[ARC5] T19/ARC-5

[Kenneth G. Gordon]

On 17 Jun 2011 at 10:17, jsloss wrote:

> I'd be interested in learning how you modified your T-19 to provide
> appropriate loading to a 50 ohm unbalanced line...

You DON'T modify it: leave it strictly stock, even if it is a hacked-up one. 

If you want to feed a 50 ohm line, use a series capacitor. In the old days, we used to use a 
variable between the antenna post and the center-conductor of the coax, setting the VFO for 
the center of the band, adjusting the cap in small steps with the power off, until we got a 
match, then substituting a fixed cap in place of the variable.

Adjust the coupling control for not greater than 1/2 meshed (45 degrees to the plate coil) 
before you start the above. Adjust the roller for about 1/2 also. Once you have the proper cap 
value at the center of a band, you can then use the roller to tune your antenna for each end 
of the band.

Sometimes using a PARALLEL cap (from antenna post to ground) is useful when you are 
feeding certain antennas, like end-fed very long wires.

>  I'm at the stage
> where I need to decide if the roller coil stays or goes!

It should stay, as when properly used, it discrimiates against harmonics and other spurious 
signals.

>  I'd prefer
> that it go which will allow me to install a small Ip meter.

Put that in the power supply.

Here is a link where you can find two documents, written mostly by our own ARC-5 Guru 
David Stinson, which explain clearly how to do this without modifying anything. Modifying isn't 
necessary. I put these up there with his permission.

http://www.w7ekb.com/glowbugs/Military/arc5pages.htm

Ken Gordon W7EKB