RF Power Watt Meter

This video will describe how to use a simple RF power watt meter to measure output power of any radio transmitter from 1 MHz to 8000 MHz. This is a handy tool to measure the output power of LoRa radio modules.
Power Meter:
www.banggood.c...
Attenuator:
www.banggood.c...

[@zerksus]

I took one apart today. On the bottom PCB is a standard AD8318 chip. It detects from 1MHz to 6/8GHz. The top PCB contains a uC, OLED, 3.3V regulator, USB to RS232 and buttons. The Good: Level/Amplitude works. The offset is very handy. The UART output is awesome if you can program so code on a PC. The Bad: The frequency setting is fake. There is a simple black wire from the AD8318's Vout to an opamp (top board) to an ADC on the uC. No way to control or filter the frequency selected. I took a 434MHz remote transmitter and measured the same results set at 434MHz and 1500MHz. The Ugly: For the price it looks like what you are paying for it. 3D print a box for it as there are many spots you can accidentally cause ESD. The uC code works best for continuous carrier RF. Modulated waves will give weird results. For better control over measurements rather build your own circuit with a separate AD8318 and uC. Is it worth buying it? If you want something that works out of the box then yes. If you want to save costs then buy AD8318 modules with just the chip on, add a small Arduino board with display. Where I live the simple module costs 1/3 of the device above. What to buy extra? You will need one or more attenuators. The normal max input is 5dBm, absolute max is 12dBm...but LORA will output 20dBm. So you will fry the AD8318 the first time you connect it directly.

[@MrCampinski]

Hi. Nice module oveview. Just one remark. Frequency setting doesn't seem to be "dummy" function! AD8318 logarithmic detector doesn't have flat input impedance over the full frequency range. Check AD8318 datasheet, there is a huge variation of input impedance in 0 to 1 GHz vs. 1 GHz + range and this has to be compensated numerically (and probably its). Therefore, I recommend always to enter input frequency if known for accurate results. Cheers.

[@zerksus]

@@MrCampinski Point taken. I will check it with an uncompenated AD8318.

[@SandeepKumar-jj7zi]

@@zerksus What did you find?

[@ovalwingnut]

Thank You! Very timely. Mine just arrived and, yes... I didn't have a clue 🙄 Now after watching your (must see TV) video I'm a trained professional. But then I woke up 🤗. It's all good... Cheers 👍😁

[@0033mer]

Glad the video helped. Thanks for the feedback!

[@W1RMD]

Love the vfd display!

[@qbqbqdbq]

Managed to burn mine out; had this and a morfeus wired together and running on the same USB power supply. Disconnected the morfeus with a light switch adapter (which doesn't disconnect ground); the supply reported power on both ports. Killed at least the top board. Don't be like me haha!

[@sosanft]

that excellent video shows all you need to know

[@rafaelqsb]

very cool. I am waiting for the LoRa repeater. Could you explain the implementation of the LoRa repeater with the Parallax Propeller. Thanks!!

[@PhG1961]

Excellent video !

[@jesseburt3954]

Cool find, thanks...if it's actually accurate this could be handy at work!

[@emptyset00]

great video - thank you. question - would this meter be suitable for detecting an RF signal with an antenna connected to the input? i'm searching for a specific signal i can detect with a SDR but want something more portable to 'search' with. thanks again.

[@0033mer]

Yes .. connect an antenna and you can detect RF signals. Without an attenuator it is very sensitive so be careful you don't exceed the max input rating. Another alternative is a broadband FSM ( Field Strength Meter ) Check out this video: kzbin.info/www/bejne/qpC1pYN5odmShsU

[@Samucas81]

Olá, em qual frequência você obteve melhor precisão?

[@SantanderDiogenes]

Great Video!. I would also want to measure a LoRa power output. How do you get a continuous RF output?

[@0033mer]

Most LoRa modules cannot transmit continuously so you can use the slowest over the air data rate (highest spreading factor) and send a large data packet. The best way would be to use a Spectrum Analyzer with a peak hold feature.

[@Shanjaq]

I wish this thing had a "sweep" function. I want to measure the RF emissions of my PC motherboard and do not know what specific frequencies to check... is it possible to send commands over the serial connection, to set the frequency programmatically for example?

[@mayankawasthi6839]

Would be helpful if the author replies to this @0033mer

[@amitsekhon]

Great video!! Sorry for asking this question as I am not a RF guy. What's the max power this unit can measure safely with a 40db attenuator? Thanks. Edit: Am I right if I say up to 3W safely with 40db atten? According to my calculation.

[@0033mer]

Yes .. for maximum input of -5 dbm for best accuracy with a 40 db attenuator, maximum input would be 35 dbm or 3 Watts.

[@YO9DOC]

nice info tnks ...to make the test with 200mw i need minimum 20dbm, or 25 dbm atenuator ???

[@0033mer]

200 mW is 23 dbm and max input level is -5 dbm so you would need at least a 30 dbm attenuator.

[@jeffhuber5804]

Great video! Did you have to install a driver so that terra term would see it as a COM port? When I plug it in I see unknown device in device manager with it and no COM port assigned.

[@0033mer]

The USB to serial converter used by the RF power meter is the CH340. I have this driver loaded to communicate with the China built Arduino Nanos so my computer recognized it and TeraTerm can be used. If you do not have this driver installed check here: www.wch.cn/download/CH341SER_ZIP.html

[@sm6ehy816]

The accuracy of the chip is only +/- 1 dB...at the best. AD8318 data sheet reveals the secrets...

[@Robbie1949]

OK do you think this would be accurate enough to calibrate an RF generator (namely a Marconi 2022 or 2022C ) in RF amplitude output. The actual power meter they suggest is a Marconi 6960 with power sensor 6912 in the calibration procedure is quite expensive at over $2000, perhaps way overpriced by some individuals considering it's a very old test instrument and sensor ?

[@0033mer]

Check out this video at the 16 minute mark where the watt-meter reading is checked with a spectrum analyzer. kzbin.info/www/bejne/aWGqZo2piah2kJo

[@requiem4adreamc]

I want to measure my alfa cards(nha) real tx power output. Can this device help me for this?

[@AxGxP]

Неужели трудно шнягу изорта вынимать хоть иногда, хотя-бы когда цифры озвучиваешь.

[@ElektronikUygulamalar]

what does frequency setting do on the oled screen do? is there some band pass filters? AD8318 cant tell which frequency the signal coming

[@0033mer]

Frequency response is not flat so the frequency of operation is needed for calibration correction.

[@ElektronikUygulamalar]

@@0033mer the pin tadc makes frequency dependent temprature compansation. Maybe they are calibrating that. Tank you.

[@MrPaulw517]

Can your listed equipment be purchased from another source (item part number or order item #)? I have not received my last Order from them, waiting for two months at this point?

[@0033mer]

They are also available from Wish, Aliexpress and I have seen them on Ebay: www.ebay.com/c/28011111911 Contact Banggood and have them check their tracking data.

[@MrPaulw517]

0033mer What is the part # for your variable attenuator? Thank you for your response, I am working with a pair of Microchip RN2903 LoRa Radio’s and I am trying to tune everything for better range.

[@0033mer]

The attenuator is a Wavetek 5080 which is no longer manufactured but you can get them surplus online. www.hamradio.no/la3tq/wt5080-1.pdf

[@MrPaulw517]

0033mer Is this variable attenuator necessary or is the 2Watt fixed item you referenced sufficient with these RN2903 LoRa Radio’s?

[@0033mer]

The RN2903 max power output is +18.5 dbm ( 71mW). The power input range of the RF wattmeter is -55 to -5 dbm. A fixed attenuator of 30dbm will attenuate the RN2903 output to -11.5 dbm which is within the limits. A 30dbm fixed attenuator is available from Banggood.

[@youpattube1]

I don't understand why you put in 40 db atten when you had set the attenuator to 30 db.

[@0033mer]

The test was conducted with the attenuator set for 40 db as indicated at 4:00. I was just demonstrating how the attenuator value is dialed in when it was showing 30 db.

[@youpattube1]

@@0033mer OK. I missed that. Interesting video.

[@JAKOB1977]

Interesting.. just got myself an RF power meter.. a USB3 RF Power meter... also a cheap unit like this at the same price... it goes a tad higher, but really don't have any use for above 6Ghz. Im also getting a tad over 60dBm with no input. though this unit does have both dBm and also uW value and changes to mW value when above, like 0dBm and trying to find common ground to sense if its somewhat accurate. Im NOOB though I do have a cheap signal generator. FY6900 60Mhz.. any easy approach / setup to validate an accuracy on such a RF unit.?

[@AnanyMangalBME]

Sir, the website in the description says that this product (RF Power watt meter) is discontinued. Then how you bought one?

[@JAKOB1977]

@@AnanyMangalBME Its not the same, I reckon its a better and newer model, I got... and when I was looking I also saw that model above, so if you want the same as in the video, you should be able to find it from Chinese wholesellers.

[@AnanyMangalBME]

@@JAKOB1977 Thanks for replying to my query! Unfortunately in India (where I live), the Chinese Wholesalers are banned by the Government of India, so I'll be looking for newer models with similar functionality. Once Again, thanks for replying to my query.

[@JAKOB1977]

@@AnanyMangalBME which sellers can you use in India.. so aliexpress, Banggood, Taobao etc, is all not valid for you in India?

[@ananymangal6769]

@@JAKOB1977 Alibaba and Taobao are banned in India, Banggood is present but the product is not available at the website. Edit: DH gate's website seems to work here but I'm not sure if its valid or not.

[@CharlyWu173]

can the antenna port b connected to an antenna?

[@0033mer]

Yes, but care must be taken to ensure that the signal from a strong transmitter will not exceed the maximum input power level.

[@aheriady]

cool stuff

[@kermets]

can you check your banggood link as they seem to say Max input is 5dBm is that correct

[@0033mer]

The title indicates -5dbm but the description states +5dbm obviously there is a mistake. The data sheet for the AD8318 indicates useable range of -55 to -5dbm. Max input is +12 dbm where damage occurs. www.analog.com/media/en/technical-documentation/data-sheets/AD8318.pdf

[@kermets]

Ok Great , I just got mine and a 40db attenuator. my brains not the same as it was does that mean im good for 10watts before damage ? thanks Brett

[@0033mer]

To keep the input power in the usable range with a 40db attenuator the max wattage applied will be 3.16 watts.

[@kermets]

Oh yes thanks because we started at -5 not zero. thanks heaps Brett, PS. these work great.