RHCP...
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When you transmit RHCP and bounce against a passive reflector (the moon) then the signal returning to Earth will be LHCP. Popular feed designs for EME are e.g. 'septum' feeds OK1DFC for example). One feed, two polarisations (on different terminals). If the backfire helix has this feature, I don't know.
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Thanks Remco, I really should have thought of that, the correct 23cm eme RX sense was determined by experiment (I made both senses and listened), thus EME RX was found to be a left hand thread wind of the backfire = LHCP. Rather looks like I got the sense for Es'hail (RHCP TX required) wrong in the pictures, I will up date the page tomorrow along with some measured data on the feed. many thanks ....Graham , G8HAJ
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For those of you who want to buy an uplink antenna for a dish off the shelve I recommend the antenna from Winkler: http://www.winklerantennenbau.de
38,70 Euro plus S&H
internal view...
I think it's the same model?
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Hi I0LYL de IW9EZO....
io ho acquistato questa elica, credo anche tu......peccato che il cilindretto dietro per metterla sulla parabola, attacco N sia piccolo, devo aiutarmi con una pinza a becchi per dare una mezza stretta al connettore.....vedremo come funziona...al mio NA ho un RL di -22dB se non ricordo male.....
Sto vedendo per una patch, ma non riesco a trovare foto dettagliate...ho qualche dubbio, stio provando con oatch in FR4 da 1,5mm e riflettore in alluminio, volevo provare con riflettore in FR4....fara' da capacita ?....
Saluti de__IW9EZO
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internal view...
I think it's the same model?
There is also an article in the BATC forum about the Winkler antenna.
https://forum.batc.org.uk/viewtopic.php?f=101&t=5845
Maybe someone can make measurements too...
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HI Peter,
the photo I put is taken from that forum. Maybe I should report it. I ordered this helical feed but I have not received it yet. When it will be in my hands, we will do some measure. The mechanical solution seems good and also economic. @IW9EZO
Forse vanno svitate quelle due viti, tolto il collare, avvitare il connettore e rimettere il collare. Come dicevo non è ancora arrivata e quindi le mie sono supposizioni.
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C'mon guys, helices are known for ages, so it's (at least) peculiar 'we' are reinventing/questioning them from here. Google is your friend.
I0LYL : No, that helix is not the same as G8HAJ's backfire helix.
The 'winklerantennebau.de' is just a normal helix with a different approach to match the Zo ~120 (+j0) Ω to 50 (+j0) Ω. Nothing special and could be made with scrap materials for a few euro's. Having said that, of course the 'turn key' solution in a casing, ready to be mounted in a standard satellite dish, is invaluable ; -) This makes it that the price is 38 euro's (iirc) .Just to make a statement (I posted this pic earlier in this thread, appealing to the NIH (not invented here) feelings .... nothing new (old skool!):
Of course, feel free to reinvent the wheel ; -)
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Remco, in my garage I have already built three antennas, with different solutions. With more turns and with less turns. At the end I will decide what to mount in a fixed place. This one of Winkler will serve as a reference, or I will modify it. We'll see what to do.
In any case, there was no mention of G8HAJ's backfire helix.
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Of course, feel free to reinvent the wheel ; -)
I think nobody is reinventing here anything. Some people may just prefer to buy a ready made weatherproof solution for little money..
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ciao Lucio, un po' strano che non hai ancora ricevuto l'elica, io ho potuto fare delle misure dentro la mia stanza, in merito all'elica, uso un sweep Wiltron 6647B con il network Wiltron 562, testina sino a 18,6 Ghz, accoppiatore direzionale 1-4 Ghz della Merrimac, e montata su una offset da 80.
Se non ricordo male ho ottenuto -20 o -22db di RL, magari rifaccio la misura.
Io credo che non si debba smontare nulla, vedendo le foto e' una antenna economica, molto larga di banda, e io non ho le dita giapponesi per avvitare il connettore N maschio, ma ci sono riuscito lo stesso aiutandomi con una pinza a becchi sottili, certo non puoi serrare bene, pazienza.
L'ho presa per curiosita' e per essere pronto a salire sul sat per i primi test appena accendono, per i 10 Ghz solita prima prova con LNB sat-TV e IF in chiavetta sdr con software, vediamo cosa si vede in uno span di 250 Khz, credo che passino almeno altri 15 giorni, poco importa.
Vorrrei riuscire a trovare info sulle patch a 2400 usate per l'Uplink di AO-40, sto provando a fare qualcosa in FR4 da 1,5mm e penso di di aggiungere un riflettore stesso materiale, poi vedo cosa ne esce fuori, se hai info, te ne sarei grato....
73 de______maurizio
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HI Peter,
the photo I put is taken from that forum. Maybe I should report it. I ordered this helical feed but I have not received it yet. When it will be in my hands, we will do some measure. The mechanical solution seems good and also economic.
@IW9EZOForse vanno svitate quelle due viti, tolto il collare, avvitare il connettore e rimettere il collare. Come dicevo non è ancora arrivata e quindi le mie sono supposizioni.
Lucio, I've ordered the helix before xmas, and I received it after 3 weeks. be patient the helix coming soon. 73's.
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Hello,
I read on another forum that this helix from Winkler isn't worth the money to spent for, return loss (SWR) should only be +-4dB and circularity looks very bad. So test it first before you use it.
Jerry
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Hello,
I also already built a helix antenna myself for use in an offset dish, But the weatherproof - out of the box - solution from WINKLER for an affordable price cought also my attention. I also ordered one which is specially tuned to 2400 MHz (not 2450) (you can get this without additional cost, when you write an Email mentioning this). There is probably no difference but it "feels" better :-).
Maybe WINKLER could also produce a customized 7 turn helix-feed for 0,7f/d offset dishes.
73 de Johannes
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Hello,
I read on another forum that this helix from Winkler isn't worth the money to spent for, return loss (SWR) should only be +-4dB and circularity looks very bad. So test it first before you use it.
Jerry
Oh yes I will test it. It's clear but not everyone has the availability of anechoic chamber and antenna analyzer at 2400 MHz...
I have been built some helix for AO40, but just for curiosity I want to test the WINKLER helix. The test will be done on a 1,8 mt dish prime focus.
73.
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