[GreenKeys] Re: polar loops

[Bob Camp]

Hi

A lot depends on exactly which polar relay you are driving on the polar  
side of the loop. A good one aught to operate reliably off of a couple  
of ma. You may get away with something simple like a high voltage op  
amp and a +/- 24 volt supply.

If you want to go the whole root then a +/-125 volt supply and a pair  
of FET's would do the trick. Set up the one on the + supply as a  
constant current source and key the one on the - supply. If you want to  
get exotic make the upper one a 60 ma current source and the lower one  
a 120 ma current source.

Of course the most authentic way to go would be to drive it with a high  
speed spdt relay.

	Enjoy!

		Bob Camp
		KB8TQ



On Jun 16, 2004, at 7:40 PM, gil smith wrote:

> Hi Eugene:
>
> With an adapter, you could convert a neutral-loop keyer to drive a  
> polar loop.  Something like an H-bridge of transistors comes to mind.   
> Hafta play with it a bit.
>
> The loop sense needs no change -- the zener will conduct in forward  
> mode for the other polarity.
>
> gil
>
> At 01:53 PM 6/16/2004, Eugene Hertz wrote:
>> Well, Jack (wa2hwj@)has become intimately familiar with the ticker,  
>> and I believe his assessment was it could not be modified for  
>> neutral...
>>
>> If you want to see pix (Ticker 1 has good pictures of internals)...
>>
>> http://www.hertzmail.com/5a/
>>
>> Ultimately, I would love to find/build a circuit that could take  
>> rs232 and key a polar loop +/- 60ma.  In that way I would use  
>> software to handle ascii-6-level conversion and to signal the rs232  
>> lines at the right baud rate.
>>
>> Any ideas?
>> Eugene Hertz
>>
>>
>>
>> >-----Original Message-----
>> >From: gil smith [mailto:gil at vauxelectronics.com]
>> >Sent: Wednesday, June 16, 2004 04:57 PM
>> >To: greenkeys at mailman.qth.net
>> >Cc: 'Eugene Hertz'
>> >Subject: polar loops
>> >
>> >Hi folks:
>> >
>> >Can anyone give a decent explanation of a polar loop? Eugene  
>> apparently
>> >has a polar machine, and wants to drive it -- I presume there are  
>> other
>> >polar machines out there as well, though we don't hear much about  
>> them.
>> >
>> >If I understand it correctly, a polar loop reverses the current  
>> direction
>> >for mark/space, unlike the current-on/off of a normal loop. I presume
>> >polar lines would support longer distances and do better under noisy
>> >conditions.
>> >
>> >What is needed to convert a standard loop to drive a polar machine?
>> >
>> >Can Eugene's 5A machine get a simple wiring change to bypass the  
>> polar
>> >input and drive the selector magnets directly from a normal loop?
>> >
>> >ps: Eugene: do you have any pics of your machine?
>> >
>> >thanks,
>> >
>> >gil
>> >
>> >
>> >;-------------------------------------------------------------------- 
>> -----
>> >; vaux electronics, inc. 480-354-5556
>> >; www.vauxelectronics.com (fax: 480-354-5558)
>> >;-------------------------------------------------------------------- 
>> -----
>> >
>> >
>>
>>
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