On 10/19/2016 10:31 PM, Jim Thomson wrote:
### 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 onany tube amp.
Not necessarily. Assuming your "nine band" amplifier is 160 - 10
meters, the requirement is *six* filters as 20/30 (or 30/40), 15/17
and 10/12 can be combined. Further, if the amplifier modules are
configured in push-pull the second harmonic is cancelled and the
low-pass filter requirement can be further reduced.
> You dont require ANY LP filters on any tube amp.
Yes, tube amplifiers require LP filters. However, they are built
into the output matching network. If you were to build broadband
(transformer coupled) tube amplifiers with no frequency sensitive
components between input and output *as is the case with solid state*
you would need external LP filters to achieve the regulatory
standards for harmonic suppression. Many tube amplifiers for 50 MHz
*still need* external LP or harmonic suppression to achieve the
required suppression.
## 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.
Again, a fully automatic tuner is not required. Many of the newer
devices will operate into any SWR; properly designed protection
circuits will handle the most pathological cases and *manual*
tuner is satisfactory if one is not looking for *automatic, instant*
band switching. In that regard, a manual tuner on a solid state
amplifier is no different than tuning a PI or PI-L output on a big
tube amplifier (which in most cases can't handle a 2:1 SWR if tuned
to the "wrong band" either).
73,
... Joe, W4TV
On 10/19/2016 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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