             LM317 TRANSMITTER by Harry Lythall SM0VPO
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A few years ago I built one  of those projects that never worked but it
did do something unusual.  The PSU side of a portable receiver was very
unusual as it GENERATED RF in the HF spectrum.  The fault was traced to
a couple of errors on the PCB.  After a little investigation I used the
error to build myself an HF CW (QRP) transmitter,  based upon an LM317T
voltage regulator chip!!!

The circuit is given in 317-TX.GIF & needs very little explanation.  It
operates from a 10 volt supply and regulates to about 4.5 volts. This I
used to excite the tuned circuit VC1/L1. The tapping is about 3% of the
total number of turns of L1. A 6% L1 tap I coupled to the control input
if the LM317T regulator chip and BINGO! It "hoots".  You can draw WATTS
of power from a 12% tapping of L1.

I see no reason why you cannot use a regulator chip rated at a few amps
to get even more power out. I used this circuit on the air, on 1.8 MHz,
& actually had a few contacts.  It will certainly work on the new 70KHz
band, but I do not know how far you can push it into the HF spectrum. I
have just presented notes from my lab-book, & now it is up to those who
wish to experiment a little further.

As a STARTING point for VC1/L1, L1 is the usual formula:  the number of
turns is the  wavelength in meters  and the maximum value of VC1 is the
same in pf (multip[le by 2 because it is a variable capacitor).

Files:   317-TX.GIF

Have fun, and if you have any major success, such as exceeding 10 watts,
then drop me a line and tell me what you did.

73s de HARRY, Upplands Vasby, Sweden.

If you receive this text without the pictures then please ask me to send a
personal repeat.   I only ask that upon receipt you will re-post the files
to QRP@WW from your location. My NORMAL address is: SM0VPO@SM5BKI.C.SWE.EU
Files:    317-TX.TXT
          317-TX.GIF

Have fun.        Harry Lythall - SM0VPO @ SM0VPO.SL0ZS.SOLNA.AB.SWE.EU
                 Ron Lythall   - G0TLA @ GB7NND.#23.GBR.EU
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These files are available for automatic download from two PMS's on the
packet network.  All files are compressed into a single ZIP file.  You
may request them as follows:

Packet command:   SP 7PSERV @ G0TLA.GB7NND.#23.GBR.EU
Message title :   QRP/317-TX/317-TX.ZIP @ (insert your BBS address)
Message title :   /EX (or Ctrl+Z)

                ------------- or -------------

Packet command:   SP 7PSERV @ SM0VPO.SL0ZS.SOLNA.AB.SWE.EU
Message title :   QRP/317-TX/317-TX.ZIP @ (insert your BBS address)
Message title :   /EX (or Ctrl+Z)
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Files are also available via the INTERNET at the following addresses:

http://user.tninet.se/~acz732k/
http://hem2.passagen.se/sm0vpo
