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2x2sc2879 amp construction project

Moleculo

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,200
1,686
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OK, here's the new thread on homebrewing your own amp. Someone wanna start a parts list? Anyone who has a digital cam, feel free to take pics of your own project and post them as we go!

Let's start with a 2 transistor, 2sc2879 amp. Maybe when we're done with this one, we can move on to a 4x2879 project.

Moleculo
 

Looks like all the people with the know how, that said they would be glad to help, have changed their minds.With that said heres my list, only three items.

#1- A pocket full of dollars

#2- The phone number of a builder

#3- Some masking tape to write "I Built IT" on

Assembly instructions- First count your money, then call a builder and get the biggest amp you can afford. Now strategicly place the masking tape over builders mark. DONE
 
Personaly I would like any input on a four tube 572B amp for 160-10m.I know it's a tall order but I have finally made up my mind to build one and am looking for a little info especially on biasing it for cutoff during receive.
 
Look at the schematic Mol posted in the amp section and modify it some.

For Class C groung the input transformer with a 10uH inductor. INput and output windings can be changed for better response from the transistors(aka better matching). Try 3,4,5 wraps on output with a collector-to-Collector cap of 820-1000pF and on input 3, 4 wraps with a base-base capacitance of 330-1000pF.

This will get you some where with a little playing Oh yeah mix 43 will work as well as other mixes. As far as the AB regulation circuit the one on that schematic is pretty good.
 
2-2879 amp...partial list...:)

3 wraps-input trans,2 wraps output trans, (16 awg teflon wire)
330 pf cap on top of the input trans,,,2-10ohm res..1/4 watt rated,100 ohm pot..for the var.
120 pf from the output pill strip to ground...per pill....
Ok thats a partial list of a 2-2879 pill with a var amp..
--You guys fugure the rest...:)

(edit) almost forgot to tell you about the negative feedback of the 100 ohm res connected to the (104) .1 disk caps..per pill..
:):)


AM POWER
 
hahah....this isn't really a project thread! Let's get this started for real. We can all take pics of our progress as we go and post it up.

So who wants to start the parts list?

Adam or linearone, you guys probably have the stuff in stock, why not post up the parts list, and let people know if you want to provide an outlet for some of the stuff (case, boards, etc.).
 
boards.

Yea i can sell 2-pill boards...ive got plenty...
Go to my website...and look at some of the pics there...
ok parts list?
ok here goes..
1-150pf cap
1-1000pf cap
2-120 pf caps
1-180 pf cap
2-.1 104 disk caps
1-330 pf cap
3-100 ohm res
1-100 ohm pot
1-4.7 ohm res
1- 6a relay
rg 175u
16 awg teflon coax
1/2" 43 mix input trans
1-1/4" output trans
1- switch
2-so-239 conn
1-keying curcuit
1-15pf cap
2-2879's
1-copper clad board
1-heatsink
1-case top/bottom
Ok theres ur part list:)
then there is pics on my website:)
 
If you can buy the pre manufactured circuit boards you've got half the project licked, or even if you buy the pre-assembled amplifier boards from Asia stick them in a very ugly aluminum box with some cheep switches undersized wires and stick some decals on them you could be called a amp builder too!!! Oh yah and don't forget to rate the power by the input rating to make them sound even better yet. One more whatever you do don't add any type of filtering, the filters will stop the majority of the distortion and will cause most external power meters to read a actual reading.

Just some suggestions, have fun :) .
 
jonbah said:
If you can buy the pre manufactured circuit boards you've got half the project licked, or even if you buy the pre-assembled amplifier boards from Asia stick them in a very ugly aluminum box with some cheep switches undersized wires and stick some decals on them you could be called a amp builder too!!! Oh yah and don't forget to rate the power by the input rating to make them sound even better yet. One more whatever you do don't add any type of filtering, the filters will stop the majority of the distortion and will cause most external power meters to read a actual reading.

Just some suggestions, have fun :) .
Click to expand...

ya whats up with the distortion filter ???

how about you list your project. bet you dont have one or never built one. thats what this thread is about a home project. now if im wrong list your parts show some pictures of your internal or external band filtering. wich is what i think you meant but you are confused. :)
 
For starters in my previous post I am refering to using mix 43 for input and output transformer 1/2"x1/2" on input and 1/2"x1-1/4" on output.

No offense but most people dont have the means of powering much over an eight transistor amp much less a 16+. Nor do they have a dummy load capable of handling the power.

If you want to start building I would advise you to get an adequate power supply and a dummyload. I would also say get a good rf generator but you could use a radio.

As for the wise crack about filtering, filters do not block distortion, but harmonics. As far as filtering any bipolar amp will put out harmonics without filtering.

Yes the dave design will porbably be the easiest to copy as it is seen the most and almost all of the parts are available from several resources. Again, when tuning you really need to do it into a dummyload so that you can eleminate some variables that are present when tuning into an antenna. Remember tune input so that it gives little reflect, then the output to get maximum output, then retune the input. This will get you in the ballpark. For better tuning and alignment a spec. analyzer would have to be used and again most cant afford them, even used a good one is usually $1K.
 
HUH ! Ok how about this.

Don't add any type of filtering so you can transmit harmonics all the way across the band. Oh HUH heres another one you can do. Make sure you overdrive your homebrewed amp with some sort of pre-driver circuit so you saturate the transistors AKA Pills to the state of massive distrotion this will really make that Bird SWING. And always remember to be safe, Don't ever grab ahold of your antenna and have the ole lady key down with that big amp on. You will get hurt or even killed. :D
 
Most builders of amps for the 11M band do not use filtering as it would cost a little more and most have radios that put out tremendous amounts of harmonics so it would not be that effective any how.

On a side note I have seen plenty of homebrew ham amplifiers without adequate filtering or input attuening.

I would not recommend holding an antenna even at stock voltage.

If you do not mind me asking what is the problem? If you do not want to inform anyone or have nothing positive to say then why are you here.
 

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