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Re: Icom 910H - external relay control


I use a DEM sequencer with my FT-847 since I use my radio for eme as well
as satellite and local ssb/FM operation.  The current version of the DEM
sequencer uses relay contacts for all four levels of control: Rx, Relay,
Tx1 and Tx2.  I modified the DEM by adding two mic connectors so that I
might split out the PTT from my mic to control the sequencer.  The second
mic connector goes to the radio and the radio's PTT line is controlled by
Tx2.  Very similar to what Stan has with his ARR sequncer I would guess.

My CW key also plugs into the sequencer, so no possibility of transmitting
"accidents" into preamps!  The final thing I do is all coax relays are in
the TX path when un-energized so that a broken wire will not cause an
accident either!  The relays on the tower thus will connect me to the
antenna without endangering the preamp if problems crop up!

I just placed my four eme 2m antennas back into service after along period
of time on the ground.  Should be real nice for hearing mode-B satellites I
would guess...19.2 dBi gain!


At 12:09 PM 8/27/2002 +0000, Stan wrote:
>Hello Bart,
>For many of my radios configurations:
>I use an external box with a ARR sequencer. This box is connected
>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
>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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