How to Build an RF Power Tap
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- čas přidán 6. 10. 2021
- This video covers the operation and design of an RF power tap. I demonstrate how easy it is to build one and show it working with an Amateur radio transmitter.
The design referenced comes from the QST magazine article “Simple RF-Power Measurement”, June 2001. www.arrl.org/qst
Nice and I plan on building it with one exception. I will use a wire form romex between the SO connectors to get it stability.
Excelent Job!
I need a tap and now have one. Using my nanovna I measured the SWR for this 40db version form 1mhz to 144mhz and got a maximum SWR of 1.18 at 70mhz . It was about 1.15 at 50mhz and also at 148mhz. Below 50 mhz it was much lower.
Likely I should have built it with a built in 50 ohm dummy load but I will make a short one with the correct fitting. Thank you!
Very interesting item thanks'. Also those pesky beetles I remember the sound, having lived in NC and SC.
Thank you, that was excellent.
Thank you. Very iformative, practical, and well-explained. I liked your video.
In the schematic at the start I see an error. The in & out marking are switched around on the 7805 voltage regulator.!. 73 Jan -LA3EQ
Thanks for this great idea. Could you please provide the formulas you used in your table?
Very interesting! I have been playing with a celwave dl-200, dummy load with tap. A couple other buddies of mine have also been tinkering with the same device. What has come up is that we are not seeing the attenuation we should see on the celwave device - when looking at it on the spectrum analyzer. I've hooked up a 2M mobile radio into a swr/power meter, and i see the output power at zero, when the meter is plugged in the tap. What I don't see, is that level of attenuation on the SA. The SWR power meter shows zero on the celwave tap, and 50W without it. So - that's 47db of attenuation. Should I not see that same level on the SA? Or (as I suspect), we don't have something configured right on the SA? One guy has a siglent, and the other 2 of us are using rigol 815's. Anyway, found your channel today in my quest for answers, looks like your new to youtube. Great info on your vids, keep up the good work. I'll be sharing your channel on our discord server for sure. Thanks!!
very good i also built this 40 dbm version worked a treat thank u derek g1hlp
Good vid / build & you explain/ present well. 73 K0ATV
Thanks!
Nice! Till what frequency is your design good?
I have a 6GHz 100W dummy load. How can I get a proportional sample into the TinySA from the transmission line to get an accurate power measurement?
Can you point me to a good design?
Can you share the spread sheet? What would be the best way to make a 3dB tap, a 50% power splitter? Resistor voltage dividers would have to handle too much power, right? Thanks.
Can the brass plate be replaced with copper?
Will it work for VHF and UHF bands?
I have just purchased my 1st scope for repairs, and I would like to build one of these for testing. How does a person go about finding out what attenuation is needed for the scope as to not burnout the front-end?
The solder connection on the SO239 is broken @ 8:38
Great project👍
Wow, good eyes. I had to re-watch it a few times and it does look like that joint is wiggling ever so slightly. I'll pop the cover off and check it again. Usually scopes will have a maximum peak voltage right on the front panel. If not, it would be in the manual, provided you can still find one on line
@Level UP EE Lab 👍👍
Very nicely done. I’m wanting to build one of these for test CB’s that can handle 150 watts but only put out a safe amount to the o scope and spectrum. I’m just getting started so and taking a few classes and buying my own equipment. I have bird 43 and good power supply so far. Do you have any advice on building one of these? Thanks in advance. And I have subscribed to your channel
Thanks for subscribing. The power tap I describe here is a 40dB drop at the sampling port. So you would have to check the maximum allowable power your test equipment can withstand and confirm that 40dB is safe enough. If you need more of a drop, then you would need to add additional attenuation between the power tap and your test equipment.
@@levelupeelab thanks for the response. I’m still buying equipment so I’ll be conscious about what I purchase
Building an RF tap is a simple & fun project. You may want to consider also getting a -50db 25-1000MHz slug for your Bird 43, I've been using one since the late 70's. Rule of thumb: start more more attenuation then reduce it so you don't blow out the front end of your test equipment.
Are the standard carbon composite 5% resistors sufficient for this build? Don't need anything exotic like non inductive RF rated resistors, or high precision resistors?
Standard carbon comps 5% are just fine.
Hi, I would like to build one of these to send Rf to an old school kit 1ghz frequency counter 2 questions please
1 . would I have to modify this for a Max 20watt ssb rf signal?
2 . would a plastic box be OK for 20watts Max?
Thanks in advance
The design will easily handle a 100 Watt RF signal up to at least 50MHz. However, you definitely should use a metal enclosure, it needs to be shielded.
@@levelupeelab thank you.
What program did you use to create the labels?
Just regular old PowerPoint works fine.
@@levelupeelab - Thinks!
Why not using a simple T connector to make a compact RF sampler?
The main line impedance will be kept much constant.
That's certainly an option. The impedance, though, on this particular design is essentially flat in the HF (
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