[Central-Electronics] Amplifier for CE-20

Fri Oct 7 00:08:45 EDT 2011

Eugene:

Jim makes an excellent point about the gain of a 600L over a 100V or 200V
versus driving it with 10A/B or a 20A. Like most people that have both
options, I tried driving my 600L with a 200V and never really warmed up to
combination for all of the reasons that Jim cited, and few more. 

Yes, they do look spectacular sitting together, but it occurred to me that I
was running a lot of filament and plate power just to get typically less
than 6 dB of gain over a barefoot 200V. The 100V and 200V have an RF power
control that can be used to reduce the output down to 15W or so to drive the
600L correctly, except that oscilloscope on the 100V/200V ceases to be
useful at such a low power output level, and that's a key feature with
regard to keeping the driver clean looking. Adding a high power RF
attenuator in the line to the 600L will solve that problem by allowing you
to turn the power up to where the scope is useful, but that's even more
wasteful.  I put up with the combo for about a month, after which, I married
the 600L to either a 10B or 20A on a permanent basis.  Then I hooked an old
BTI LK-2000 to the 200V. That amplifier drives to full output with about 75W
from the 200V to produce about 1300W on 75M, which is over 12 dB of
increase.  

Here's the frosting on the cake.... I can run around 300W on AM using that
combination, and people tell me the 200V sounds quite respectable even with
the stock phasing network and audio filter.  It can only go uphill from
here!  Just my 2 cents worth of experience on the subject. Your own mileage
may vary considerably!  

Remember, nothing in the boatanchor world beats the sound of a CE SSB
rig....Enjoy!

73, George - W1LSB

-----Original Message-----
From: central-electronics-bounces at mailman.qth.net
[mailto:central-electronics-bounces at mailman.qth.net] On Behalf Of Jim
Candela
Sent: Wednesday, October 05, 2011 7:34 PM
To: W2HX; central-electronics at mailman.qth.net
Subject: Re: [Central-Electronics] Amplifier for CE-20

Eugene,

   Last Saturday at the Belton hamfest there was a 200V just sitting on a
table by itself...nobody around it. It was absolutely mint too!! No tag, or
anything. Had a new 3-wire power cord too. Yes that 200V would look so nice
besides my 600L!

  So anything goes here, but this one mans opinion concerning amplifiers is
that to justify the cost and bother, I want at least 6db gain (4X power, or
1 S-Unit at the receiver). Anything less, and I'd be better
off optimizing the antenna farm.

  So take your 100V, a 100 watt PEP radio, and the 600L, a 300 watt PEP
amplifier. You might get 400 watts PEP on high line with solid state
rectifiers (instead of 816's), and that will just get you 6 BD. So a 600L
for $1200 bucks, and over 100 pounds gives you barely 6 db at the other end?
The 600L input overloads at < 10 watts PEP as well, so overdrive is a huge
issue. There is no ALC here to assist. Is this an ideal match? :-)

  Now take a 20A at 15 watts PEP, and boost that to 300 watts PEP. Thats 13
db gain, and > 2 S-units. Now we got an effective combination. more
appropriately matched such that the driver cannot literally fry the
amplifier input. Still with the 20A driving a 600L, overdrive is possible.
No ALC here either.

  So, I'm out on a limb here, but to me, a 600L is operationally a better
match to the 20A, 10A, B exciters. Then again a museum of CE gear would
always have the 600L sitting next to the 100V, or 200V. The 20A would be in
a box up in the attic. :-(

Jim
WD5JKO

________________________________
From: W2HX <w2hx at w2hx.com>
To: 'Jim Candela' <jcandela at prodigy.net>;
central-electronics at mailman.qth.net
Sent: Wednesday, October 5, 2011 1:55 PM
Subject: Re: [Central-Electronics] Amplifier for CE-20

why is the 600L a better match for the 20A than the 100/200V? I always
thought since they were in very similar cabinets (600L/100/200V) that they
were designed to work together.

And while on the subject, anyone have a nice condx 600L to sell? Has to be
nice (to match my 100V) and in good operating condx

thanks!

73 Eugene W2HX

-----Original Message-----
From: central-electronics-bounces at mailman.qth.net
[mailto:central-electronics-bounces at mailman.qth.net] On Behalf Of Jim
Candela
Sent: Wednesday, October 05, 2011 11:59 AM
To: central-electronics at mailman.qth.net
Subject: Re: [Central-Electronics] Amplifier for CE-20

Tom,

     The best choice here is the CE 600L amplifier. It is a better match 
to the 20A than it is to the 100V/200V series exciters. If you are 
looking for something cheap, look for a Dentron MLA-2500 with used up 
finals. These amps are sometimes cheap, work 160M, and are ripe for a 
wide choice of tube substitutes. If your real lucky, you might find one 
with just one dud tube. That would be almost perfect to your needs.

    I have a MLA-2500 here, and I shoe-horned a 8877 in there. The gain 
is about 13 db, and a 20A gives about 15 watts PEP (depending on the 
band - 40, 15, 10 less), so 15 watts with 13 db gain provides 300 watts 
output.

    If your into home brewing, a single, or dual 813 amplifier (grid 
driven) would fit the bill nicely, and do so on a budget.

Jim
WD5JKO

On 10/4/2011 12:56 PM, Tom Elmore wrote:
>   Hello, I am still looking for an amplifier that I can drive with my 20A
exciter mainly on 160 meters. I would like something capable of at least 1
to 300 watts output.
> I have a Johnson Courier that I use with my 10 B but don't really want to
start hacking that one up.
>
>
>
>
>
>
>
>
> Thank You
> Tom ElmoreKA1NVZ
> Anchorage, Ak
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