I strongly urge one to use the "keying loop" provided by the Tentec Omni
VI
Plus system. Although it requires different and additional circuitry
within
the amp, it allows the switching to take place before RF is generated by
the
transceiver and subsequently applied to the amp thus the amp T/R relay has
switched and settled.
Good solution, but the extra circuitry required within an older non-TT amp
to establish a keying loop is beyond the means of most users. The sampling
of the Omni Six's "T" buss results in the closure of most amp relays before
RF is applied and has been tested with vacuum relays, PIN diodes, and even
fast open-frame relays with success.
But Bob raises an excellent point. The amp's internal relay still needs to
be fast enough no matter what scheme is used for QSK or semi-break-in. But
let's say that the HA-14 cannot switch in time without hot-switching when
sampling the Omni Six's "T" buss.. No problem. Simply move the Key-All
sample input line from the Omni's "T" buss right back to the input of the
lifted base resistor of the TO-92 transistor used to key the Omni's loud
relay for the amp. The Omni will not key the amp with lightning speed, but
this is exactly the condition wanted with sluggish amps. The T/R delay time
can also be set with variable drop-out time from the Omni's menu.
With either sampling point, the Omni will still key the amp silently, and
that is his goal.
I should have also mentioned that any time this portion of the circuit is
modified, a scope is an absolute necessity to ensure that hot-switching does
not occur. At the very least, this needs to be observed once after the
modification is complete and tested at low transmit power at high WPM
speeds. I use a commercial Bird RF sample, but an inductive sample loop
coupled close the rig's PA is adequate for a scope sample. If hot-switching
is occurring, it will be very apparent on the scope.
Paul, W9AC
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