CB and Ham Radio Techs Love Their Bird Wattmeters

[bd139]

I reckon the casing is more impressive than what is likely to be inside it 

[Grandchuck]

Interesting.  The one rated at 3dB is the most expensive ... because it dissipates the most, I suppose.

[xrunner]

I reckon the casing is more impressive than what is likely to be inside it 

Yea I know that's possible.  I might get one to test and inspect inside. I can always return it for any reason and get a refund.

Interesting.  The one rated at 3dB is the most expensive ... because it dissipates the most, I suppose.

Yes another possibility is to get two to work together - like a 3 dB and then a 40 dB after that so they wouldn't get as hot. 

[bd139]

I would use a 40dB tap or directional coupler and a load if I needed lots of attenuation. Power attenuators have pretty horrible temperature coefficients unless you spend a lot of money. They are also actually directional (with respect to dissipation) which can lead to the magic smoke if you aren't paying attention.

[joeqsmith]

Many of them are symmetrical. 

https://barryind.com/pdf/Attenuator/Leaded/H04Z-0100J2T-00C36-X.pdf

Obviously the heatsink will not be able to dissipate the rated power if placed inside of a case. 

I used one of their flange mount parts to repair my eBay JFW attenutator.
https://barryind.com/flanged_attenuators.html

You may want to consider higher quality used from more reliable source than eBay: 
https://www.surplussales.com/RF/RFAtten-4.html

If you have to dissipate 10W, it's still 10W.  There's no magic that I am aware of.  If you find it, please post!!  Then again, only two cups of coffee, so maybe I missed something.   

[xrunner]

I would use a 40dB tap or directional coupler and a load if I needed lots of attenuation. Power attenuators have pretty horrible temperature coefficients unless you spend a lot of money. They are also actually directional (with respect to dissipation) which can lead to the magic smoke if you aren't paying attention.

Yep everything you said is true and good advice. I bet even your own family members rarely say that to you. 

I mean I could use a directional coupler and external load now with the power meter I just finished and call it a day. I was just thinking if it could be built all in a self contained enclosure. That's why I didn't want to go over ten watts because of the need to remove the heat. I figured I could remove ten watts with a decent temperature-controlled fan. Might not be realistic though. 

Obviously the heatsink will not be able to dissipate the rated power if placed inside of a case. 

If you have to dissipate 10W, it's still 10W.  There's no magic that I am aware of.  If you find it, please post!!  Then again, only two cups of coffee, so maybe I missed something.   

All true, again I said before I would have to use a fan to remove the heat if inside a box. Never thought otherwise. But it may be a pie-in-the-sky idea. Wouldn't be the first time. 

I think the best way to proceed is to get a 10W attenuator and do a stand-alone heat exchange experiment. Dump 10W RF into it and see how well a fan will work cooling it. If that doesn't do a good job cooling it, then I can't do the project as I envisioned. First things first ...

Parts referenced:

https://barryind.com/pdf/Attenuator/Leaded/H04Z-0100J2T-00C36-X.pdf

I used one of their flange mount parts to repair my eBay JFW attenutator.
https://barryind.com/flanged_attenuators.html

You may want to consider higher quality used from more reliable source than eBay: 
https://www.surplussales.com/RF/RFAtten-4.html

[bd139]

It's always 10 watts but for how long. I can still smell the 100W dummy load vapour in my wallpaper if I sniff it hard enough 

To clarify directional attenuators, they certainly aren't all like that - my bad should have said

[fourfathom]

Regarding reliable attenuators, I bought this one on Amazon:

https://www.amazon.com/gp/product/B07DYCM6W9
It was supposedly 50dB, 100W (and definitely asymmetrical).  But the measured attenuation was something like 43dB.  It was quite flat up to at least 1GHz, and for my needs 43 is as good as 50, so I stuck a "43" label on it and use it anyway.  I have no idea about temperature stability, or actual power handling, I just use it to knock a few Watts down to something my other attenuators and analyzer can handle.

[joeqsmith]

It's always 10 watts but for how long.

I think that's really the question.   Like every handheld DMM with a high current feature,  they may show 10A max but you will always have a qualifier of time and duty cycle.  A 10W attenuator may handle 10W just using it as a dump.   

If the idea is to mechanically protect it and to keep the box water tight so the hams can not only take it into the mountains, but can also deep sea dive with it as well,  maybe something fancy like heat pipes or just sink it to the water tight aluminum case.   

[joeqsmith]

Regarding reliable attenuators, I bought this one on Amazon:

https://www.amazon.com/gp/product/B07DYCM6W9
It was supposedly 50dB, 100W (and definitely asymmetrical).  But the measured attenuation was something like 43dB.  It was quite flat up to at least 1GHz, and for my needs 43 is as good as 50, so I stuck a "43" label on it and use it anyway.  I have no idea about temperature stability, or actual power handling, I just use it to knock a few Watts down to something my other attenuators and analyzer can handle.

Funny, their photo shows it's 40dB.     

[fourfathom]

Funny, their photo shows it's 40dB.   

The listing has attenuation levels from 1 to 50dB.  The label on the one I bought says "50dB"  So I made a new label -- problem solved!

[joeqsmith]

It would be interesting to run it up to temperature and see how it effects it.   Especially if the plan is to try and use it to measure power.

[bd139]

If the idea is to mechanically protect it and to keep the box water tight so the hams can not only take it into the mountains, but can also deep sea dive with it as well,  maybe something fancy like heat pipes or just sink it to the water tight aluminum case.

Perhaps they should just put an N connector on a hand grenade and sell that to the hams 

[joeqsmith]

If the idea is to mechanically protect it and to keep the box water tight so the hams can not only take it into the mountains, but can also deep sea dive with it as well,  maybe something fancy like heat pipes or just sink it to the water tight aluminum case.

Perhaps they should just put an N connector on a hand grenade and sell that to the hams 

50 ohm loads seem common but attenuators with PL259s seem very rare.   This could be another product for Xrunner to sell. 
https://mfjenterprises.com/products/mfj-262b

[xrunner]

50 ohm loads seem common but attenuators with PL259s seem very rare.   This could be another product for Xrunner to sell. 
https://mfjenterprises.com/products/mfj-262b

No Mighty Fine Junk clones here! 

I can't compete with MFJ or Chinese prices. Only quality products which means hams won't shell out the dollars for them. 

[joeqsmith]

50 ohm loads seem common but attenuators with PL259s seem very rare.   This could be another product for Xrunner to sell. 
https://mfjenterprises.com/products/mfj-262b

No Mighty Fine Junk clones here! 

I can't compete with MFJ or Chinese prices. Only quality products which means hams won't shell out the dollars for them. 

MJF did not appear to offer fixed attenuators with PL259s.   I think you may have the market cornered.

[bd139]

Their ATUs are pretty good attenuators. Until you fix the shitty soldering.

[xrunner]

No I haven't given up guys, I just got into a big upgrade on my 3D printer - a new design direct drive extruder. I had to fabricate a part in-house to get the new extruder to fit and then that led to getting a new build plate too. I'm still looking at attenuators so I hope to get one to test. 

[joeqsmith]

No problem.   I have been busy testing a high dollar Keysight handheld meter.  So the directional coupler patents are on the back burner for now.   

[joeqsmith]

If you plan to sell your Watt meter to the hams with SMA connectors, make sure you supply the metrology grade drill bits with it. 

[xrunner]

If you plan to sell your Watt meter to the hams with SMA connectors, make sure you supply the metrology grade drill bits with it.

LOL - OK I'll bite. What is the person trying to do  - make calibration loads or ... don't ask? 

I ordered the attenuator that Amazon had (40 dB 10W) along with some other stuff from my accumulated shopping list this morning. But after the order was placed, I noticed the attenuator was a 30 dB not 40 dB. I don't think I made a mistake when I added it to my list. I've never made a mistake before. Well I thought I did once but I was mistaken about that time. I had to delete it from the order so I'll have to place another order. A 30 dB would work, but it's a little to close to the edge for comfort.

And yes I was warned it might be crap, but we'll just all go on that adventure together when I check it out. 

Attenuator

[bd139]

LMAO that's a short load. I bet he dips it in his ash tray for a 50 ohm ref...

Have my AD8307's for my attempt. However just moved house and have no time to pick this up at the moment.

[xrunner]

LMAO that's a short load. I bet he dips it in his ash tray for a 50 ohm ref...

Have my AD8307's for my attempt. However just moved house and have no time to pick this up at the moment.

Good to see you in the forum my friend. Was hoping you would come back if we posted here again. 

[joeqsmith]

I suspect that they watched a video I made on how not to blow up the NanoVNA after I saw several hams post how they had damaged theirs.   In that video, I talk about discharging the coax and I had the grill starter connector in my hand and showed shorting a BNC connector with it.  It was not my intent that the hams would see this and think it was a good idea to start shorting their connectors with drill bits but here we are (monkey see monkey do). 

Hams, don't use your calibration standards or drill bits to discharge your systems.

[bd139]

LMAO that's a short load. I bet he dips it in his ash tray for a 50 ohm ref...

Have my AD8307's for my attempt. However just moved house and have no time to pick this up at the moment.

Good to see you in the forum my friend. Was hoping you would come back if we posted here again. 

Still here. Like asbestos or mould. Difficult to get rid of