I presently own a SS 1.2KW ham amplifier. This is my second unit as the
first was replaced when the finals (4 out of 8) FET failed. The unit uses a
total of 8 MRF-150 transistors. Unit #2 is now working fine but I am
cautious about trying to run it at its rated 1200 watts pep output. BTW,
the second unit burned out half of the 8 FETs so the factory has replaced a
total of eight transistors. The only thing I think I have learned is to
NEVER accidently apply 90 watts driving power to the amplifier or to try to
operate it in key down conditions without reducing the RF output about fifty
percent. The factory says it can run 1200 watts output PEP on CW and SSB
but does not give any duty cycles or list at what output it can operate
continuous duty.
I am considering take a step back in history to an Alpha 9500 with a ceramic
8877 and a key down rating of 1500 watts output continuous duty cycle. An
Alpha sounds like a deal compared to a $30,000 amplifier. Rockwell Collins
has nice 1KW and 4KW SS amplifiers. I suppose they would be willing to
sell one to a ham that didn't mind the price tag. Maybe it is time to
design power transistors that can be replaced like tubes. Even a klutz can
change a 8877 if he can afford a replacement and makes sure the high voltage
(3500+) is discharged from the power supply.
Tom AG8K
-----Original Message-----
From: Ron Castro
Sent: Thursday, February 24, 2011 1:39 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] KPA 500
I talked to a manufacturer who makes commercial SS amplifiers, and they do
have one that is bullet-proof, auto-tune for 1.5 MHz to 30 MHz, 1.5 kW which
is designed for military and short-wave broadcast. It's rack mount and only
a few rack-units. ...and it only costs $30,000! Wow, such a deal!
Ron N6IE
www.N6IE.com
----- Original Message -----
From: "Rob Atkinson" <ranchorobbo@gmail.com>
To: <tentec@contesting.com>
Sent: Thursday, February 24, 2011 10:04 AM
Subject: [TenTec] KPA 500
Big difference between designing a rig to operate on only one
frequency like a broadcast rig and designing a solid state QRO box
that will operate from medium wave up through VHF and make it plug and
play idiot proof.
rob
K5UJ
<<<Tubes are still a good way to go for high power, but it's true that
there isn't
much profit in the ham amplifier market. The price and durability of
solid
state devices will improve and make them more viable in the future, just
as has
happened in the broadcast industry. Just a few years ago, SS amps for FM
broadcast didn't make financial sense over 3 kW, but now they do for power
levels up to the 20-40 kW level. AM broadcasters went SS a long time ago
and I
don't think there are any vacuum tube units being sold in the 50 kW or
lower
levels. The same will happen for HF ham radio...it will just take
time.>>>
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