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T/R Switches for RF Amps..Yes or No

May 3rd 2012, 01:33


Joined: Feb 27th 2008, 09:26
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Total Posts: 0
Having never used an RF amp but considering getting one for my handheld to use mobile, and then later perhaps get one for my HF rig. I am confused as to whether some sort of switching from tx to rx needs to be installed between the radio and the amp. Some diagrams show amps connecting directly to the radio, while some articles I read speak of a switch/relay between the radio and the amp. Could someone clear this up for me? I don't want to max out my checking account for a nice amplifier(s) and then find that I need to buy or build some sort of relay box before I can get on the air with it. Or, worse yet, trash my rig through ignorance...
May 3rd 2012, 13:25


Super Moderator

Joined: Apr 4th 1998, 00:00
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Nearly all amplifiers sold for amateur service include a bypass switch--about the only exception I can think of are microwave amplifiers sold to highly advanced hams.

The switch/relay you read about has to do with interfacing old amplifiers with new rigs--back them--it wasn't unusual to use line voltage relays for switching--I actually had a line voltage relay for a short time with my first station. Some new rigs can't handle much voltage or current, so it is necessary to use an interface to prevent damaging the internal relay or switching device.

Getting an amp for a mobile sounds like a good idea, but may not be a good idea in practice--handheld receivers are severely compromised to maximize battery life--they are much more prone to interference than mobile radios.

An HF amplifier can certainly make a difference, particularly for casual voice--it is much easier to find a ragchewing partner when you are loud. Surprisingly enough, many DXers actually do quite well without an amplifier--many DX stations don't run an amplifier either--if you can hear them then they can certainly hear you! But, being loud certainly is an asset in pileups.

Zack Lau W1VT
ARRL Senior Lab Engineer
May 3rd 2012, 15:56


Joined: Feb 27th 2008, 09:26
Total Topics: 0
Total Posts: 0
Thank you muchly, Zack, for taking the time to clear up my confusion. No more angst about the amp issue for me.

John Davis AE7JD

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