[TenTec] Omni VII Speech Processor Question

Fri Mar 15 10:56:31 EDT 2013

OK Carl, that makes sense.
But the DSP operates quite like an RF clipper, in that the "harmonic"
distortion that AF clippers typically have is not present in it.
In that respect, both DSP compression and RF compression are superior to AF
compression.
I agree, I can't see a reason for the RF compression to be better than DSP.

What I have understood based on feedback from people who have had the 715
and its predecessor, it makes a big difference compared to older rigs with
no speech processor or just AF processors, but not much difference compared
to new rigs with DSP compression.

73
Rick, DJ0IP

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Carl
Moreschi
Sent: Friday, March 15, 2013 3:42 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Omni VII Speech Processor Question

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 at 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 at 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 at ameritech.net>
> To: "Discussion of Ten-Tec Equipment"<tentec at 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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