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Motor for Cap in Mag Loop

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johnpierce

Motor for Cap in Mag Loop

I have seen general definitions about motors for driving a capacitor in Mag
Loop. But I have not seen a recommendation of a specific type to look for
on Amazon or Ebay. For starters I am looking for a 12vdc reversible motor.
I would like to start with a simple push button system for tuning. Maybe I
will consider a stepper later. I think that would need some computer
control. I am also wondering what RPM to consider for use on the lowest
frequency (40mtrs). The capacitor I am expecting to use would not have a
stop and could travel a full 360 degrees.

John

Ad2F

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Matthew Cook

Re: Motor for Cap in Mag Loop

John,

Firstly build your loop with your chosen capacitor and see how much Q you
can achieve. From there you can work out by how much (or how little!) you
have to rotate the shaft per kHz of change. This will then dictate how
you computer control your loop.

Unfortunately you need to start at the other end of the project first and
work backwards to find the right motor and gearbox. Transmitting loops
with high Q can be fiddly to tune and then hold in tune, especially when
they are only 3kHz wide.

73

Matthew
VK5ZM

On 28 October 2016 at 12:36, johnpierce <[hidden email]> wrote:

> I have seen general definitions about motors for driving a capacitor in Mag
> Loop. But I have not seen a recommendation of a specific type to look for
> on Amazon or Ebay. For starters I am looking for a 12vdc reversible motor.
> I would like to start with a simple push button system for tuning. Maybe I
> will consider a stepper later. I think that would need some computer
> control. I am also wondering what RPM to consider for use on the lowest
> frequency (40mtrs). The capacitor I am expecting to use would not have a
> stop and could travel a full 360 degrees.
>
>
>
> John
>
> Ad2F
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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NJ8M

Re: Motor for Cap in Mag Loop

In reply to this post by johnpierce

A stepper motor or a cheap 12 volt servo motor with a 1 to 2 rpm turn rate
hooked up with a 5 dollar circuit board that pulses the dc to the motor.
All can be had on ebay for about 40 dollars.

additionally, insulate the motor shaft from the cap shaft and mount in
plastic because the rf will mess with things. Use beads on the leads to the
motor. An antena company in Italy will send you the butterfly cap and the
controller for about 300 dollars and it is already wired and ready for a
loop. They make square loop antennas but you can buy any thing they sell
and that is the easiest way to do it and it is pretty bomb proof.

It will allow you to be away from the antenna and not near any RF. They
have the best system that is pre-fabed. Here is the link.

http://www.dolstra.nl/Antennes/HF/Magnetic%20loop/
INAC%20Loops/Inac_loops.htm

You can get the direct order from Inac from googling it.

Vy 73,

Morgan Bailey NJ8M

On Thu, Oct 27, 2016 at 10:22 PM, Morgan Bailey <[hidden email]>
wrote:

> A stepper motor or a cheap 12 volt servo motor with a 1 to 2 rpm turn rate
> hooked up with a 5 dollar circuit board that pulses the dc to the motor.
> All can be had on ebay for about 40 dollars.
>
> additionally, insulate the motor shaft from the cap shaft and mount in
> plastic because the rf will mess with things. Use beads on the leads to the
> motor. An antena company in Italy will send you the butterfly cap and the
> controller for about 300 dollars and it is already wired and ready for a
> loop. They make square loop antennas but you can buy any thing they sell
> and that is the easiest way to do it and it is pretty bomb proof.
>
> It will allow you to be away from the antenna and not near any RF. They
> have the best system that is pre-fabed. Here is the link.
>
> http://www.dolstra.nl/Antennes/HF/Magnetic%20loop/
> INAC%20Loops/Inac_loops.htm
>
> You can get the direct order from Inac from googling it.
>
> Vy 73,
>
> Morgan Bailey NJ8M
>
>
>
> On Thu, Oct 27, 2016 at 9:06 PM, johnpierce <[hidden email]> wrote:
>
>> I have seen general definitions about motors for driving a capacitor in
>> Mag
>> Loop. But I have not seen a recommendation of a specific type to look
>> for
>> on Amazon or Ebay. For starters I am looking for a 12vdc reversible
>> motor.
>> I would like to start with a simple push button system for tuning. Maybe
>> I
>> will consider a stepper later. I think that would need some computer
>> control. I am also wondering what RPM to consider for use on the lowest
>> frequency (40mtrs). The capacitor I am expecting to use would not have a
>> stop and could travel a full 360 degrees.
>>
>>
>>
>> John
>>
>> Ad2F
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
>
>

Twan at pa0kv.nl

Re: Motor for Cap in Mag Loop

In reply to this post by johnpierce

John,
I started with a $5 5RPM DC motor (DX.COM).
Using two buttons (left&right) for control. Not that easy to fine-tune using an SWR-meter.
Last year I switched to a stepper motor, bought controller hardware and developed
a program in Visual Basic.

Check my website for building info and free download.
http://www.pa0kv.nl/magnetic_loop.html (see "part 2" for the stepper)

Twan - PA0KV

I have seen general definitions about motors for driving a capacitor in Mag
Loop. But I have not seen a recommendation of a specific type to look for
on Amazon or Ebay. For starters I am looking for a 12vdc reversible motor.
I would like to start with a simple push button system for tuning. Maybe I
will consider a stepper later. I think that would need some computer
control. I am also wondering what RPM to consider for use on the lowest
frequency (40mtrs). The capacitor I am expecting to use would not have a
stop and could travel a full 360 degrees.

John

Ad2F

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html
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