[amsat-bb] Helix vs. loopers

[Steve Raas]

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 with 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 Uplink.

 

Thoughts, Ideas & comments please.

 

 

-Steve Raas

N2JDQ

FN20vg