A DSP speech processor is not an RF clipper. In DSP you are working
with signals that are all numbers. You can modify the numbers according
to some clever algorithm and increase the average talk power. Then the
numbers get converted back to an analog signal that represents the
amplitude and frequency of the numbers.
Even though it would seem that this scheme should provide the best
results possible, the RF speech processors do a better job. In a
classic RF speech processor, the audio signal is first converted to an
RF signal. Then the RF signal is clipped. Then the RF signal is
filtered and converted back to audio. The advantage of clipping at RF
is the harmonics produced at RF are much higher in frequency and can be
easily filtered out. When you clip at audio, the harmonics are still in
the audio range and cannot be filtered out.
Carl Moreschi N4PY
121 Little Bell Dr.
Hays, NC 28635
www.n4py.com
On 3/15/2013 10:25 AM, Rick - DJ0IP / NJ0IP wrote:
Gary, I disagree, it is not an AF clipper.
It may not do as good of a job of amplifying and clipping as the 715 does,
but then that's a question of design.
If it is operating in the DSP, it is RF, not AF.
Bob says it operates in DSP. I am assuming he is correct.
The DSP frequency is too high to be AF.
It also means it won't have the harmonic distortion that AF clippers have.
73
Rick, DJ0IP
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of GARY HUBER
Sent: Friday, March 15, 2013 2:29 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Omni VII Speech Processor Question
I've kept the 715 to use with my OMNI-VII. I also have a FLEX-1500 as
sub-receiver of the OMNI-VII using the N4PY modification and DXLab Commander
to slave it. The FLEX-1500 has a panadapter mode with peak hold option
which I use to capture and compare the power distribution in the transmitted
envelope of the OMNI-VII.
The TT-715 speech processer is of course a RF-clipper, external to the
radio. It may not sound pleasing, but it can increase the average power in
the transmitted (RF) envelope by six dB and get through QRM or poor
propagation.
The internal speech processing of the OMNI-VII being an AF compressor cannot
increase the average power by that much, but it does help you get through.
See http://www.sm5bsz.com/dynrange/dubus405/dubus405.htm for an unbiased
explanation.
I will send png graphics of various microphones and processing methods used
with my OMNI-VII and captured with my FLEX-1500 in panadapter mode direct to
those requesting same.
73 ES DX,
Gary -- AB9M
-----Original Message-----
From: d.e.warnick@comcast.net
Sent: Friday, March 15, 2013 6:37 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Omni VII Speech Processor Question
I had the 715 with my Omni VI+'s and loved it. When I got the Omni VII, I
used the internal processor (only 10%) and I get so many unsolicited
comments on the audio during contests and while working DX, that I sold the
715. I believe the internal processor is RF based, but either way, the other
stations love the audio enough to comment on its quality.
And all this from a guy who doesn't really like SSB, but much prefers CW.
For me, TenTec does it all very well.
73
Dave
WA3F
----- Original Message -----
From: "Richards"<jruing@ameritech.net>
To: "Discussion of Ten-Tec Equipment"<tentec@contesting.com>
Sent: Friday, March 15, 2013 3:54:22 AM
Subject: Re: [TenTec] Omni VII Speech Processor Question
Interesting -
Stan at TenTec HQ says the Omni VII built-in
speech compressor uses "AF Based" compression.
And... yet...
Page 31 of my owner's manual states:
"The speech processor used in the Omni VII is a
DSP generated RF compressor. ... RF Compression
raises the average output power... with a digitally
generated RF speech processor... we have the
advantage of calculating the RF envelope before
modulation is performed..."
Page 38 Specifications says:
"Speech Processor: RF compression, 0-9 adjustment."
So... perhaps one might understand how I came to wonder about this.
The phrases, "DSP generated RF compression" and "RF compression" do
not exactly sound like "AF compression" to me.
;-)
Parenthetically... I paid my dues and purchased the Model 715 when it
first came out. I was just wondering if it was redundant, if the Omni
VII function was, in fact, RF-based at it sounded (to me, anyway) in the
owner's manual.
THANKS AND HAPPY TRAILS.
----------------- JAMES - K8JHR ----------------------------
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