Homebrew PWR/SWR Meter: Part 1 - Thoughts and Ideas

Video looking at the initial thoughts and ideas for a homebrew PWR/SWR meter.

[@elliotsever8308]

Excellent video. Intruduction to developing SWR meter.

[@deBug67]

On the matter of displays. The small OLED type with dark background has built-in DC to DC converter that creates RFI so keeping of att receive might be a good idea. Can probably be powered from Arduino output pin so Arduino could power on display when output power is sensed.

[@CharlieMorrisZL2CTM]

Agreed. I have had lots of problems with the small 0.96" display. Not so much with the bigger ones.

[@richvantrease]

I really like this idea. It would be interesting to see the difference in accuracy between the loop type sensor you first mentioned, and the toroid loop. As for display, my preference is arduino based because then you can easily pass the values along to a computer or something, and could also trigger a power reduction if SWR is too high. As per the display, I'm more of a digital display guy, but I think a hybrid display with both meters and oled would be cool. Really appreciate your videos. Please keep them coming.

[@CharlieMorrisZL2CTM]

Thanks Richard. Looks like an Arduino based meter will be the way to go. I'm all for that as I get to do some software engineering too.

[@moustaphamuhammad7013]

Charlie Morris I use the regular LCD 20 x 4 characters or any easy to find easy to use one.

[@CharlieMorrisZL2CTM]

Thanks Moustapha. I'm going to use a variety of displays.

[@radio655]

Excellent project! Some thoughts: The loop method is mostly used on VHF and above. The toroid works well on HF. There are more options - the three voltage method and the resistive bridge. The bridge works good with QRP. Be careful with the choice of display. Some displays create plenty of HF noise, especially smaller Chinese Oled ones.

[@CharlieMorrisZL2CTM]

Thanks Jan. I was hoping if I made the loop long enough-say-5cm then it should be ok for HF. As you point out, there are many ways of making these. I'm hoping to have a circuit that can be left in circuit and not consume too much of the transmitted power. I've certainly experienced OLED noise too, especially with the small 0.96" screens. Thanks again Jan.

[@radio655]

Charlie, I use a classical circuit (one toroid for the current, a direct tap with divider for the voltage) for SWR measurement in an antenna controller that is based on an ATMEGA controller. Depending on the power that you intend to measure, one can trick the chip into some flexibility with its ADC analog voltage levels by changing between internal to external reference. That could get you around the need for amplifiers.

[@CharlieMorrisZL2CTM]

That's good to know thanks Jan. I might set the ext Vref high for high range, and use the int Vref for low range. The series will probably experiment with a range of methods, so it will be interesting to see how it pays out.

[@deBug67]

For sampling I guess you could simply sample the HF directly via 1k to rectifier diode and cap. Would give same DC for all frequencies. Pick-up methods is non linear with frequency buy has advantage that you can pick-up reflected as well as forward power but if you simply want a power meter direkt sampling would be more broadband and sensetive, but I don't know if that is a factor in this design? 73 from Sweden

[@CharlieMorrisZL2CTM]

Thanks Harry. I guess I was thinking about having a power and SWR meter. I wonder if the non-linearity of the pick up loop is an issue if its just for the HF band. I'll guess I'll see. My initial thought of not using a toroid was to make it easy and accessible. Sounds like some experimenting needs to be done!

[@moustaphamuhammad7013]

Here's what I really need and also all my problems comes from. bad tuning with the antenna can kill your day if you don't have one of those meters! Good I'm waiting😀

[@CharlieMorrisZL2CTM]

Great. I'm going to see if I can make an effective meter without the use of toroids. Hopefully, it will be sensitive enough.

[@m0khz]

Great project, 1 to 20W, arduino, TFT and AD8307 based would get my vote, but whatever route you take I'm sure I'll learn a lot :)

[@CharlieMorrisZL2CTM]

Thanks. I'm going to factor in cost and ease of getting the parts (not just me, but others too). The AD8307 certainly works well, but costs me around $20 + shipping. If I can emulate that using-say-a LM358 then I'll give it a try first. We'll see how things play out.

[@m0khz]

Understand looking forward to seeing the LM358 implentation.

[@CharlieMorrisZL2CTM]

@@m0khz Hopefully, it will work. That's what experimenting is for!

[@M0XXQ]

Hi Charlie, my suggestion would be to use one of the Nextion graphical displays then you can have a whole host of widgets and graphs/meters that are totally software configurable. This gives you the additional benefit of making a suite of test equipment using one Nextion display, you could have an RF power meter, Antenna Analyser, Intelligent Field Strength Meter, SWR Bridge, RF Signal Generator and many more by designing a plug and play system where each module has its own Micro Controller and which does all the specific function logic and sends a unique ID per device so when you plug the Nextion display head in it knows which GUI to display depending on what module you have hooked up. Sorry for the brain fart, just thinking out loud over my morning coffee here in Blighty :) Cheers and 73 Rob M0XXQ

[@CharlieMorrisZL2CTM]

Hi Rob. I will look into those displays and the idea of a suite is appealing. At this stage I'm still working out what I want (need) in addition to the MFJ tuner I already have. My plan is to start playing around with different ways to generate the DC, then look at ways to display it. Cost is a driver as well as ease of getting the various parts. Enjoy that coffee!

[@M0XYM]

Really interested in this. I can't add to the requirements as I haven't got the experience but I look forward to the project developing and following along at home. I wanted to comment so that you know you have a very interested (albeit generally silent) viewer.

[@CharlieMorrisZL2CTM]

Thanks Kevin. I really appreciate the feedback! Thanks again.

[@aleweber]

Hi Charlie! Nice project. You can use an AD8307 rf log amp with dc out to be read it from analog input of arduino instead a diode and get a better read of rf. And for display I prefer to use 2x16 but anyone of those would do a good work. 73!

[@CharlieMorrisZL2CTM]

Thanks Alejandro. I have a AD8307 here. I might try a simpler approach first, then fall back on that if needed.

[@kg6hum]

I always like test equipment with some type of logging ability, so an Arduino with some type of serial output would be nice. I could also see an advantage to measuring lower than 1 watt since many WSPR or other digital mode kits put out much less than a watt.

[@CharlieMorrisZL2CTM]

Cheers Rob. I probably will add an Arduino for the sake of it. I'd argue too that purchasing two moving coil meters would be significantly more than a Nano and screen. Adding serial put would be east too.

[@CharlieMorrisZL2CTM]

Cheers Stephen. Looks like two possible ranges then; 100mW to 1W, and 1W to 10W.

[@kg6hum]

@Stephen Morton You could have a basic antenna analyzer by sweeping your transmitter through a range of frequencies and recording the SWR. That would work best if the transmitter also had computer or control or at least frequency logging.

[@raafatalheety826]

Good

[@CharlieMorrisZL2CTM]

Cheers Raafat.

[@socketwench]

I would really like to see the arduino version with an LCD display. It is a constant frustration for me to see so many QRP projects based on rare, no-longer-manufactured, or "it was in my junkbox" components.

[@CharlieMorrisZL2CTM]

Hi Tess. I hear you. Would you prefer to see a numerical display or moving needles on the LCD (or both)?

[@WHalphen]

Here's an additional challenge. Put a forward bias on the diodes so they operate in a more linear range and can be used at very low power levels.

[@CharlieMorrisZL2CTM]

That's an idea. I'll jot that down.

[@CT7ARQ]

This IS a project i really need. Started one last year but never ended because of the work (navy military) all the parts ended on outher projects. Realy like to see on a 16x2 lcd or a small nokia lcd or some small lcd, cheap parts and if possible no torroid winding. Power: i run now qrp whit my uBITX and outher projects 100mW to 1W, and 1W to 10W/15W will be good. Keep the project and will build one to as a folow up. 73 de Pedro CT7ARQ

[@CharlieMorrisZL2CTM]

Thanks Pedro. I'll do some comparisons between toroid and non-toroid pick ups. As I have said before, I am not trying to make competition grade equipment, but instead use simple circuits. That may or may not work here, we'll see! I'm going to do a mixture of displays, one with a 16x2 and one with a LCD with moving needles. Thanks too on the power levels.

[@dl2ab]

For a HF-Power/SWR-Meter i have used toroids, because of a better coupling. Maybe you can use some of my desciptions, circuit, Arduino-Code or photos even it is in german: wiki.funkfreun.de/projekte/swr-meter_kurzwelle and in this zip-file: wiki.funkfreun.de/_media/projekte/hshb-swr-meter.zip Last year i have added some components to add analyser functions. The documention is still not finished and i want to make some changes to the arduino-codes (one for analyser, one for the TouchLCD), but maybe it can be useful for your ideas: wiki.funkfreun.de/projekte/swr-analyser

[@duwaynes7529]

I have done several versions of Arduino based SWR/Pwr meters. One was stand alone with TFT display The other is one I am incorporating in a BITX type transceiver. that uses a OLED display. Have been thinking about doing a stand alone with two OLED displays to simulate one of the original Analog meter types. For the pickup I ended up using the same basic circuit with amplifier used in the no longer produced Norcal Power/ SWR meter. Some information on the ones I built on my blog. kv4qb.blogspot.com/2016/02/qrp-swr-meter.html kv4qb.blogspot.com/2018/04/stand-alone-simulated-analog-meter.html DuWayne KV4QB

[@glynnhm0lsg308]

simple build - cheap and easy to access parts - detailed step shots so we can see what your doing?

[@falsedragon33]

Perfect place for a nextion screen

[@CharlieMorrisZL2CTM]

Hi Mike. Yes, I'll probably look at one of those or something similar for the SSB rig. The AM rig will be fixed to the local AM net.

[@MatthewN8OHU]

My view; Arduino with an oled display showing decimal values would be the easiest to do. Maybe a Teensy and dual displays, one with SWR, the other with output power.

[@CharlieMorrisZL2CTM]

Thanks for that.

[@MatthewN8OHU]

@@CharlieMorrisZL2CTM you're welcome.

[@kcnicely]

I would be interested in an arduino based swr watt meter similar to this one, but lower power and using a tft or other graphical display. I like the idea of having a serial interface as well. www.telepostinc.com/Files/phipps-1.pdf

[@CharlieMorrisZL2CTM]

Thanks Ken. That's certainly a capable meter. I might start simple (and hopefully effective/useful) and go from there. I think I might order some more AD8307s.

[@ivanlam5783]

Two analogue meters looks more stylish...

[@CharlieMorrisZL2CTM]

Agreed. Expensive though to buy new, well at least here. I'm probably going to make an add on to the exiting rig.