I would just like to say "Amen" to what George said. It is certainly
true.
The TenTec 234 speech processor is the same type of processor that
George describes. It pulls about 15 ma from a 13 V DC supply, so it
might be a bit hard on a battery.
I have used a 234 processor on all of my TenTec rigs, since the 234
came out. If I were to turn it off, people who know my voice would
tell me my audio sounded "thin". No one has ever said I had
distortion.
To put it another way, the proper used of RF processing adds about as
much punch as a small amplifier, but does not need to add distortion.
73,
Ken, W8EK
-----Original Message-----
From: George T. Baker <w5yr@swbell.net>
To: Bill_Ames@hyperion.com <Bill_Ames@hyperion.com>
Cc: caitlyn@netferrets.net <caitlyn@netferrets.net>;
tentec@contesting.com <tentec@contesting.com>
To: <tentec@contesting.com>
Date: Tuesday, October 19, 1999 4:02 PM
Subject: Re: [TenTec] Mic. and speech processor questions
>
>Bill, you have to be a little careful about lumping all "speech
>processors" into the same heap.
>
>I run r-f processing at all times with my Icom IC-765, but not with
the
>internal processor, which does in fact sound awful. Instead I use a
>1970's Comdel processor that generates an SSB signal at 500 KHz,
clips
>and filters it, and then heterodynes it back down to baseband audio.
The
>resulting audio is then fed to the 765 mic input.
>
>Note that this is NOT audio clipping or compression, which is almost
>always disastrous on SSB. It is true r-f clipping and filtering, the
>result being very low distortion accompanied by a large increase in
>average speech power and a significant decrease in the
peak-to-average
>ratio of the speech waveform. For average speech, voice peaks are
>typically 14 db greater than average. As you point out, effective
>clipping does make the voice stand out, but this does not have to be
as
>the result of distortion.
>
>I run the Comdel such that the average power output while talking is
a
>factor of four times that with the processor out of the loop. That
>amounts to a 6 db average power increase. I can get 12 - 15 db but
find
>that 6 db is adequate.
>A two-tone signal fed into the system emerges as a clean two-tone
with or
>without processing. That is a very demanding and telling test for any
>processing system.
>
>The surprising part is that virtually no one ever spots that I am
using
>processing and nearly every contact comments on the "clean, sharp
audio."
>My voice is naturally rather deep and resonant, so I do not find that
>processing does much for me in the way of enhancing my voice for the
>radio.
>
>The clue here is to start with a good mic (I use the Heil Pro Set
with
>HC-5 now but for years used the D-104), use a very good r-f processor
>adequately but sensibly, and then make sure that the rig is not
>overdriven. I monitor all transmissions on all modes with a Monitor
Scope
>and run frequent two-tone checks.
>
>Also, one eye on the wattmeter is a good idea. I normally see 10-15
watts
>output while speaking without processing and 40-60 watts with
processing,
>all for 100 watts output keydown or peak. These are typical figures
for
>most male voices. The power meter also points up the flip side of
>processing: much higher average power demand on the rig amplifiers
and
>power supply which many modern rigs just cannot provide. Processed
SSB is
>much like RTTY in its duty-cycle requirement. Processing also
introduces
>problems with background noise in the shack as most of us have
observed
>with some stations.
>
>Not trying to quarrel with you, Bill, but speech processing gets such
a
>slam most of the time that I just wanted to report a case where it
works
>and works very well. It is sadly true that most of the "built-in"
>processors found in modern rigs are "marketing after-thoughts"
included
>just to permit another "feature" to be touted. But the products of
>yesterday - the Comdel and the Vomax, in particular - are still
around to
>enable a station to greatly enhance its effectiveness and retain a
clean
>signal.
>
>72/73, George AMA 98452 R/C since 1964
>Amateur Radio W5YR, in the 54th year and it just keeps getting
better!
>AutoPOWER Systems, Fairview, TX (30 mi NE Dallas) Collin County
>QRP-L QRP-ARCI FISTS NORCAL ZOMBIE ARS 10-X 33.2 N 96.6 W EM13RE
>
>
>Bill_Ames@hyperion.com wrote:
>
>> One should never use a speech processor when quality audio is
required. If the
>> speech processor is doing the very best it can, and is successful,
then the
>> voice will stand out as louder with more voice power in less
bandwidth. The goal
>> here is communication under adverse conditions. At all other times
the speech
>> processor should not be used. The only exception I can think of is
when the
>> persons normal voice does not drive the rig sufficiently. This
could be a result
>> of spectral range and power distribution of their voice.
>>
>> Bill Ames
>> KB1LG
>
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>
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