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eHam Forums => HomeBrew => Topic started by: AB2AX on January 21, 2023, 05:42:54 AM

Title: Tuna tin- is there a way to increase output
Post by: AB2AX on January 21, 2023, 05:42:54 AM
Hi,
   I would like to fab up a tuna tin 40 mtr xmtr from parts mostly on hand.
  Is there a simple way of beefing up the output by a watt or two.
   Like a different xsistor or something simple?
   Thanks Patrick
   
Title: Re: Tuna tin- is there a way to increase output
Post by: G4AON on January 21, 2023, 06:42:25 AM
You might look at the Universal QRP transmitter for a slightly higher power output stage, depending on what you have in your junk box.

 http://www3.arrl.org/files/file/Technology/tis/info/pdf/0604028.pdf (http://www3.arrl.org/files/file/Technology/tis/info/pdf/0604028.pdf)

If you use the VOX keying circuit, the original R and C values aren’t quite right. Check my altered circuit for more appropriate values:
 https://www.qsl.net/g4aon/pdfs/SSB_TX_Control_v2.pdf (https://www.qsl.net/g4aon/pdfs/SSB_TX_Control_v2.pdf)

73 Dave
Title: Re: Tuna tin- is there a way to increase output
Post by: K4WH on January 21, 2023, 07:10:04 AM

I'm sorry, but I have to.  "Catch a bigger Tuna".
Title: Re: Tuna tin- is there a way to increase output
Post by: AI5BC on January 21, 2023, 07:42:40 AM
You cannot tuna fish, but you can tune a piano.
Title: Re: Tuna tin- is there a way to increase output
Post by: N7EKU on January 21, 2023, 07:59:08 AM
Hi,

Check the qrpme.com website documentation for their TTII kit.  There is a mods sheet for it which describes increasing power and fixing its chirp problem.

A bettter circuit would be to copy the Rockmite TX section.  On mine I can get over 1W out by reducing the final emitter resistor value and changing its collector choke to one wound on a ferrite instead of the molded one (which has higher losses).

73
Title: Re: Tuna tin- is there a way to increase output
Post by: WB6BYU on January 21, 2023, 08:45:15 AM
Three things determine the output power:
the drive level, the impedance presented by
the output matching network, and the
final transistor gain and power dissipation.
(Assuming that the supply voltage is fixed.)

Substituting a better output transistor may
help in some cases:  the 2N4427 is a favorite,
while the 2N3553 or 2N3866 are more rugged
(designed for 28V aircraft radios) but somewhat
lower gain at 12V.  Because they are designed
for VHF use, they will have higher gain at HF.
Other types will work as well, including those
designed for CB use.

Assuming the oscillator stage provides enough
drive, modifying the output network so it
presents a lower impedance to the final will
increase the output power.


While it has been a few years since it came out
I seem to recall that there was a following article
“Boots for the Tuna Tin 2” that was a power amp
(perhaps 5 watts output?) intended to be used
with it.  That would be another approach,
especially if you are starting with an original
circuit board.

If you really want to go retro, you could use
the TT2 to drive a 6V6 or 6AQ5...
Title: Re: Tuna tin- is there a way to increase output
Post by: WA3SKN on January 21, 2023, 09:24:31 AM
Just add a 8877 tube final!
First, what is you power supply capable of?

-Mike.
Title: Re: Tuna tin- is there a way to increase output
Post by: SWMAN on January 21, 2023, 10:31:29 AM
5BC
 You don’t have it exactly right.
You can tune a piano but you can’t tuna fish.
REO Speedwagon.  1976
Title: Re: Tuna tin- is there a way to increase output
Post by: K4WH on January 21, 2023, 11:57:45 AM
5BC
 You don’t have it exactly right.
You can tune a piano but you can’t tuna fish.
REO Speedwagon.  1976


Great album, and I mean I actual still have the album.
Title: Re: Tuna tin- is there a way to increase output
Post by: SWMAN on January 21, 2023, 01:18:22 PM
My neighbor across the street from me was their first drummer with the band.
Title: Re: Tuna tin- is there a way to increase output
Post by: W1VT on January 22, 2023, 06:10:56 AM
Military electronics typically runs on 28 volts.  This means that there are usually 28V versions of all the popular transistors used by hams.
You may want to consider doubling the voltage to 24 volts and swapping in higher voltage parts.  As well as improving the heat sinking.

Zak W1VT