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Re: Icom 910H - external relay control



Hello Bart,

For many of my radios configurations:

I use an external box with a ARR sequencer. This box is connected
directly
to the microphone. Mic PTT is fed to the sequencer.  

Four Sequencer outputs control:
		mast mounted legal limit low noise preamplifier DC power,
		The PA PTT, 																the IPA PTT, 
		then the transceiver PTT. 

Mic audio is passed thru a cable with transceiver PTT, back to the
transceiver.

Other PTT output controls use phone jacks.

The sequencer channel #1 output is wired to provide  +DC power to the
mast mounted preamplifier on RX only

I use a ground to TX scheme, but a +V to TX is possible.

An alternative sequencer is the Down East Microwave Inc. sequencer
with 4 channels of sequenced output, 2 each SPDT (NC-NO-Common)
"hard" relay contacts per channel. Another is the SSB/USA offering.

Configurable as your heart desires, +V, -V, GND on any output channel,
TX or RX

Caveats with using the transceiver to control the external
sequencer functions: 

	Usually, the spec is unknown on how much current the radio can
	sink or source to the external legal limit coaxial relays
	on the tower with the preamplifier. 2 each TOHTSU coaxial relays 
	= 0.18A each, plus the preamplifier = ~0.4 Amps.
	One older PA required the PTT GND to TX to sink 200 mA.
	
	If the radio output gives a PTT ground on TX, the ground
	may not be exactly  0.000 VDC but rather the voltage drop
	across a open collector transistor to ground. Only my FT-1000MP
	has a relay "hard" contact for the PA PTT control. 
	Other radios use solid state switching.
	One power amplifier, where PTT enabled the power supply on TX,
	required 0.00V to switch to TX.

	Measure the current needed on the PTT ground to TX lines
	to be sure you are within safe limits.

	If you exceed the radio's unpublished switching limits, 
	you will probably need a surgeon's skills to complete
	SMT repair.

	Be sure to measure the PA-IPA-transverter PTT, GND to TX for:
	Voltage open circuit (Voc),  and current short circuit (Isc)
	for all external connections to the radio.

	For legal limit, a external sequencer is needed to properly enable
	and disable system components, resulting in long term
	reliability, better contest scores, and better DX.




Stan, WA1ECF




"Jahnke, Bart, W9JJ" wrote:
> 
> Gang, anyone out there have a source for a mod (add on) to control an external relay (to control external KW amplifier bypass relays) using the IC 910H?
> 
> Thanks,
> 
> --Bart W9JJ
> 
> w9jj@arrl.org
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