"Lee" wrote in message
...

"Richard Clark" wrote in message
...
On Sat, 08 Oct 2005 08:05:35 GMT, "Lee"
wrote:

Use the old stand-by of the screwdriver antennas, a screwdriver
motor.

Tried that, it has far to much torque even on low volts .... damaged
the
gearing on my spare cap :-/

Hi Lee,

One way to control that, at least speed-wise, is to turn the DC
voltage into pulse-width modulated voltage. You are always applying
the same voltage, but you turn it on for a short-to-long time, and off
for a long-to-short time over any interval. You change the speed by
changing these times. This is more properly called Dwell Time.

Yes, i`ve been looking into that and it seems the best way to go, a local
supplier has a panel mount version in stock £15.00 ($16.00??)......so!!.

Typo ($26.00??)......


This offers the prospects of maintaining a constant torque over a
considerable range of speed. I'm not certain by what you mean about
"too much torque," unless you have too much resistance for the gears
to drive....

Not enough resistance, the capacitor comes to the end of its travel but
the
torque wants to continue..... hence the damage to my spare capacitor!!!.

Regards.

Lee...G6ZSG......

73's
Richard Clark, KB7QHC

Lee wrote:
Seriously, any ideas to slow the tuning rate will be most welcome .

What's wrong with a gear-head motor? I have some in my junk box.
--
73, Cecil http://www.qsl.net/w5dxp

Lee wrote:
Seriously, any ideas to slow the tuning rate will be most welcome .

The latest QST has a 6 RPM 12v gearhead motor from All
Electronics advertised on page 161 for $13.75. Runs 3
RPM at 6v.
--
73, Cecil http://www.qsl.net/w5dxp

Hi Lee

Two thoughts

Re stepper motors. You can often find them in old junked scanners. A
nice cheap source. If you are feeling really cheap the interface can
intially be a simple TTL counter cct and some pass transistors. I once
used one off my PC parallel port for an EzAl antenna system.

Also look at the possibility of using a piston capacitor and driving
that with a threaded bar connected to your motor. This may still be a
little fast though. You might also get away with a long lever and
threaded bar arrangement if turning a standard rotary capacitor. Kind of
limits you to something less than 180 degrees tho.

A car windscreen wiper motor is another possibility also through a
threaded bar. (Overkill on the torque tho)

Cheers Bob Vk2YQA

Lee wrote:
"Richard Clark" wrote in message
...

On Sat, 08 Oct 2005 06:26:31 GMT, "Lee"
wrote:

Seriously, any ideas to slow the tuning rate will be most welcome .

On Sat, 08 Oct 2005 12:50:30 GMT, "Lee"
wrote:
torque wants to continue..... hence the damage to my spare capacitor!!!.

Hi Lee,

Then the proper design incorporates a travel limit switch.

73's
Richard Clark, KB7QHC

For a stepper motor check
http://www.herbach.com/Merchant2/mer..._Cod e=H2-553
and for the controller check
http://www.alliedelec.com/Search/Pro...p?SKU=316-0061

"Bob Bob" wrote in message
...
Hi Lee

Two thoughts

Re stepper motors. You can often find them in old junked scanners. A nice
cheap source. If you are feeling really cheap the interface can intially
be a simple TTL counter cct and some pass transistors. I once used one off
my PC parallel port for an EzAl antenna system.

Also look at the possibility of using a piston capacitor and driving that
with a threaded bar connected to your motor. This may still be a little
fast though. You might also get away with a long lever and threaded bar
arrangement if turning a standard rotary capacitor. Kind of limits you to
something less than 180 degrees tho.

A car windscreen wiper motor is another possibility also through a
threaded bar. (Overkill on the torque tho)

Cheers Bob Vk2YQA

Lee wrote:
"Richard Clark" wrote in message
...

On Sat, 08 Oct 2005 06:26:31 GMT, "Lee"
wrote:

Seriously, any ideas to slow the tuning rate will be most welcome .

On Sat, 08 Oct 2005 12:58:53 -0000, Lee
wrote:
Hi Lee,
Some years ago i used a 1 RPM reversible dc motor from Edmond Scientific
supply. you may want to look see if they still carry them if not an Email
to them may produce the Manufacter's name. It work very well with my home
brew 30 to 15 mtr Mag loop.






--
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

On Sat, 08 Oct 2005 12:53:11 GMT, "Lee"
wrote:


Doesn`t work with a magloop!!!.....thanks anyway.

Why is that?

Owen
--

"Owen Duffy" wrote in message
...
On Sat, 08 Oct 2005 12:53:11 GMT, "Lee"

wrote:


Doesn`t work with a magloop!!!.....thanks anyway.

Why is that?

Owen

==========================
Because there is only one phase - that which corresponds to the motor
driving voltage.
----
Reg.

On Sat, 8 Oct 2005 21:36:59 +0000 (UTC), "Reg Edwards"
wrote:


"Owen Duffy" wrote in message
.. .
On Sat, 08 Oct 2005 12:53:11 GMT, "Lee"

wrote:


Doesn`t work with a magloop!!!.....thanks anyway.

Why is that?

Owen

==========================
Because there is only one phase - that which corresponds to the motor
driving voltage.

Call me thick, I still don't understand why you can't sample the RF V
and I and feed them to a phase detector to provide an indication of
whether to adjust the capacitor up or down to achieve resonance (V in
phase with I).

Owen
--