Yeah... I got the model number wrong. I meant the 3403. Digtal, true RMS. I used it for Y Factor measurements at IF before getting an AIL 2075.
Oops. -John ============= > Well John, > > Neither do you with regard to the hp-3400A RMS voltneter. It is spec'd to > only > 10 MHz ! From 50Hz to 1 MHz it is +/-1% and at 10 MHz it is rated at > +/-5%. So > at 10 MHz it is no better then the spec of Bird 43 slug type power meter > (if you > believe them). > > The old hp-434 Colorimetric power meter (i.e., measures heat content of > applied > power) is only good for 5%, but than can be improved somewhat with applied > techniques. However, this unit has the frequency range of DC to 12 GHz. > > The best you can do with an analog scope is 3% measurement of the screen > display. If you were to assume the load resistor whose voltage drop is > being > measured was perfect, then 3% is the best you could do. Obviously, such > is not > the case so some allowance would have to considered because the resistor > is not > perfect, so, again, about the best you can do is in the area of 5%. The > newer > digital displayed readout scopes are really no better. > > As someone pointed out, the best you could trust an Amateur type power > meter > would be 20% into a perfect "load" without some serious calibration > efforts and > recording the offsets at various frequencies. As most all Amateurs would > be hard > pressed to understand and quantify their "load," they are really kidding > themselves to use the meter for anything more then a relative forward > power > indicator. > > "J. Forster" wrote: > >> > At 08:30 PM 12/1/2009, J. Forster wrote... >> >>In fact, on the Tek 7704 or 7704A (I forget which) there were "No >> >>Cost" >> >>options of maximally flat frequency response OR best pulse response. >> >>OR! >> > >> > Sure, if you're using a 150 MHz to try and measure accurately at 100 >> > MHz, you're not going to get absolute accuracy. I'm not familiar with >> > that particular scope, >> >> Really? The most successful 'scope in history. >> >> > but would bet the difference appears as peaking >> > at the extreme. In the absence of circuitry which deliberately changes >> > it, the response of an analog scope is (very nearly) Gaussian. >> > >> > Can you quantify the difference between those options when measuring a >> > 50 MHz (1/3 BW) signal? >> > >> > Since the OP is a ham, I assume his quest is relative to commonly >> > available power meters for that market, most of which can't be >> expected >> > to do better than 20% accuracy, maybe 5% at the high end ( >> > http://www.telepostinc.com/lp100.html ). >> > >> > Sure, you can buy an uncalibrated 3400A (good to ~150W), and get some >> > unknown amount worse than 5% accuracy. >> >> Apparently, you don't know what an HP 3400A is. >> >> Stick to political blogs. >> >> -John >> >> =============== >> >> > Or a 432a (good to a whole 10 >> > mW!) for <$100, plus another $100+ for the mount/cable. Now you've got >> > something which is good to a couple of %, with an _extremely_ limited >> > range (and practically useless for many ham applications). >> > >> > A Gaussian scope is predictably off ~3% @ BW*0.3. A decent scope will >> > have a vertical amp accurate to a couple of percent. With a 1% load, >> > you can measure at the 5% level of a $400 dedicated wattmeter (from < >> 1 >> > uW to 400W, and to the 2000W ham limit if you invest in a 100:1 >> probe), >> > for little cost. >> > >> > "Accurate...simple and inexpensive." Many non-appliance-operator hams >> > will already have a scope, so the cost is a $10 resistor (for a 100W >> > rated Caddock, which should be good for a few seconds of full power, >> > enough to make the measurement). >> > >> > Finally, as I've already mentioned, one can make a simple peak >> detector >> > using a rectifier, and measure the DC voltage off that. >> > >> > >> > >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.