[amsat-bb] Helical Antenna for 2-meters
Edward R Cole
kl7uw at acsalaska.net
Wed Feb 8 01:58:15 UTC 2017
It helps to be multi-lingual <smile>. Sounds as you got it under control.
I used a 16 element CC cross-yagi for AO-10 and the phasing harness
was not according the dimensions one would calculate but it
worked. I traded it for a M2 436CP42UG for AO-40 (which I still
have) and the CC 20 element 2m satellite antenna. 2m went kaput
early so I used the 432 yagi a lot for uplink in mode-US or LS. I
had a 50w linear which was overkill (usually ran about 20w). The
dish photo I shared was my mode-S downlink using preamp to two Drake
M2 is marketing an 8 element cross yagi CP antenna for 2m which is
probably just right in gain. Its pretty spendy, though. If you have
a couple 3 or 4 element yagi's you can combine them for CP and even
switchable in sense using a relay or two.
I am using a 2M7 by M2 linear yagi and only have 26 elements of the
big M2 436 antenna mounted. Not QRV yet as I am planning major
changes next summer.
GL on whatever you decide.
At 03:45 PM 2/7/2017, Dave Mann wrote:
>I just finished assembly of the Cushcraft cross-polarized yagi which
>I bought from a fellow Ham. It was like new. Now I remember what I
>really didn't like like about that Antenna. I put one together back
>in 1978 or thereabouts. Putting the phasing harnesses on was quite
>the job! I managed to remember curses in four or five different
>languages (tnx Army language school). Anyway it's all together and
>I mounted it vertically on a 10 piece of pvc pipe for testing. SWR
>was almost 1:1 over the range 432.5 to 437.0 then rose slightly as I
>approached 437 MHz. I'm a happy guy now. Next project is either
>the 2-m Helical we've discussed here, or two 3-element yagis with
>circular polarization. I already have the yagis, so that would be a
>no cost option.
>Sent from my iPad
> > On Feb 7, 2017, at 18:23, Edward R Cole <kl7uw at acsalaska.net> wrote:
> > Just scale the dimensions proportionally (except wire diameter);
> > ratio = 144/435
> > I built a 14 turn 437 MHz helical back in 1996 to receive the MGS
> beacon and built a 2.4 GHz 6-turn helical for 33-inch offset dish
> feed for AO-40. Plenty information in Amsat Archives. Original
> Kraus-W8JK design is optimistic in gain calculation.
> > http://www.kl7uw.com/Satellite%20feed.jpg
> > W9EK had good construction hints in prior publications.
> > For receive-only do not sweat getting a good SWR. I used a 1/4
> wavelength long 1/8 inch wide brass strip, run from connector to
> beginning turn of the helix for impedance matching. Space the
> point of connection to the helix about 3/16 inch above the ground
> plane reflector. Natural impedance of a helix is 140-ohm.
> > On air experience with the 432 helix was that a ten element CP
> crossed element yagi is better. But if you desire CP the helix is
> a natural, though not perfect.
> > 73, Ed - KL7UW
> > http://www.kl7uw.com
> > Dubus-NA Business mail:
> > dubususa at gmail.com
> > _______________________________________________
> > Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> > to all interested persons worldwide without requiring membership.
> Opinions expressed
> > are solely those of the author, and do not reflect the official
> views of AMSAT-NA.
> > Not an AMSAT-NA member? Join now to support the amateur satellite program!
> > Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
73, Ed - KL7UW
Dubus-NA Business mail:
dubususa at gmail.com
More information about the AMSAT-BB