CB and Ham Radio Techs Love Their Bird Wattmeters

[xrunner]

Is your friend with the Bird planning to have you add digital to their meter as well?

Not that I know of (at this time). 

Keep thinking I should get some sort of high end hamish Watt meter and do some sort of shoot out with it. 

***
Maybe something like this:
https://static.dxengineering.com/global/images/instructions/mwr-fx775-fx3.pdf

With the PC interface, we could compare screen update rates.

Yikes - ~$720! Yes please get one. 

To make a long story short, I am not going to use the Daiwa at all. I was going to strip it of the dual directional coupler, but sparing details I discovered, the coupler is a piece of junk. Now I think I want to start off with a good commercial dual directional coupler and build on that.

I didn't find much on Ebay that would handle my requirements (144 to 450 MHz, 100W), but I'm tempted to get this one to play with -

https://www.ebay.com/itm/404241326088

Putnam RF Components 06XN0 1621-C50 Dual Directional Coupler 25-400MHz 500W

The label states "25 to 400 MHz, 500 W, coupling outputs -50 dB" but I really need it to go up to 450 MHz. I can find NO spec sheet at all anywhere on it. I might take a chance and bet that it will still be usable up to 450 MHz. Joe, in your opinion (if you have one) would I get a usable output at 450 MHz? Even if it was -60 dB it would be OK. But who can say without a datasheet or testing?

 

[joeqsmith]

Not too surprised about the coupler's poor performance.   I take if that you didn't feel you could calibrate it out.   

I looked as well for data for the one you linked, no luck.   Sorry but I am going to be little help and would have to buy one before give you any advice about it.    The $60 may be better spent on a used name brand part like Narda or HP.    Maybe something like this:

https://www.keysight.com/us/en/product/778D/coaxial-dualdirectional-coupler-100-mhz-to-2-ghz.html   

If you decide to get one, consider posting the data for it.  Maybe its the deal of the year. 

[xrunner]

If you decide to get one, consider posting the data for it.  Maybe its the deal of the year.

I'll think about it overnight. I may well get one just to see, it's not like it's unusable for a range of ham bands. It could cover 10m, 6m, 2m, and 1.25m. 1.25m is the 220 MHz ham band. It's not used much but it is a valid band. Of course the most needed band of the range it covers would be 2m (144 - 148 MHz).

So eh - why not get the Putnam part and see what it does? I'll gamble the coupler would give a usable signal @ 450MHz it'll just be outside of the specs (-50 dB) they advertise, but as long as it's not too low I can account for it. I'll take data and post the response curves, maybe someone will find the data and make use of it.

Place your bets. Anything to keep the thread going. 

[joeqsmith]

Place your bets.

TC, directivity, flatness and insertion loss will match the price.    If it was decent enough, it could be plugged into my cheapo log detector.   Even if it was poor, I could do something beyond point slope for correction.

If it looks good and I use it with mine, here's another hammey Wattmeter for the shootout. 
https://www.microham.com/Downloads/SMORF_English_Manual.pdf

[xrunner]

Place your bets.

TC, directivity, flatness and insertion loss will match the price.    If it was decent enough, it could be plugged into my cheapo log detector.   Even if it was poor, I could do something beyond point slope for correction.

Acknowledged.

Product ordered this morning. New old stock. I can't find the company active anywhere on the web.

If it looks good and I use it with mine, here's another hammey Wattmeter for the shootout. 
https://www.microham.com/Downloads/SMORF_English_Manual.pdf

Interesting. I went to their website but try as I may I could not find that product in their current list of offerings (only support). Might not be made any longer.

[joeqsmith]

Product ordered this morning. New old stock. I can't find the company active anywhere on the web.

The case and connectors alone may be worth it.   If you can, try characterizing it outside of it's frequency range. 

For the shootout, there's also this one which is "simply the best".
http://www.telepostinc.com/lp100.html

Maybe something like this Calculating SWR / Power Meter for the baseline.   Needs a little work...
https://www.ebay.com/itm/165816668328

[xrunner]

Maybe something like this Calculating SWR / Power Meter for the baseline.   Needs a little work...
https://www.ebay.com/itm/165816668328

Mine will be calculating too - but a lot smaller. 

[joeqsmith]

You could always call them and see if they kept the datasheets for it.  Guessing from the photo, they continued to produce them after the company was sold.

https://www.quantictrm.com/high-power-combiners-couplers-hybrids

[joeqsmith]

Another vintage Bird meter for sale.  This one is strictly SWR, 0.2-0.4 kilomegacycles.  May look nice in one of the hams display cases.   

https://www.ebay.com/itm/166120518891

[xrunner]

Another vintage Bird meter for sale.  This one is strictly SWR, 0.2-0.4 kilomegacycles.  May look nice in one of the hams display cases.   

https://www.ebay.com/itm/166120518891

Display case for the serious collector yes ... or a dirty garage shelf which is already stacked to the ceiling with long forgotten electronic junk, bending under the strain of the weight it holds. Each dusty item on the shelf being - at the time it was acquired - the greatest find the ham ever ran across. Since it's for 200 to 400 "MC" in which lies the mostly unused 1.25m band, it will likely end up on one of these shelves, to be the underpinning to hold up even more junk as the years pass.

Received the Putnam model 1621-C50 dual directional coupler today. It indeed looks to be in new condition and very well constructed. If it works as good as it looks, I can see why another company would want to acquire Putnam.

It's interesting that the N connectors were attached with two different types of screws - two Phillips head and two hex head each. Both connectors are like that.

My goal is to characterize it this weekend. The forward and reverse outputs are supposed to be -50 db, 25 thru 400 MHz. Remember my bet was that it's going to be usable up to 450 MHz. I would like it to be at least usable for the 2m and 70cm ham bands, but if it is indeed functional up to 450 MHz, I can claim any SWR / power meter I build with it is usable for all ham bands 10m thru 70 cm.

[joeqsmith]

Note the single smoothed cap screw on each SMA without a split lock washer. 

[EE4all]

Yeah, that's all a bit strange. I am interested to see the full characterization of that unit. I was thinking to pick up a few for some RF amplifier projects. They have 400-1000 MHz ones available too that they rate to 1000 watts. Hmm.

[xrunner]

Note the single smoothed cap screw on each SMA without a split lock washer.

I did see that also. Interesting ... 

Yeah, that's all a bit strange. I am interested to see the full characterization of that unit. I was thinking to pick up a few for some RF amplifier projects. They have 400-1000 MHz ones available too that they rate to 1000 watts. Hmm.

Hi. Yea I saw those as well. I will be posting plots of my findings here since I've not been able to find the spec sheet for it, someone may be able to use it. Way back in this thread I built two power meters (not in-line power meters) that used an AD8310 and AD8307 log amp, which was controlled by an Arduino Uno board. Joe also made his own version too.

So given that I already have my own "core" system to use, I can adapt it to this coupler to make an SWR / power meter with higher quality components than what I have found used in most ham meters. That's the long term plan at this time. 

[xrunner]

I was able to get a couple of plots done today. Using the Rigol DSA 815TG, I first did an insertion loss test. Results were good (see plot).

Next I checked the output of the FWD port from a range 1 MHZ to 500 MHz. Recall the advertised range is 25 to 400 MHz with a coupling of -50 dB, and I want to be able to use it up to 450 MHz. As you can see, my desires have been met and I can easily use it at 450 MHz. It's only off by 1.12 dB @ 450 MHz. You can see the output starts to curve @ 400 MHz (the advertised upper F). Even so, if you know how to account for a variation at any point, you can use it with no problems at all. Anything like that will be accounted for in the software of my project.

I also reversed all the connections, using the output as the input, the REV then being the FWD port. No differences in the plots were noted from the original setup.

Conclusion: So far this unit seems to be a very well designed dual directional coupler. I am not through with testing though. Next up I want to use a more powerful signal from a Baofeng hand held radio that can output up to 5W (+37 dBm). I will first accurately measure the transmitter power with my hp 437B power meter. Then connecting it to the coupler, I'll measure both the FWD and REV power levels at the same time using two power measurement devices, record the levels, and calculate an SWR using a 50 ohm load giving SWR 1 (it won't be 1.000 since nothing is perfect). For the conditions of SWR 2 & 3, I will use a little test rig I made years ago that is a switch selectable RF load and presents both these SWR levels to a test transmitter.

The Daiwa cross needle SWR meter allows you to read an SWR of up to 5 (the next last graph line is infinity). However, any SWR of 2 to 3 or above is reason to check your transmitting system. In other words, reading an actual value of SWR 4 or 5 doesn't really help you all that much.

[joeqsmith]

Looks like it would be some work to use it at the lower HF bands.   Any plans to pull it apart? 

In other words, reading an actual value of SWR 4 or 5 doesn't really help you all that much.

I was assuming rather than just forward and reflected like the typical hammy meters, you would calculate the load power and the SWR was just along for the ride.   

[xrunner]

Looks like it would be some work to use it at the lower HF bands.   Any plans to pull it apart? 

Maybe later on, but not yet. Since it's working so well let sleeping dogs lie ...

In other words, reading an actual value of SWR 4 or 5 doesn't really help you all that much.

I was assuming rather than just forward and reflected like the typical hammy meters, you would calculate the load power and the SWR was just along for the ride.

In addition to calculating VSWR and measuring FWD and REV power, I can calculate return loss and use that to estimate load power in a simple way, but I'm not so sure it's that easy to get an accurate load power from an in-line VSWR meter given the vast array of situations out there in terms of poor equipment and various other use of below-average connectors and such being used on the setup, from a review of this topic on the internet today. But if anyone wants to chime in I'd be more than happy to take advice - I'm not opposed to insights on this topic from more experienced people out there.

Another thing this meter could do, since it's going to be software-based, is to allow the ham to enter an estimated dB line loss based on the specs of the particular coax they are using and the estimated length. That is definitely a useful parameter to include for more accurate results as well.

I didn't get much done today but I did need to accurately measure the output power of my little test transmitter on VHF & UHF, for further testing of this coupler. I noted the low and high powers on both VHF & UHF, using a 40 dB att. and a hp 436A. The power being transmitted in watts in the pic is left as an exercise for young players (-2.57 dBm and a 40 dB att. in-line.) 

[joeqsmith]

... vast array of situations out there in terms of poor equipment and various other use of below-average connectors and such being used on the setup, ...

True.  I was considering what ever the meters sees on it's output as the load, not the antenna.  No doubt a ham could have a 40dB attenuator in line with their antenna and the meter will not know.  The antenna could be a dead short and with the 40dB attenuator, it looks pretty good.   And even if we have everything perfect, that tells us very little about how the antenna radiates. 

http://wvraclub.org/technical-documents/understanding-swr/

[EE4all]

Now you have to also get a calibration certificate for the power meter, sensor, and attenuator, so the shootout will be valid. Heh.   

[joeqsmith]

Now you have to also get a calibration certificate for the power meter, sensor, and attenuator, so the shootout will be valid. Heh.   

It depends what metrics are used.   To measure power, we certainly need a known references.   Beyond your list, you may also want to consider having calibrated load standards as well.   When I showed my meter,  I talked about how I cross checked everything and how the RF generator was calibrated after my repairs.  Because my PC has access to most of my test equipment it is fairly easy to compare measurements like I show.   

Beyond calibration, we also need a references that are capable of making the measurements.   For example, say we have a Bird that the factory rates for 10% of full scale (or what ever).   We have it calibrated and it passes.   Now we try to use that to check the accuracy of a unknown device that is spec'ed to 5% of reading.   Most of us understand we can't but some hams would be, its a Bird, it meets cal, it IS the standard.   

[EE4all]

Yes, you got the point. Sheesh, I wasn't even thinking about yours though. Yeah, some are probably like that in their thinking. I have a few Birds, but I know exactly where they sit compared to more accurate, precise, and repeatable gear that I have. I use the Birds for exactly what they are good for... fairly close and quite repeatable Swiss army knife meters (different elements), that are rugged enough for a lot of day to day checks, and that I don't mind to loan out (to save my higher end stuff from such requests).

For my shack setup, I really like Wavenode's offering, and I have a few of theirs, along with several couplers.

For the bench, I use Agilent/HP power meters and sensors, one set of which is still within a yearly cert still by a little.

[joeqsmith]

For my shack setup, I really like Wavenode's offering, and I have a few of theirs, along with several couplers.

Looking at their products,
https://wavenodedevelop.com/controllers/wn-2m/

I couldn't even tell you the min / max power it could measure or what the resolution was.  I would think that would be pretty basic specs and I am sure it's published somewhere.  Just not important enough to call it out in the main spec.  They do state +/-5% but you are left to guess what that means.   

Maybe post some details about the ones you have.  Why do you like them.   

[EE4all]

I like them for the shack because they can show digitally a good enough reading for day to day ham operating both locally or remotely (PC remote), and let me know if something is amiss, all while only taking up a small desk spot. It's as simple as that, just good utility usage. That said it is at least as accurate as a Bird, so meh. Again, there is better test gear for when it's needed.

Some details for the sensors are on these pages: https://wavenodedevelop.com/sensors/

I have a few of their base meters and several sensors for HF through UHF, both low and high power. It's a nice out of the box solution for utility and some automation (it has some relays, thresholds, and etc). One could do all that with an Arduino, circuit, and couplers, but I have way more fun projects and hobbies than time, so I just bought into this solution. Maybe one day...

[joeqsmith]

I looked again and still can't find anything about the minimum RF level they can be used at or what their resolution is.    The do state that they "... will display SWR accurately at power levels > 5 watts".   So I assume they don't have very good sensitivity or resolution.   Funny as their heading is:

"Home of Precision R.F. Wattmeters"

They do state "16-bit RISC microprocessor, 12-bit A/D converter, and precision peak/ average detection circuitry for each sensor." but they don't talk about the interface from the sensor to the ADC. 

My homemade meter can easily read down to -30dBm with a 24bit converter.  When I demo'ed it, I show reading SWR with only a mW applied.   Those low cost log amps make simple work of it.   

Because they can use a PC for the interface, I was curious what sort of sustained data rates they could achieve, and again I could not find anything about it.   
With my homemade meter, the sustained rate is about 6kHz.  During the video, I mentioned having a hardware filter with a 2kHz cutoff in there.   

They do talk about have some sort of peak detect circuit.   Mine does everything in software and is limited by the sample rate and filter. 

With the Bird having a +/-5% of full scale and you need to find detectors that are scaled properly.  You wouldn't want to use a 100W detector with +/-5W error to measure a 10W signal.   Of course, then you have to swap detectors , direction and calculate by hand.    I would hope any product today would far out perform one. 

When I first visited the Wavenode site, the first thing that stood out to me was their products looked like something I would have homemade in the 90s.   

[EE4all]

Theirs is 12 bit according to this link:
https://wavenodedevelop.com/wp-content/uploads/2019/12/WaveNode_Family_Digital_Station_Monitor_12__2_2019.pdf

Then a bit more here:
https://wavenodedevelop.com/wp-content/uploads/2019/03/Technote-101-Mindin-interface.pdf

Yeah, they could use a specifications document, eh.

It's a niche product for a ham shack, not for a lab. Of course you can build something better. For shack usage it only needs to be good enough for the intended purpose. 

[joeqsmith]

Yeah, they could use a specifications document, eh.

If I were going to buy one, I would certainly want a lot more information than what they show.   It could be they have no programmable gain stage to scale the signal.  This would make sense that they have that 5W lower limit.  If you look at  the pages you provided for their couplers, you would think they would at least have S parameters for them.  Basically nothing.  Again, it would be interesting for you to provide some details about their performance.   

It's a niche product for a ham shack, not for a lab. Of course you can build something better. For shack usage it only needs to be good enough for the intended purpose. 

IMO, that's pretty much a universal statement with anything I buy, not just test equipment.  Always get the right tools for the job.   Nothing to do with it being a lab or not.   For those interested in CB radio for example,  the Wavenode needs more than 5Watts to measure SWR.  I assume they still limit them to 5Watts max, so it seems to be the wrong tool for that application.  The Bird on the other hand offers a 5W element for this band.     

Hard to say how my homemade Watt meter would compare against some of the commercial products.  I guess that's the idea of having a shoot out.   I've done something similar with handheld meters where I test them to failure using a common set of conditions.   Just like we have Bird fans, we see the same with the meters.