|To:||Jim Forsyth <firstname.lastname@example.org>,"Tower Talk List" <email@example.com>,Jim Brown <firstname.lastname@example.org>|
|Subject:||[TowerTalk] ARR Preamp Failures|
|From:||W0UN -- John Brosnahan <email@example.com>|
|Date:||Tue, 05 Oct 2004 09:16:39 -0500|
At 08:33 AM 10/5/2004, Jim Forsyth wrote:
I don't know which model you have but I looked on their web site and they have 25 watt models and 160 watt models. Took me about 30 seconds to find that out.
So I owe K9YC an apology--ASSUMING he is using the 160 watt model.
On the other hand my original statement IS true. RF switched preamps are PRONE to this type of problem by their very nature. The sensitive FET gets clobbered with RF for as long as it takes the preamp switch circuitry to detect the RF and actuate the relay. Which also would seem to imply that the radio is hot switched into the antenna. Meaning there is no load on the radio for some number of milli-seconds.
One wonders if the extra 1 to 3 dB of feedline loss might help play a role in keeping the RF voltage from getting too extreme under the switching transients.
And K9YC never mentioned the actual failure mechanism. I ASSUME that the FET died, but it might have been something else like the relay or the detection circuitry. But with a number of failures it is clear that the system is not functioning correctly. And whether that is due to a problem with this particular preamp, or with the preamp design in general, or with a system problem in the shack is not yet determined.
In any case it is not REALLY a topic for Towertalk--especially in view of Steve's recent reigning in of the off-topic messages.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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