[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Re: Helix antennas,



For built units, SSB Electronics are fabulous, and
fully weather-proof. ICom also has outdoor,
mast-mounted units. For build-your-own, Down East
Microwave (DEMI) has some nice kits, but you have to
roll-your-own outdoor enclosure. I've used Tupperware
containers from the supermarket with good results, but
they'll eventually fall apart from UV exposure
outside.
Advanced Receiver Research (ARR) also has units, but
they, too, require an enclosure for outdoor use.
I'm sure there are more, but these are the ones I have
experience with.
73, Jim  KQ6EA

--- Zachary Schrempp <ke7eyq@gmail.com> wrote:

> For those of you using preamps, which kinds do you
> find to be the best
> bang for the buck on 144 and 435 MHz, and where do
> you usually
> purchase them...or do you homebrew them?
> 
> Zach KE7EYQ
> 
> On 5/14/06, k5oe@aol.com <k5oe@aol.com> wrote:
> > Zach,
> >
> > > Thank you all for your input. It is nice to have
> so many helpful
> > > people give antenna advice.
> >
> > One of the things AMSAT members are best known for
> is giving people advice :-)  Seriously, Steve's
> reference to Kent's Cheap Yagi is a good choice for
> the current fleet of LEO's.  They are easy to build
> and tune and have the simplicity of a linear design.
>  Any pair of Yagi's in the 3-5 elements range are
> more than good enough for all the LEOs.  Adding at
> least a 70 cm preamp (at the antenna) is always the
> best money you will spend.
> >
> > Save the helix effort for 1.2 GHz and up:  I no
> longer have the page on web, but I built and used a
> 70 cm helix based on the AF9Y design (I used an
> aluminum pan for the reflector :-)) and found it
> fine for transmit, but not a good receive antenna
> for that band.  The reason?  By it's nature the
> helix is very widebanded (thank you Dr. Kraus), a
> real convenience when building a transmit antenna,
> but not so good for receive selectivity.  I found
> the wideband UHF noise allowed into the receiver
> (amplified by a wideband UHF preamp) to greatly
> degrade receive perfomance.
> >
> > Many people enjoyed success with helices on AO-40,
> including me, but that was a few years ago now and
> things have changed considerably since then.  The
> explosion of WiFi sources very near the 2.1 GHz band
> may very well have changed the spectrum profile
> enough to make a helix+preamp unusable in any
> densely poplulated area below 15 or 20 degrees
> elevation.  For S-band downlink on P3E and Eagle, I
> would suggest a narrow-banded antenna/feed such as a
> patch or Yagi is a better choice.  For uplink on 70
> cm or L-band, a helix is still a great choice. 
> FWIW, I employed a pair of concentric helixes for
> L/S on a 4' dish for about 6 months and they worked
> fine.  I replaced the helices with the dual patch
> feed now shown on the web page and was much happier
> with that arrangement (better s/n, the real
> difference).
> >
> > 73,
> > Jerry, M0MOE
> > ----
> > Sent via amsat-bb@amsat.org. Opinions expressed
> are those of the author.
> > Not an AMSAT member? Join now to support the
> amateur satellite program!
> > To unsubscribe, send "unsubscribe amsat-bb" to
> Majordomo@amsat.org
> >
> 
> 
> -- 
> Zachary Schrempp, KE7EYQ
> AMSAT #36023
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are
> those of the author.
> Not an AMSAT member? Join now to support the amateur
> satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to
> Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home