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[Amps] Hot Switching

To: <amps@contesting.com>
Subject: [Amps] Hot Switching
From: Ian White, G3SEK" <g3sek@ifwtech.co.uk (Ian White, G3SEK)
Date: Fri, 15 Nov 2002 16:45:39 +0000
KL7RA wrote:
>Ian
>
>Interesting comments on hot switching, some remarks:
>
>>It depends on the combination of the transceiver, the amp and
>> the voice.
>
>I have not seen any hot-switching problems using commercial ham
>amps, but I have only operated Alpha, QRO and the AL-1500  with
>QSK installed. The "export" only amps usually don't have QSK and
>I notice now it's becoming a $200 option on some models.
>
The Ameritron and some Alphas use PIN diode QSK, which is very fast and 
will work fine... if the transceiver timings will let it.


>I measured the wiper travel time on several Dow-key relays using
>a counter and 10 kHz source that could handle a dead short. I had
>shorts on the NC/NO ports and the counter would only see the
>10 kHz when the wiper was in motion. The average time from start
>to close was around 12-14 milliseconds depending on the bounce
>from the contact cleaning slide action. I was not able to improve that
>time much even increasing the coil DC to over twice. Maybe 2 or 3
>milliseconds was all. Dow-key RF relays in amps no longer work
>with modern radios even with speed up circuits.
>
I wonder if that's due to the very long spring arm - probably the harder 
you hit it, the more it will bounce so you don't gain much.


>>only simple answer I can think of is to use a contest logging program
>>with a built-in DVK facility and a hard-wired PTT output - the
>program
>>will have a user-configurable delay between PTT and the start of
>audio
>>output (same for CW keying also).
>
>Not sure one is available. The problem is Logging software can insert
>the PTT signal before the DVK pulse when the F key is hit but it needs
>to know when the DVK voice message is over so it can release PTT.
>
>Speaking for TRLog which has CW and paddle PTT control, no PTT
>signal is available for a DVK. The DVK boards I use turn on and off
>PTT
>with the message. My suggestion was to have TRLog insert PTT for 20
>miliseconds then remove it. By then the DVK PTT signal would hold the
>amp relay until the end of the message.

That seems to be the general technique - get a fast PTT/keydown signal 
to the amp, any way you can, and the existing software/hardware will 
take care of the rest.

-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                            Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

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