The Orion II AM Receive Audio Distortion Problem---FIXED


Ten Tec responded to my review below after listening to the audio clip and to an Orion II at their factory.  Jack Burchfield determined that the problem was a result of the new AGC scheme that employs a dual loop that has been tweaked to ignore static pops during weak band conditions.  This was the scheme that introduced the “Hang Time” menu adjustment.  Its downside is that unless the hang time is set very high, distortion of an AM waveform results, which is what I was hearing in the first audio clip.  I took Jack’s advice and slowed down the hang time to 4.00 seconds and made a stereo recording with the TS-870 on the left channel and the Orion II on the right.  Using SAW 32+, I split the channels and made two MP3s of identical audio segments from a 40 meter short-wave broadcast station.  Also, both receivers were adjusted so that the bandwidth roll-off response at -3 dB was the same.  The setting on the 870 was 2.5 kHz and on the Orion II 5250 Hz.  Compare the two clips, and you’ll see that except for the AGC action, they sound virtually identical:


TS-870 Audio              Orion II Audio


-----------Below is the previous review about the problem posted a few days earlier-----------------------


This has been on my “fix it” list for awhile, and recently I sent Ten Tec an MP3 clip comparing the received audio from the O2 compared to my trusty Kenwood TS-870.  They e-mailed me back and said they could not hear the difference or the distortion!  Can you?  Listen to the clip and decide for yourself.  The first 60 seconds is the Orion II and the last 60 seconds is the TS-870:


Orion II vs. TS-870 receiver Audio clip


The Orion II had its bandwidth set to 6 kHz, and the TS-870 was set at 3 kHz, even though when you listen to the clip it sounds the other way around!  Both receivers were using the same antenna, and tuned to the same AM broadcast station, KGO in San Francisco for the test.  The ‘870 had its internal AM audio AGC disabled (makes AM sound better, but it’s not fair to use it in this comparison), and both radios had default AGC timing set.


This test does not demonstrate an even more serious associated problem that sounds like digital over-drive distortion during sky-wave fading.  The 870 handles the fades the way every AM radio I have ever heard does, but in the Orion II, there is audible break-up and clipping distortion.  I will make some recordings in the future to document this problem and post them here.


For comparison, here are spectrographic views of each receiver’s bandpass using random noise:


Orion II AM 6 kHz

TS-870 AM 3 kHz