Astatic 600 swr/wattmeter ?....

roadrage said:

I was acually just reading about this subject and you are right. Most meters that are affordable to the common operator are RMS meters. The "peak" setting on this meter will read peak RMS, not true peak to peak. For a meter to read true peak to peak or for it to read peak envelope power, it needs a powered circuit to do so. Other wise it will be too slow for any accurate reading. And these are much more expensive. But ave RMS and peak RMS are good enough for us to get an idea of what our radios are doing. Bird meters have a powered circuit and have the ability give true peak to peak readings, but even they are +/- %5 accuracy.

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Not to be picky but there is no such thing as RMS power. It is AVERAGE power. Oddly enough RMS voltage times RMS current yields AVERAGE power not RMS power which is a misnomer. As for the Bird meters, only the peak meters have the proper circuitry to detect and display true peak power. The average reading Bird meters have +/-5% accuracy while the peak reading Bird meters have only +/-8% accuracy.

Not to be picky but there is no such thing as RMS power. It is AVERAGE power.

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So Right.
If you search here on the forum, you will find links that I have posted that will tell you what RMS, Peak and AVG power is.
The Bird 43 reads AVG power, and if you install a peak kit in it, will read Peak power.
There is no such thing as a RMS watt in RF, it is a improper term that Dosy has pasted on the front of there watt meters for years and Audio enthusiast Have coined and used for a long time.


And Captain, I was on 3.846 late last night listening to 3 or 4 guys taking about the AL-80 one of them was using....another ham piped in a and asked " how many watts will it do RMS" the Frequency went dead silent for several min....he asked again...some one said " here we go"

73
Jeff

http://www.eznec.com/Amateur/RMS_Power.pdf


Cliff notes:

It should be noted that the term “RMS power” is (mis)used in the consumer audio
industry. In that context, it means the average power when reproducing a single
tone, but it’s not actually the RMS value of the power.
Summary
I’ve shown that:
 The equivalent heating power of a waveform is the average power.
 The RMS power is different than the average power, and therefore isn’t the
equivalent heating power. In fact, the RMS value of the power doesn’t
represent anything useful.
 The RMS values of voltage and current are useful because they can be used
to calculate the average power.
For those who are interested, mathematical derivations are readily available and
can be found on various web sites and in textbooks. What I’ve tried to do here is
to present the basic concepts with as little mathematics as possible. Questions
are welcome – send them to w7el@eznec.com. And I’d appreciate very much if
anyone finding an error would notify me so it can be corrected.
Roy Lewallen, W7EL
.

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OK, aside from incorrect term`s used by the makers of watt meters, what the basic concept of most of the watt meters used in the Amateur and CB radio service are not that Accurate.
If you are worried about a 10/15% error at full scale on your meter it really is not that critical and you should not be.
IF you had a Broadcast Lic, and needed to verify power output then you should be concerned about how accurate you test equipment should be.
Even the World renowned Bird Watt meter can show various levels of power, and is subject to error.
Slugs can be damaged, meters can be dropped and effect operation.
As One of the members has already Said, if you are in the Service ( Army/Navy/Air Force) there are rigorous standards that must be adhered to.
I used to have test equipment that had NASA calibration stickers on them.
They had a date when they were last tested, and when they were required to be tested again...
Outside of the service, I doubt there will be a time you go into your local HAM/CB shop and be shown a Meter with a BIRD or NASA calibration sticker on it because we do not need that kind of accuracy.

Here is an example of the Bird with A Peak kit on it, and how a simple thing like Speech processing can effect it.

http://vk1od.net/measurement/SsbTxPower/MeasureSSBTxPower.htm
If you need CRITICAL power measurements there are other way to measure power that are more " accurate"

I would not worry about it too much....most watt meters used in the radio we play are close enough.


73
Jeff

AudioShockwav said:

And Captain, I was on 3.846 late last night listening to 3 or 4 guys taking about the AL-80 one of them was using....another ham piped in a and asked " how many watts will it do RMS" the Frequency went dead silent for several min....he asked again...some one said " here we go"

73
Jeff

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Maybe he was wondering about "Bird watts" while using the Right-Meter-Scale.