[UK-CONTEST] Winkey

[paul at greenrover.demon.co.uk]

Frank Hunter wrote:
> Mike Harris wrote:
>> G'day folks,
> 
> Hi Mike!
> 
>> Unleashed my microHAM CW Keyer for the first time this weekend, driven by 
>> SD.  Worked perfectly well albeit it gives a feeling of semi-detachment 
>> from the CW.  I am, however, having some difficulty coming to terms with 
>> the slight difference in timing between the microHAM and the internal 
>> keyer in my K2.  Both in iambic mode B.  Having driven the K2 since 2000 I 
>> find I can be all over the place with the MH, extra trailing dot, and I am 
>> also falling out with the Bencher.  

The original winkey keyer uses an A/D input on the pic - this input 
measures the resultant voltage created by shorting combinations of 
resistors to ground.

The current through the key contacts is just a few hundred microamps 
which means that the slightest bit of oxidisation or RF noise can cause 
erratic behaviour.

I eventually used smaller resistors to make the current greater but 
maintaining the correct voltage relationship.

The original values are 10K + 10K and 4.7K, ISTR using much lower values 
  as I wasn't at all bothered about keeping the current consumption low.

from memory you need:

no paddle = 5V
dit = 2.5V
dah = 1.7V
both = 1.2V

As this is a fairly high impedance input, making sure the lines are free 
of RF is important so both good decoupling and screened leads are essential.

Personally I'd have read the paddle lines on separate inputs.

HTH

Regards Paul

-- 
73 de Paul GW8IZR IO73TI
http://www.gw8izr.com