[SixClub] SIX Meter amps

Mon May 9 09:36:03 EDT 2005

Hi Roger,

Thanks for your imput. I guess my main question
centered around the fact that I have aquired a
pristine  SB-1000 modified to run solely on 6M. I have
yet to use this amp because I still have to get 220
run into my shack. That being said, I wonder if I
should sell the SB-1000 and then buy another (newer)
amp that would put out the same approx amount of power
(800 Watts+-) and be able to be used on both 6M and hf
frequencies (perhaps even with a smaller footprint).
That way when the 220 is in place I won't have to have
two seperate amps (one for 6M, one for hf use.)

So, tell me what you recommend.

73,

John Carson kd5srw

--- "Roger (K8RI) on Six" <50MHz at rogerhalstead.com>
wrote:

> An amp is an amp, is an amp...  Well, not quite, but
> virtually any modern 
> tube amp can be converted to 6-meters.  I'm assuming
> you are still referring 
> to amps for conversion.
> 
> The SB220 is so popular as they are cheap, simple,
> and the conversion is 
> easy.
> Any amp using voltages close to those of the 220 and
> a Pi network could use 
> the same components, otherwise it's relatively
> simple to use the formulas in 
> "the handbook" to come up with the L/C values
> needed. If instead of a Pi 
> network it's a Pi/L then you have one more
> inductance value to compute.
> 
> On something like the Henry 2K4 (which I have) you'd
> also need to convert 
> one of the input circuits to 6-meters as it uses a
> tuned input circuit on 
> each band. These are plug in modules.  I'd modify,
> or preferably create a 
> new one using the same L/C ratio tuned for 6-meters.
>  It's not necessary, 
> but will reduce the drive requirements and give a
> slightly better match to 
> the exciter.  The 2K4 definately does not have a
> small foot print and it is 
> tall as well.  That and it weighs around 160#.
> 
> Amps, such as the readily available Alpha 76 series
> are now relatively 
> inexpensive, but still more than the 220s.  I've
> seen some beautiful ones go 
> all the way from $700 plus to over $1,500 with the
> norm being close to or a 
> tad under $1,000 and tending down. Even 374s (the
> auto tune unit with 
> 8874s).
> 
>   They are very easy to drive and typically 50 to 60
> watts of drive will 
> give the legal limit with a pair of good tubes. The
> ones with three 3CX800s 
> just loaf along at the legal limit.  The 76A is a
> bit larger than most 
> tranceivers but at 65# weighs about 10# less than an
> SX-101A receiver <:-))
> 
> That brings me to the reason these amps are
> relatively cheap.  Their tubes 
> are not!  The 8874 is expensive and retubing one
> will probably cost more 
> than what the amps are selling for at present.
> There are no direct replacement tubes for the 8874.
> OTOH the tubes in the 
> 3-tube version should last almost forever unless
> abused as they are just 
> loafing along.
> 
> I've heard of them being converted to the 3CX800
> which is the tube I belive 
> used in current Henry  and Alpha HF models along
> with the 8877. Their VHF 
> models were using the 3CX800 and 3CPX800.  The
> 3CPX800 has the same ratings 
> with the exception of the capability of much higher
> cathode emission and can 
> run close to twice the power of the 3CX800.  (The P
> stands for "Pulse")
> 
> If memory serves the 3CX1200 is an *almost* direct
> replacement for the 
> 3-500Z, but with an external anode.  Now that'd make
> for an impressive 
> looking replacement and you'd never have to worry
> about over working them, 
> plus I think the grids are capable of serving as a
> dummy load<:-)) with 50 
> watts dissapation each.
> 
> Alpha was using the 4CX1600B in their 6-meter amps,
> but the tube became 
> almost impossible to get and I can find no current
> information on Svetlana. 
> Their site is up and running, but excludes US users.
> I believe Radio Parts handles the Svetlana line but
> they have that infernal 
> price of "call".  I do not know about availability. 
> I've seriously thought 
> of picking up another 76A, (2 or 3 tube version) and
> converting it to 6 
> meters.    Even with purchasing a nice one, buying a
> pair of new 3CPX800s 
> and doing the conversion it'd still be about half or
> less the cost of any of 
> the new 6-meter amps.
> 
> Strangely enough, my link to the Alpha site produces
> a "not found" although 
> there is no 404 error so the URL must still exist. 
> Still strange, the Henry 
> site does not list any HF, or tube type amps. They
> only list VHF and UHF SS 
> amps.
> 
> Have I missed something?
> Is no one making high power HF tube amps anymore?
> 
> The conversions basically depend on how savy the one
> doing the conversion.
> 
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
> www.rogerhalstead.com
> > Seeing all the comments re: Six Meter amps I was
> > wondering if there are recommendations for new or
> > recent vintage amps that are designed with six
> meter
> > usage in mind. I always hear abour Heathket
> SB-220's
> > and SB-1000's, is there anything a bit more
> "modern"
> > that is as good, near to them in power output and
> > perhaps with a smaller footprint? And what about
> ease
> > of use...
> >
> > John Carson kd5srw
> >
> >
> >
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