[Amps] Flex Power Genius XL 2KW amplifier

[Jim Garland]

I agree mostly with Victor's comments, but would like to expound on a 
couple things about QSK and semi-QSK which appear to cause confusion.

(1) Most modern transceivers have provisions for delaying RF to an 
amplifier, usually through a menu setting, to give the amplifier T/R 
relays a chance to close before zapping them with RF. In modern 
transceivers, there is more to this delay than meets the eye.

Consider, for example, the K3 and Flex 6000 series transceivers. The K3 
defaults to an 8msec delay, through menu setting TX DLY, and is 
adjustable up to 20msec. The Flex is adjustable from 0msec up to more 
than 1000msec.This delay does NOT mean that any CW characters sent by 
the operator will be lost if they occur before the delay is reached. 
There are no dropped dits, even if CW at 60wpm is sent from the git-go. 
Instead, a memory in each tranceiver records what the operator is 
sending and plays it from scratch once the TX delay is reached. With the 
K3, the entire delay range is brief enough that an operator probably 
wouldn't notice what's happening, but if the Flex is set near its 
maximum delay of 1000msec, the effect is VERY noticeable.In this case, 
the Flex remembers everything sent for the first second, and then time 
shifts the transmitted signal by that amount. In other words, if you 
send "Op here is Jim" during the first 1000 msec, then when the amp 
finally comes on line a second later, it faithfully amplifies "Op here 
is Jim" without missing a beat. It's quite a weird thing to listen to.

(2) The K3 has only a TX DLY menu setting, but the Flex also has an 
adjustable ACC TX output setting. (Actually, depending on the model, 
there are several ACC TX outputs, most associated with RCA jacks, and 
these have independently settable adjustments.) These are the cables 
(s)that go to the amplifier relay jack, and their delay determines has 
soon the amplifier is brought on line after the key is pressed. Like the 
TX DLY line, the ACC TX line is adjustable from zero to over 1000msec. 
Normally the ACC TX delay is set at zero, so the amplifier doesn't have 
to wait around any longer than necessary. Frankly, I don't see why that 
delay should ever be greater than zero, but maybe there's some reason 
having to do with SO2R operation.

The speed of the T/R switching is a consideration, but for semi-break-in 
and full break-in relay chatter is also an issue.Open frame relays 
(including those with plastic covers) are inherently noisier than vacuum 
relays. Also, with QSK and semi-break-in, the wear and tear on relays 
can be considerable. With respect to the Flex Power Genius XL, it's not 
clear that the T/R relays are sequenced properly for CW operation. The 
company hasn't published any circuit diagram of the amplifier yet, but 
for CW operation proper sequencing is essential to avoid hot-switching 
and SWR blips reflected back to the transceiver when the amp is keyed.

73,

Jim W8ZR




On 10/12/2018 10:26 AM, Vic Rosenthal wrote:
> Most CW ops that do not use full QSK do operate semi-QSK. And in that case the delay between the amp key signal being asserted and the t/r relays closing and settling reliably is just as critical as full QSK. Many non-QSK amps are deficient in this area, which leads to hot switching, chopped initial characters, loud initial transients, etc.
> There is also the annoyance of the noise in the shack from clunky relays, also an issue with SSB VOX.
> Personally I use full QSK less than 10% of the time, but I would want a QSK-capable amp even if I never used it.
>
> Victor 4X6GP
>