Is that VSWR of 65:1 key-down transmit at 1,700 watts, without any pulsing? So
if I accidentally transmit normal hand-sent slow CW into a bad antenna
mismatch, no damage will occur?
I've gotten really suspicious of those high SWR claims for solid-state power
devices because they are always qualified heavily by duty cycle.
--Cathy
--------------------------------------------
On Tue, 12/6/16, Ken Durand <N4zed@comcast.net> wrote:
Subject: Re: [Amps] Stock up on tubes?
To: "'Jim Thomson'" <jim.thom@telus.net>, amps@contesting.com
Date: Tuesday, December 6, 2016, 4:14 AM
Ampleon has added a new
LDMOS power transistor to its family of extremely rugged
power transistors designed specifically for use in high
power amplifiers operating in the 10 to 500 MHz. Suiting use
in a wide variety of broadcast and industrial applications,
and capable of operating with a VSWR up to 65:1, the device
is rated to deliver 1,700 Watt CW or 1,900 Watt pulsed.
https://www.everythingrf.com/News/details/3046-1900-watt-ldmos-power-transistor-for-broadcast-industrial-and-medical-applications
Ken
N4zed
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com]
On Behalf Of Jim Thomson
Sent: Monday,
December 05, 2016 11:05 PM
To: amps@contesting.com
Subject: [Amps] Stock up on tubes?
Date: Sun, 4 Dec 2016 22:48:45
+0000
From: Bill Turner <dezrat@outlook.com>
To: Amps group <amps@contesting.com>
Subject: Re: [Amps] Stock up on tubes?
On Sun, 4 Dec
2016 15:43:53 -0600, Kim wrote:
>When the SS devices are as easy to use
*and* and cheap enough to meet
>our
current hollow state device's price point, vacuum tubes
will go the
>way of the dodo. We're
progressing rapidly towards that, but it'll be a while,
yet.
REPLY:
In terms of the device itself,
that day is already here. The LDMOS devices from NXP are
fully capable of replacing tubes in a legal limit amp and
the price already beats tubes too. A pair of them that
easily puts out 1500 watts is around $400. Compare that to
an 8877.
You can be sure
designers are working hard to build the circuitry around
them that will soon make tubes pretty much obsolete.
FlexRadio already has a legal
limit amp that is awaiting FCC approval using said devices
and they expect approval before the end of the year.
As with everything, time will
tell.
73, Bill W6WRT
## Problem with SS is.....
they typ only run 50% eff. To get 1.5 kw CCS output
on
RTTY / FM, data modes, you require 3
kw dc input. 3000-1500 = 1500 W CCS
dissipation..
= 5115 BTUs.
## 1500 watts CCS
dissipation is one helluva lot of heat to try and
dump....which is not going to
be quiet
anytime soon. That would be a feat in itself...
just check out dishtronic.
## Then you require a myriad of 2 kw CCS
rated LP filters, and be able to relay switch em.
## Then you require the 2 kw
CCS rated auto tuner...so the SS amp doesnt blow its
brains out....
ditto with the myriad of LP
filters...and associated relays.
Plan B
is use enough devices so its rated for 2.5 kw out into a
1:1 SWR, so it will handle 1.5 kw
into
a 2:1 swr. Then use LP filters that will
handle 1.5 kw CCS into high swr.
## Then you require the 50 –100
vdc switching type power supply... but that is
not an issue these days.
## Then cross your fingers that the end
product doesnt have lousy IMD... like dishtronics –30 db
pep ( IMD-3),
which is no better than any
sweep tube amp from the 70s.
## an auto tune tube amp is
still the biggest bang for the buck..for
now. Any manual tune tube amp
is an even bigger bang for the buck....
provided you dont require instant band change.
Jim VE7RF
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