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Bird meter
- Thread starter Ziploc
- Start date
Short answer is use a scope or get a pep kit for your bird meter.
On AM it depends what you modulate the carrier with. With a single tone 100% mod is 4 times the carrier...pep that is. In this case the bird with no pep kit will show no swing with modulation.
A human voice with some natural asymmetry can be different. It can even change with mic element polarity. If the radio has some swing mods done or an amp is being driven well into gain compression the waveform distorts. Average power continues to climb and pep stays about the same. Anything other than textbook test conditions make the textbook answer invalid.
For an AM carrier average and pep should be equal. If they aren't turn the mic gain all the way down. If they are still not equal your meter is wrong or something is oscillating. An oscilloscope is helpful here.
For SSB the average (bird) watts will be equal to pep if you use a single tone. Average power will be much lower with your voice. Average power will come up some if you use compression of some kind.
On AM it depends what you modulate the carrier with. With a single tone 100% mod is 4 times the carrier...pep that is. In this case the bird with no pep kit will show no swing with modulation.
A human voice with some natural asymmetry can be different. It can even change with mic element polarity. If the radio has some swing mods done or an amp is being driven well into gain compression the waveform distorts. Average power continues to climb and pep stays about the same. Anything other than textbook test conditions make the textbook answer invalid.
For an AM carrier average and pep should be equal. If they aren't turn the mic gain all the way down. If they are still not equal your meter is wrong or something is oscillating. An oscilloscope is helpful here.
For SSB the average (bird) watts will be equal to pep if you use a single tone. Average power will be much lower with your voice. Average power will come up some if you use compression of some kind.
543 is right.
If you could just calculate what your peak power is from an average wattmeter number, there would be no need for peak-reading meters.
It's all about the modulated waveform. Called the "envelope", since it looks like it encloses the RF carrier viewed directly on a 'scope.
A lab-perfect audio sine wave, modulated at exactly 100% will show a PEP power four times the Bird's average reading. The Bird will kick upwards only the tiniest bit when this kind of modulation is turned on and off.
Your voice waveform doesn't look like a sinewave, and that four-to-one rule is only an approximate one for voice audio.
There are a lot of ways your voice waveform can be distorted by a radio's transmitter. Some of those will cause the average reading to be boosted, but not the peaks that carry the sound. This results in a "tight", fuzzy sound.
And there are techniques to boost the peaks without increasing the average power by the same factor. Doesn't necessarily sound any better, but the only way to see the audio waveform's peaks is with a 'scope or a meter that can 'capture' the brief peak value and hold the meter needle up during the 'valleys' between those peaks.
Your average meter reading is a part of the picture, but only part.
73
If you could just calculate what your peak power is from an average wattmeter number, there would be no need for peak-reading meters.
It's all about the modulated waveform. Called the "envelope", since it looks like it encloses the RF carrier viewed directly on a 'scope.
A lab-perfect audio sine wave, modulated at exactly 100% will show a PEP power four times the Bird's average reading. The Bird will kick upwards only the tiniest bit when this kind of modulation is turned on and off.
Your voice waveform doesn't look like a sinewave, and that four-to-one rule is only an approximate one for voice audio.
There are a lot of ways your voice waveform can be distorted by a radio's transmitter. Some of those will cause the average reading to be boosted, but not the peaks that carry the sound. This results in a "tight", fuzzy sound.
And there are techniques to boost the peaks without increasing the average power by the same factor. Doesn't necessarily sound any better, but the only way to see the audio waveform's peaks is with a 'scope or a meter that can 'capture' the brief peak value and hold the meter needle up during the 'valleys' between those peaks.
Your average meter reading is a part of the picture, but only part.
73
I'd like to ask a very "related" question.... even if it exposes just how much of a "novice" I am in this field....... I'll take the hit to get the answer.
If you can fully align your radio such that:
1) you can measure and calculate dead key RF power at some level (I don't care... 4 watts, 5 or 6, you pick!), and
2) you can show that modulating audio is clean, distortion free, and approaching 100% without exceeding, and
3) you can show that particularly 2nd harmonics are down as far as they can go
does it really matter what average power or PEP are? I know it may sound like I am trivializing the issue but if the radio can do the basic things for which it is designed then as long as you can put it on an antenna and make contacts.... does it really matter?
And, to be sure, I am not in any way, knocking anyone who wants to know...... I'm just curious about this simple point....
"If it is well set up for basic functionality, can you really push it for better AVG or PEP without negatively affecting the basic alignment?
Thanks in advance for helping the "education" continue.
Bob
If you can fully align your radio such that:
1) you can measure and calculate dead key RF power at some level (I don't care... 4 watts, 5 or 6, you pick!), and
2) you can show that modulating audio is clean, distortion free, and approaching 100% without exceeding, and
3) you can show that particularly 2nd harmonics are down as far as they can go
does it really matter what average power or PEP are? I know it may sound like I am trivializing the issue but if the radio can do the basic things for which it is designed then as long as you can put it on an antenna and make contacts.... does it really matter?
And, to be sure, I am not in any way, knocking anyone who wants to know...... I'm just curious about this simple point....
"If it is well set up for basic functionality, can you really push it for better AVG or PEP without negatively affecting the basic alignment?
Thanks in advance for helping the "education" continue.
Bob
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