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Re: Easy to make, low cost omni-directional antennae



I have just been involved with the sats since February
and also wanted an omni for base station use.  I
started with a simple 1/4 wave ground plane (19" for
2m, 6 1/2" for 70 cm), later tried homebrewing Jerry's
Eggbeater II, and then bought a second-hand M2
eggbeater and the ARR preamp.  I noticed little or no
difference between the 3 antennas, certainly not
enough to justify the relatively high price of a new
M2 eggbeater.  The preamp helps a lot but, as Jeff
says, SO-50 is still quite weak.

Have not tried the Lindenblad.  Not many are using it
or talking about it, so I doubt it is all that great. 
Same for the turnstile.

I do far better with a 5w HT and a handheld Arrow than
I do with an IC-7000, ARR preamp, and any of the omnis
I have tried.  However, unlike some people, I don't
really enjoy standing in the yard holding the Arrow
antenna for 15 minutes.  So I usually work from
inside.

If you do go omni, get it high enough to be in the
clear.  And unless you get a preamp, use very good
coax and keep the line as short as possible.  You can
get a 70cm receive-only preamp from Ramsey Electronics
for $17, but with that you'll need a separate coax
line for the 2m uplink, or a duplexer.  The ARR is the
cheapest RF switching preamp and it's over $125.

I also homebrewed one of Kent's dual band LEO cheap
yagis, see
http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf.
It can be built for $10 and it works as good or better
than the far more expensive expensive Arrow, although
it's not quite as portable.  As Jeff mentioned, the
Arrow unscrews into very small pieces and fits in a
suitcase, very nice for air travel.  The cheap yagi
elements are glued to the wood boom, will fit into a
car trunk but is not suitable for air travel, unless
someone comes up with a different way to attach the
elements to the boom that allows easy removal.

Have not tried this, but I'm almost certain that a
cheap yagi mounted at a fixed 20-30 degree elevation
and rotated with an old TV rotator will be less
expensive and give substantially better results than
any omni, even an omni with a preamp. 

Good luck and 73,
Bill NZ5N
**********************************
Date: Thu, 27 Mar 2008 07:37:20 -0700
From: Jeff Mock <jeff@mock.com>
Subject: [amsat-bb] Re: Easy to make, low cost
omni-directional
	antennae
To: Graeme Nelson <zl2gdn@gmail.com>, "'AMSAT-BB'"
	<amsat-bb@amsat.org>
Message-ID: <47EBB120.30806@mock.com>
Content-Type: text/plain; charset=ISO-8859-1;
format=flowed

Hi,

I'm new to satellite stuff and I had essentially the
same requirements 
as you.  I live in a dense urban environment so I have
more QRM
 problems 
than most, limited roof space, and I try to keep a low
profile and not 
get the neighbors too excited.

I wound up purchasing two eggbeaters from M2, one for
70cm and one for
 2m:
    http://www.m2inc.com/products/vhf/2m/eb144.html

They work well, they are well-built, and are great for
AO-51, 
ISS-digital, and GO-32.  I also wound up getting an
ARR masthead preamp
 
for the 70cm eggbeater to compensate for my long
feedline to the roof
    http://www.advancedreceiver.com/page10.html

To tell you the truth, the two eggbeaters are marginal
for me working 
SO-50.  It is just above the noise and I don't feel
like I hear it well
 
enough to transmit.  If you want to listen for weak
signals you might
 go 
straight to a directional setup with more gain.  I
feel a rotator in my
 
not-too-distant future...

Eggbeaters aren't terribly portable.  The copperweld
loop is going to 
spring loose when you take it apart and poke someone
in the eye, so I 
don't move them.  For portable I got and Arrow-II
handheld 70cm/2m
 yagi. 
It's great fun and seems to be popular.  I used it
with an old
 Icom-W32A 
HT on vacation and used it to work AO-51.  It breaks
down really small,
 
fits in a little bag, and I can put it together in
less than 5-minutes:
    http://www.arrowantennas.com/146-437.html

jeff
AD6EO

Graeme Nelson wrote:
> Hi all,
> 
> I'm wanting to make an antenna for "talking with the
birds", mainly
 ISS and 
> LEOs.  Thank you to Don ZL1THO and John KB2HSH for
the suggestions
 and 
> encouragement they have already e-mailed me.
> 
> I have done some more thinking since then and come
up with the
 following list 
> of criteria for the first antenna I make for
satellite work:
> * easy to make
> * lost cost
> * omni-directional
> * good performance, especially for satellite work,
without moving it
> * portable enough that I can pack it into the van
when I go on
 holiday and it 
> won't take up much space (it needs to share the
space with all the
 stuff for 
> my wife and 3 children, as well as me).  It would
also be nice to be
 able to 
> store it in the corner of my office at work if I so
desire.
> 
> When I started looking in earnest last Friday, a ham
colleague of
 mine did a 
> Google search an came across a turnstile antenna
that looked
 promising 
> (http://www.wb8erj.com/turnstile_antenna.htm).  That
evening, I
 noticed the 
> eggbeater on the web site of John KB2HSH
 (http://kb2hsh.blogspot.com/), which 
> looks nice and easy to build.  I then did some
searching and came
 upon the 
> Eggbeater II by Jerry K5OE
 (http://members.aol.com/k5oejerry/eggbeater2.htm), 
> arguably a better fixed antenna for satellite use
than the original
 eggbeater. 
>   A while later, I also found the EZ-Lindenblad by
Tony AA2TX 
> (http://www.arrl.org/qst/2007/08/monteiro.pdf).
> 
> I am currently leaning towards the EZ-Lindenblad
(for 2m) and a
 parasitic 
> Lindenblad (for 70cm ... when I get hold of the
design; I intend to
 e-mail 
> Tony about it if/when I go ahead with the
EZ-Lindenblad).
> 
> How do these antennae compare performance-wise?  Am
I leaning in the
 right 
> direction (EZ-Lindenblad), or should I be looking at
something else?
  Your 
> input would be much appreciated.
> 
> TTFN.,
> Graeme
> ZL2GDN


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