[Amps] new amp race

[Jeff AC0C]

The YC156 is a great tube but it has two issues - assuming you have a good 
tube.

First (minor issue) is the grid current limit is 100 mA and with low B+ you 
can get serious grid current with moderate outputs and/or slight mis tuning. 
Not a gating item but something to be aware of.  The second and more serious 
issue is the Cout on the YC156 is massive.  Getting that tube to run on 20m+ 
takes work.  It can be done but it is a challenge even if you have serious 
skills and time.  Of course on 40m & below, the Cout is not a problem.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Thomas Walsh
Sent: Tuesday, May 23, 2017 8:58 AM
To: Jim Thomson
Cc: amps at contesting.com
Subject: Re: [Amps] new amp race

Ditto on the yc-156 or better known ,as the
3cx5000A7, it will run on Ep of 3kv and higher,
at 25w in you get 1.5kw out, input imp.= 25ohms,
even the pulls from the mri world which only down
by a db or two will still produce 4-5kw out cw.
This means with 25w in and legal limit out, it is
really only idling! The bias is class AB and the
specs call for 1A idle current, that is for pulsed service with 10kv plate 
E, but it runs just fine
with 500ma idle and much less plate E in cw mode, granted a little skewed on 
the chart but only NCL's will bitch about this. It has fantastic imd specs 
at full pwr, so with the greatly reduced power levels used in ham radio, it 
is almost perfect!
And the best thing is - no socket to mess with!
Drill a 5.25 inch hole and you're done.
Tom,
W2CO



Sent from my iPad

> On May 23, 2017, at 06:55, Jim Thomson <jim.thom at telus.net> wrote:
>
> Date: Sun, 21 May 2017 10:07:13 -0400
> From: "Carl" <km1h at jeremy.qozzy.com>
> To: "Catherine James" <catherine.james at att.net>,
> <amps at contesting.com>, "Jim Thomson" <jim.thom at telus.net>
> Subject: Re: [Amps] new amp race
>
> <A 2 el Shorty 40 isnt out of anyones capability as Cushcraft has proven 
> for
> <several decades and now more brands are available with decent performance 
> as
> <compared to the rotary dummy loads of the past.
>
> <There are several 2500-3000 W amps on the used market using commonly
> <available tubes and homebrew is still alive and well with the bigger 
> Russian
> <tubes as well as Eimac. The Chinese 3CX3000A7, built with Eimac supplied
> <tooling, is a fine tube and a bargain in the $800 range. Use one of the 
> 400W
> <rigs or an AL-600 booster amp. A SB-200 works fine if 160 isnt requires.
> <Bigger Eimac and European/Chinese tubes are readily available.
>
> <Carl
>
> ##  A 3CX-3000A7 is a superb bang for the buck, instant on too.  50 ohm 
> input,  –59 db IMD3.
> 4 kw ccs anode dissipation.   225 watt  CCS grid diss.
> 50 w in = 1.5 kw
> 100w   =  2.5 kw
> 150w = 3.5 kw
> 200  = 5.1 kw
> 400 =  8.5 kw
>
> ##  Its the ultimate...sleeper tube.   Heres the ultimate blower for the 
> 3x3 tube.
> http://www.goldmine-elec-products.com/prodinfo.asp?number=G20814
> Puts out  70 cfm  @  1.2 inches of water pressure.   With that back 
> pressure, current
> draw is only .4 amp  from the 120 vac line.  It uses an EC motor instead 
> of an AC motor or DC
> motor.   Variable speed is built in....using an external 10 K pot. Blower 
> doesnt even run luke warm.
> Tube requires 67 cfm @ 1.2 inches of water pressure...@  40 deg C inlet 
> air temp = 104 deg F.
> Now you will never have 104 deg F in the shack, nor will  you ever diss 
> 225 watts of grid diss...so the
> actual blower requirements are even less.  The tube is essentially doing 
> nothing at 5-6 kw out, not even breaking
> a sweat on rtty.   Not bad for a tube that is only 4.94 inches in diam.
>
> Jim   VE7RF
>
>
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