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In post 17730 I wrote: "Jeff has a bunch of really good blog posts about directional couplers." Here's the blog post I was thinking of but could not find:

There is also a version of LTSpice for Mac OS/X. The menus are pretty non-standard, but the program is solid.

It could be a NanoVNA-H v3.3 by Hugen. He did make some in the "sandwich" style before he used plastic cases. BTW - from the picture it looks like your battery is swelling. If so time to get rid of

All Nanovna 1st iteration devices , including the H are all essentially the same and can use the same firmware.?The newer unit is the H4 and the F, both which use different processors and different

Look at the attached photo.... on the back of my 2.8" nanoVNA you can read "NanoVNA", but on the PCB it is clearly readable "NanoVNA-H", followed by the version number 3.3 So, is my unit an -H model,

hi, I took the original query "amp" as amplifier - final amplifier power level. bark less - wag more

The N5ESE probe sees the peak to peak voltage across the diode. The diode should be rated for at least 50 volts, and have just a few pF of capacitance when reverse biased. The low capacitance

Most DVM's cannot measure voltage or current at a mhz or more. Best bet with a DVM is to use a diode RF probe such as this: http://www.n5ese.com/rfprobe1.htm Keep the power down to something

A current transformer is probably a better way to measure the current. 100:1 turns would be nice. There's some trickiness in making a good transformer, but it is galvanically isolated, and

The original question was sparked by having a radio (HF frequencies) that no one can hear transmissions from. The transmission line includes surge protectors, baluns, and HF coax and connectors. Of

Yes, indeed.. Put a T in the coax near the antenna, say, 1/10th wavelength away, and by measuring voltage and phase you could measure fwd and reflected, etc, as well.

Assuming it's a sine wave and assuming the load is resistive, a $1 Harbor Freight DVM and $0.50 worth of diode RF probe with calibration chart should do far better than 5% accuracy in measuring power.

Differentiating between the "currents going in both directions" doesn't work so well in the case of DC, we need AC signals for that. Jerry

The original query was to "test power level (amps) at antenna?". Assuming he means watts instead of amps, we still have to figure out what he means by "at antenna". If he wants to know the power

But, the beauty of this method is that one is not locked to 50-ohms. If one chooses to use something other than 50-ohms the measurement is still correct. Dave - W?LEV

Assuming the dummy load is 50 ohms (viz all that discussion on the list about the loads for the NanoVNA) Most oscilloscopes don't have very tight tolerances on their amplitude accuracy. A Rigol DS1000

This method is highly likely more accurate than the Bird Watt Meters at 5% of full scale and other wattmeters offered into the amateur market. Excellent procedure! Dave - W?LEV -- *Dave - W?LEV*

I measure power into my 50 ohm dummy load by transmitting in CW and measuring the RMS voltage on my scope. P = V*V/50.

Jeff has a bunch of really good blog posts about directional couplers. As I recall, he had a thorough analysis of the Tandem Match, showing exactly how it arrived at a figure for SWR. Unfortunately,

Jeff, You are correct,. Power delivered to the load is Forward-Power minus Reflected-Power. Unfortunately, none of the popular SWR meters actually measure power. What they do is sample RF voltage and