Folded dipole in France

[halfwave]

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.

IMG_20170430_105453-01.jpeg

Does anyone know why they are like this? rather than having an folded Omni dipole.

[yellowbeard]

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.

[halfwave]

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

[Maximus]

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


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[Albert H]

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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[nrgkits.nz]

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.

[Maximus]

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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[nrgkits.nz]

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.

[radionortheast]

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.

[Maximus]

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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