No need to disable the exciter if it closes the amplifier relay before
RF starts flowing. Hook up a dual trace scope to the radio. On channel
to the relay puling a 9 volt battery to ground through a 1k resistor,
and the other to sample the transmitter RF.
With this measurement now in hand, determine your relay switching speed.
Now with the relay speed measurements made, Will the relays hot switch?
If there is enough time, no need to do anything else but hook up and enjoy!
I have a large writeup in the 2014 ARRL handbook on the CD. Although the
handbook is not out yet, it will be soon.
Also see http://www.w0qe.com/amplifier_timing.html for some typical
swtiching speeds of a few radios. Notice how crappy the IC7000 is! Opens
the "relay line" (although it's not a relay, its the H-Send line. But
this can be easily changed by using the T8 line). T8 works perfectly.
But you have to modify the radio to get T8 out the back of the radio.
I digress...
73
Jim W7RY
On 11/7/2013 1:46 PM, Bill Putney wrote:
Has anyone cracked this nut yet? I'm doing a mod to my Henry 2KD-4 to
replace the open frame T-R relay with Gigavac relays. I'm using the
SEQ-QSK sequencer to drive the relays. I want to use the "TX-INH"
(transmit inhibit) line into my FT-2000 to keep it from sending power
to the Henry while the relays are in motion.
The "TX-INH" line is on pin 8 of the "Band Data" plug on the FT-2000
and is intended for use with Yaesu's amps. Trouble is there isn't a
spec for that line I can find. So I looked in the VL-1000 service
manual to see what Yaesu does with it. Now I'm even more confused. The
lead starts out life as an open collector pulled up to +13.8V with a
10K resistor on the "Main" board. It then goes on to a connector board
where it is diode clamped to between +5 and 0 after a 1K resistor.
I've seen other references online to it being +13V to inhibit transmit
and 0 enable transmit. That seems at odds with it being clamped to the
+5 and gnd rails in Yaesu's amp.
Any thoughts?
Thanks, Bill - WB6RFW
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