I once built a pair of 813's as a linear grounded grid amplifier driven off
my
pair of 6146B. Worked great, I then tried a pair of 250th in GG and they worked
fine
as well.
I always wanted to play with some VT-127's, they are neat looking tubes.
EIMAC actually
made a ion vacuum gauge tube using that tube.
I have a VT-158 but wondered if there was some way to suppress its VHF
oscillation and
use it as a HF amplifier tube but with the VHF hairpin's build in I doubt it.
73
Bill wa4lav
________________________________________
From: Carl [km1h@jeremy.qozzy.com]
Sent: Wednesday, December 23, 2015 5:23 PM
To: Fuqua, Bill L; Tom Osborne; amps@contesting.com
Subject: Re: [Amps] 813's
I save my glow bottles for Class C AM use and as modulators. A couple of
304TL's can really light up the room as can HK-354C's, and 250TH's. Some
long years ago I ran a pair of VT-127A's (aka 100TS after WW2) on 40 and 20
CW only at close to 1200W out, the white plates never seemed to weaken them
but I did use plenty of air.
I also have a pair of 6C21's (pulse 450TL's running way overvoltage on the
filaments as short life wasnt important) and havent run them anywhere near
their best glow as regular 450TL's.....yet.
Too bad none of those oldies are good linear amp tubes.
Carl
KM1H
----- Original Message -----
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
To: "Carl" <km1h@jeremy.qozzy.com>; "Tom Osborne" <w7why@frontier.com>;
<amps@contesting.com>
Sent: Tuesday, December 22, 2015 11:28 PM
Subject: RE: [Amps] 813's
One problem was that most articles stated that a pair of 813's would work
operate
at 2kW PEP or about 1200 or 1300 Watts PEP output. I can see why they seemed
"unclean" since
many hams built these amplifiers from magazine articles and pushed the pair
of 813's to the 1 kW average
plate input power limit on SSB. But four good 813's should do today's legal
limit just fine at 2.5 or 3 kV.
That would be like running four 4-125A's or even better 6155 and you can
watch the plates glow too.
Which brings up a question I have, anyone ever try 4E27A's in grounded grid?
73
Bill wa4lav
________________________________________
From: Carl [km1h@jeremy.qozzy.com]
Sent: Tuesday, December 22, 2015 6:05 PM
To: Fuqua, Bill L; Tom Osborne; amps@contesting.com
Subject: Re: [Amps] 813's
While the 813 was rated at 125 PD it was a very conservative CCS and over
years of use Id rate them in the 200-225W range for ICAS service. Compare
the size with the Cetron 572B anode and you can see why; Svetlana and
Chinese are only 125W but the new ones may be higher. This is only for the
graphite anode versions; the later sheet metal version used would melt down
as fast as an 811A in a AL-811 series amp.
With a good tube final exciter such as the Kenwood hybrids the IMD is in the
low -30's real dB; that is about -37 ARRL dB's.
With an SS exciter and an untuned input there is no flywheel effect loading
on the exciter so IMD is typically 3-5dB worse.
The best IMD with a tuned input is at around 2700V but it varies little from
2500 to 3000V when output remains the same; 4 full emission tubes will
easily do 1300-1500W with a little help from a fan.
Carl
KM1H
----- Original Message -----
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
To: "Tom Osborne" <w7why@frontier.com>; <amps@contesting.com>
Sent: Tuesday, December 22, 2015 1:15 PM
Subject: Re: [Amps] 813's
> Graphite is always messy, I have gotten it on hands clothes and it is
> hard to wash out.
> I think perhaps they should not have earned such a reputation. I believe
> the problem stems from the
> fact that most 813 amplifiers in the early days had untuned inputs and
> that they were pushed
> harder than they should have been. Mind you these tubes in triode
> connection are about like 572B's.
> They have even less plate dissipation than 572B's but I suspect the idea
> of pushing them to
> 2kW PEP plate input was just too much. Also, most used 813's I have gotten
> had very little
> emission left. That is an indication that they were used beyond the point
> where if pushed to
> get full gallon output they were probably producing a very dirty signal. I
> think if you use
> a good pair, with tuned input and don't try to push them too hard they
> will be just fine. Treat them
> as if they were a pair of 575B's.
> 73
> Bill wa4lav
>
> ________________________________________
> From: Amps [amps-bounces@contesting.com] on behalf of Tom Osborne
> [w7why@frontier.com]
> Sent: Monday, December 21, 2015 1:57 PM
> To: amps@contesting.com
> Subject: [Amps] 813's
>
> Why are 813 tubes considered 'dirty'?
>
> I have an old amp in the attic I haven't used for a long time that has a
> pair of 813's in it I have read somewhere that they are a very 'dirty'
> tube. I'd assume that means lots of spurs or something.
>
> Just wonder why that would be. 73
> Tom W7WHY
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