>>Our measurements on popular xcvrs over the past 10 years or so (e.g.,
>>TS-940, TS-950S/SD/SDX, FT-1000D, IC-781) found the shortest delay between
>>T/R relay external contact closure (to actuate the amp T/R) and output of
>>initial RF to be ~7 ms. If I remember correctly the 950 was much longer.
>>
>? Owners of FT-1000Ds have reported seeing RF output at 5mS.
>
>FWIW, my resent measurements of three popular transceivers are as follows:
>
>TS-950SDX -- 15ms
>FT-990 -- 10ms
>FT-1000mp -- 8ms
>
>Unfortunatley, the FT-990 does not activate the T/R line until 7.5ms after
>key closure, leaving only 2.5ms for the amp's relay to close!
? does the amplifier control signal pass through a relay in the 990?
> Further, this
>rig cuts the full 10ms off the CW waveform, resulting in very
>choppy-sounding CW in QSK mode and first-element clipping in VOX mode. This
>becomes noticable above 20WPM and gets worse as the speed is increased. My
>measurements agree with those that appeared in QST when the 990 was first
>reviewed. Bottom line, unless you use it with a PIN diode amp, safe
>switching with the 990 requires either an amp with built-in T/R sequencing
>(Alpha, Ten-Tec, Amp Supply, to name three) or an external sequencing
>circuit. You have to add some weight to get rid of the choppy sounding QSK
>and first-element clipping. You can do that with a keyer or there's a neat
>interface box described in the April 1987 issue of QST that will take care
>of both the sequencing and weight.
>
>The 950 and 1000mp activate the T/R line immediately upon key closure, and
>should be suitable for use with a vaccum relay amp. The 950 chops about
>2-3ms off the waveform, which is not audible to me. The 1000mp doesn't chop
>anything off. In fact, it looks like the 1000mp might even add a ms or two
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|