I have one of these.
I bought it from Amazon UK.
It was available a bit cheaper via AliExpress etc, but next day from Amazon.
It seems to compare well with my other power and swr meter.
Ive seen that it’s 18 Watts max (no way 80W…), but I can’t find where I read that just now.

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Any idea how accurate it is? I'm not looking for super precision :-)

Thanks,

Marc

WA6HBR

Hi I have a Bird 4391M(really big iron, 25W min/10kw+ with expensive slugs) but I like this one as QRP swr/wattmeter:

Size is comparable to the Bird slugs, LOL.

Beware:
It says 80W but it should be 10W max(look around this is just the first link I came across)
It is really tiny, see SMA connectors. Smaller than a cigarette box. It comes with SMA to BNC adapters.

Display is *really* tiny as well.

You can also have readings thru the USB cable (see below).

It has also an internal battery, difficult to have something more handy for portable operations.

Giuseppe Marullo

IW2JWW - JN45RQ

PS: here it is with my QCX mini portable setup(compare to the QCX mini!):

Terminal output:

-- 
Yes, that really is my last name.

/g/QRPLabs/topic/85145834#70678

as suggested by K5BCQ

Giuseppe,
I have this mini meter as well and checked it for accuracy. The accuracy in power readings is very poor below about half a watt, being 60% low at 100mW. Above half a watt, it reads between 20 and 10% low up to the 24-Watt level where it was still working. The SWR reading has better accuracy as long as there is enough power to indicate SWR.
There is a calibration function in its menu for which there is no documentation. Any change I made to the calibration number did modify the power reading but the SWR was always very wrong.
The unit runs for a very long time on the internal battery.
Gary
W9TD

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Hi Gary,

never thought of it as a lab grade precision instrument. BTW, the much celebrated Bird is like 5%(CW), 8%(PEP)? and10%(SWR) so not a precision instrument either:

AFAIK the request was for a QRP wattmeter(not SWR),? so 5W: 100mW is not QRP, I am wondering if it is supposed to work? at all.

When I would like something better I have a NanoVNA V2 Pro (claimed 90dB dynamic range, see: ) but not handy for field and somewhat delicate. No power reading either, I could only use a good analog scope.

Anything better you will need deep pockets, that quickly becomes *very* deep pockets.

How did you check accuracy at 100mw and below? Just curious about the depth of your pockets...LOL

Giuseppe Marullo
IW2JWW - JN45RQ

PS: how do you enable the calibration menu? didn't check any doc around

Giuseppe,
I have a USB connected power reader that measures from? 10dBm (10 mW) to -50 dBm, up to 500 MHz. I used attenuators to bring the watt-level measurements into its range. It only cost $126 in 2012? when I acquired it.
Gary
W9TD

Giuseppe,
BTW, the nanoVNA is not capable of measuring power. You would need the tinySA to measure power.
Gary
W9TD

Giuseppe,
To enter calibration you use the terminal which you show you have connected to the device. Press 'h' to get a help display. I tried varying 'i' and 'e' with poor results. Besides the four menu selections shown in the help, there is 'f' for Vfwdcorr, 'r' for Vrevcorr and 'g' for get EEPROM data and display.? I just discovered those three by pressing every key on the keyboard, I had not known of them before and maybe they could correct the readings.
Gary
W9TD

Giuseppe,
BTW, when RF power is applied to the device, it sends the data over the terminal. That is how I measured the accuracy as I could get what the meter was reading and what my power meter was measuring at the same time over USB.
Gary
W9TD

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On 1/22/2024 8:43 PM, Gary W9TD wrote:

Giuseppe,
BTW, the nanoVNA is not capable of measuring power. You would need the tinySA to measure power.

>>When I would like something better I have a NanoVNA V2 Pro (claimed 90dB dynamic range, see: ) but >>not handy for field and somewhat delicate. No power reading either, I could only use a good analog scope.

I said it could not measure power, I could use a Tek 2465B but it is not calibrated, or better I don't trust its calibration. I also have a scalar spectrum analyzer, ( HP ESA L1500) but you need a proven attenuator.

I have a chinese power meter but I don't trust it. Waiting to get a old hp bolometer (like HP-436) but probe prices are outrageous even for stuff very old.

My "lab" stops at a DMMCheck+ and a HP 34401A (5.5 digits) for the time being.

I am acquiring a 6.5 digits DMM (Fluke or Datron) and a rubidium oscillator, but we are in dangerous territory, this stuff brand new is in 3K/10k+ range but it is surplus, so any disclaimer applies.

So far better a 40yo instrument than a brand new chinese anyday. We will see how it goes.

Gary
W9TD

Hi Gary,

BTW, when RF power is applied to the device, it sends the data over

the terminal. That is how I measured the accuracy as I could get what the >meter was reading and what my power meter was measuring at the same time over USB.Hi Gary,

How do you compare the reading coming from the device? What do you use for checking against?
TIA

Giuseppe Marullo
IW2JWW - JN45RQ

I used a simple program to read and average three readings from both the mini meter and my USB power meter that I mentioned cost me $126 in 2010 or so. I changed the RF power manually using my 100 watt transceiver.
Gary
W9TD

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Do you have a link about it?

Thanks.

Giuseppe Marullo
IW2JWW - JN45RQ

Giuseppe,
It is a jupyter notebook python program. I used an Anaconda3 installation.
Gary
W9TD

On Wed, Jan 24, 2024 at 02:38 PM, Shirley Dulcey KE1L wrote:

I use the QRPometer from NM0S electronics. It was originally a 4SQRP kit; the designer now sells an updated version. He sells them through a store on eBay:?

?

I also built this QRPOmeter and it seems to work quite nicely. Fun build.
Dean - KC9REN

?

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>It is a jupyter notebook python program. I used an Anaconda3 installation.

Sorry Gary,

I was meaning the hw device, maybe I am missing something but I didn't see it posted. Just curious what are you using.

I see there are different QRP options, like the one Shirley and others indicated but buying from Italy is not that easy, outrageous shipping and customs fees to start with.

UK source is impossible now, couriers charge whatever they feel to account for Brexable artistic add-ons, Ebay shipping program is a joke and so on.

Not to mention some US seller refuses to ship to Italy (they have their respectable opinions, I don't blame them).

As I said, probably the real option for me is to get a old bolometer, but I will do when I will have some money to spare for an old HPIB unit.

I have slugs up to 1-2kw but sadly nothing under 50W, so the Bird is out of question for this kind of stuff.

I am building a high power (1kW+) swr kit from ebay, wondering if could be adapted to QRP levels...

Giuseppe Marullo
IW2JWW - JN45RQ

I still think the least expensive, educational, and accurate mWattmeters are the ones from China listed on various sites like eBay for around $26. These use the tried and true AD8307 log amplifier which has been around for years and is known for excellent accuracy. They are all designed for 50ohm systems which is what we want. They can be powered by 6-12 VDC and run quite well off a 9V battery for portability.

The output is in dBm and very easy to convert to mwatts. Even easier if you use one of the Mini-Circuits "dBm-Volts-Watts Conversion Charts" available free online. Just search for? "dBm-Volts-Watts Conversion" and download from Mini-Circuits. DO NOT download the "free" print service from "One Source" because it will attempt to also provide a new browser to your computer.?Sneaky dogs. Also print several copies, they are as easy to misplace as 1/2" and 9/16" sockets. The mWattmeter has an internal 50 ohm terminator, so all you need is a battery, the mWattmeter, and the 30dB attenuator connected to your QMX/QDX rig output (and some cables)

The other thing you need to do is provide a reasonable non-inductive 30dB attenuator. A good 30dB Pi attenuator can be made from qty 1 CMF50787R00F and qty 2 CMF6052R300FKR from Mouser. They are both 1% resistors and the 53 ohm resistor is rated at 1W. You can parallel/series the 53 ohm resistors for more power if they get too hot.? The attenuation calculates to 30.01dB. 30dB is convenient because it will attenuate watts to mwatts. Keep any aattenuator leads SHORT so you don't introduce too much inductance.

73 Kees K5BCQ