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Author Topic: Spikes?  (Read 28723 times)

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jonjorobb

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Spikes?
« on: June 01, 2009, 08:25:36 PM »
Ive just noticed a few Spikes to the south. Possible extention range due weather? or just the usual spikes?

Thanks,
Jonjo

WAL 2T

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Re: Spikes?
« Reply #1 on: June 05, 2009, 11:13:08 AM »
There was a big VHF/UHF tropo opening on the Tuesday so it wouldn't surprise me if your increased reception was due to a similar but less intense type of enhancement. This type of enhancement is quite common on calm, clear summer evenings when the ground cools as the evening draws in: an inversion layer may form which refracts VHF and UHF signals beyond the normal radio LoS. This is often very selective in that the bloke 2 miles down the road might not hear what you're hearing for example.

Chris

Under the EGGP 27 Centreline & 15nm from EGCC

Squad 701

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Re: Spikes?
« Reply #2 on: June 05, 2009, 11:58:42 AM »
Hi WAL 2T/Jonjo,
Tuesday was when I got this extreme spike in the North-West,
off the coast of Donegal !

WAL 2T

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Re: Spikes?
« Reply #3 on: June 05, 2009, 12:34:51 PM »
It's quite an interesting one to consider really as an atmospheric pressure driven  tropo duct would normally only extend up to about 10,000ft or so. I wonder if anyone noticed the altitude of any aircraft recived under enhanced conditions over the past few days?

Having said that and given that the tx power of these transponders is relatively high (around 250W I believe) I guess it's possible that a ground reflection from a higher altitude aircraft could make it into a duct.

Wouldn't rule out meteor scatter either which would be consistent with receiving short bursts of data over over long distances for a short period of time (just as we use weak signal data modes like JT65 and FSK441 on the ham bands).
Chris

Under the EGGP 27 Centreline & 15nm from EGCC

jonjorobb

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Re: Spikes?
« Reply #4 on: June 05, 2009, 05:34:42 PM »
OK, Thanks for the great explanation.
Thanks too 701!

Jonjo