"Still wondering about the TXInhibit feature though and whether (A) it's
a normal feature of most transceivers and (B) is it a useful feature for
modern amps like the Acom when wishing to operate CW/ full QSK? 73,
Stewart Rolfe, GW0ETF"
This is a useful feature if your transceiver's RF output power is available
before the amplifier relay finishes switching. This is more of an issue
with non-QSK amplifiers rather than with QSK amplifiers, since non-QSK amps
tend to use large power relays with relatively long (15-20ms) switching
times. As an example, I currently have a Yaesu MKV (which will be replaced
with a K3!!) that has a 0-30ms adjustable "amp enable to RF power output"
delay. The default delay is 5ms. I recently modified my ALS-600 amp for
QSK using high speed signal relays which switch in about 3ms. So the amp is
on-line before the RF is available, and so there is no problem hot-switching
the MKV. I have also used my MKV with both an EXPERT 1K-FA and a THP
HL-1.5KFX amplifier - and both of these amplifiers are QSK amps. However,
the 5ms delay of the MKV is faster than the relays in either of those two
amplifiers. So I could have connected up the TX-INH input to the MKV to
ensure that the MKV can't put out RF power until the amp says it is OK to do
so (the EXPERT has this output, but I don't remember if the THP does). BUT
- rather than do this I just set the MKV delay for 10ms. I see that the
TS-480 and TS-2000 have minimum delay specs of 10ms. The TS-2000, OMNI VII
and ORION all have 15ms minimum delay times. I measured the "HSEND to RF
output" delay time on an IC-7000 and IC-706MKIIG (ICOM doesn't have this
delay spec'd) and found the delay to be 10ms and 13ms repectively.
Phil - AD5X
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