[ARC5] The TN-6 MF Loading Coil

[Mike Hanz]

On 3/15/2013 9:22 AM, David Stinson wrote:
> Concerning the TN-6 antenna loading coil:
> The ARC-5 manual instructs that the TN-6 should be inserted
> between the MF transmitter and the RE-2 antenna relay.
> This, of course, leaves it out of the circuit when one of the HF 
> transmitters is selected.
>
> However- since the RE-2 would be feeding a very electrically-short 
> antenna at MF, the TN-6 loading coil
> would place a very high-voltage node at the antenna switch.
> Using a 50-foot wire as a trial antenna, I can easily light a nearby 
> 6-foot fluorescent tube.
> While the RE-2 is robust, I think this would be hard on it.  And if 
> the ground bonding wasn't perfect,
> all kinds of nasty things could happen, including across any Hi-Z 
> bonds in the aircraft body anywhere close by.
> The A.R.C. engineers were no dummies.  Likely I, rather than they, am 
> missing something.
> Any insight?

It's certainly a concern, Dave.  Perhaps the saving grace is the robust 
HV design of both antenna relays (the same one is used in both the TN-6 
and RE-2) and the relatively low power output of the transmitters.  I 
suspect that the ARC engineers did a risk analysis of the potential 
(sorry for the pun) for arcing and decided it was pretty low.  For a 
higher power transmitter like the ART-13, it would probably be worth a 
little more analysis.

     73,
  - Mike