Jim:
Check my website again for an update on what you heard. After an e-mail
from TT, I learned that the hang time of the AGC must be increased to 3-4
seconds to alleviate the distortion. So I made another recording, which is
posted at:
http://n6ie.com/The%20Orion%20II%20AM%20Receive%20Audio%20Distortion%20Problem.htm
There are two clips of an single transmission from a short-wave broadcast
station on 40 meters. The recording was made in stereo using the Aux
outputs of both receivers into a Berhringer mixer (no processing or EQ) with
both receivers fed from the same antenna using a 'Tee' connector. The 870
was on the left channel and the Orion II on the right with both outputs
recorded simultaneously. The high frequency cut-offs were carefully
adjusted using random noise and the spectrum analyzer in Audio Test Bench so
that both had their -3dB points set the same. Low frequency roll offs were
set as low as possible (PBT=0 on the Orion II, Lo Cut=0 on the 870) and
audio levels were set as close as possible to each other. Recording was
done in 44.1 kHz .WAV file in SAW Plus32 and the channels then split into
two separate files which were then converted to MP3 using Ultimate Encoder
at 128 kbps. The AGC was at the AM default level on the 870, and 7 dB/sec
on the O2 with 4.00 seconds of hang time.
The improvement is remarkable. There is slightly less bass on the Orion and
both radio's AGC actions were different, but otherwise distortion,
especially during deep fades, was nearly the same in both with a slight
subjective advantage going to the Orion II. Also, the Orion II has less
op-amp noise when listening in the headphones than the aging TS-870.
Considering the legendary audio of the 870, that's a very good report for
the Ten Tec!
TT says they will address the issue in a future update.
Ron N6IE
www.N6IE.com
(Formerly N6AHA)
----- Original Message -----
From: "James C. Owen, III" <k4cgy_list@yahoo.com>
To: "Ron Castro" <ronc@sonic.net>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Friday, January 26, 2007 12:11 PM
Subject: Re: [TenTec] AM Receiver distortion in Orion II
Hi Ron,
I hear a difference but I wouldn't classify it as distortion
or muddy. What it sounds like to me is the Orion II has much more
bass boost than the TS-870 or the TS-870 has bass cut or boosted
Treble. How did you record this? Did you take if directly from
the speaker? or did you use the line output? The TT speaker I
think has much more bass than most of the other speakers. In fact
when I first put the TT speaker on my Jupiter I almost took it
out of line and put the old Motorola mobile speaker I was using
back on. The mobile speaker allowed many more highs to pass or
cut the low's or both. But after using the TT speaker a few days
I realized that it gave much better reception as far as reduced
interference from nearby stations and even the NR worked better.
However if I was going to use it a lot on broadcast I would go
back to the speaker with the greater highs.
73 Jim K4CGY
--- Ron Castro <ronc@sonic.net> wrote:
One of the items on my "wish list" for the Orion II is to fix
the AM receive audio, which sounds to me like a problem in the
DSP code that causes distortion and 'muddy' sound. It's most
noticeable during selective fades that cause a serious clipping
effect. Last night, I made an MP3 of a local AM radio station
comparing the O2 to a TS-870, and sent it to TT service. This
morning, TT said they couldn't hear any difference between the
two receivers. Is it my ears or what? The link to the clip is
below. The O2 is the first 60 seconds and the 870 is the
second 60 seconds. Bandwidth on the O2 is 6 kHz, while the 870
is 3 kHz, although as you'll hear, it sounds just the opposite!
http://n6ie.com/OrionII_vs_870.mp3
Can anyone besides me hear the difference?
Ron N6IE
www.N6IE.com
(Formerly N6AHA)
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