CB and Ham Radio Techs Love Their Bird Wattmeters

[A.Z.]

One thing I need to do is to keep the display from showing meaningless numbers, such as when no power is actually being transmitted it will display a meaningless VSWR. I will choose to treat any display that is below 100 mW as below the lower limit of this power meter, and also not show a VSWR in that condition.

Instead of putting a lower limit to the measured power, why don't you set the SWR to zero when both the displayed FWD/REF values are zero ? I mean, after rounding the values for display, you check if they're "zero" and in such a case the SWR won't be shown, it shouldn't be so difficult and will allow to take measurements even with very low power; that said, what intrigues me is the fact that with FWD and REF at zero (or some really small value) the device shows that SWR value, I wonder if there's some bug in the code calculating SWR, maybe an overflow or something like that ?

[xrunner]

Should read 1.198, not 1.2.  I've been told hams need three places beyond the decimal point. 

I'm trying to wean them away from that sort of thing. They're lucky I'm not showing the tenths as either zero or .5 - whichever is closest. 

Instead of putting a lower limit to the measured power, why don't you set the SWR to zero when both the displayed FWD/REF values are zero ?

Oh here you are. You've been very quiet but I knew you would pop up here again.

The values will not ever be "Zero" as read from the log amp - it's called the noise level.

Furthermore, this is for hams - not the likes of people who frequent this form. They have no use for measuring the power of low wattage emissions, not to mention the SWR of same. What they are interested in is the highest power they can get out of a radio without it melting.

I've never associated with any ham who talked about wanting to see the power of their 0.25 watt transmitter or anything even lower that that. ¹

Therefore, the lower power level that MY project will measure is 0.1 W as a lower limit. Anything lower than that the unit is rendered STANDBY waiting for a power to measure higher than 0.1 W, and therefore there is no VSWR to calculate.

... what intrigues me is the fact that with FWD and REF at zero (or some really small value) the device shows that SWR value, I wonder if there's some bug in the code calculating SWR, maybe an overflow or something like that ?

There is no "bug in the code calculating SWR". As I stated before, the display only shows a few decimal places. If the power calculated out of the log amp is even 100 microwatts there is a power level existing - not "Zero" power. You do realize that these log amps can respond to power levels as low as 1 e-10 W?

Here's what intrigues me: What "really small value" (whatever that means in your mind because you didn't say), for FWD and REV power (not zero power), would not show any calculated SWR?



1.Disclaimer: I do not say there are NO hams who would do this, it's just I've never met one.

[joeqsmith]

Furthermore, this is for hams - not the likes of people who frequent this form. They have no use for measuring the power of low wattage emissions, not to mention the SWR of same. What they are interested in is the highest power they can get out of a radio without it melting.

So it won't correctly read the output power of my pulsed spark gap transmitter?

My last power meter for it was a white LED...

[A.Z.]

@xrunner

stop trying to "troll around" and read my post, I wrote to check the ROUNDED values, that is the ones sent to the display ? Got it now or do you need a torch, a map and both your hands to find your a** ?

[xrunner]

@xrunner

stop trying to "troll around" and read my post, I wrote to check the ROUNDED values, that is the ones sent to the display ? Got it now or do you need a torch, a map and both your hands to find your a** ?

Calm down - you're lashing out now. Well, I do it my way and I'm very satisfied with it. If you would do it another way more power to you, but we just don't see eye-to-eye. It's OK happens all the time on the forum. 

[A.Z.]

oh, I am calm, no need to calm more or I'll just go hit the sack; it isn't a matter of "doing it differently", just a matter of LEVERAGING a different point of view to solve a given issue, then, if you prefer going for a 100mW floor, go for it, but you could easily avoid that, up to you.

[xrunner]

Furthermore, this is for hams - not the likes of people who frequent this form. They have no use for measuring the power of low wattage emissions, not to mention the SWR of same. What they are interested in is the highest power they can get out of a radio without it melting.

So it won't correctly read the output power of my pulsed spark gap transmitter?

My last power meter for it was a white LED...

It's really a strange coincidence you mention something like that right now, because I was thinking about another small "power meter" project. Like your LED - it's a minimalistic design¹, a minimalistic indicator. No such thing as watts or dBm will be displayed on it.

The other day before I put the small power meter back in it's case, I was curious about something. How well would the AD8307 react to very near-field WiFi signals. It isn't rated for anything above 500 MHz, but what does it cost to try? As you can see in the picture, it does in fact respond to 2.4 and 5 GHz emissions provided they are very close to it's antenna.

In fact, with an environmental noise level of -64 dBm as measured by the meter far away from the router, it responds to WiFi signals giving a reading from -61 to -42 dBm sitting where you see it in the pic, constantly fluctuating of course ... but that's what want to see.

Now, you can buy El Cheepo WiFi indicators like the one in the link here -

eBay auction: #142649112454

But that isn't at all what I want to make. I don't want sophistication, I want minimalistic. Very minimalistic - like your LED. In fact, what I have in mind could be made with an LED using PWM, but I have another indicator I want to use.

I'm still thinking about this idea but to keep people reading here entertained and the thread going, I will make it. I'll be back ...

1.

The Power of Less: Understanding Minimalist Design

In a society bombarded with constant stimuli and overflowing information, the minimalist design stands out as a breath of fresh air. At its core, minimalist design is about embracing the philosophy of “less is more.” It seeks to eliminate unnecessary elements and distractions, distilling a design down to its essential components. Stripping away the superfluous, minimalist design creates a sense of focus, clarity, and purpose.

https://medium.com/@studiashriftu/the-rise-of-minimalist-design-embracing-simplicity-in-a-complex-world-d24336138baf

[joeqsmith]

I remember seeing some articles in QST or something, using light bulbs and wire for their SWR meter, maybe.  It's fuzzy. 

That slotted line I put together for that demo using a ruler measured frequency and SWR fairly accurately.  Wouldn't want to try this at lower frequencies but at 10GHzish , a hammer, sheer and soldering iron worked good enough.   Still, consider how much time it too to measure frequency. I could have used my GPS referenced  microwave counter and been far more accurate and got an answer much faster.  Simple is not always better, but never hurts to go over the basics.

****
Found it in an old ARRL handbook I had from 1954. 

[xrunner]

The minimalist indicator for this project will be -

A Blue Bar

(of varying heights)

[xrunner]

The minimalist WiFi emission indicator will use a Nano board, an AD8307 log amp, a 124 x 32 blue OLED, and a salvaged WiFi antenna. I trimmed down a program I had already written for another power meter project to give a simple text indication of the power level being received. The received noise level at a far distance from the router is ~ -72 dBm with this setup. At a far distance from my router this setup shows no fluctuation of the power level.

If I set it very near the router antennas it gives quite a nice power fluctuation. In the snapshot I captured -63.99 dBm, but just watching it I can see fluctuations go up to -45 dBm. That's a nearly 30 dB range. This is exactly what I want to detect and see - power fluctuations, not a constant power level. Also, I do not care about the actual power being measured, all I want to see is power fluctuating.

I will use this information to make a fluctuating bar on the display, nothing else. It's minimalistic. It simply shows the observer that there are actually rf emissions coming from the router. If there is no "bar" but just a single line at the bottom, you are at the noise level. The max size of the bar will be associated with the max dBm that is ever seen by the unit. All other levels will be scaled appropriately between those two levels.

The router does have two different LEDs, which below them in white letters simply say "2.4 GHz and "5 GHz", and the LEDs flicker. This of course means that the router had the WiFi function enabled by a user in the menu and that data is being passed to that sub-system. It does not, however, actually tell you in an absolute way that rf is being emitted from the unit. It means that it should be emitting rf, but is it really doing that? You cannot simply look at the router and tell.

To check that, you'd have to use a device such as another computer with a WiFi adapter or a smart phone to see the SSID, or a spectrum analyzer. But those are not minimalistic devices. All that this project is meant to do is tell the user that rf is actually being emitted if they want to do a fast check on a problem with WiFi in the house. It has nothing to do with whether the internet can be reached. This can run 24/7 and once you get used to the way the bar constantly changes you will know what to look for if there is a concern about the WiFi signal in your house. If you can't access the internet with a WiFi device, and the bar is not fluctuating, then you know there is a problem with your router's transmitter very quickly. It's just a quick warm fuzzy feeling that you can see very quickly if you have a concern - nothing more.

[A.Z.]

the minimalistic device is nice, but... something allowing to do this

https://www.ekahau.com/solutions/wi-fi-heatmaps/

would be even nicer

[joeqsmith]

I evaluated those cheapo BLE radios for work.  It would provide the RSSI.   Attached image showing coworker's showing up for work, taking lunch, going home, cleaning crew showing up, security checks.  My software would record stats about their phones.   Notice how the traffic on the second day increased.

[xrunner]

the minimalistic device is nice, but... something allowing to do this

https://www.ekahau.com/solutions/wi-fi-heatmaps/

would be even nicer

Thanks, but I'm starting to wonder if something easier for the ham community would be the way to go. Putting all this work into power meters and such, months of work, when I could design something simpler and make money.

Like this! A holder for Bird slugs. What could be easier? A long rectangular solid with six holes in the top. Could do it in Tinkercad in a few minutes. I could start printing them several at a time on the bed and get an entire 1 kg roll of cheapo PLA for the same price as I'd sell one holder for. Probably make 30 to 40 off one roll. Wow I need to re-think how to spend my time. 

This guy is selling his 3D printed holder for $19.99 and the thing doesn't even prevent your expensive slugs from falling out of the holder at the jobsite. Selling 40 for $20 ea, is $800! Nice touch adding the maker name in large lettering to the front -

eBay auction: #256202181562

[joeqsmith]

...starting to wonder if something easier for the ham community would be the way to go.

A Bird meter is easier...  Oh wait...

That last hamster  polluting the channel was suggesting anything placed between the radio and antenna will mess up their SWR.  I've had a few hams post that same dribble now.  So, the SWR meter, cables, connectors must all be removed to get an accurate measurement.  That is how you minimize your design sir!       

[xrunner]

That last hamster  polluting the channel was suggesting anything placed between the radio and antenna will mess up their SWR.  I've had a few hams post that same dribble now.  So, the SWR meter, cables, connectors must all be removed to get an accurate measurement.  That is how you minimize your design sir!   

Yea sure it's the observer effect -

In physics, the observer effect is the disturbance of an observed system by the act of observation.[1][2] This is often the result of utilizing instruments that, by necessity, alter the state of what they measure in some manner. A common example is checking the pressure in an automobile tire, which causes some of the air to escape, thereby changing the pressure to observe it. Similarly, seeing non-luminous objects requires light hitting the object to cause it to reflect that light. While the effects of observation are often negligible, the object still experiences a change (leading to the Schrödinger's cat thought experiment). This effect can be found in many domains of physics, but can usually be reduced to insignificance by using different instruments or observation techniques.

https://en.wikipedia.org/wiki/Observer_effect_(physics)

The true SWR of the system, avoiding anything extraneous placed between the radio and antenna, exists un-observed (we believe). However, we must have an SWR meter in place for a measurement of the SWR. But once placed in-line, we cannot know what the SWR was in the previous case (the case with no extraneous instruments). But you might say "Leave the SWR meter in-place and you can define that as the state of your system. But that goes against what was stated before -

"That last hamster polluting the channel was suggesting anything placed between the radio and antenna will mess up their SWR.  I've had a few hams post that same dribble now.  So, the SWR meter, cables, connectors must all be removed to get an accurate measurement."

So its a real conundrum for sure. No one really knows what the SWR is of their most basic system: Transceiver, coax, antenna.


I added the scaling function needed for the Minimalist WiFi monitor to auto-scale itself to the near-field WiFi emissions. It will, upon start-up, detect the power level received and from that initial value will start keeping track of the Max and Min levels seen over time.

It uses these Max and Min levels to create a map for the bar scaling. The Min hold dBm is Bar level Zero, and the Max hold dBm is Bar level 127. All values in-between are scaled and mapped accordingly in the range 0 to 127.

If you move the Minimalist WiFi detector to a new location, simply reset the processor, and it will start the scaling to the new values in the current location.

The text readout is not normally displayed to the user, it is only data presented for engineering purposes should the developer (me) uncomment the appropriate sections. The data in shown in the picture would result in a bar height of 4 units of the range 0 to 127 of this OLED display. This is because the currently received signal level is -72.65, which is not much higher than the Min hold value of -73.26.

Note: The bar in the pic is actually changing - just use your imagination.

[vk6zgo]

The true SWR of the system, avoiding anything extraneous placed between the radio and antenna, exists un-observed (we believe). However, we must have an SWR meter in place for a measurement of the SWR.

You can substitute a VNA for the transmitter & measure the SWR, etc.
That gives you the figures for the antenna & cable.
If you then restore the SWR meter, measure the resulting SWR, etc, with your VNA & it is very close to your first result, you know that the SWR meter is not contributing much to any SWR reading in the normal configuration.

Of course, if you really want to be fussy, you can access the last coax connector prior to the antenna, test the antenna at that point, & see what the SWR etc, looks like.
If you have infinite energy, or an off sider, you can then calibrate the VNA so that its measurement plane is at that last coax, go back down the ladder to your "hamshack" & test again
 
All that data can then be tabulated, & the VNA graphs overlaid to make it easy to compare all the configurations.

Of course, if the output impedance of your VNA & radio don't match, there may be a few anomalies.

[joeqsmith]

There could be a problem that doesn't show up when testing with small signals like a VNA, giving the operator a false sense that everything is good.

One way to avoid such problems, use a radio with an integrated antenna.  Perhaps a cell phone.   

[vk6zgo]

There could be a problem that doesn't show up when testing with small signals like a VNA, giving the operator a false sense that everything is good.

One way to avoid such problems, use a radio with an integrated antenna.  Perhaps a cell phone.

Indeed there could be, although commercial installations don't seem to have such problems.
With high power Broadcast stuff we measured antenna characteristics with low powered test equipment.

An integrated antenna is usually quite inefficient, you can't easily measure power, & such an antenna would be pretty unwieldy at HF.

Thinking back to the "rip everything out of the antenna feed" school of thought, a perennial question from Noobs on ham radio forums is: -

"How come the SWR meter on my radio, the one on my ATU & the one after it all read differently?"

Some long suffering person will try to point out that the SWR meter between the ATU output & the antenna feed will, hopefully show the SWR of the feeder & antenna, whereas if the ATU is correctly adjusted, both its meter & the one on the radio will show a very low SWR reading, approaching 1:1.

As to the difference in the latter two meters, such devices obviously vary in accuracy.

The Noob, all at sea, will ask multiple, even more confused supplementary questions, until someone spouts the inapplicable, but attractive truism about everything adding to SWR.

Noob will run with that & hold it close to his heart for the rest of his days.

[joeqsmith]

Nice thing about the cell phone, you don't care about such things.  My wife has never tried to talk to me about connector choices and VSWR.   You also have the massive infrastructure at your finger tips with towers, repeaters and man power to keep it all running.  Not to mention some cutting edge technology that is constantly be updated.   

"How come the SWR meter on my radio, the one on my ATU & the one after it all read differently?"

You know, I bet that does happen more often than we want to admit.  If the goal is just to gain more members, you need to dumb down requirements.  No ham left behind may be good for the numbers but bad for raising the bar. 

[xrunner]

Pretty much stuck inside due to the cold, so working on projects.

The minimalist WiFi indicator is working, but it detects a random large signal which doesn't occur frequently. This biases the Max hold value too high for most of the other signals. I put in some timing so the scaling will get reset every x minutes (currently set to 15 minutes).

As far as a case, I had a few of the small old school Pomona metal project boxes, but they were a little too small to hold all the components. The next larger case I have would come from scavenging the one shown which holds a SignaLink USB sound interface. These are (were) used to connect a HAM rig to your PC, for digital modes controlled by the computer.

I have two in a drawer which aren't being used now. The simple fact is modern HAM HF radios have the USB sound interface built-in, so the SignaLink is now mostly an anachronism. It would be useful for the older HAM radios, but I have none of those older ones and I sure don't want any. I have two of these SignaLinks, so one case will be sacrificed for science (the guts kept in a bag). I plan on the case being utilized in a vertical position for my project.

I'll continue updates to this project here, perhaps someone else can pick up the slack, and come up with some new projects for this thread. Joe, vk6zgo, someone else? Perhaps reminisce about Bird power meters, CBers, some power measuring gizmo from Ebay, or something else to keep the thread going.

[vk6zgo]

Pretty much stuck inside due to the cold, so working on projects.

The minimalist WiFi indicator is working, but it detects a random large signal which doesn't occur frequently. This biases the Max hold value too high for most of the other signals. I put in some timing so the scaling will get reset every x minutes (currently set to 15 minutes).

As far as a case, I had a few of the small old school Pomona metal project boxes, but they were a little too small to hold all the components. The next larger case I have would come from scavenging the one shown which holds a SignaLink USB sound interface. These are (were) used to connect a HAM rig to your PC, for digital modes controlled by the computer.

I have two in a drawer which aren't being used now. The simple fact is modern HAM HF radios have the USB sound interface built-in, so the SignaLink is now mostly an anachronism. It would be useful for the older HAM radios, but I have none of those older ones and I sure don't want any. I have two of these SignaLinks, so one case will be sacrificed for science (the guts kept in a bag). I plan on the case being utilized in a vertical position for my project.

I'll continue updates to this project here, perhaps someone else can pick up the slack, and come up with some new projects for this thread. Joe, vk6zgo, someone else? Perhaps reminisce about Bird power meters, CBers, some power measuring gizmo from Ebay, or something else to keep the thread going.

I really like the idea of the "mimimalist" indicator.

It is nice to play around with Spectrum Analysers, etc, but sometimes being able to look at a "go/no-go" indicator is just the thing!

[joeqsmith]

I'll continue updates to this project here, perhaps someone else can pick up the slack, and come up with some new projects for this thread. Joe, vk6zgo, someone else? Perhaps reminisce about Bird power meters, CBers, some power measuring gizmo from Ebay, or something else to keep the thread going.

You can always buy a Bird, and maybe some other modern meter and start comparing them with yours. 

[xrunner]

You can always buy a Bird, and maybe some other modern meter and start comparing them with yours.

Perhaps, perhaps.

As far as the WiFi monitor, I'm working on a little design to replicate the look of rubber bumpers you see on test equipment or other gear. I saw this done in another thread so I sat down and tinkered up my own version. I'm still making some changes to the design but you can get the idea from the pic. It just adds kindof a cool look to the case.

And if nothing else, my projects need to look cool ... 

[A.Z.]

Some ideas regarding the Wattmeter

https://sites.google.com/site/lofturj/15-power-and-swr-meter-rev-ii

[xrunner]

Been busy but I worked some on the case, which will be sitting vertically. I'm using a blue I2C 128 x 32 pixel OLED display. This will simply be a blue bar indicating the changing amount of power detected from the WiFi antennas.

The common notation of the size of this OLED which you find on various stores is "0.91 inch OLED". Not sure why they want to use inches instead of mm, but the actual size of the pixel field is 23 mm (0.91") x 6 mm.

Yes well, that's all fine and dandy, but there's a couple of cute choices the people who make this part chose. First, there are no mounting holes, tabs, or pins at all. The PCB could have been made larger to provide them (like other OLEDS) but no, we'll leave that issue to the customer to figure out. We really don't care about helping them in this respect.

Second, it woulda been nice if you could have assumed that the OLED pixel field would be centered both horz. and vert. on the PCB. Then if you designed a nice front plate with a window opening for the OLED display, the PCB would also be centered around that as well, thus making it easier to do.

However, the makers of this part decided that it would be better to give the buyers a challenge. Let's stick the OLED display to the PCB off-center under the glass (but not say how much), just enough to make them work harder to get it mounted properly. So you find out you have to light up the whole display and make little fiddly measurements and find out how much to off-center your mounting hole to get it to look right. You can see what I had to do in the picture. I really want to thank them for giving me a challenge at no additional cost.

I printed the front panel in a tan PLA I had which came from Atomic filament. It almost perfectly matches the tan paint already on this case. I'm just going to put some dots of tacky glue to hold the OLED in place, with possibly a small crossbar beam across it also.