Assuming you set your processor's limiter to 100%, you still need
to set the output level to the radio so it doesn't overmodulate. Even
just 101% modulation means clipping; pump that with 100% average noise
and you have the potential for some serious bleedover. And there's no
way for the average user to determine the precise point at which his
radio is at 100% modulation. Radios are set at the factory for 95% to
98% modulation to allow for slight variations in tolerance that happen
during normal operation; for you to claim that your processor limits
modulation to 100% all of the time is not only absurd, it's impossible
because of the tolerance limitations of the radio.

I think this is the last of your comments I didn't have time to
respond to before. You are certainly correct that you need to set the
radio so it doesn't overmodulate. In the VoiceMax installation
instructions it says that for a precise modulation level, you should
use a scope. While it's true there's no perfect way to do this without
a scope... you should be able to get reasonably close by having an
assistant monitor your transmission during the adjustment. This is
also covered in the VoiceMax installation instructions. Even levels up
to 110% modulation will not cause excessive bleedover. The people you
hear on the air bleeding 20+ channels are usally running a combination
of excessive power with perhaps upward of 130% modulation. That is a
deadly splattering condition all right.

However, I don't agree with your statement that factory radios are set
to 95-98% possible modulation. There is no way there is enough margin
here to assure they will not exceed the 100%. That's why they they
normally set to around 85%. Both my Cobra radios were in that
vicinity. I have never put a factory radio on the scope and seen more
than 90%!

On Tue, 10 Jul 2007 13:00:41 -0700, Telstar Electronics
wrote in
. com:

Assuming you set your processor's limiter to 100%, you still need
to set the output level to the radio so it doesn't overmodulate. Even
just 101% modulation means clipping; pump that with 100% average noise
and you have the potential for some serious bleedover. And there's no
way for the average user to determine the precise point at which his
radio is at 100% modulation. Radios are set at the factory for 95% to
98% modulation to allow for slight variations in tolerance that happen
during normal operation; for you to claim that your processor limits
modulation to 100% all of the time is not only absurd, it's impossible
because of the tolerance limitations of the radio.

I think this is the last of your comments I didn't have time to
respond to before. You are certainly correct that you need to set the
radio so it doesn't overmodulate. In the VoiceMax installation
instructions it says that for a precise modulation level, you should
use a scope. While it's true there's no perfect way to do this without
a scope... you should be able to get reasonably close by having an
assistant monitor your transmission during the adjustment. This is
also covered in the VoiceMax installation instructions.


Such a procedure is pointless unless the assistant is monitoring on
the second and third harmonics.


Even levels up
to 110% modulation will not cause excessive bleedover.


But they will cause harmonics, especially on the television.


The people you
hear on the air bleeding 20+ channels are usally running a combination
of excessive power with perhaps upward of 130% modulation. That is a
deadly splattering condition all right.


Adjacent channel bleedover is caused by audio harmonic distortion
bypassing the 3kHz filter. RF Amplifiers only amplify the bleedover.
Modulation level is not a factor because overmodulation only creates
RF harmonics (e.g, being heard on 54MHz, 81MHz, etc.), which is also
caused by non-linear linears.


However, I don't agree with your statement that factory radios are set
to 95-98% possible modulation. There is no way there is enough margin
here to assure they will not exceed the 100%. That's why they they
normally set to around 85%. Both my Cobra radios were in that
vicinity. I have never put a factory radio on the scope and seen more
than 90%!


I have a shelf filled with CB manuals, both Sams and factory manuals.
Except for some of the old tube-type radios, the modulation adjustment
for all of them is around 95 to 98% -- I didn't pull those numbers out
of a hat. If you've never seen more than 90% then either your scope is
too slow or you need to learn how to use it properly. And that's why
scopes are not recommended for modulation alignment, which is usually
done with an RF voltmeter or demod probe, and an audio source with a
fixed amplitude and frequency (a sig-gen, not someone yelling AAAUUDIO
into the mic). You should really read some of these manuals -- some of
them also describe how to adjust the mic audio AGC circuits....

On Jul 10, 7:16 pm, Frank Gilliland
wrote:
Such a procedure is pointless unless the assistant is monitoring on
the second and third harmonics.

Frank lives in a black & white world. The real world is gray Frank...
and isn't perfect. I agree that in a perfect world... one would use a
scope to get to the target 100% modulation. In the real gray world...
not everyone has a scope.. and therefore would have to resort to the
next best method... the listening assistant. After all you always talk
about the "empirical" method being so good... are you getting away
from that thinking now?.. lol
www.telstar-electronics.com

On Wed, 11 Jul 2007 05:43:31 -0700, Telspam Electronics
wrote in
. com:

On Jul 10, 7:16 pm, Frank Gilliland
wrote:
Such a procedure is pointless unless the assistant is monitoring on
the second and third harmonics.

Frank lives in a black & white world. The real world is gray Frank...
and isn't perfect. I agree that in a perfect world... one would use a
scope to get to the target 100% modulation. In the real gray world...
not everyone has a scope.. and therefore would have to resort to the
next best method... the listening assistant. After all you always talk
about the "empirical" method being so good... are you getting away
from that thinking now?.. lol


I addressed the issues without ranting. I laid out logical arguments
in a clear and concise manner. I used verifiable facts to support my
conclusions. I posted well within the protocol that -YOU- established.
But it's clear that when you are proven wrong all you do is break from
your own protocol and go into a "sour grapes" mode of damage control.
Well, no more clemency for you, Brian. In fact, why don't you go back
to ignoring me again.... it's more fun that way.

You can get an RF probe for just about any DMM. It won't show
waveforms, but it costs a -lot- less than a scope, and in this
application is more accurate. As for a signal generator at the input,
any old audio oscillator will do, even the output of the sound card on
your computer. Just run it through a pot to get the desired voltage.
And the manual will cost you all of $10 on ebay. So you can keep your
scope and your gray world -- I prefer a little more contrast in my
reality, especially when it's easier, more accurate, and a lot less
expensive.

And BTW, I live in Washington, not California. I've stated where I
live about a jillion times since you've been in this group. Learn to
read.