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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