[ARC5] T19/ARC-5

[Brian Clarke]

Hello Joe,

As others have said, the first option is to do nothing to alter the Tx. In 
the end - your end - it will be worth far more. Further, the original 
designers supplied a vacuum capacitor with the antenna changeover relay 
(BC-442, RE-2 / ARC-5) with instructions in the operating manual for 
connecting it in series or parallel with the antenna feed to match other 
impedances than that presented by a short airplane antenna. Let me know if 
you need a vacuum capacitor - I have a couple of spares, and a spare BC-442.

A very keen Command colleague has added a completely reversible mod to raise 
the output impedance. Lift the ground wire from the coupling coil on the RF 
PA tank coil; insert a few turns of insulated house-hold mains wiring wire 
around the cold end on the RF PA tank coil - you will need to experiment to 
get the right number of turns. Keep the loading coil in order to make fine 
adjustments as you change operating frequency. Damaging the front panel to 
insert a meter reduces resale value to less than 1% of SFA. If you want to 
use coax to feed your antenna, make up a small adapter between your coax 
connector and the output terminals on the BC-442 or RE-2; I have seen later 
versions of these with a ground terminal close to the control cable 
connector.

The only time you need to measure Ip is when setting up the padder capacitor 
in the RF PA circuit, ie, looking for a plate current dip; you only need to 
do it once - the plate tuning capacitor will track nicely over the whole of 
the 80 m band. After that, use the meter on the BC-442 or RE-2 for adjusting 
coupling / matching to your antenna.

73 de Brian, VK2GCE.

On Saturday, June 18, 2011 3:17 AM, Joe Loss asked:

> I'd be interested in learning how you modified your T-19 to provide 
> appropriate loading to a 50 ohm unbalanced line.. .  I'm at the stage 
> where I need to decide if the roller coil stays or goes!  I'd prefer that 
> it go which will allow me to install a small Ip meter.