In article , Patrick Turner
wrote:

John Byrns wrote:

Patrick, before I get into a point by point rebuttal to your comments, let
me briefly summarize my current understanding of the difference between
the traditional RC diode peak detector load network with its exponential
decay, and the current source load you use which has a constant linear
sawtooth decay.

The following discussion does not consider problems due to the effects of
a non ideal diode, or those due to an AC/DC load ratio that isn't unity.

It appears that the current source load is the best from the point of view
of tracking the modulation wave form, however with a fixed current source
operation is only optimal at one fixed carrier level, if a wide dynamic
range is to be achieved for the detector, then means must be provided to
cause the current source to track the carrier level.

No, this isn't so. The current source is used precisely because it does
provide the same good performance regardless carrier or modulation level.

Patrick, this is a joke right? This is the really simple stuff, this
isn't one of the more complex and subtle points that we can all get
wrong. I am going to try and keep things simple by just sticking to this
one point. It is easily demonstrated that your claim is wrong with
respect to increasing carrier levels. Your circuit discharges the peak
hold capacitor with what is a reasonable approximation of a current
source, which means that the discharge is at a fixed rate of volts/sec.
Assuming a given fixed modulating frequency, and depth of modulation, the
maximum slope of the modulation that must be tracked by the voltage on the
peak hold capacitor is proportional to the average carrier amplitude.
That implies that if the carrier level is increased by say 6 dB, then the
slope in volts/sec that must be tracked increases by a factor of two,
while the discharge slope of your constant current circuit remains fixed,
ultimately leading to tangential clipping at some carrier amplitude. On
the other hand, while the traditional RC circuit has its problems, it is
not affected by the average level of the carrier that is feed to it. If
the average carrier increases by 6 dB, the peak modulation slope that must
be tracked increases by a factor of two as before, but since the discharge
current is not fixed, and varies in proportion to the carrier level, the
discharge slope also increases by a factor of two, and there will be no
additional tangential clipping with the traditional circuit when the
average carrier level is increased.

The bottom line is that the traditional circuit can handle any carrier
level no matter how large, without an increase in tangential clipping,
while the tangential clipping in your circuit, with a fixed discharge
rate, increases as the carrier level increases above the design point,
hence a poor dynamic range.

Now specifically what is wrong with what I have just said, where is my
error? This is the simple part of the problem, it is not even the complex
stuff where we all go wrong from time to time, yet you don't seem to be
able to grasp it.

There was never any intention to have superlative AGC control in this radio
of mine.

I never assumed that was your intention, but since your detector is
sensitive to the average carrier level, it is relevant, but that's not the
real reason I wondered out loud about your AGC circuit. The real reason
was that I was simply curious about the performance of an AGC system with
a single controlled stage, given that most radios use a minimum of two
controlled stages.

Some of the convenience benefits of the traditional AGC philosofy were
traded away for a more linear performance of the mixer and IF tubes, which
work with fixed bias.

That's fine as far as it goes, but it creates a problem for a detector
with a fixed discharge current source, and the consequent sensitivity to
overload that implies.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

"John Byrns" wrote in message
...
In article , Patrick Turner
wrote:

John Byrns wrote:

Patrick, before I get into a point by point rebuttal to your comments,
let
me briefly summarize my current understanding of the difference
between
the traditional RC diode peak detector load network with its
exponential
decay, and the current source load you use which has a constant linear
sawtooth decay.

The following discussion does not consider problems due to the effects
of
a non ideal diode, or those due to an AC/DC load ratio that isn't
unity.

It appears that the current source load is the best from the point of
view
of tracking the modulation wave form, however with a fixed current
source
operation is only optimal at one fixed carrier level, if a wide
dynamic
range is to be achieved for the detector, then means must be provided
to
cause the current source to track the carrier level.

No, this isn't so. The current source is used precisely because it does
provide the same good performance regardless carrier or modulation
level.

Patrick, this is a joke right? This is the really simple stuff, this
isn't one of the more complex and subtle points that we can all get
wrong. I am going to try and keep things simple by just sticking to this
one point. It is easily demonstrated that your claim is wrong with
respect to increasing carrier levels. Your circuit discharges the peak
hold capacitor with what is a reasonable approximation of a current
source, which means that the discharge is at a fixed rate of volts/sec.
Assuming a given fixed modulating frequency, and depth of modulation, the
maximum slope of the modulation that must be tracked by the voltage on the
peak hold capacitor is proportional to the average carrier amplitude.
That implies that if the carrier level is increased by say 6 dB, then the
slope in volts/sec that must be tracked increases by a factor of two,
while the discharge slope of your constant current circuit remains fixed,
ultimately leading to tangential clipping at some carrier amplitude. On
the other hand, while the traditional RC circuit has its problems, it is
not affected by the average level of the carrier that is feed to it. If
the average carrier increases by 6 dB, the peak modulation slope that must
be tracked increases by a factor of two as before, but since the discharge
current is not fixed, and varies in proportion to the carrier level, the
discharge slope also increases by a factor of two, and there will be no
additional tangential clipping with the traditional circuit when the
average carrier level is increased.

The bottom line is that the traditional circuit can handle any carrier
level no matter how large, without an increase in tangential clipping,
while the tangential clipping in your circuit, with a fixed discharge
rate, increases as the carrier level increases above the design point,
hence a poor dynamic range.

Now specifically what is wrong with what I have just said, where is my
error? This is the simple part of the problem, it is not even the complex
stuff where we all go wrong from time to time, yet you don't seem to be
able to grasp it.


John,

You seem to be limiting your considerations to the 'tangential clipping' and
not to other distortions that will occur. With the simple RC circuit the
decay of the signal differs from positive to negative peaks in the
modulation. This imparts an assymetry to the recovered signal. You are
trading one type of distortion for another. Using a constant current to
drain the capacitor provides a more linear output and one where slew rate
limiting can be easily computed as a function of frequency and amplitude.
Using a resistor to drain the capacitor provides an output where slew rate
limiting is more a function of frequency and less of amplitude.

However, if you know the maximum amplitude and modulating frequency of the
signal you are trying to detect, then for either detector one can determine
the proper component values for the desired result. These are the tradeoffs
that go into every design.

I suggest that those who are interested and/or following this discussion
would be well served by doing some modeling of the two proposals and
consider the results and how they are affected by changes in the input
signal. For a simple approach you could consider an ideal diode and signal
source, a capacitor and either a current source or a resistor. Try various
amplitudes and modulation levels.

Both circuit approaches work within their limitations. The question is 'what
are the limitations?'.

Suggestion: Consider a triangle wave for the modulation source. The math is
a lot easier.

Hint: Linear is good.

Once you understand the limitations of each circuit topology, then you can
understand how it interacts with the rest of the radio, or what requirements
each places on the rest of the radio.

Have fun, I'll be watching,

craigm


There was never any intention to have superlative AGC control in this
radio
of mine.

I never assumed that was your intention, but since your detector is
sensitive to the average carrier level, it is relevant, but that's not the
real reason I wondered out loud about your AGC circuit. The real reason
was that I was simply curious about the performance of an AGC system with
a single controlled stage, given that most radios use a minimum of two
controlled stages.

Some of the convenience benefits of the traditional AGC philosofy were
traded away for a more linear performance of the mixer and IF tubes,
which
work with fixed bias.

That's fine as far as it goes, but it creates a problem for a detector
with a fixed discharge current source, and the consequent sensitivity to
overload that implies.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

In article , "craigm"
wrote:

"John Byrns" wrote in message
...

Patrick, this is a joke right? This is the really simple stuff, this
isn't one of the more complex and subtle points that we can all get
wrong. I am going to try and keep things simple by just sticking to this
one point. It is easily demonstrated that your claim is wrong with
respect to increasing carrier levels. Your circuit discharges the peak
hold capacitor with what is a reasonable approximation of a current
source, which means that the discharge is at a fixed rate of volts/sec.
Assuming a given fixed modulating frequency, and depth of modulation, the
maximum slope of the modulation that must be tracked by the voltage on the
peak hold capacitor is proportional to the average carrier amplitude.
That implies that if the carrier level is increased by say 6 dB, then the
slope in volts/sec that must be tracked increases by a factor of two,
while the discharge slope of your constant current circuit remains fixed,
ultimately leading to tangential clipping at some carrier amplitude. On
the other hand, while the traditional RC circuit has its problems, it is
not affected by the average level of the carrier that is feed to it. If
the average carrier increases by 6 dB, the peak modulation slope that must
be tracked increases by a factor of two as before, but since the discharge
current is not fixed, and varies in proportion to the carrier level, the
discharge slope also increases by a factor of two, and there will be no
additional tangential clipping with the traditional circuit when the
average carrier level is increased.

The bottom line is that the traditional circuit can handle any carrier
level no matter how large, without an increase in tangential clipping,
while the tangential clipping in your circuit, with a fixed discharge
rate, increases as the carrier level increases above the design point,
hence a poor dynamic range.

Now specifically what is wrong with what I have just said, where is my
error? This is the simple part of the problem, it is not even the complex
stuff where we all go wrong from time to time, yet you don't seem to be
able to grasp it.


John,

You seem to be limiting your considerations to the 'tangential clipping' and
not to other distortions that will occur.

On the contrary I alluded to the other problems in my post above where I
said "while the traditional RC circuit has its problems". The problem is
that Patrick has a very thick head, so I am trying to keep things simple
so he might get the point.

With the simple RC circuit the
decay of the signal differs from positive to negative peaks in the
modulation. This imparts an assymetry to the recovered signal. You are
trading one type of distortion for another.

Yes I think I discussed this in another recent post, although I didn't
call it asymmetry, I called it a problem with the negative peaks, at least
I hope I actually posted that bit, and that it didn't get edited out, I
will have to check back in the message archive. In the interest of full
disclosure, I will also own up to having talked in a previous message like
the negative peak problem didn't exist in the traditional circuit, this
seems to be the tack most text books take, concentrating on the point of
maximum slope. It may be justifiable, as just like the tangential
clipping in the high slope area, the negative peak problem is related to
both modulating frequency and modulation depth, creating a problem only
with heavy modulation at high frequencies. For the reader who may be
confused by this negative peak asymmetry problem, it should be noted that
this is not the same clipping phenomenon caused by a poor AC/DC load
ratio, and that the negative peak clipping caused by a poor AC/DC load
ratio is not frequency dependent. All in all I don't believe the
asymmetry you are talking about is a serious problem in practice, but that
is an individual matter of judgment.

Using a constant current to
drain the capacitor provides a more linear output and one where slew rate
limiting can be easily computed as a function of frequency and amplitude.

If you look closely at the operation ot the constant current "drain", you
will see that it too has a distortion problem at the negative peaks, and
it affects all modulating frequencies, unlike the traditional circuit
where the asymmetry tends to disappear at lower modulating frequencies.

Using a resistor to drain the capacitor provides an output where slew rate
limiting is more a function of frequency and less of amplitude.

I wouldn't say that.

However, if you know the maximum amplitude and modulating frequency of the
signal you are trying to detect, then for either detector one can determine
the proper component values for the desired result. These are the tradeoffs
that go into every design.

Quite true.

I suggest that those who are interested and/or following this discussion
would be well served by doing some modeling of the two proposals and
consider the results and how they are affected by changes in the input
signal. For a simple approach you could consider an ideal diode and signal
source, a capacitor and either a current source or a resistor. Try various
amplitudes and modulation levels.

Both circuit approaches work within their limitations. The question is 'what
are the limitations?'.

I don't think Patrick will approve this sort of activity.

Suggestion: Consider a triangle wave for the modulation source. The math is
a lot easier.

Hint: Linear is good.

Once you understand the limitations of each circuit topology, then you can
understand how it interacts with the rest of the radio, or what requirements
each places on the rest of the radio.

Have fun, I'll be watching,

This is all way too complex, I was trying to keep things simple for
Patrick, and get him to try on one small bite sized piece at a time. The
first piece is how the modulating frequency and depth of modulation affect
the tangential clipping in the high slope part of the wave form with the
two circuits.

Once that is grasped, then he can move on to the negative peak asymmetries
both circuits have, but that is considerably harder to understand.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

John Byrns wrote:

In article , Patrick Turner
wrote:

John Byrns wrote:

Patrick, before I get into a point by point rebuttal to your comments, let
me briefly summarize my current understanding of the difference between
the traditional RC diode peak detector load network with its exponential
decay, and the current source load you use which has a constant linear
sawtooth decay.

The following discussion does not consider problems due to the effects of
a non ideal diode, or those due to an AC/DC load ratio that isn't unity.

It appears that the current source load is the best from the point of view
of tracking the modulation wave form, however with a fixed current source
operation is only optimal at one fixed carrier level, if a wide dynamic
range is to be achieved for the detector, then means must be provided to
cause the current source to track the carrier level.

No, this isn't so. The current source is used precisely because it does
provide the same good performance regardless carrier or modulation level.

Patrick, this is a joke right? This is the really simple stuff, this
isn't one of the more complex and subtle points that we can all get
wrong.

I am not joking when I said that the best performance under all conditions is
possible with a CCS, or a large value R with a fairly large 55v across it
to approximate a CCS.

Using CCS is new age stuff, and one never saw any CCS anyplace in domestic
electronics because there was always a cheaper crummier way to get the job done.

I am going to try and keep things simple by just sticking to this
one point. It is easily demonstrated that your claim is wrong with
respect to increasing carrier levels. Your circuit discharges the peak
hold capacitor with what is a reasonable approximation of a current
source, which means that the discharge is at a fixed rate of volts/sec.

Thank goodness the rate of discharge is fairly constant, regardless of AM%
and for the lower Audio F.


Assuming a given fixed modulating frequency, and depth of modulation, the
maximum slope of the modulation that must be tracked by the voltage on the
peak hold capacitor is proportional to the average carrier amplitude.
That implies that if the carrier level is increased by say 6 dB, then the
slope in volts/sec that must be tracked increases by a factor of two,
while the discharge slope of your constant current circuit remains fixed,
ultimately leading to tangential clipping at some carrier amplitude.

The innitial part of the discharge slope from the 270 pF and 1M that I use is
quite steep,
but quite fast enough to allow a few volts of 10 kHz audio AM, without tangential
distortion, where the discharge slope cuts off part of the negative going sine
wave.

Try my circuit on a breadboard, and you will see that all's well!!!!!!

How many times must I suggest you try something new for a change!!

On
the other hand, while the traditional RC circuit has its problems, it is
not affected by the average level of the carrier that is feed to it. If
the average carrier increases by 6 dB, the peak modulation slope that must
be tracked increases by a factor of two as before, but since the discharge
current is not fixed, and varies in proportion to the carrier level, the
discharge slope also increases by a factor of two, and there will be no
additional tangential clipping with the traditional circuit when the
average carrier level is increased.

The bottom line is that the traditional circuit can handle any carrier
level no matter how large, without an increase in tangential clipping,
while the tangential clipping in your circuit, with a fixed discharge
rate, increases as the carrier level increases above the design point,
hence a poor dynamic range.

I found the typical traditional circuit suffered from tangential distortion just
like any other.

Whatever the the diode detector circuit is, it should be set up
to be able to produce a large enough voltage without tangential or other
distortions
and I believe my circuit produces the least compared to the traditional.

When you try my circuit instead of wasting an enormous amount of time on
discussions,
you will see the superiority of the circuit I have posted.



Now specifically what is wrong with what I have just said, where is my
error? This is the simple part of the problem, it is not even the complex
stuff where we all go wrong from time to time, yet you don't seem to be
able to grasp it.

I am able to grasp it, but I have limited time to discuss something so trivial,
and and you won't even give the idea of mine a try, so WTF do you know about
my idea if you have not tried it?

I have tried yours, and a pile of other variations.



There was never any intention to have superlative AGC control in this radio
of mine.

I never assumed that was your intention, but since your detector is
sensitive to the average carrier level, it is relevant, but that's not the
real reason I wondered out loud about your AGC circuit. The real reason
was that I was simply curious about the performance of an AGC system with
a single controlled stage, given that most radios use a minimum of two
controlled stages.

There is adequate AGC for local stations.
The mixer and IF amps are working in their linear regions,
and the main purpose of the AGC is to prevent IF overload.

The detector is quite linear regardless of whatever level of IF is present
up to about 10vrm of output, but I ask only 3vrm of audio output.
There is SFA distortions from my detector.





Some of the convenience benefits of the traditional AGC philosofy were
traded away for a more linear performance of the mixer and IF tubes, which
work with fixed bias.

That's fine as far as it goes, but it creates a problem for a detector
with a fixed discharge current source, and the consequent sensitivity to
overload that implies.

I dson't think so.

BTW, I tried shunting the secondary of an IFT while monitoring the signal at the
primary.
As I predicted, the primary signal reduced about 1 dB.

You have said the primary signal will increase when the seconday is shunted, ie
gain will increase, but I saw no sign of that.

Patrick Turner.





Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/

John,

You seem to be limiting your considerations to the 'tangential clipping' and
not to other distortions that will occur.

On the contrary I alluded to the other problems in my post above where I
said "while the traditional RC circuit has its problems". The problem is
that Patrick has a very thick head, so I am trying to keep things simple
so he might get the point.

Unfortunately, you have not yet done a proper comparison measurement
of a traditional detector driven off an IFT secondary,
and compared the results to what I have proposed and posted using two CF tubes.

I don't have the time to spend on discussions that get nowhere with someone who
hasn't the time
to connect a handful of parts on a bench, and do some real work, instead of
endlessly talking around the subject, and making incorrect statements about skull
bone thickness.

Patrick Turner.

Perhaps we can get back to detectors again eventually, but for now I have
had quite enough of them, so I will bite my tongue and refrain from
further comment on specific detectors for the moment.

In article , Patrick Turner
wrote:

There is adequate AGC for local stations.
The mixer and IF amps are working in their linear regions,
and the main purpose of the AGC is to prevent IF overload.

The term "local stations" as used above has also been used recently in
several other threads. I am curious what the readers of this forum would
consider to be a "local station"? What would be the range of received
field strengths that would define a "local station"? I am curious what
the range of field strengths might be that a receiver designed for "local
stations" would have to cope with?

Here in the US IIRC the FCC considers the "primary" service area of a
station to be defined by the 2 mV/M field strength contour. Also IIRC the
FCC requires a field strength of 5 uV/M for coverage of the primary City,
and recommends 20 uV/M for City coverage. One of these numbers, 2 mV/M, 5
uV/M, or 20 uV/M could probably be considered to be the lowest field
strength a "local station" would have. I will arbitrarily pick the 5 uV/M
City grade coverage number as the lower limit. At the upper end of the
scale here in the US the FCC requires 50 kW class A stations to have a
minimum unattenuated field strength of 2.56 Volts/Meter at 1 kM.
Depending on how close one wants to be to such a station and receive it
without overload, we might expect a received field strength of as much as
1,000 mV/M. Without checking the actual numbers in my notebook, which are
based on crude measurements and calculations using the local ground
conductivity and FCC propagation charts, I think the field strength of the
local 50 kW stations is about 300 uV/M in my workshop, so I will again
arbitrarily pick that number as my upper limit.

I would therefor consider a "local station" to be one having a received
field strength somewhere in the range of 5 mV/M to 300 mV/M, requiring a
receiver with total dynamic range of at least 36 dB. Does anyone have any
alternate thoughts on the meaning of "local station" as applied to
receivers?

BTW, I tried shunting the secondary of an IFT while monitoring the signal
at the primary.
As I predicted, the primary signal reduced about 1 dB.

You have said the primary signal will increase when the seconday is
shunted, ie gain will increase, but I saw no sign of that.

It will, something was screwed up in your experiment.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

In article , Patrick Turner
wrote:

John,

You seem to be limiting your considerations to the 'tangential clipping'
and not to other distortions that will occur.

On the contrary I alluded to the other problems in my post above where I
said "while the traditional RC circuit has its problems". The problem is
that Patrick has a very thick head, so I am trying to keep things simple
so he might get the point.

Unfortunately, you have not yet done a proper comparison measurement
of a traditional detector driven off an IFT secondary, and compared
the results to what I have proposed and posted using two CF tubes.

I'm not sure what "proper comparison measurements", or "CF tubes", have to
do with the theoretical aspects of tangential clipping? Unfortunately I
don't possess an AM generator that is adequate for making these
measurements, that is a generator that will do 100% negative modulation,
or anywhere near it, with low distortion. It isn't clear that you possess
such a generator either, and you seem to have engaged in a certain amount
of shucking and jiving with respect to the actual performance of your
detector.

Why don't you describe the AM generator you are using, how close it gets
to 100%, and what the distortion is at that point? I know you are using a
CRO to check for distortion, rather than a distortion analyzer, but still
if the generator has serious distortion at the extremes of modulation it
could mask some of the faults in a detector.

I don't have the time to spend on discussions that get nowhere with
someone who hasn't the time to connect a handful of parts on a bench, and
do some real work, instead of endlessly talking around the subject,

I am working on such a project, but first I must solve the AM generator
problem. I am beginning to get an idea or two as to how I can overcome
the AM generator problem. You have nearly pushed me to the point of
action in my workshop, as Danger Dave did a few years back with respect to
the workability of an amplifier design I had been contemplating for
several years. Once I built it, Danger Dave was quickly proved to be full
of it, and I expect a similar result again, once you have motivated me
sufficiently. But first lets hear more about the AM generator you are
using for your tests?

and making incorrect statements about skull bone thickness.

As they say, "if the shoe fits wear it"! I remember the "thick as a
brick" thread from earlier this year, where you clearly demonstrated the
thickness of your skull. For those don't remember, that adventure might
have been called the "octave" matter. It was related to the slope of the
attenuation curve of an RF tank circuit, IFT, or other similar circuit.
Workshops, simulations, and what not didn't enter into the matter because
you had conveniently measured, plotted, and posted the response curves for
an AM aerial circuit which made a perfect example for discussion. The
trouble started when you and your fellow countryman Phil Allison claimed
that the slope of the attenuation curve of a tank circuit was stepper
close to resonance and that the slope of the attenuation progressively
became less steep as you moved away resonance. I had been under the
impression that the slope of the attenuation curve actually increased as
you moved away from resonance, and asymptotically approached a slope
determined by the order of the filter. After a few back and forths it
became obvious to me that the problem was one of the different frequency
reference points we were using, you and Phil were using Zero frequency as
your reference, while I was using the center frequency of the filter as my
reference. At that point I said I completely agreed with your
conclusions, given your frame of reference, but you refused to accept my
concept of using the filter center frequency as an alternative view of the
situation, and told me it just wasn't valid. That is a perfect example of
a thick skull, since generally there are alternate definitions for things,
and as long as they are consistent with the facts, in that case your
measured and posted results, they are just as valid as what you may
consider to be a more conventional viewpoint, although in the case of the
"octave" matter I am not entirely sure yours was the conventional
viewpoint, but the bottom line was they both worked, and you denied that
my approach had validity.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

"John Byrns" wrote in message
...

The term "local stations" as used above has also been used recently in
several other threads. I am curious what the readers of this forum would
consider to be a "local station"?

I have no idea what they use to describe them now... but I remember that
AM's used to be basically classed as either Local (frequencies such as
1230.. 1 KW or less daytime power), Regional (frequencies such as 620... 5
KW-50KW daytime power) and Clear channel (frequencies such as 1160.. 50 KW
daytime and nighttime power). Locals were generally required to go off the
air at dusk unless they had specific nighttime authorization, which
generally required drastic power reduction and/or directional antenna system
(most with nighttime authorization would run at 250 watts, but I know of
some that run as little as 10 watts nighttime... as in why bother??)

Brenda Ann Dyer wrote:
"John Byrns" wrote in message
...

The term "local stations" as used above has also been used recently in
several other threads. I am curious what the readers of this forum would
consider to be a "local station"?


I have no idea what they use to describe them now...


The local "graveyard" stations are on 1230, 1240, 1340, 1400, 1450 and
1490. Nearly all are 1000 Watts day and night.

--
Mike Westfall, N6KUY, WDX6O
Los Alamos, NM (DM65uv)
Online logbooks at http://dxlogbook.gentoo.net
Remove the Reptile to Reply

In article , "Brenda Ann Dyer"
wrote:

"John Byrns" wrote in message
...

The term "local stations" as used above has also been used recently in
several other threads. I am curious what the readers of this forum would
consider to be a "local station"?

I have no idea what they use to describe them now... but I remember that
AM's used to be basically classed as either Local (frequencies such as
1230.. 1 KW or less daytime power), Regional (frequencies such as 620... 5
KW-50KW daytime power) and Clear channel (frequencies such as 1160.. 50 KW
daytime and nighttime power). Locals were generally required to go off the
air at dusk unless they had specific nighttime authorization, which
generally required drastic power reduction and/or directional antenna system
(most with nighttime authorization would run at 250 watts, but I know of
some that run as little as 10 watts nighttime... as in why bother??)

Well yes, a "Local" station is an obsolete FCC term for what are now
called class C stations. Class C stations operate with full power both day
and night by the way. That isn't exactly what I was asking about though,
considering the FCC doesn't have dominion over Australia, which is where
the post originated that used the term.

I was using the term in the context of a receiver designed to receive only
"local stations", and not intended for receiving distant stations, as for
example the old AA4 radios that didn't have an IF amplifier stage, where
the converter drove the detector directly.

What I was wondering was what range of field strengths those "local
station" receivers might have been intended to receive?


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/