[Amps] Stock up on tubes?

[Jim Thomson]

Date: Sun, 4 Dec 2016 22:48:45 +0000
From: Bill Turner <dezrat at outlook.com>
To: Amps group <amps at 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