CB and Ham Radio Techs Love Their Bird Wattmeters

[xrunner]

Tight case fit on the sides. When connecting cable with crimped SMA on output of log amps it extends a little too far on both sides. I'm talking about the output of the log amps, a DC voltage which does not require an SMA (RF grade) connector. I will remove them from both log amps and just use some RG-174 to send the signals (FWD and REV level indication) to the processor board. The parts I made were going together well though, so will get that pic out soon.

[joeqsmith]

Looks like your board is also a bit off centered like mine was.   

[xrunner]

Looks like your board is also a bit off centered like mine was.

Yea it's obvious, but I just checked some measurements. The case is made so that the hole for the SMA part is centered left to right, OK.

But the board is the problem. The center trace for the inner conductor of the coax cable is NOT in the center of the board - it's offset. But it's close enough so that a casual glance at the board, by someone asked to make a case for it, might assume it to be centered. The trace could have been centered left to right, but it wasn't, which doesn't really affect the operation of the board.

Never assume anything. The old saying "never assume anything because it makes an ASS out of U and ME" applies. 

[xrunner]

Here's how all the parts go together, at least up to this point. I'll still need to put copper tape on the inside of the case though. Now I need to work on the side vertical case risers, and the front and the back face plates. Then wire it all up, calibrate it again, and add some graphics to the basic data that I already had working. Should take me into next year at this rate. 

[vk6zgo]

Here's how all the parts go together, at least up to this point. I'll still need to put copper tape on the inside of the case though. Now I need to work on the side vertical case risers, and the front and the back face plates. Then wire it all up, calibrate it again, and add some graphics to the basic data that I already had working. Should take me into next year at this rate. 

It already looks better than the stuff some well-known firms turn out.

[xrunner]

I connected the electronics shield and breadboard I was previously using to the Due to make sure it was still functioning like I last left it (minus the inputs from the log amps). It was. Never know with a cat hanging around here.

But mainly I needed to get an idea of the size needed for the two side risers I need to 3D print. I put on a new blank shield without the headers on top to check the height. Also set on top a 3.3 V regulator but I sat it flat because I don't want it to sit high the way they installed the pins. I will remove the pins and re-install my own so it lays close to what you see. Looks like a riser of a couple cm will do the job.

I also received in the mail some RG-402 semi-rigid & male SMAs for same. This is mainly for one reason, for me to practice making these types of RF lines. After looking at Joe's project I realized I needed this knowledge myself.

But, once made, I will replace the two short coax jumpers I'm using for the DC out of the Putnam coupler. DC you ask? What are you talking about? Well, let's put it this way - "DC" as Joe defines it.

 

[joeqsmith]

Looking good.  Risers are going to be an 'H' beam?   Are you planning to run the RF connectors out the sides to make it easier to place in-line? 

[xrunner]

Looking good. 

Thanks.

Risers are going to be an 'H' beam?

Pic attached. A series of "H" figures I suppose you could say.

I decided to get the side risers finalized. I re-dimensioned the part I had already drawn up to fit the observations I made recently regarding the needed internal case height. I will 3D print these in the next few days and see if they will work for the project.

Addemdum: Oh I just thought of one more addition to that part for strength, I will add tomorrow.

Are you planning to run the RF connectors out the sides to make it easier to place in-line?

Naw, this ain't no inline meter in the sense of a Bird. Every desktop SWR / power meter I've ever had has the RF connections out the back panel

[joeqsmith]

I was thinking 'H' or 'I' like an I-beam that the case will ride in the two channels, locked into place.  You have a screw and fingers on one side.  If I push from the outside in, what prevents the plastic from cracking? 

Every desktop SWR / power meter I've ever had has the RF connections out the back panel

I could send you that RS70 that comes out the sides.   Funny, not one ham claimed to have a working one and tore it down.   I may decide to go ahead and add a strap to that coax and see if I can adjust it.   Can't believe the shit people sell, and get away with it. 

[xrunner]

I was thinking 'H' or 'I' like an I-beam that the case will ride in the two channels, locked into place.  You have a screw and fingers on one side.  If I push from the outside in, what prevents the plastic from cracking?

Good observations. 

It would have to be a large force for it to crack. However it's possible it would be able to be pushed in a bit mainly at each end (not in the middle where the screw is). I'm going to add a horizontal reinforcement "rib" to help prevent any bending. I could even make the riser thicker towards the inside of the case and it won't affect the look of it as viewed from the outside. We will see if or how many  revisions to the design are needed.

I think the case after all this is going to look nice. Black front and back panels, and a black riser on each side with yellow OLED display.

Every desktop SWR / power meter I've ever had has the RF connections out the back panel

I could send you that RS70 that comes out the sides.   Funny, not one ham claimed to have a working one and tore it down.   I may decide to go ahead and add a strap to that coax and see if I can adjust it.   Can't believe the shit people sell, and get away with it.

Yes I'd like to see if you can get it calibrated. Throw down challenge to you.

[joeqsmith]

Throw down challenge to you.

       That poor meter.   If I try and tackle it, I'll record it just for you.  Maybe I could sign it and then sell it on eBay as the one and only RS70 that actually meets the claimed specs..  Oh wait... I still may not be that good....  Let me get back with you on that one.

[F4IUJ]

Hello all,

Another ham here, feel free to fire at will, I have a thick skin...

Interesting project, I haven't read the whole thread so apologies if this has been mentioned already... A Dutch ham has opensourced a fairly similar project, info can be found there : https://groups.io/g/RadioStuff
Yes, you don't really need a Bird wattmeter nowadays...

73, (just to wind up the engineers)

Yannig - F4IUJ

[xrunner]

Some iterative design here. I almost got it right the first pass. But that's only good for horseshoes and hand grenades.

When I measured the slot spacing in the original case I came up with 26.0 mm spacing. However, the panel had to be bent a small bit as you can see in the pic, to get it to fit. I could tell the ribs were not exactly spaced right. I turned on more lighting and inspected the measurement again. It turns out the spacing on the case is closer to 25.8 mm. Who spaces things at 25.8 mm rather than 26.0 mm? OK fine whatever - fixed in the drawing.

I added a horizontal rib on the inside surface for stiffening. However I realized also that the front and back faceplates will prevent the riser from being pushed in at the ends. So that's all good and works.

The last problem was when I designed the part where the screw goes through, it was glaringly off center from the case screw hole on the 3D printed part. That was simply a matter of me not dimensioning the spacing at all - I just forgot and probably got distracted. So that's now fixed.

That black filament was near the last on the roll, which was called "Deep Black". I will switch to the new roll which is called "Jet Black". It's supposed to be a better black. So I can compare it to this last print.

[joeqsmith]

I hadn't thought about the two ends of the spaces resting against the front and rear face plates.  That should prevent the condition I mentioned.   Planning to use N bulkheads for the main connections? 

[xrunner]

N bulkheads - no. Standard SO-239s. Hams and SO-239s go together like peach pie and vanilla ice cream. 

[joeqsmith]

I would have guessed that the manufactures would have changed to N for their 2M and up.  That old Drake I have uses the 239 but that radio is limited to about 30MHz.     

[xrunner]

I would have guessed that the manufactures would have changed to N for their 2M and up.  That old Drake I have uses the 239 but that radio is limited to about 30MHz.   

The manufacturers of ham equipment have used N connectors on some transceivers in past years that were for 144 / 440 MHz bands, but mostly don't anymore. For example the IC-7100 can use the HF, 144, and 450 MHz bands, but doesn't have N connectors. However the IC-9700 which can use the 144, 440, & 1200 MHz ham bands has three RF outputs. The 144 MHz band has an SO-239, but the 440 and 1200 MHz bands have N connectors. But again most 144/440 MHz transceiver don't have N connectors.

So for the 440 MHz band, why does one radio use an N, and the other doesn't? Don't ask me.

[joeqsmith]

Looking at Amphenol's site:
https://www.amphenolrf.com/rf-connectors/uhf-connectors.html

Impedance Non-Constant
Frequency Range DC - 300 MHz (DC - 1 GHz on Extended Range Designs)

They do not explain the GHz extended range designs.  Looking on Digikey, they claim several are good well above 1GHz.   I wonder home my crap adapters I bought for the Watt meter would compare with a decent N. 

[vk6zgo]

My ancient Icom IC490 (circa mid 1980s) has an N connector, but my early 2000s IC400, which was sold for use on business bands around 400-500MHz, & also for the Australian UHF CB band, depending upon its programming (It can also be programmed for the Amateur "70cm" band, as mine is) comes, as standard, with a SO-239 on the back.

It seems Icom have given up trying to educate not only hams, but all those business users as well.

[xrunner]

Looking at Amphenol's site:
https://www.amphenolrf.com/rf-connectors/uhf-connectors.html

Impedance Non-Constant
Frequency Range DC - 300 MHz (DC - 1 GHz on Extended Range Designs)

They do not explain the GHz extended range designs.  Looking on Digikey, they claim several are good well above 1GHz.   I wonder home my crap adapters I bought for the Watt meter would compare with a decent N.

I looked at that link ... is that the datasheet per se? I didn't find a more detailed one listed there. One that perhaps had some graphs to gaze upon. 

I'll try to find an actual datasheet on the PL-259 later, I mean there must be one with actual plots out there somewhere. I've never tried to find one.

 

The ham manufacturers could have settled on using N connectors on UHF and above back in the day and stuck with it. By now the hams would have learnt to use them. But alas they didn't, and now the PL-259 / SO-239 is so entrenched it wouldn't do any good to start. Most hams will not make up a new cable with an N male connector for a radio that has the N female. All they will do is grab an adapter and screw it on - F*ck it, problem solved. So what purpose did manufacturing the radio with an N connector actually achieve? 

[vk6zgo]

Looking at Amphenol's site:
https://www.amphenolrf.com/rf-connectors/uhf-connectors.html

Impedance Non-Constant
Frequency Range DC - 300 MHz (DC - 1 GHz on Extended Range Designs)

They do not explain the GHz extended range designs.  Looking on Digikey, they claim several are good well above 1GHz.   I wonder home my crap adapters I bought for the Watt meter would compare with a decent N.

I have seen some strange looking SO-239s over the years with the insulation having an "air gap" in it, maybe those are what they are referring to.
The business end of all the PL259s I've seen look the same, though, no matter which type, so I can't see how just modifying the socket would work.

[joeqsmith]

The ones that are in that cheap RS-70 Watt meter that doesn't work has a semi sort of air line.   

I used some lowish end N adapters I have and tried to compare them with the two N to UHF adapters using the LiteVNA.   Started out calibrating the VNA from 50k - 8G.  I then took a baseline measurement.

Next an SMA male to N male, N female barrel,  N male SMA female was inserted. 

Last, the N female barrel was replaced with the two N to UHF adapters which were connected with an Amphenol UHF female barrel.   

We can see from the TDR plot, the impedance of that UHF mess is very unstable and reaches about 27 ohms.  FWHH is about 30mm, which oddly enough is about the length of that UHF mess. 

If I plot S21, at 500MHz the loss with the UHF mess is about 0.4dB.   

Conclusion, UHF connectors make a poor mans Betty standard

[joeqsmith]

Impedance plot for the UHF mess to 500MHz. 

[vk6zgo]

Looking at Amphenol's site:
https://www.amphenolrf.com/rf-connectors/uhf-connectors.html

Impedance Non-Constant
Frequency Range DC - 300 MHz (DC - 1 GHz on Extended Range Designs)

They do not explain the GHz extended range designs.  Looking on Digikey, they claim several are good well above 1GHz.   I wonder home my crap adapters I bought for the Watt meter would compare with a decent N.

I looked at that link ... is that the datasheet per se? I didn't find a more detailed one listed there. One that perhaps had some graphs to gaze upon. 

I'll try to find an actual datasheet on the PL-259 later, I mean there must be one with actual plots out there somewhere. I've never tried to find one.

 

The ham manufacturers could have settled on using N connectors on UHF and above back in the day and stuck with it. By now the hams would have learnt to use them. But alas they didn't, and now the PL-259 / SO-239 is so entrenched it wouldn't do any good to start. Most hams will not make up a new cable with an N male connector for a radio that has the N female. All they will do is grab an adapter and screw it on - F*ck it, problem solved. So what purpose did manufacturing the radio with an N connector actually achieve? 

All the remaining "bricks n' mortar" Electronics shops near me stock a few crimp type "N" connectors, but crimp PL259s have disappeared.
They have many of the horrible PL259s, though!

N to SO239 adaptors are unknown at those same shops, so it has to be eBay or somewhere else on the net, making it easier to just fit the N to the long cable or make up a short lead to do the conversion.

A handful of hams are so fanatical about matching that they replace all the SO239s on their radios with N flange connectors.
This is not always easy, as many radios use nonstandard SO239s with only two mounting holes.
I do what I can, & don't agonise too much.

[joeqsmith]

I was thinking Xrunner was trying to be a leader rather than a follower.   First, building anything is a huge step ahead.   Then attempting to piece together a VSWR Watt meter with software... another notch up.  Then not bowing to Bird is the gold standard makes him even further up the food chain.   Then flushes all those bonus points down the toilet by using a 1930's unstable connector....     

Really though, I doubt those mini heaters... I meant adapters from Amazon are going to compare with a high grade UHF connector.   Maybe when you get this thing built up and have your parts you can measure them.   I looked through Amp's UHF products and if I select frequency, there is no other option than 0.3GHz.