[BC] SS versus thermionic finals

[Robert Meuser]

There are solid state TXs and then there is the DAX which worries me. It 
does not appear to be user friendly repair wise. I have only seen one on 
the NAB floor but I saw lots of surface mount parts on the PC boards. 
The reports I have gotten from those who were beta sites were not 
impressive. Hopefully some of that dissatisfaction has been resolved.

I have seen tube transmitters severely damaged by lightning and I 
believe either flavor requires proper lightning protection.  As for EMP, 
I am not a sure as you that even a tube TX could survive that.  The 
transmitters that will survive are the ones completely off line not 
connected to an antenna of a power source. A few stations have such an 
arrangement.

Remember with both lightning and EMP what does not come down the antenna 
can come in through the AC supply which is solid state regardless of the 
RF amplifier technology.

R


John Lyles wrote:

>Interesting discussion, really a variety of opinions on it. The Harris DAX 1 kW DSP PWM transmitter is about $17K delivered. 
>
>I wonder if people worry about this anymore: Lightning susceptability and EMP
>
>SS transmitters require active or passive lightning protection on the output, whereas tube finals don't, due the nature of the design having high voltage DC already. 
>
>EMP. Solid State transmitters don't have a chance with this. Of course, the days that we worry about USSR dropping the bomb here are gone. But the chances of an airborne explosion of a nuclear device, can generator horrendous impulse. Tube finals survive it, SS don't. Its a given. Hardening can be applied, as the military has done, but significant cost added. 
>
>Just another thought to factor in besides cost alone.
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