NN1G TX Stability


From: W. Daniel (pandora!daniel@Think.COM)
Date: Wed Jun 08 1994 - 13:56:16 EDT

Hi Gang,

        Ok, now that I've got the OHR Classic working, I am back to my
previous task of fixing and super-charging the NN1G Mark II. I've just added
a TA7205 audio amplifier to the output with a small internal speaker into my
very compact (HWD is 2"x4"x6") case with RIT working fine. Now I have the
unenviable task of trying to stabilize the TX section. The TA7205 circuit
comes from pg. 4-38 of the 1994 ARRL Handbook and the IC costs about US$1.30
each here, which is quite cheap considering what it does.

        Can anyone help me please. My TX side is really awful and unstable.
Tends to break into oscillation. Also produces a nasty "click" while keying.
I suspect the click is an initial burst or parasitics before the oscillator
settles down.... any ideas welcome. There are so many NN1G kits out there,
someone must know, so help me God!!!

        Other than that this is getting to be a really nifty little rig.
Compact and easily carried around. Now I don't need to bring headphones
along with the ample output from the amplifier built on a 1" x 1.5" board
mounted inside the case.

        The other gripe I have is the poor mechanical stability of the
vernier/air variable combination. The way the shaft is coupled requires a
fairly rigid case but mine isn't quite so. I may change to another type with
internal reduction drive. That should stabilize things some what, and give
me more space inside the case on the side. Oh well.. my desk is clear and
now with the OHR Classic done, I can catch some shut-eye.

        BTW, IMHO, my ARK 20 is a better performer than the Classic, but of
course, it cost me THAT much more!

        Upcoming projects ...

1. To kit up some NN1G's for our local club, SARTS.
2. Add the A & A Engineering frequency counter to the Classic.
3. Recalibrate my watt-meter.
4. Fix the NN1G TX stability problem.
5. Put up an inverted-V for 40M or multi-band.
6. May try out the loop antenna feature in QST.
7. Get the A & A Eng. spectrum analyzer kit working (for a friend).
8. Fix the Gary Breed 20M xcvr (for another friend, 9V1ZH).
9. Rework the case of the Classic.
10. Think about fixing the TX sequencing on the Radiokit QRP-20.
11. Bring XYL on a holiday (for putting up with me! HI HI!)
12. Send Chuck some green paper for the K5FO Newsletter.

        If anyone has any experience with any of the above, I'd appreciate
their advise. Especially concerning the performance of the A & A frequency
counter, the one featured in the 1994 ARRL Handbook.

        Other good news, my XYL is actually trying to learn morse!!! It's a
miracle but if she gets her ticket, she will be the second XYL in the
history of this country to get a ticket. Now, that's history in the making.
:) Now I can give her some kits for X'mas :)

72 es 73,

| Daniel Wee  | daniel%pandora@csah.com             | ** Man needs more
| UUCP1.12b   | daniel.wee@f516.n600.z6.fidonet.org |  than a new start, he
| SNEWS 1.91  | csah.com!pandora!daniel             |  needs a new heart! **

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