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" <[email protected]> To: "Bob- W7LRD" <[email protected]> Cc: <[email protected]> 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 <[email protected]> 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" <[email protected]> > > *To: *[email protected] > > *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 [email protected]. 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 [email protected]. 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 [email protected]. 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
