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Author Topic: A simple shortwave pirate transmitter build  (Read 12181 times)

Offline RadioAnarchy

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Re: A simple shortwave pirate transmitter build
« Reply #15 on: September 06, 2013, 2107 UTC »
nope. do not know.  not much math involved.
Plus I have made so many different transmitters,
I just know what will work.

these class-E  switching transmitters are different.
still kinda an experiment.
Actully, when I first started making these with the
IRF510 back many years ago, I cound not figure out my
problems.  I did not know there was anything
called class-E amplifiers.  or G, or H.
After I learned that stuff, then I figured out
the problems I always have had. 

L4 does no matter, as long as it is over a certain amount.

L3 is determined experimentaly, to tune up.  there is really no
math formula for what this should be,

L2 does not matter, as long as it is in a certain range,
with a core that works for RF.   L2 stores the energy pulse
to be supplied, and smoothed out with C5, to the network of L3 / C6.

L1 was just made to have a high enough reactance for the oscillator circuit
to work.








 

Offline ff

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Re: A simple shortwave pirate transmitter build
« Reply #16 on: September 10, 2013, 0013 UTC »
OK Brother RA.  I have finished my basic Guerilla build.  So far I have only been able to get 1.1 watts out of it, but I will continue to tinker.  I am powering from a 12V gel cell.  The oscillator is putting out a nice 11.6 Vp-p signal so I feel that section is doing its job.  With L3 originally 4 turns on a half ferrite, I was able to get a range of 0.9-1.7 watts output, depending on turns spread.  At 1.7 watts the final stage was drawing about 420 mA and the IRF was getting hot quickly.  Deciding I needed more inductance, I took a WHOLE ferrite and wound 5 turns on it.  With a good spread I'm only getting the aforementioned 1.1 watts output.  However, now the IRF stays stone cold and is only drawing 280 mA.  I feel that with mine, I still need to add more inductance, but I've run out of free time for now.  I know that from building many LULUs, the IRF 510s vary greatly and that could be another reason for low output.  I'm looking forward to playing some more and will keep you appraised of the situation... 73

BEHOLD! - My messy workbench...
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« Last Edit: September 10, 2013, 0045 UTC by ff »
Hailing from the upstate boondocks region of the progressive paradise which once was New York State

Offline RadioAnarchy

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Re: A simple shortwave pirate transmitter build
« Reply #17 on: September 10, 2013, 1443 UTC »
"ff" - yes, I changed to a PNP transistor at the oscillator, to cut out a few parts.

so across L1 to ground the signal should go up to at least 5 or 6 V and then go
down below ground level about the same amount..  and it is a dirty signal waveform,
but it works. .

the way I test all this is to put a 47 to 100 Ohm   2 Watt resistor in the place
of where L2 is in circuit with the IRF510 drain.  and also disconnect the output network (L3), and
shunt capacitor (C5).   then you can see an almost square-wave across this resistor
going from ground to 12 volts.  the IRF510 just needs to be ON about half of the time.

with the circuit all together, for C5, from 470 to 1000 picoFarad is OK...  
you can take this part out, for another check,  but then there will be a big
flyback voltage spike up to 100 volts or so, and the internal protection Zener
diode will conduct. This will clip out positive going modulation.

and the output power, the load on the IRF510 drain is determined by L3 and C6.
so maybe lower C6 to 680 or 470, and play with L3.   add more turns then
spread them out.

I have never had any problems getting 10 watts or more output with this type of
circuit, the flyback mode circuit.  I just throw it together and it works.
I have made many like this.  I will build
another one as this circuit shows in the next few days or so.

also. measuring the output power... into a 50 Ohm dummy load.
and you have an oscilloscope.     look for about 25 to 27 volts going
in each direction (50 to 54 volts peak to peak)   that is around 6 to 7 Watts.

just some tips, in case somebody does not know.  
after all, this is a "Black Art"

.....
« Last Edit: September 10, 2013, 1447 UTC by RadioAnarchy »