Review of the QRP Guys UnUnTenna Plus

[@shaofuchang515]

The most innovative part of the design for me is that when set on "tune" the radio never sees more than 2:1 or so on the antenna, and so you can send your carrier to your hearts content and it won't damage the radio, you're not scrambling at the knobs. Relieved to see they supplied extra enamel wire lengths, because some of us are lousy at it. 73 de KN4GEI

[@va2wlt]

You could try glueing a small tube around the LED to keep it out of the light, making it easier to see when it dims.

[@warplanner8852]

Excellent idea!

[@andrewd4890]

Really well presented and produced. The shots of specific components as you described how to orient them correctly were very well done. And it gives me a better understanding of what this device can do once it’s built. Thanks. Vk1da

[@Inkling777]

Many thanks! I just finished the QRP Guys's handy Power/SWR/Dummy Load and I'm finding it a delight. I just wish I'd know the trick you mentioned of using a smartphone to photograph its tiny torrid. It took me about a dozen tries before I was certain I'd gotten the number of turns right. I also got lucky. A tiny steel box for powering recessed lighting I picked up at a thrift store for $1 proved just the right size to give it a solid container. I do wish QRP Guys would offer a 3D printed case for their devices. For portable gear, I'm nervous about having the components exposed.

[@RobMacKendrick]

Thanks Michael! Nice clear and thorough tutorial. I like the Guys, but am little troubled by the lack of housings for their kits. Where I live weather and sea air are a given, so this device would be marginally useful till I figured out at least a rudimentary enclosure. (Yeah I could use a plastic bag and a rubber band, but that's fiddly and inelegant. ) Anyway, thanks for the once-over!

[@g0pot]

Yes, this is definitely a fair weather option unless you box it up...I guess that allows you to personalise the tuner a bit :o)

[@zendoc62]

I put this kit together some time ago and I’ve experimented with a wide range of non-resonant wire lengths, counter poise and feedline lengths and I’m yet to discover a combination that will allow a reasonable SWR on 40m. But as you found, 30 and 20m are easy to find a match. I suspect the tuner design used here doesn’t have the range to match the low impedance you’d expect with a short radiator on 40m and after a 81:1 impedance transformation . It’s a pity, because 40m is a useful band for QRP right now and it’s otherwise a nicely designed kit. I tried changing the unun to 4:1 and even removing it completely and still can’t find a combination of wire lengths that yield a satisfactory SWR on 40m. 73 de VK7JB

[@g0pot]

zendoc62 I’ll go back out to the field and test some longer elements then and see if I have the same issue. While making the video I was also interested in making a vertical so I was limited to a 9 - 10m radiator. I’ll report back here with my findings.

[@zendoc62]

Michael Sansom Excellent Michael - I’ll look forward to hearing your experience. I tried various configurations of vertical, sloping and inverted V radiators and both tuned, elevated radial and simple counterpoise wire lying on the ground for RF return. As expected, feedline length also influences tuning of the system. I enjoyed your video very much BTW, so thank you! 73, VK7JB

[@dgkrompholz]

@@g0pot Any conclusions regarding the ideal 40m configuration?

[@g0pot]

@@dgkrompholz For portable/SOTA I now stick to an EFHW as I don’t need to fuss with counterpoises and tuners. Check out the 3-band EFHW design on my webpage at www.peanutpower.co.uk/efhw. Of course, when mounted as an inverted V on a low pole (6-10m), any EFHW, dipole, long wire, etc is predominantly an NVIS aerial…great for shorter range contacts, not so good for DX.

[@dgkrompholz]

@@g0pot Thanks but I was referring to the antenna you reviewed in this video, and inquiring about the ideal feed line length for lowest swr for 40m, assuming a 35' counterpoise.

[@sandraabarca6029]

Very nicely explained that’s a project I will be taking on . Ty 73s🍺😎🎙

[@bradbuck7891]

Great presentation! Not a lot of “ums” or “uhs”(just a few near the end) and I didn’t have to speed it up! ( I listen to some at 2x) Nice project!

[@shaofuchang515]

could you provide a source for your travel paddle?

[@billdumke211]

Thanks for the warning about 40m not working. I have a 43 foot vertical and the qrpguys kit for the 40m - 10m Multi Z Tuner. If that does not work on 40m, I will let you know.

[@porkyfedwell]

I think he was saying that it didn't work only because he didn't have a long enough radiating wire for 40m

[@edkretchmer2167]

I'm wonder what capacitance the varicons should be. The manual says to adjust the trimmers on the back of the varicons to MAXIMUM value but I am unable to find what a typical value would be, just because I am curious.

[@cwqrpportable]

Nice video; very informative and I appreciate your laid back style of presentation. Thanks es 73 de VA3YG

[@firewaterforgeofarizona4304]

Could a builder solder the 50 ohm resistors on the back side of the PCB?

[@g0pot]

Yes, you absolutely could and, in hindsight, I think this would have been the best adaptation!

[@m1cxf]

Just a thought about the resistors obstructing the counterpoise connection. Could they be fitted to the other side of the board?

[@smellthecoffee5314]

Great video -thanks. Question - Can you use it horizontal ? what difference would it really make ?

[@g0pot]

Yes, in terms of the radiating wire I was using it in a vertical configuration but you can set it up however you like: vertical, horizontal, a sloper, inverted Vee, inverted L. As it has a counterpoise it does lend itself to using it as a vertical but you could operate from, say, upstairs in a house, run the radiating element horizontal to a tree and just hang the counterpoise vertically from the window. So many options!

[@smellthecoffee5314]

@@g0pot - Thanks for the prompt response Michael. Very interesting - a versatile antenna for sure . If used horizontally do you know if there is a recommended height for best propagation ?

[@g0pot]

@@smellthecoffee5314 That is a really good question with a not so simple answer. Firstly, it depends on what sort of distance you want to work. Lower hight might make for a poor ‘take off’ angle but if you are trying to work stations in your region then this ‘NVIS’ setup might actually give you the best option. Typically to give a reasonably low take off for a horizontal dipole we aim to get it half a wavelength high…so the band you are working on influences that. Mostly people just try to get it as high as they can. If you want to know more about aerial performance and modelling hit me up on email. Look up G0POT on QRZ.com.

[@smellthecoffee5314]

@@g0pot great answer - I’ll keep that info in mind - thanks

[@michaelhiggins7365]

Excellent video, nicely done. I'm wondering something though. Because this is an Un Un as well as a Tuner, can I assume this will do a much better job tuning a Random Wire to a KX-2 or KX-3, than using the built-in Elecraft Tuner alone?

[@g0pot]

Michael Higgins It’s rare for me to attach something that an Elecraft tuner can’t cope with. An un-un is simply trying to bring the impedance of your aerial into a range that your radio can cope with and therefore it can help where your ATU is struggling on its own, however, because this also has the variable capacitors to help ‘tune’ the aerial I’m less clear on the effect of connecting it in serial with another ATU. In truth, if your Elecraft ATU can’t cope I’d simply change the length of the random wire by half a metre or so.

[@richardiancarpenter534]

Thanks for the video, Michael! Would it be possible to reverse the wingnut at the bottom (the one close to the resistors) so that it's on the opposite side of the PCB? de KB3MBM

[@g0pot]

Absolutely...the wing nut assembly can easily be mounted on the underside of the board and it wouldn't affect the connectivity or access to the wire strain relief. The only impact would be raising the profile/thickness of the board. I opted to keep the wing nuts on top because this will travel in the shallow side pocket of my cabin bag on flights and I wanted a nice flat surface against the bag outer so as not to cause wear or snags. It's also nice to be able to see (visually) the wire firmly connected to the terminal posts while using the controls so you know it's all connected properly...minor stuff though.

[@richardiancarpenter534]

@@g0pot Good to go! I want to get one of these and/or their 40/30/20 vertical antenna tuner to use with my MTR3B.

[@CroPrepper]

Seems same as the qrpguys vertical without tuner.

[@kirkp_nextguitar]

It’s odd that the LED lights up when transmitting in the Operate switch position. It should be out of the circuit in that position. I guess it’s due to coupling between T3 and one of the other toroids, but I’d expect them to be better isolated. My QRPguys EFHW Mini-Tuner never lights the LED in the Operate position.

[@g0pot]

I think you're right, the SWR bridge circuit isn't grounded or shorted so likely it's picking up enough stray RF to light the little LED. Not an issue but every time it catches my eye I think I've forgotten to flick the switch back to 'Operate'!

[@kirkp_nextguitar]

@@g0pot On my most recent deployment with a 32 foot wire tuned for the 20m band I noticed the LED on my EFHW Mini-Tuner is now lighting when in Operate mode! It’s very dim but noticeable. Before the tuner was outside and now it’s indoors, so maybe I didn’t notice it before due to ambient light. It still tunes well. I often double check with a NanoVNA and the LED always gets SWR below 1.5. I’ve only had problems tuning if I was sloppy about deployment or had a poor counterpoise. It’s a good product.

[@ChrisGrazioli]

How many feet of coax are you using from ununtenna to your radio? I have 25ft coax and 29 ft of 26awg with the suggested counterpoise of 1/4 wave 8.2ft for 10Meter. I can receive fine but can't seem to transmit and the SWR is trash

[@g0pot]

Similar to you. I’ve used coax lengths of about 50cm up to ~10m and it was OK. I’m sure I tried it on 10m…I’ll try and set that up this weekend and see how mine fairs and report back here.

[@ChrisGrazioli]

@@g0pot kind of annoyed, I wanted to love this dopey lil thing. I'm using with my new Xiegu G90, maybe I'm asking too much out of my skillset at this point. I just got this radio and updated to the new firmware. Out of the box I got a ton of signals from far away places but I cant transmit for nothing!

[@g0pot]

@@ChrisGrazioli OK, ran tests this morning using 8.8m (vertical) radial and about 4.83m counterpoise laying on the ground. I'm only using 5W from a KX2 and I used about 50cm of coax as this should give me worse results than a longer length. Tuned perfectly on 10m and 15m too. Drizzle and a flat battery prevented me trying more at this time. Look me up on QRZ and send me an email and I'll share pictures and more info. Your G90 has an ATU built in I think so you do have other options. Make sure the G90 ATU is bypassed when using the UnUnTenna otherwise you may have trouble tuning.

[@g0pot]

@@ChrisGrazioli ...one other observation Chris, I think the G90 can put out up to 20W. The UnUnTenna Plus is really for QRP (those polyvaricon capacitors don't handle much power). I would recommend keeping power to 5W CW or 10W SSB when using this aerial tuner.

[@g0pot]

Further measurements using 8.8m (vertical) radiator and 4.8m counterpoise laying on the ground). This tunes with a good dip in LED brightness on 30, 20, 15 & 10m. 40m and below won’t tune with this short wire. On 12m I can tune the aerial but the dip in LED brightness is almost impossible to see. I can’t tune 17m but I think an 8.8m element is quite close to a half wave on 17m (8.2m?) so the feed-point impedance of the wire is likely too high for the matching unit. I don’t have 6m on my KX2 so can’t try this band. Hope that helps.

[@QRPCW]

Interesante!!!!, me gustaría probarlo Buen vídeo, gracias 73

[@firewaterforgeofarizona4304]

Have you tried to tune it up using a nano vna before connecting to a transceiver?

[@g0pot]

For portable, SOTA and POTA I try to keep things as simple as possible so I aim to avoid carrying additional stuff like SWR meters and analysers. That said, their are certainly some small and lightweight options out there now so it’s definitely an option.

[@firewaterforgeofarizona4304]

@@g0pot True, every bit of kit counts when ascending a hill/mountain. Recently discovered your channel. Great stuff. 73, Kf7rcm.

[@kirkp_nextguitar]

@@g0pot I won’t take my NanoVNA in the field, but I’ve used it in the backyard to check my QRPguys EFHW Mini-Tuner to gain confidence it’s giving a good match and to give me an idea of the bandwidth around the tuning frequency. When the LED dims, SWR is always well below 2:1. When the LED goes out completely the SWR is always below 1.2:1. The matching circuit is much different from the Ununtenna Plus, but the absorptive bridge LED circuit is identical. I now have high confidence in it, since it’s never failed to provide a good match.

[@oldgiapetto]

I'm finding that mine refuses to "tune", that is, reduce the brightness of the LED with a 41' wire and 30' counterpoise. The manual suggests removing 1-2 turns from T-3. Has anyone else encountered this problem? If it's really common, I wonder why the build manual has not been changed.

[@g0pot]

Are you only having this issue when tuning on a specific band or do you get the same issue across multiple bands with these element lengths?

[@oldgiapetto]

@@g0pot The LED refuses to dim on 20-30-40. However, I can change the apparent SWR on my MFJ analyzer when in Transmit mode.....not low enough that I'm comfortable using it, but it will change the SWRs a bit.

[@g0pot]

@@oldgiapetto OK, good that you could try that with the aerial analyser. The fact that’s it’s not giving you a low enough SWR in the analyser explains, perhaps, why the LED isn’t dimming. You might need to try some different wire lengths. I think for mine I have a 41’ element and a 17.5’ counterpoise (I went with an 1/8 wavelength for lowest band as a counterpoise). I’ll check my current wire lengths later in case I’ve modded these.

[@oldgiapetto]

@@g0pot Yes, I also have a 41' wire.

[@g0pot]

@@oldgiapettoI’ve just remeasured my elements and can see I have a 29’ radiator and 16’ counterpoise. I did prefer the 41’ element but needed something sorter for operating from hotels. This will tune on 40m but is more effective for 20m and up. I think I reduced my counterpoise from 17.5’ to 16’ to tune more successfully so that maybe something for you to try.

[@GoAmateurRadio]

The first and only time I threw a wire out a hotel window the person a few floors below me tugged the wire and it broke. How do you avoid that?

[@g0pot]

Ha…that’s unfortunate. Most hotels now only allow windows to open a little to stop people falling out. This can make getting a wire out of the window tricky but also makes other people accessing it less likely. I confess I only do this after dark when people are less likely to notice.

[@TennesseeArborist]

Why not have just soldered the resistors to the other side?

[@g0pot]

was following the build instructions and had no idea their was going to be a problem until I fitted the screws and wing nuts. The QRP Guys could have issued an addendum to the build notes to highlight this necessary change.

[@Inkling777]

@@g0pot Having the dummy load resistors spaced above the PC board is a plus, since it allows more air to circulate around them. In their Power/SWR/Dummy load kit the QRP Guys specify that the resistors are to be spaced above the board for that reason.

[@FoxtrotMike]

Hello there Michael, greetings from Chile! I wanted to ask, would you recommend this antenna as the option for QRP? I´m looking for one to use together with my MTR3B. Thanks in advance and keep making cool videos! :)

[@g0pot]

CA3CFM While a dipole is probably better, this aerial and tuner does give you some flexibility. An alternative that I’d like to recommend is a trapped (or linked) EFHW. Check out my build at peanutpower.co.uk/efhw. I use this for SOTA with my MTR3B.

[@FoxtrotMike]

@@g0pot Thanks a lot. Gonna check in that direction.

[@oldgiapetto]

No matter what I do, my unit refuses to tune up on 40 meters. I've tried different lengths of wire, different radials, changed the winds on the toroid as directed by QRP Guys.....and nothing works. Pretty disappointed.

[@g0pot]

That’s odd that you’re unsuccessful even trying all that you have. I wonder if one of your polyvaricon capacitors is faulty or out of spec? I have a feeling that in 40m I’m right in the range of them. What length driven element and counterpoise are you trying?

[@shaofuchang515]

the instructions were a little confusing with the two trimpots under the polyvaricon caps themselves, where you have to set them to the maximum position, the caps that was included did not match the diagram but while they did put a photo of the updated one its a page below and soldering world have taken place thereby preventing you from changing those. I wonder if your caps are out of trim as a result?

[@nathanjames4242]

Do you think it would be possible to replace the LED indicating circuitry with a connector that went to a MicroVNA instead?

[@g0pot]

I guess if you want to use a MicroVNA you could leave the SWR circuit switched out (just put the switch in the operating position) and attach your VNA to the BNC connector. Or are you thinking about leaving it inline while you operate? I didn’t think that was possible with a VNA?

[@nathanjames4242]

@@g0pot I was thinking about leaving it hooked up so that the tune/operate switch would send the signal to the microvna for tuning. then switching back to operate would take the Microvna out of the circuit. Basically so the Microvna replaces the LED light.

[@g0pot]

@@nathanjames4242 Yes, looking at the circuit diagram at qrpguys.com/ununtenna-plus I guess you could omit the SWR components and connect S1B to your VNA...maybe add a PCB mount SMA socket if that’s what your VNA uses. Check out the circuit diagram and you’ll see the potential.

[@FoxtrotMike]

Hello Michael! I have a QUESTION: How does affect the toroid in the making of the EFHW? I mean, I started to see how to build it (from your site) but right now I can´t find the toroids you include in the project (I´m in Chile). I have a couple of T50-2 and T94-2. Is there a way to use them? A way to calculate the performance with any of those and re-plan the project? Thank you in advance.

[@g0pot]

When I built a prototype I used a much larger toroid and that worked. I guess different core materials (powdered iron or ferrite) and different mixes and different sizes will result in different matching characteristics. I would grab a couple of options and try them out. I found that the bandwidth changed with different cores but so long as it creates a transforming match for the bands you want then all is good. I tested this by adding the windings to a core then connecting a ~2.5 to 3kohm resistor to the output and measuring the impedance over the HF bands using an aerial analyser looking for a result of 50 ohms.

[@FoxtrotMike]

@@g0pot Wonderful. Thanks again!!!

[@7X2TT]

Always a pleasure watching yor video's. Thx for sharing Michael 😊73 de M0NPT / 7X2TT

[@AnthonyTaylor-o5j]

Hernandez Deborah Martinez Anthony Wilson Ruth

[@nr3rful]

Sounds like there was not much thought gone into this. I'll pass