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Re: [Amps] Amplifier lifetime

To: <>
Subject: Re: [Amps] Amplifier lifetime
From: "Paul Christensen" <>
Date: Fri, 6 Oct 2017 15:07:21 -0400
List-post: <>
Bill's suggestion of using a scope to evaluate system timing is a good one.
Hot-switching does not always occur on "make," meaning the leading edge of
the CW keyed element.  For example, the Icom 7300 transceiver hot-switches
on "break" when using some fast-switching amplifiers like the Alpha 87A.  

In QSK mode, the 7300 releases the amp key line approximately 3 ms. before
the RF waveform decays to zero.   A scope shows a clean ramped leading edge,
but a truncated falling edge on break when using an amp in QSK mode.  The
7300's TX DELAY menu does nothing to correct this type if hot-switching.
Amps like the Alpha 89 and Elecraft KPA500 will not allow switching back to
Rx until RF has decayed to zero.  It's odd that the Alpha 87A and 89 key
lines behave so differently, but they do.

Concerning the 7300, the fix is easy enough.  Icom simply needs a firmware
update to pulse-stretch the key line in QSK mode by more than 5 ms.  They've
been aware of the issue for more than a year, but to date, they've expressed
no interest in fixing the problem. 

Paul, W9AC

-----Original Message-----
From: Amps [] On Behalf Of Mark Robinson
Sent: Friday, October 6, 2017 2:47 PM
Subject: Re: [Amps] Amplifier lifetime

DX Engineering make this

I am using it on my TS930S since it used to cause a hot switching software
trip on the Acom 1000.

Mark N1UK

On 05-Oct-17 11:53 PM, Bill Turner wrote:
> ..........
> One method I have heard of but never used myself is to key the 
> amplifier first and then have the amp key the transceiver. Simple 
> enough on key down but key up is a little more complicated. You need 
> some kind of logic box to unkey the transceiver first and then unkey 
> the amp, just the reverse of key down. Perhaps such boxes are 
> available on the market?  I haven't ever seen one.
> 73, Bill W6WRT
> _______________________________________________

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