Hi Joe,
At some point in DSP, audio processing, synthesis, etc-all thrown into a bag and each manipulated withnumbers or programming, we sort of lose base with whatwe are doing. We could create AM, FM, PM, SSB, PSK,FSK, what have you.
And as amateurs and technical people, it'd be good if we
--- Jeff DePolo WN3A <[EMAIL PROTECTED]> wrote:
>
> I guess this begs the question - at that point,
> where you're doing
> preemphasis and modulation via math versus analog
> circuitry and synthesizing
> the modulated carrier, do you call it PM or
> preemphasized FM? I would argue
> the latter
> I think we're on two different wavelengths here. What
> I am talking about is practical application, not
> theoretical mumbo-jumbo.
OK, yes, I'm talking about the theoretical limitations. Your earlier post
said that "even theoretical PM falls apart at low frequencies", and that's
where I disa
--- Jeff DePolo WN3A <[EMAIL PROTECTED]> wrote:
>
> > I guess I'm not following your logic. If you could
> get
> > a PM exciter to produce a .01 Hz tone at 5 KHz
> > deviation, the amount of audio required at 1 Hz
> would
> > be 40 dB below that. The amount of audio required
> to
> > modulate 5Kh
[EMAIL PROTECTED] wrote:
Actually, if we could get everyone to adjust
> their repeater deviation to 4 kHz, a lot of adjacent channel problems would
> be
> reduced to acceptable levels. Just a thought..
>
> Thank you, Paul, K3VIX (a 26-year Motorola veteran designer).
>
> 73,
> Bob
>
>
E
> I guess I'm not following your logic. If you could get
> a PM exciter to produce a .01 Hz tone at 5 KHz
> deviation, the amount of audio required at 1 Hz would
> be 40 dB below that. The amount of audio required to
> modulate 5Khz deviation at 1KHz tone would be 60 dB
> below the 1 Hz level, or
Thanks Joe that was a fun read.
John Lock KF0MWichita KS kf0m at arrl dot net
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]Sent: Tuesday, April 13, 2004 12:20
AMTo: Repeater-Builder@yahoogroups.comSubject: Re:
[Repeater-Builder] Re: Audio
--- [EMAIL PROTECTED] wrote:
> Hi Joe,
>
> This is an interesting article:
>
>
http://www.repeater-builder.com/rbtip/fmtheorydiscussion.html
>
> He suggests that de-emph came first to get around
> the
> rising noise of an FM receiver. In any case, I think
> most people agree that it was done fo
Hi Joe,
This is an interesting article:http://www.repeater-builder.com/rbtip/fmtheorydiscussion.htmlHe suggests that de-emph came first to get around therising noise of an FM receiver. In any case, I thinkmost people agree that it was done for noise controlpurposes, which it does do well. If
Hi Laryn,
It was just over a year ago that there was a long thread about FM and PM. Someone posted a link to a short magazine article (Ham Radio, it seems it was, but not sure) that shed light on the fact that PM was the first popular method of modulation for land mobile use. I've searched
Hi Joe,
> In one universe, all hams use phase modulators and phase demodulators.> The terms 'preemphasis' and 'deemphasis' are unheard of. The whole> system has flat response. Since their phase demodulators track> their phase modulators, the hams communicate via voice and data over> their PM
--- [EMAIL PROTECTED] wrote:
> Hi Joe,
>
> You want us to believe that PM is why we Pre-emp FM.
>
> Yup. It's a PM world, and you must make your FM
> equipment work in that world.
>
>
> That's simply not the case. This is not supported by
> anything I have ever seen or read, only by you.
>
>
> [EMAIL PROTECTED] wrote:
>
> To further state the case, assume that there are two
> parallel universes.
Que "Star Trek" theme music... ;->
> In one universe, all hams use phase modulators and phase demodulators.
> The terms 'preemphasis' and 'deemphasis' are unheard of. The whole
> system has
Hi Joe,
Bob (S-Com Bob), would it be a fair statement to say that traditionally,transmitters have generally been PM (either true PM or emphasized FM),but receivers have been FM all along? I base this on your last post.
Yes, absolutely!
To further state the case, assume that there are two
Hi Joe,
You want us to believe that PM is why we Pre-emp FM.
Yup. It's a PM world, and you must make your FM equipment work in that world.
That's simply not the case. This is not supported byanything I have ever seen or read, only by you.
These are conclusions we drew from old documents
Well, if nothing else, that page shows that even back then, people used
FM and PM interchangeably. In the beginning of the article, it touts
their "frequency modulated (FM) system", but later it states "success of
the system was due to choosing phase modulation".
Bob (S-Com Bob), would it be a fai
>
> Again, I think you're off base with your supposition.
> You want us to believe that PM is why we Pre-emp FM.
> That's simply not the case. This is not supported by
> anything I have ever seen or read, only by you.
>
Not that I really care but look at this as to why PM was used for the FM
trans
--- [EMAIL PROTECTED] wrote:
> Hi Joe,
>
> I'd like to look at the above statement for just a
> minute. Since we're all in agreement that PM has a
> 6db
> per octave inherent "pre-emp" (that would be 20 dB
> per
> decade), let's look at the numbers in something
> other
> than a "theoretical" ligh
--- Jeff DePolo <[EMAIL PROTECTED]> wrote:
> > Real modulator voltages have to start somewhere as
> a
> > reference. If we take .1 volt P to P to deviate a
> PM
> > exciter to 5KHz of deviation at a 1KHz audio tone,
> > then it will take 1 volt P to P to drive the same
> > modulator to 5KHz deviat
Hi Joe,
I'd like to look at the above statement for just aminute. Since we're all in agreement that PM has a 6dbper octave inherent "pre-emp" (that would be 20 dB perdecade), let's look at the numbers in something otherthan a "theoretical" light- ie; real numbers.Real modulator voltages have
> Real modulator voltages have to start somewhere as a
> reference. If we take .1 volt P to P to deviate a PM
> exciter to 5KHz of deviation at a 1KHz audio tone,
> then it will take 1 volt P to P to drive the same
> modulator to 5KHz deviation at 100 Hz of audio. I
> think everyone will agree with
--- [EMAIL PROTECTED] wrote:
> Hi Joe,
>
> Fact: PM does not reproduce DC well. Actually, it
> doesn't reproduce DC
> at all (beyond a spike) because in DC there is no
> change in the phase of
> the signal. The closer you get to DC, the worse PM
> will perform. FM, on
> the other hand, has no suc
Coy Hilton wrote:
First I would like to read each of your personal definitions of FM and PM, then your dissertations on exactly why one is better than the other, Complete.
I apologize, this is long.
Definitions:
FM: Modulation of a carrier that its instantaneous frequency differs
f
Or a 80D or 140D ...
Neil
wd8chl wrote:
>
> > Hi Skipp,
> >
> > > And we've seen some sloppy engineering in the
> > > design of the audio and limiter circuits.
> >
> > What you're saying here Bob... is that you've
> > owned at least one Icom IC-230 at some time in
> > the past.
> >
> > :-
Hi Joe,
By 'different repeaters', you mean with different cutoffs, right? Or doyou mean specifically designed for the circuitry it will be driving?
I'm thinking that different discriminators put out different levels, and their impedance is pretty high so you don't want to load them, things
> [EMAIL PROTECTED] wrote:
>
> The board being discussed on this list with the high-order filter and
> the limiter, assuming it's designed right, would be an excellent
> addition to the repeater builder's arsenal. Replace the 'blob' and get
> around the soft limiting and the other problems. We tal
Hi Joe,
> As a blanket statement, the above is not true. I can generate> a beautiful 10 Hz or 1 Hz or 0.01 Hz phase modulated output at any> deviation you want using one of the newer function generators.OK. I'll accept that. However, let me add that if you consider theaverage stock exciter, i
> [EMAIL PROTECTED] wrote:
>
> Hi Joe,
Hi Bob.
> Fact: PM does not reproduce DC well. Actually, it doesn't
> reproduce DC
> at all (beyond a spike) because in DC there is no change in
> the phase of
> the signal. The closer you get to DC, the worse PM will
> perform
Hi Joe,
Fact: PM does not reproduce DC well. Actually, it doesn't reproduce DCat all (beyond a spike) because in DC there is no change in the phase ofthe signal. The closer you get to DC, the worse PM will perform. FM, onthe other hand, has no such limitation.
As a blanket statement, the ab
Hi Coy,
First I would like to read each of your personal definitions of FM and PM, then your dissertations on exactly why one is better than the other, Complete.
FM and PM are both referred to as "angle modulation" because the the radio wave's "angular velocity" (frequency or phase) is b
True, but were they members of this list? ;-> (my original selection)
There are now over 2000 members. I suspect the number of repeater
trustees is still far greater - especially globally.
Joe M.
wd8chl wrote:
>
> --- In Repeater-Builder@yahoogroups.com, mch <[EMAIL PROTECTED]> wrote:
> >
> > Y
I don't believe any definitions of PM and FM matter. PM is a Phase
Modulator, and FM is a Frequency Modulator. What is important is what
each does to the signal, or requires to maintain the 'status quo', or
integrity, of the signal.
If you're going to limit your range to 300-3000 Hz, there is litt
Hi Skipp,
> And we've seen some sloppy engineering in the > design of the audio and limiter circuits.What you're saying here Bob... is that you've owned at least one Icom IC-230 at some time in the past. :-)
While the mobiles probably suffer from the same kind of engineering shortcuts, I
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