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
