[amsat-bb] Re: Helix vs. loopers
w7lrd@comcast.net
w7lrd at comcast.net
Mon May 7 21:13:43 PDT 2007
Steve and all
I believe simply lengthing a helix will reach a point of diminishing returns. It would be better to stack a couple or even four twenty or so turn turn helix antennas (from VE3NPC). You could with proper phasing generate a CP signal from a couple of loopers. I just haven't heard of anyone doing that, though it looks good on paper.
73 Bob W7LRD
Seattle
-------------- Original message --------------
From: Steve Raas <sraas at optonline.net>
> In reading much of the discussion that has hit the BB lately in regards to
> antennas I figured Ide toss in my questions to the group.
>
>
>
> In trying to figure out which style antenna is going to suit my needs best I
> have a few questions.
>
>
>
> #1 Is a linear polarized antenna less efficient than a RHCP antenna when
> trying to receive or transmit to a rhcp signal / receiver?
>
>
>
> #2 If yes.. in theory how much?
>
>
>
> #3 In looking @ pre-built helix options for 1.2g I have found the DSH23-12
> which is a 23 cm RHCP 12 turn helix 14.5 dBic gain in a machined radome for
> best weather protection. 1.2-1.3 GHz bandwidth. 50 ohm feed wit h N (f)
> connector on 8" backplane. All stainless hardware; Designed for PHASE 3D
> uplink operation. Wide bandwidth actually covers from 900 - 1600 MHz (
> copied verbatium from the www.directivesystems.com website. In looking at
> the specs of this helix, it seems it may not have the desired gain for P3E
> or others. In 'theroy' is it possible to make a 24 turn helix , and if so
> would I be correct in thinking that double the turns would provide at or
> near 3.0 db of additional gain?
>
>
>
> #4 If yes to question 3 would this antenna be @ or near double the physical
> length?
>
>
>
>
>
> In a email I sent to Dave @ Directive he told me that the loopers he has can
> be arranged for vert/linear or horizontal polarization, so I do think that a
> looper although a great antenna may not be the best single antenna solution
> for 1.2 Uplin k.
>
>
>
> Thoughts, Ideas & comments please.
>
>
>
>
>
> -Steve Raas
>
> N2JDQ
>
> FN20vg
>
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