[amsat-bb] Re: Helical Antenna on 70 cm

[i8cvs]

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 at gmail.com>
To: "Bob- W7LRD" <w7lrd at comcast.net>
Cc: <amsat-bb at 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 at 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 at gmail.com>
> > *To: *amsat-bb at 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]
> > _______________________________________________
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> >
> _______________________________________________
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