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Re: [Amps] Stock up on tubes?

To: 'Jim Thomson' <jim.thom@telus.net>, <amps@contesting.com>, Ken Durand <N4zed@comcast.net>
Subject: Re: [Amps] Stock up on tubes?
From: Catherine James <catherine.james@att.net>
Reply-to: Catherine James <catherine.james@att.net>
Date: Tue, 6 Dec 2016 14:26:03 +0000 (UTC)
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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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