Hi Rolf, NR0T
The KLM has the model 435-40CX crossed yagi i.e. a 20+20 crossed elements complete with a on board switching relay and phasing harness to get RHCP or LHCP from the shack
Since the above model is relatively old I don't know if you can get one of it actually in USA but the KLM now M2 produces similar models with better performance.
I have a 435-40CX still available on market in Italy at convenient and reduced price and it works very well.
Just for experimentation I have modified and upgraded this antenna to get four polarizations H-V-RHCP-LHCP on switching from the shack using four small coax relays and phasing harness on board of the antenna.
You can see this modifications reading my articles " Switching four Polarization on a 70 cm Crossed Yagi" published by the AMSAT Journal March/April 2007 Part-1 and May/June 2007 Part-2
Have fun !
73" de
i8CVS Domenico
----- Original Message ----- From: "Rolf Krogstad" rolf.krogstad@gmail.com To: "Bob- W7LRD" w7lrd@comcast.net Cc: amsat-bb@amsat.org Sent: Tuesday, May 14, 2013 4:04 AM Subject: [amsat-bb] Re: Helical Antenna on 70 cm
Thanks, Bob.
Is there a commercial yagi available for 435 MHz which is R-L switchable?
Rolf NR0T
On Mon, May 13, 2013 at 8:21 PM, Bob- W7LRD w7lrd@comcast.net wrote:
the helix is a nice antenna...however...once wound for either RHCP or LHCP there's no going back. So switching from R to L or L to R is out of the question. Unless of course the chosen polarity is always compatible with the satellite in use. Unless you have L and a R helix and switch between them, that can get a "little" involved. Many times it is very convenient to be able to switch between L or R during a pass, at times it can make the contact happen. This is of course is easy with a L/R CP yagi. I have used a helix for L band (1.2ghz ) as well as feeds for a 2.4ghz dish. They are a fine antenna with a fair amount of bandwidth. For a 16+ turn helix I have used stainless steel "U" channel for the center support. If Clair, VE3NPC is listening, he's the resident helix guy. Just my opinion, your mileage may differ. 73 Bob W7LRD Seattle
*From: *"Rolf Krogstad" rolf.krogstad@gmail.com *To: *amsat-bb@amsat.org *Sent: *Monday, May 13, 2013 9:22:57 AM *Subject: *[amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb