Email from K8TJ 11/11/09. His opinions and comments are his own:



Well Dave, all I can do is go by my experience because everyone seems to have an opinion on proper/safe amplifier keying these days. I have only heard of one incidence with a TS-950SDX and Collins 30L1. The rig literally exploded but it was actually traced to the 3200V HV for the 3-500's had shorted across the keying line somehow so the guy pumped 3200 volts into his Kenwood. Glad I wasn't around to witness that!

I have been making and selling relay keying cables for going on 5 years now on eBay with over 8,000 cables sold all over the world. My experiences has been that ANY Kenwood or Yaesu radio on the market today can and will key virtually any amplifier directly from it's keying circuit but of course a relay would provide total isolation between the radio and amplifier.

It's just a matter or personal preference on the YaeWood's but there is no question about it on Icom's. ALMOST all Icom's have poorly designed keying circuits which is just above TTL level which can't be used for anything other than keying a low current relay coil. Icom's definitely need a keying/isolation relay between the rig and amplifier. If not, you will INSTANTLY fry the external keying circuit.

The relays I use are rated at 200V and will handle up to 2 amps of switching current. The relays have a diode installed across the relay coil. I do give discounts for quantity orders and I urge any of your readers to view my 14,000+ feedbacks on eBay for CW-MAN and you will see what the buyers have to say about my cables.

Regarding the need for ALC... In this day and age with most all of the 100 watt solid state rigs ALC is not needed between the rig and amplifier unless your wanting to limit your drive to the amp for some reason. 

In a nutshell ALC is only needed IF your radio's maximum output exceeds your amplifiers maximum input ratings. Most amp's today will handle up to 120 watts of input and the rigs today even though they are rated at 100 watts, most only put out in the 85-90 watt range TOPS. So you can see that using ALC is of no consequence with 100 watt rigs. Use it if you want but it's not mandatory.

Now then, if you have rig such as FT-2000 with 200 watts maximum output you had BETTER use the ALC voltage from your amp to limit your rigs maximum output down to within the amplifier's drive limits. You could just turn your RF power level down BUT what if you forget and hit your brand new Alpha amp with 200 or 400 watts by accident ? Would not be a pretty sight.

Hope this info helps you can have your readers email at [email protected] with any comments or questions.
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Tim, K8TJ
Trustee for K8EY & WB8OGM Club Stations
[email protected]
"CW FOREVER"




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