The 1340 vfo tunes backwards--as the vfo freq goes up,
the rx/tx freq goes down. Taking a winding out of the
torriod moves the vfo freq up, which ultimately moves
the rx/tx freq down. You want to increase the winding
turns. Or, maybe if you really space the windings out
you can get it up there.
If you need more magnet wire, Radio Shack has a nice
package of them. More on this in a moment.
Moving the windings about only affects the capactance
of the inductor (the capacitance brought about by the
windings--from each loop to the next), not the
inductance of the coil. Varying the winding distance
affects the total capactance of the circuit, which in
turns affects oscillation frequency.
Here's a few thoughts about the 1340, in case you
haven't heard about them:
I used candlewax on my vfo torroid to secure it. Bad
idea if you ever leave the radio in the car in August.
Unless if your idea of fun is realigning things.
I placed a reverse battery diode (a 1N400x, in series
with the 12V wire to the power switch) *after* blowing
the radio up twice. Think about adding this reverse
battery diode, early on, before anything happens.
I replaced the 1 turn freq pot with a 10 turn
precision pot. Easier to set the freq.
The output has a tendancy to oscillate. Make sure
that the output torroids have the windings reasonably
apart. I could take a photo and place it online if
need be--I know I can't explain it well, but one photo
would accomplish alot.
I added a simple connector to the speaker wires, so I
could seperate the two halves easier. Almost any
connector would work.
Others have taken the metal housing, not the bottom
clamshell but the metal piece right above it, and
milled out as much as possible, under the pcb. That
way, in case the need arises, one does not have to
unmount the pcb from all that metal piece--it is a
major work to do so, as you will find out!
Lastly, and this is something that I am thinking of
doing, is to rewind the vfo torroid with a wire that
is much heavier than what TenTec gives in the kit. I
have a Small Wonders Lab's kit, and the instructions
don't even mention securing this torroid (very similar
vfo design), but uses a heavier wire. Maybe a nice
heavy wire would help stability.
Good Luck!
KB1CKT
Shawn Upton
Pembroke, NH
***************
Message: 7
To: tentec@contesting.com
To: <tentec@contesting.com>
Date: Tue, 4 Sep 2001 02:05:46 -0400
From: "Paul E. Sojka, Jr." <ultrafixedwing@juno.com>
Subject: [TenTec] 1340 Kit
I'm putting together a 1340. I find that it's putting
out in the 6975
to
7025 range right now. How can I bring it up to the
novice portion. Will
taking a winding out of the T1 toroid and pushing trhe
windings closer
together help?
It's still in the construction stage right now.
Thanks,
Paul
KS2S
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