[Amps] triode or tetrode

[Carl]

----- Original Message ----- 
From: "Roger" <sub1 at rogerhalstead.com>
To: <amps at contesting.com>
Sent: Sunday, August 29, 2010 11:40 PM
Subject: Re: [Amps] triode or tetrode


>
>
> On 8/27/2010 4:02 AM, Jim Thomson wrote:
>> Date: Thu, 26 Aug 2010 06:33:06 -0700 (PDT)
>> From: Jim Hoge<knowkode at verizon.net>
>> Subject: [Amps] triode or tetrode
>>
>> I am kicking around the idea of a new amp ( I want 160m capability which 
>> my
>> current amp doesn't have) and have a few questions for the gurus and 
>> those that
>> have theses beasts. Am I better off with a triode or tetrode based amp? 
>> Does it
>> really matter? How about a one or a two holer amp? How much headroom 
>> should I
>> look for in a legal limit amp? Some designs are nearly at the limit of 
>> the
>> tube(s). How about auto tune capability? Do the amps that have this 
>> feature find
>> the best match or will an override/manual tune do a better job? Any other
>> tidbits of wisdom?
>>
>>
>> Tnx,
>> Jim W5QM
>>
>>        Alpha 9500 Auto-Tune
>>        HF Amateur Service
>>        1.5 kW RF Amplifier $7,950 +
>>        shipping and handling
>>        Alpha 8410 Manual
>>        HF Amateur Service
>>        1.5 kW RF Amplifier $4,995 +
>>        shipping and handling
>>
>>
>> ##  how much money do you want to spend ????
>>
>> ##  A GG triode is the way to go.  Forget the 2 x holer.   If you need 
>> more HP, you don't put
>> 2 engines under the hood of your truck.
> But that is because you don't have room.  The speed record setters use
> multiple engines, up to one for each wheel.
> The new hybrids and electric cars use either two or four.
>>   200 w of drive into a  YC-156 will peg a 10 kw slug,
> I only have a 100 watts available, but that's still enough drive for
> enough output to require rebuilding most of my antenna system.
>> and you can get a YC-156  for  $200.00  to $300.00
> Or at $385 for one tested and with a guarantee.
>>    200w  into a 3CX-3000A7 will peg a
>> 5 kw slug.  No socket, and no parasitic suppressor required for the 
>> YC-156.
> I don't think the 4CX3000A7 requires one either.
>> Used vac caps
>> are cheap. A  4800 vac  10 kva  hypersil pole pig  [120 lb, 1 cubic foot]
> I'd be glad to settle for something in the 6 to 8 KVA range at  a
> reasonable price.
>>    will run a YC-156
>> nicely.  1/4"-3/8"-1/2" copper tubing is dirt cheap at home depot. 
>> Gigavac G-2 vac relays
>> are cheap for hams.  6A10 diodes are cheap. HV 450 v lytics are 
>> cheap..esp the 2000-4000 uf
>> variety.
> Although it has a 6 minute warm up and the 4CX3000A7 is instant on
> (almost).  I'm looking at the 4CX3000 which is tested at the factory for
> IM and a minimum of 5300 watts out. An 8 KVA transformer should do well
> although to get the full power at CCS would take  a 9KVA.
>
> I don't know of any other power tubes specifically tested for IM at
> production.  At any rate that tube will work well up through 2-meters
> But I do like compact, even if the RF deck is on the desk and the PS
> goes on the floor. The problem for me is the YC156 and 3CX3000A7 are
> about 9" tall  while the 4CX3000A7  is almost 8" tall (give or take a
> tad) Compare this to the 4CX1500B at just shy of 5" and a pair of them
> or the Chinese FU728F will easily run 4 KW nominal or 5 KW PEP.
>
> It's purely a personal choice but I like *relatively* compact desk top
> units. OTOH no way are any of the really good tubes going to give an amp
> the size of most of today's transceivers. Actually most will be about
> twice the size of the venerable old Alpha 76A.
>
> True, the power used by the filaments on these tubes doesn't exactly
> make them green, but with the instant on feature it doesn't have to set
> on all the time I'm in the shack. With my commercial amp, I turn it on
> when I walk in and off when I leave.   The YC156 uses the next to the
> least filament power at roughly 225 watts, but it takes a 6 minute warm
> up. The other two are instant on but run about 360 watts just to light
> the fire and it would be a good idea to use a step start or ramp up the
> filament voltage for maximum tube life.  OTOH the PS should use step
> start or a ramp up any way.  The big drawback to the 4CX3000A7 is the
> socket which appears to be like the one used for a 4CX1500B, but on
> steroids and they are not common which is probably why the 4CX3000A7s
> are *usually* found for a reasonable price.  New price is more than a
> new 8877.
>
>> ##  You can beat Alpha, et all, at their own game, and get 6-8 X  more 
>> power to boot.   You will get
>> 30k hrs  from a new 3CX-3000A7.  Lowest imd tube, period. [-58 db pep]. 
>> Use a PI net, with
>> a low tank Q..like 8-10..and it will be very broadband.    A  L-PI is 
>> used on the upper bands.
> For what I have and am likely to have in the future, I need something
> that will be happy with 100 watts of drive.
>> ##  You can use the 225W  CCS  grid in the 3x3  as a dummy load for your 
>> XCVR. Since the grid is
>> bonded to the chassis via a grid  ring, the grid diss is actually a lot 
>> higher.  A simple grid fuse + cathode
>> fuse provides ample protection.  A high power Glitch R + HV fuse provides 
>> the protection in the B+ portion.
> I really like that part about the YC156.
>> ##  I use the Array Solutions wattmeter  for the hi-swr protection.
>>
>> ## Then you end up with the...'real deal'.  The metering is simple.  I 
>> use  separate grid/plate current
>> meter's.. and ditto with B+.  You won't get this kind of satisfaction 
>> from an Alpha, or any other
>> amp.   Want  QRP... use a 8877, or any of the other fine tubes out there. 
>> I end up using vac caps
>> either way, so it's a moot point.  Chinese 3CX-3000A7 / 3CX-6000A7's  are 
>> cheap... and will last
>> a lifetime.   GS35B  is a good tube too, no suppressor required either.
>>
>> ##  Do you want a...'me too'  shoe box on the desk ?    There are plenty 
>> to pick from.
>>
> I want both! <:-))
>
> 73
>
> Roger (K8RI)
>> Later... Jim   VE7RF


It should be possible to package a YC-156 amp in an Alpha 77 size box with 
just the HV transformer remoted. Im not talking about one of those built for 
show amps in the mags or on web pages but something that doesnt require an 
industrial size model shop and is easily servicable. I stresss easily 
servicable.

Carl
KM1H