You can skip the automatic antenna tuner. Use an aim with the tuner to
set the tuner correctly for as close to a match as is possible.
Once the input to the toner sees an SWR of 1:1 and J=50 ohms hit it with
the amp. I do that with my tube amp into a dummy load, when I switch to
the antenna I never need touch the tuner or amp controls.
No, it's not as fast as an auto-tuner, but even with the auto tuner the
amp can't go on with full power for the tune operation and the external
tuner makes building more simple.
73
Roger (K8RI)
On 10/19/2016 Wednesday 10:31 PM, Jim Thomson wrote:
Date: Tue, 18 Oct 2016 18:20:45 -0500
From: Kevin <kstover@ac0h.net>
To: amps@contesting.com
Subject: Re: [Amps] Ampleon BLF189XR 1900W LDMOS transistor
announcement
W6PQL tested the NXP BLF188XR, the device he uses in his 1KW amps, and
came up with 1100W before hitting 1dB compression and it's a 1400W
"peak" device.
If I was building one with the BLF189XR I'd still use two devices. Run
each at 750W out and not stress anything. Might actually get an SSPA
that will do full legal, any mode, no time limit as long as you can move
the heat.
The big question is the low pass filter. The single most expensive part
of an SSPA.
### This is my problem with these SS amps, the LP filter. And you require
a myriad of them, not just one of em. On a NINE band ham amp, you would
require a bare minimum of SEVEN 1.5 kw CCS rated LP filters... AND you have
to be able to switch them in / out. You dont require ANY LP filters on any
tube amp.
## You also forgot the SS amps also require the fully automatic, 1.5 kw CCS
rated
antenna tuner. Again, a tube amp doesnt require a tuner. A SS amp will blow
its brains
out with swr. None of em will operate full power into a 2:1 swr.
## Your typ SS amp operates at 50% eff at best. So for a 1.5 kw CCS rtty /
FM
signal, the heat sink would have to be able to dissipate 1500 watts CCS.
That’s
a helluva lot of heat to deal with, which means a bunch of noisy fans.
## can it all be made to work, sure, but its not as simple as folks are trying
to make out.
An FM broadcast TX only requires a single LP filter, and the LP filter does
not require any
switching scheme. The FM broadcast TX doesnt even require a TR relay, since
its on
TX. Nor does the FM broadcast TX require an automatic ant tuner..nor does it
need to be
linear, imd is a non issue.
## Will 2 x BLF189XRs even do 1.5 kw pep with real low IMD ?? I dont mean typ
ham
junk either.
Jim VE7RF
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