[TenTec] O2 AM Distortion FIXED!

[Ron Castro]

I got a nice e-mail from Jack Burchfield at Ten Tec about the AM distortion problem.  He listened to my recording and agreed that the Orion II didn't sound as good as it should, and explained that the dual-loop AGC system with the new adjustable hang time has to be slowed down to sound good in AM.  He suggested using a hang of 3 to 4 seconds.  

I increased the hang time to 4 seconds and that cured the distortion!  I didn't realize that the two AGC loops were so independent and I had been thinking that a slow decay time coupled with a hang time of more like .5 seconds would eliminate AGC distortion from the equation.  It does take a very long hang to clean up the sound.  The short hang time is apparently what was causing the clipping and the "crunched" sound due to severe loss of dynamic range.

I made a new recording that I will place on my website later that demonstrates how AM sounds when the settings are changed.  I recorded a 40 meter short-wave broadcast station on both receivers simultaneously with the 870 in the left channel and the O2 in the right.  I split the channels and made separate MP3 files of each radio.  I also backed off the bandwidth of 870 and matched the O2 so the -3 dB points were at the exact same frequency.  Both receivers were fed from a T connector to the same antenna.  The results were outstanding!  The only noticeable difference is the AGC action, and that the O2 handled the really deep fades better than the 870.

Good work TT!  I'll mark that off the 'fix' list...

      Ron N6IE
 www.N6IE.com
(Formerly N6AHA)