[TenTec] Orion - What's this trim pot?

[Dave Heil <k8mn@earthlink.net>]

I'm finally getting around to doing the sweep mod on my Orion.  I 
removed the covers this evening.  I know about the master transmit audio 
gain pot and the contrast post under the lip of the front panel.
Can someone tell me the function of the pot which is behind the top edge 
of the front panel and visible after removing the top cover?  There is 
an access hole for it on the black, ventilated metal strip just behind 
the panel.
73,

Dave Heil K8MN