Step Attenuator Design, Build and Test (073a)

[@anlpereira]

Wow, I'm always waiting for next videos from Ralph. They are very didactic. Learn a lot. Thanks

[@eie_for_you]

Thanks! I'm so glad that you found this helpful. ... BTW, only 768 tests 🙂🙂

[@abbyck]

I was just looking up to build a multi step attenuator last week. This is right in time

[@eie_for_you]

WOW! Isn't *that* cool! I'm glad that it is going to work for you! 🙂

[@kaneobrien3915]

Good video. Minor correction its only 256 combinations of switches, 2^8 not 8 factorial.

[@eie_for_you]

ACK!!! You are very, very right!!😬

[@berndb.5097]

Ralf that was funny, when you introduced your old step attenuator and showed it open, I actually had to look in my drawer to see if mine was still there 🙂 73 Bernd

[@eie_for_you]

LOL! 🙂

[@HA7DN]

Thank you for your work, I really like this piece of test equipment. Now I only have to appoint a volunteer from our club to buid this!

[@eie_for_you]

You are very welcome! Believe it or not, the hardest part of the project was creating the enclosure out of sheet metal. You are welcome to my *scribbles* for that if you like. 🙂

[@johnclements3441]

Love the stacked resistors 😀

[@eie_for_you]

Thanks! It actually makes the assembly easier and gives better performance.🙂

[@Grassland-Outpost]

Thanks for sharing this very useful project. 73

[@eie_for_you]

You are very welcome! 🙂

[@W1RMD]

I've got the commercially built one that looks like it's 1960's military, but has no name on it. It has 4 dB of attenuation on it before you even flip any switches. All of the resistors, switches and connections look and test okay, so who knows? This one we talked about before. The resistors ARE configured in such a way that you ALWAYS have SOME attenuation if it's in line. An odd feature. Thanks and have a Happy Thanksgiving to you and your family!

[@eie_for_you]

You are right. That does seem odd. Did you run it through with the nanoVNA to see its frequency response and SWR? I would LOVE to see those results from 1 MHz to 500 MHz. 🙂 Happy, thankful Thanksgiving to you and yours, too!😁

[@W1RMD]

@@eie_for_you I'll have to re check and see my measurements. I used a NanoVna to get the 4 dB measurement initially. Take care.

[@eie_for_you]

@@W1RMD Enjoy! 🙂

[@W4EMB]

DE W4EMB, absolutely outstanding.. Thank you.

[@eie_for_you]

You are very welcome! ...... BTW, only 768 tests 🙂

[@pucci1510]

Tnx for Video very nice to learn

[@eie_for_you]

I'm glad that you enjoyed the video! ... BTW, only 768 tests 🙂

[@WG5Xradio]

What do you estimate the maximum input wattage to be? For instance, from a Ham Radio? Thanks.

[@eie_for_you]

I would not apply any more than 250 mW to the input either AC (e.g. RF) or D.C.(3.5 V) 🙂

[@ornithopterindia]

👍Thank you sir.

[@eie_for_you]

You are welcome! 🙂

[@DustinWatts]

I don't know what EDA you used, but you can create a ground pad next to each switch, which is much easier....

[@eie_for_you]

I am not familiar with the TLA EDA. This design is based on my own investigation back in the impedance controlled traces in preparation for my video on the subject and on the work I did for the RF power splitter project in preparation for that video. 🙂

[@DustinWatts]

@@eie_for_you By EDA I meant electronic design automation. So what program you used to make the board....

[@eie_for_you]

@@DustinWatts Oh yeah! Now I remember! Thanks for the reminder. I use DIPTRACE (diptrace.com/). They have a free version that does a LOT. At one point I had to upgrade to the next level up because my project exceeded the free pincount by like 10 pins! It has an awesome library of parts. I have some videos which feature this program starting with an introduction to Schematic Capture (kzbin.info/www/bejne/e4WmnIZ7pZ5nq68) and working through designing the PCB. 🙂

[@Alex-M0OOV]

Excellent, thank you for this, thoroughly enjoyed watching the video! What is the maximum RF power handling capability of this system? Also, can I ask what was the power of the RF signal you used for testing?

[@eie_for_you]

Thank you! Testing-wise, I used the default output of my VNA, 0 dBm, 1 mW. As far as maximum power handling, I'd keep it at 250 mW, 24 dBm or less. By the way, I did a quick test to 1 GHz ... it kept reasonably decent SWRs up to 800 MHz! 🙂

[@Alex-M0OOV]

@eie_for_you Thank you, the reason I asked about power used for testing is that I've heard SWR measurments can, to some extent, be influenced by incident power (i.e. if the power is low and there are losses when/if the signal is reflected, the SWR will appear low). However, I don't have much practical experience, only what I read in books or saw on KZbin. So not questioning anything, just trying to get a complete picture.

[@eie_for_you]

@@Alex-M0OOV Gotcha! I'm not sure that incident power has any significant effect. Impedance is impedance is impedance irrespective of the power applied to it. However, impedance can change with incident power as elements heat with increased power. This might be what they are referring to(?) 🙂

[@Alex-M0OOV]

@@eie_for_you I'm referring to losses in the 'transmission line'. If these losses they are high, they could be misleading and result in a low SWR (this appears to be the case for very long and lossy coax). I'm wondering if low incident power in any system can also mislead and pose a risk of showing low SWR.

[@eie_for_you]

@@Alex-M0OOV You are right about losses in the transmission line making the SWR at the end of the transmission line appearing lower than they really are. This effect is accentuated as you go up in frequency as the losses are greater. This is why we calibrate the measurement instrument we use to measure the SWR of the attenuator at the *end* of the transmission line where the unit to be tested will connect. This way, all of the effects of the transmission line are taken into consideration in the measurement. The only thing that shows up in the actual measurement is the unit we are testing. 🙂

[@Joe-ho6fo]

What’s it used for.

[@eie_for_you]

Suppose you are testing something like a receiver which will tolerate signals up to, but not to exceed, -40 dBm. Your signal source will only go as low as 0 dBm. Now what? We insert this step attenuator between the signal source and the receiver and select 40 dB of attenuation. Now the receiver is happy and you can proceed with your test.

[@WACkZerden]

subbed

[@eie_for_you]

Welcome to "Club EIE!" 🙂

[@wa4aos]

Great video, thanks. I have several KATE attenuators I've used for years which use toggle switches instead of the slide switches. I understand well, how to use them but never gave much thought to the design. Its more involved than I ASSUMED. 73 de WA4AOS

[@eie_for_you]

Yeah, I was kind of surprised, too. RF is weird stuff and it is so easy to get it "angry" so it doesn't cooperate. :-)