Hi,

I'm currently on holiday in France and was looking at their aerials, as you do when out and about

I noticed that the fm rx aerials seen to be a folded dipole which is then bent up and down at opposing ends. See attached photo. It's the aerial just above the satellite dish.
Does anyone know why they are like this? rather than having an folded Omni dipole.

That'd be for mixed polarity, a lot of continental big boy broadcasters seem to transmit in either horizontal or vertical but not mixed. This puts the onus on the listener to have a suitable aerial if they want the most available stations.

Cheers for the info Yellowbeard. That makes sense as to why it's shaped like that then.

Yep looks like a mixed polarised Triax or Vision aerial. Definitely not a transmit antenna lol


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Actually, in concept, it's not too far removed from a turnstile aerial! They're designed for mixed polarisation as well and show a loss in each plane, but the aggregate field strength is the same as a single dipole.

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It looks like a quad port LNB on the dish also. I used to have a large 3.7m aluminium dish here in Auckland, NZ to receive over-spill from the Australian spot beam on Ku band. I used a dual-pol Invacom quad port LNB with scalar ring and it worked quite well, although alignment of the dish and placement of the LNB was quite critical, I managed to get SNR of around 55% on the stronger transponders, others it was down at around 43% just enough to not pixilate. Some of the channels were encrypted with Irdeto1 and the keys common knowledge.

That's quite impressive being able to receive the Optus spot beam in NZ. I bet the Irdeto 1 was fun before they switched over to NDS.

People do similar things in Spain to receive the UK spot beams from Astra 28.2e.


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Yes, Irdeto1 was decommissioned. Now it's all Irdeto2 and NDS. Irdeto2 was more difficult to get working without a legitimate sub card, required hex files programmed onto blank cards the same way you'd program a 16F84 PIC to use with a TSA5511 pll. I used to use ICProg and the hex files could often be found floating around on various forums with the updated keys compiled inside them. The sat receiver I mainly used was the Dreambox for its Linux capabilities and the fact many softcams exist for it. These days it's Netflix for me.

this aerial has no gain, has minus 3 db figure in the horizontal plane, meant to be mix pol, its alright if you've got nothing else, more likely better used as a recieve aerial, it won't be wide band, problaly sent your signal back down into the tv, also folded dipoles usually have a balun to convert the impredence, theres a good chance it won't handle more than afew watts.

It is indeed a Triax:

https://m.elfadistrelec.ee/et/fm-aerial ... p/17810369

http://imageevent.com/holl_ands/omni/fm ... iaxfmzigma


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