[Amps] SB220 T/R relay substitution

[Ian White, G3SEK]

Alan Ibbetson wrote:
>>Date: Fri, 15 Nov 2002 16:25:35 +0000
>>From: "Ian White, G3SEK" <G3SEK@ifwtech.co.uk>
>>Subject: Re: [Amps] SB220 T/R relay substitution
>>
>>Tony Wanschura wrote:
>> >Does anyone know how much delay there is on the IC765 and 746 between
>> >PTT signal and RF output?
>>
>>On the 746 in all modes, it's about 12-14ms between the first
>>key-down/PTT and the start of RF output.
>
>On my 765 RF output begins 8.5ms after key/PTT closure (after that the 
>RF has a risetime of 3.5ms for 100% output on CW). This is the same on 
>QSK, or VOX, or if the rig is held on tx with the MOX switch.
>
>On QSK, RF output begins to decay within 0.5ms of key up and takes 
>another 3.5ms to reach zero. Hence the CW elements are each clipped by 
>8ms on QSK.
>
>If the tx is held on, eg with VOX, then the RF does not begin to decay 
>until a little over 8ms after key up. So the RF follows the keying 
>pretty much exactly, except it is all delayed by 8-8.5ms
>
>>The HSEND/VSEND outputs on the
>>DIN accessory sockets are the fastest for amp control, and they go low
>>about 5-6ms after key-down.
>
>On the 765 the "Send" voltage (+6v rx, 0v tx) follows the keying input 
>pretty much exactly, with no delay.
>
>...
>>So if you use HSEND/VSEND to key the amp, you have about 6ms for the amp
>>to get ready.
>
>So with the 765 you have 8.5ms for the amp relays to pull in.
>
Thanks - duly noted.

>>(Or if anyone in my part of the UK is prepared to lend me their MP for a
>>day, I'll happily measure it here!)
>
>I just bought an FT1000MP MkV. I no longer work for a company which 
>loans out digital storage scopes so it's kinda hard for me to make 
>these same measurements on the new rig. I'd happily loan it to you Ian, 
>but I live in Canterbury which is over the other side of the country 
>from you. Are you keen enough to fetch it? :-)

Thanks for the offer - but if I did, I'd only be using a conventional 
short-persistence scope.

Single-shot measurements can still be done using the storage devices at 
the back of your eyeballs, and the other device immediately behind them. 
Just set the timebase to single-shot, turn the brightness all the way 
up, and trigger it from the falling edge on the morse key. You can 
easily see and remember where the trace went.

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