[Amps] 160-6m amp designs?

[Radio WC6W]

Hi Steve,
  Welcome to the group!

   The 8877 is a fine choice.  Be sure to include a
grid overcurrent trip for reliability.

   Covering 160-6 in a single amp invites some
challenging problems with regard to the output network
and the plate choke.

   Some ancient thoughts on the plate choke problem
may be seen on my webpage: 

http://wc6w.50webs.com/wc6wamps/index.html?fr62.html

   If you do the math, you'll discover that the tube
output capacitance is all that's needed for the input
capacitor in a Pi-L output network on 6 meters. The
regular input capacitor, which would still likely have
to be a vacuum capacitor for the remaining 160-10m
range, could switched out by means of a vacuum relay
on 6 meters.   6 meters could then be tuned with a
variable coil -- a small roller coil, a variable
geometry assembly or some kind of variable reluctance
thingy. 

  Alternatively, a small (.5uH or so) coil may be
inserted between the plate and the regular input cap.
creating another L stage in the output network.  All
of the 6 meter coil components should be large
geometry -- at least 3/8" diameter copper tubing.  

  160 meter coverage may require padders on either, or
both, the tune & load capacitors depending on what
values you can acquire.
   
  The input network should be located as close as
practical to the tube cathode for 6 meter operation. 
The RF ground currents from the input network, as well
as the output tuning & loading caps, should all be
terminated as close as possible to the grid.

73 & Good morning,
   Marv WC6W 

P.S. -- The last (23rd edition) of the Radio Handbook
by Orr and the one of the ARRL handbooks from the
1980's may prove to be useful reference material.


--- steve d <kc8qvo at yahoo.com> wrote:

> Hi All, I am new to the group. I am a student at OSU
> and would like to use an amp as a project for a
> class this quarter. My goal is to cover 160-6m with
> 1500w. I have been researching the past few months
> and have found very few amps that fit this constrait
> or are close. The ACOM 1000 is the only commercial
> tube amp I found, and N4IS has a home brew amp 160-6
> with a pair of 3cx800's (I think) but there is no
> detail on his site - just pictures. 
> 
> I would like to use an 8877 because of their
> popularity, quality, and manufacturing lifespan
> left. I am open to all ideas since I am in the
> learning phase right now. I have heard it is easier
> to get a wide frequency range out of a pair of tubes
> rather than just one.
> 
> If you know of any designs out there on the net that
> I can take a look at please let me know. I don't
> have access to back issues of any magazines (other
> than QST, and only back to 01).
> 
> You can read more about the project on my website
> http://www.kc8qvo.com/2008/01/amplifier-ideas.html
> 
> Steve, KC8QVO
> 
> 
>      
>
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