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

Re: Helix and preamp issues

There is a design for a 70/23cms preamp, by G0MRF, described in this month's
Oscar News (AMSAT-UK).
He describes this as being designed for satellite opperation, with very good
strong signal handling (for mode VU/J). I would think that this would be an
ideal partner to a 70cms helix.
Try a google for his website.

I have built one and it will go on my helix for 70cms. I will report my
results (when I finish the full system rebuild).


Jerry wrote:
>> 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.
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