoke with the chopper pilot and we were reading each other 5's.

Some crude trigonometry later and, between the two of us, the curvature of the earth produces a hill approx 28000' high and so obviously the signal was bounced.

Anyone else experienced similar?

[Tidbinbilla]

It's called the "re-transmit" phenomenon :E

TID

[triadic]

There is no re-transmit on 126.7 !

Certain atmospheric conditions can produce conditions which allow comms over ranges much greater than normal. Have seen (heard) it first hand talking on the ground between Derby and Hedland some years back.

[NAMPS]

Try Googling "Tropospheric ducting".

[Islander Jock]

NAMPS :ok: What I would have guessed to.

I recall operating an army VHF radio up at Lancelin range in the 80s and was picking up comms from Puckapunyal in Victoria. They certainly didn't teach us anything about that during our radio courses. :confused:

[Cap'n Arrr]

I remember being overhead YPEC near Newcastle, and hearing a Jabiru doing circuits at Parkes.:ok:

Arrrr, they be o'er thar horizon!

[QSK?]

Ppruners:

This phenomenon is referred to as "Sporadic E" (go to: http://en.wikipedia.org/wiki/Sporadic_E_propagation for more info). During Sporadic E conditions VHF and UHF radio range is increased significantly due to some of the signal being bounced off a very small cloud of heavily ionized atmospheric gas. In other words the VHF signal is temporarily acting like a HF signal.

There have been recorded occasions in the past where this phenomenon has caused problems for ATS in Australia. On one occasion (lasting 3 days) in 1975 on one of the old Port Hedland FIA frequencies (I think it was 120.7), FSO's and pilots were sharing the frequency with Dili Tower in Timor! The Port Hedland FSOs and Australian pilots were even able to talk directly to the Dili tower controllers on VHF 120.7, and did so. Another occasion in 1979 involved Sydney FS sharing a VHF frequency with Auckland Control and also being able to talk directly to the NZ controller on VHF.

[flying-spike]

I seem to remember when working in Brisbane FS that VHF range down the coast was enhanced by a coastal inversion. I wouldn't discount a more "technical" cause though like airservices linking the frequencies for a while.

[Towering Q]

Since when does ATC link 126.7?:confused:

Besides there is a whole lot of 'not much' between the two locations, except for the Caiguna transmitter, or possibly the one at Nullabor, both of which are out of range from Tjuntjun, especially at 3000ft.

Any ATC'ers care to comment.

[NOSIGN]

Could an overvoltage condition on the comm unit contribute?

[Keg]

Years ago as a clubbie I was working the radio room at Wanda (Cronulla, Sydney) and talking to one of the Surfers Paradise patrols on VHF! :eek:

[Towering Q]

You are openly admitting to having been a clubbie!:eek:

TQ...a frustrated inland surfer.:sad:

[airmuster]

Experienced the same thing yesterday whilst flying inland from YCAR. Had just lifted off when I heard helicopter departing YDRA, also on 126.7.
Thats around 270nm and got him 5's also.
Good ol days we use to call it "skip", but that was HF

[carbon]

Having admittedly limited knowledge of the subject, as TID said, isn't this just a repeater station at work?

[Keg]

You are openly admitting to having been a clubbie!

I was a young and silly teenager at the time. No one holds it against me these days! :}

[404 Titan]

carbon

126.7 isn’t put through a repeater as it isn’t an ATS frequency but rather a CTAF frequency.

Back in the days before D-ATIS was available in Hong Kong, it was widely known by CX crew that there was a spot at about 330-350nm HK where you could pick up the ATIS on VHF. Normally you wouldn’t be able to receive it until 250nm.

[Plazbot]

I don't know the specific freqs but sit next to the dudes up and around Broome etc and they get ducting from some tower freq in Indonesia.

[triadic]

I also recall either a Timor or Indonesian Tower frequency on 118.3 being heard at DRW.

In days gone by when FS covered the country with just a few frequencies, 122.1 and 120.7, it was much more common. Allocation of many additional frequencies on ATS has kept the same frequencies 300-400nm+ apart and the 'bounce' or 'skip' as we used to call it is not as common.

126.7 is used country wide and is more likely to produce the effect when the conditions are right.

[Jet_A_Knight]

Fancy all that!

And you could only have a 60/40 chance of getting SY RADAR on the ground at BK.:ugh:

[Chips]

same thing happens over here under a strong inversion (can happen upto VHF frequencies), can sometimes hear transmissions from the south island. about 400nm away

[The Chef]

The other day I was over the bite, at FL380 on centre 132.7 - and we were getting MEL ATIS breaking through. Thought that was pretty cool.