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Re: PM demodulation

Started by Allan Herriman November 5, 2004
On Fri, 05 Nov 2004 10:11:08 +0800, Steve Underwood <steveu@dis.org>
wrote:

>Allan Herriman wrote: > >> >>All "solid state" finals for broadcast FM have been around since the >>'80s. At the time, they were better in terms of reliability, but not >>initial purchase price. >> >>I don't know how the comparison stands today. >> >>Regards, >>Allan >> >> >I said big FM transmitters. 100kW ERP from a silicon final stage? I >haven't seem that used
You're right. At 100kW, valves (tubes) still rule. Can't license anything like that around here though. Here's a 40kW solid state job from Harris: http://www.broadcast.harris.com/product_portfolio/product_details.asp?sku=WWWZDD40CD I think that's about as powerful as they get.
>Up to a couple of kW things are OK, but you need to stack too many well >matched transistors to keep scaling things. Minor mismatches cause a lot >of stress, and reliability tends to be rather poor.
Interesting. Usually solid state transmitters are used because they are *more* reliable (= more cost effective in the long term) that the valve units they replace. That was certainly the case for the microwave SSPAs produced by a company I used to work for. Regards, Allan