I have preamps on multiple VHF and UHF antennas on the same tower
mast. All preamps are powered off together by a master sequencer so
if I transmit on one band all others are off. The TR relays also are
switched at the same time disconnecting all preamps from their
antennas when any one band is in transmit.
Exception are the HF antennas and two VHF antennas that are used on
FM (only one has an in-line preamp which is RF switched). I run
1300w on the eme array (ERP=135 kW) which is about 130-feet away with
no issues observed. The two antennas point at each other when the
Moon is in a particular position (az=235) but Moon is usually
elevated above the FM antenna (a yagi) by about 30-degrees so RF is
down about 25-dB in the direction of the FM antenna. Space loss for
130-feet lowers RF to a non-damaging level for receiving devices
(which I consider < 0 dBm).
Interestingly, the personnel RF safe zone on-axis for the 2m eme
signal is 75.52m (247-feet). But it is safe at head height directly
under the eme tower which is 13.7m (50-foot). I would not transmit
when anyone climbed the other tower.
A very nice program called EMRCalc is available from VK3UM to
evaluate RF safety zones from your antenna.
73, Ed - KL7UW
-----------------------
From: Don Wilhelm <[email protected]>
To: [email protected]
Subject: Re: [Elecraft] 144XV construction experience?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
That caution is not restricted to the Elecraft XV series transverters,
but is appropriate for any receiver that uses sensitive devices for the
receiver front end. The XV series uses the AT F 34143 for the preamp
front end. Yes, that is a sensitive device that can be damaged by high
RF input. It is prudent to use means to protect that front end from
excessive RF from other nearby transmitters whether that be an Elecraft
product or any other brand.
73,
Don W3FPR
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[email protected]
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