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First Homebrew HF power amp

Discussion in 'Amateur Radio Amplifiers' started by N7GTB, Jan 9, 2012.

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  1. WB9ZIQ

    WB9ZIQ Ham Member QRZ Page

    Hi Vern, Sorry about the delay in responding. Don't check these postings very often. I'll try to take some photos of that 813 amp shortly. You could probably convert it to a monobander on 160M. You might have to add capacitance on the tune and load. I usually add mica hivoltage caps in parallel rather than find bigger air variables when going to a lower band. If you do a monobander you can wind your own tank coil to resonance and it certainly makes it easier when you eliminate the band switch. That 813 amp probably would need a filament choke to run class B grounded grid. I've got one that I was planning on using for it. (1/2 inch ferrite rod with 28 bifilar turns of #14 formvar coated wire.) You could probably pull the tank coil and band switch and use it on your 4-400 amp. Regarding the comments about the "joy" of building from scratch, by getting a homebrew amp that someone else has constructed, you can still build from "scratch". The main purpose of getting someone elses project is accumulating the hard-to-find parts. Trying to buy heat dissapating plate caps, tube sockets, and other components separately will cost you big. (check ebay on that). By the way, there are two good 813's in the amp deck already. Could send an additional one that would get you a spare set it you want to run 2 in parallel. WB9ZIQ
     
  2. N7GTB

    N7GTB Ham Member QRZ Page

    Hi Ray, I sent you a PM... 73, -Vern
     
  3. 2E0ILY

    2E0ILY Guest

    Hi Glen, may I ask if this was from a published design, or a pure one off? I have just bought, but yet to pick up, a nice looking Collins 30-L1 linear, but of course that won't hit top band 160 meters. I am toying with building a single band amp just for top band. Semiconductors are an option, but their fragility in face of a whoopsie or senior moment is off putting to me, so a tube amp is appealing more at the moment. Without bands witching it shouldn't be too complex internally or mechanically. Would you mind telling me a little more about what you have built please? Thanks.
     
  4. N7GTB

    N7GTB Ham Member QRZ Page

    Hope to have photos of the latest progress next week. As I might have mentioned, tube sockets, Plate choke, HV blocking caps and plate tuning should be in place...

    73,
    -Vern
     
  5. AF6LJ

    AF6LJ Ham Member QRZ Page

    Can't wait to see it.
     
  6. N7GTB

    N7GTB Ham Member QRZ Page

    Ok, sorry about the poor quality photo...

    rf_deck2.JPG

    ...tube sockets, (dud) tubes as place holders, bread slicer, plate choke, etc... That coil in the background is just for size, and not for use. I constructed it initially in the hopes of incorporating it, but is just too 'ugly' and I have no idea how the hot melt glue will stand up under power.

    I'm machining mounting holes and what not, so everything was deconstructed so that nothing becomes damaged in the process...

    73,
    -Vern
     
  7. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I see a problem!

    The tube anodes aren't connected to anything.:p

    I'm not sure, but I think in engineering school they taught us that all the tube elements should be connected to something.:eek:
     
  8. AF6LJ

    AF6LJ Ham Member QRZ Page

    Free-space Interface.
     
  9. N7GTB

    N7GTB Ham Member QRZ Page

    I realize this doesn't look like much at the moment, but it is coming along. I plan to have a lot more time to work on it now that night classes are over...

    73,
    -Vern
     
  10. K9FV

    K9FV Ham Member QRZ Page

    Vern - I've not posted much lately but have been following the thread. Looking good - that "bread slicer" sure looks good. A GREAT HB job there. Looking forward to more photos.

    Sue, good thinking - I knew there was someway Vern had power to the anodes - "free space Interface" it is<:)

    73 de Ken H>
     
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