[amsat-bb] Re: Easy to make, low cost omni-directional antennae

[Tony Langdon]

At 06:17 AM 3/28/2008, Bill Dzurilla wrote:

>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.

The Lindenblad is said to be quite good, but requires a bit more 
mechanical work to build.

>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

A directional antenna really does improve things on 70cm.

>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 wouldn't bother with a switching preamp, unless you're planning on 
using the omni for transmitting (e.g. for working the ISS 
repeater).  You certainly don't need a switching preamp to work any 
of the Mode J birds, because the uplink is on a different band, and 
you want full duplex capability if you can have it.  In any case, a 
good masthead preamp is a must for omnis.


>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

I have had a lot of success with a homebrew directional 
antenna.  Only reason I would consider an Arrow is for the 
portability as you mention.

>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.

I have heard this can work well, though I've never tried it.  You 
will want to make sure that the Yagi only has moderate gain, as you 
will need a fairly wide pattern, so that the satellite can still be 
on the edge of the main lobe at high elevation.

73 de VK3JED
http://vkradio.com