[Amps] Questions on Alpha 8410

Jim Thomson jim.thom at telus.net
Wed Mar 1 13:14:50 EST 2017

Date: Wed, 01 Mar 2017 09:56:45 +0800
From: Alek Petkovic <vk6apk at bigpond.com>
To: AMPS <amps at contesting.com>
Subject: Re: [Amps] Questions on Alpha 8410

Correct. The overshoot, generates a DC voltage which holds the drive 
down for the next bit of the rf envelope. The overshoot has already 
passed out of the radio and through the amp.

However, if you have a permanent, constant voltage applied to the ALC 
line of the transceiver, you can set it up so that you will not get 
overshoot or overdrive.

Learned that from VE7RF.

73, Alek.

## Simplest method to derive a fixed ALC voltage for the xcvr is to use a 9 vdc
battery and a 50k or 100k  pot.  Most xcvrs  want to see negative vdc on their
alc input.  On a yaesu  FT-1000D or MK-V,  -6 vdc  will reduce the PO  down
to nothing.   9vdc   wired to ends of the pot.  Wiper and positive end of pot is wired
to the alc jack.  Wiper goes to the alc hot side.  Positive side to xcvr chassis. 

##  Then u can dial up any alc voltage u want  from 0-9 vdc, and tweak the PO
of the xcvr to an exact fixed amount, like say 76 watts.  Scream all  you want, and it
will never exceed 76 watts pep out.  The alc voltage has already been derived, and sits there
all the time.   Zero overshoots, cant happen. 

##  9 vdc / 50k =  .00018 amps.        9vdc / 100k =  .00009 amps.  Open off one leg of the
battery when not in use via miniature toggle switch.     9-18 microamps is dick for current.
Battery will last a loooong time. Array solutions uses the exact same scheme on their wattmeters,
to shut down the xcvr, in the event of a high swr on the output of any amplifier.   In that case, the pot
is tweaked such that the PO of the xcvr is zero.   Thats one way to shut off an amp, in the event of
detected high swr.   Opening off the key line is another method.  Opening off the TX inhibit lead on the
din connector on the back of the yaesu and most other xcvrs is a 3rd method..and all 3 methods
work good. 

Jim   VE7RF

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