>RE: FT 101 E Peak Envelope Power MFJ 948 Tuner Reply
by K7KBN on September 4, 2007 Mail this to a friend!
Steve - I think the folks at Bird know what they're talking about.<
::Yes, they do. I wrote some of their marketing collateral for them back in 1969.
>Their Model 43, as I know you know, measures CW power (which is the same thing as PEP, for all practical purposes - or so I have been trained to believe).<
::Nope, your training is very wrong. CW and PEP are the same power when using CW, which is a continuous wave mode, providing the CW signal isn't interrupted by keying to add communications intelligence. FM and PEP would also be the same, and for the same reason; no amplitude modulation. As soon as you go to any AM mode including SSB, there are huge differences in measurement requirements and a Bird 43 cannot measure PEP at all, unless the operating mode is CW or FM where there is no amplitude modulation. Bird 43 cannot measure PEP for AM, for SSB, for pulse modulation...
>It has NO internal batteries or external power supply of any sort, for any purpose.<
::That's true, it doesn't need any since a CW signal is continuous wave. A keyed CW signal (A1A) is an interrupted continuous wave. If you send dits and dahs when using a Bird 43 to measure power, you'll see it indicates *WAY* less power than if you just close the key continuously and send a carrier. That's because it can't measure PEP. If you use a Bird 43P (the PEP version of the same meter), you'll see the continuous carrier or the dits-and-dahs sending will both read the same power.
>The Model 43P DOES require batteries or external power for operating the Peak (not PEP) reading circuitry.<
::The 43P is a "PEP" reading meter, by definition. Again, no matter what anyone calls it, there are only a few ways to indicate power according to the I.T.U., which regulates all transmitters everywhere in the world including here. PEP is one of them. "Peak" is not one of them.
>Whether such instrumentation as Peak RF Wattmeters is necessary (and maybe it's not, judging from your last post) is not for me to determine. However, if as respected an authority in the field as Bird chooses to design, manufacture and sell such instrumentation, I'd imagine they have a good reason.<
::Well, sure they do. A Bird 43 and many other instruments are very useful for measuring the output power of FM transmitters, for example: No amplitude modulaton means an FM signal is the same as an uninterrupted CW signal. It's CW power. Bird 43s can also be used to measure the carrier output power of an AM transmitter, as long as you're only interested in measuring carrier power. It can't measure the PEP power of an AM transmitter, which is the only thing amateur radio operators should be concerned with, since we are regulated by PEP power and not carrier power in Part 97.
-WB2WIK/6