Fixing a Chinese "QRP Manual Days" Antenna Tuner Kit

Presented at 9/7/2021 meeting of the River City Amateur Radio Communications Society, Sacramento, California. Fixes for the Chinese "Zerone 1-30 MHz Manual Antenna Tuner kit."
00:00 Introduction
01:20 Comparison of QRP Tuners and Kits
04:03 The Zerone "Manual Days" Tuner Specifications and Reviews
05:20 The Kit Parts
06:45 The Circuit Description
10:10 Correcting Errata and Other Issues
15:35 The Project Build
17:05 NanoVNA Testing and Results
19:50 Conclusion
20:55 Discussion
The kit requires drilling the enclosure, soldering components on a PC board and winding a 36 turn toroid inductor with 12 taps.
The English kit instructions are very poorly translated from Chinese with errors. In this video I describe several changes that yield a working unit.
Still photos are posted at photos.app.goo.gl/zY3cQaQDLFs...
Manufacturer's specifications: 1-30 MHz, 15W maximum power, impedance matching range 40-300 ohms.

[@DrAlNguyen]

Thank you for your contribution to the ham radio community. I'm pretty new at kit building and recently tackled my first homebrew , a 2 meter Pi-network antenna tuner that went pretty well. I was looking for a HF tuner and, as you mentioned, the price is pretty hard to beat. Without your very clearly explained video, I don't think I would have been able to successfully build this kit. Thanks! 73!

[@bruceweight7319]

Thanks again for the video. Due to your good video I got mine together and it seems to work pretty well. I was very careful not to overheat the terminals while soldering the core connected up. I did end up with one position that is catchy. I took your idea and used some smaller transformer wire and did all but the center pin of the rotary switch in that wire. It made it look pretty good.

[@MakeDoAndMend1]

Just made one of these chimese ATU low cost unit. Surprised how we'll it works. Thanks for your video .cheers from old George in the UK 🇬🇧

[@dracicidasempronius4754]

Im fixin to get one of these kits. Very helpful!!

[@simonfoley4984]

Thanks Carol .... Without yuor help I would not have realised that I wired the toroid the wrong way around !

[@kp4md]

I am glad to have assisted! :)

[@quebirt]

Very helpful presentation. Thank you all, and thank you Carol. This makes these cheap little units useful.

[@bruceweight7319]

Hey I bought one of the ATU 100 Kit's that has the one big tune button and two extra buttons on for bypass mode the other button is to get manual tune mode or auto tune mode . I paid about twenty for the main board and all the components smd already installed and chip programmed. Had to wind coils etc. Solder relays and coils on. Only hard part was connecting the two aux switch lines. Paid 30 dollars for the case, got the one with Pl-259 connectors. Works fantastic. It does take about 5 watts to tune. There is things you can do to Chang it to a QRP only tuner.

[@yuefei9887]

Great Presentation, thank you for putting this information together and sharing it.

[@kp4md]

You're welcome

[@PY2RKC-QRA-MIRO]

Saudações !!! acabo de verificar a PCI que recebi e o responsável corrigiu a serigrafia . TKS & 73 !!!

[@robc3863]

Great video, thanks, have just ordered one for my uSDX rig to use with a telescopic whip, hopefully it'll work well with your corrections! 73, Rob

[@Soupie62]

A bargain buy, salvaged with some good sleuthing skills. Well done!

[@kp4md]

Thank you!

[@bruceweight7319]

Thanks for the wonderful video. I am considering building one for my QCX transmitter and I am glad I watched you video. This is a very useful video. DE KB7CQ

[@2yiz]

Thanks for video I try to repair my tuner because not work before

[@billbates7810]

Nice clear video, I have built one but I didn’t encounter any issues, nut I did have heads up from a previous KZbin video some years ago. God bless, Bill G6ATO.

[@quantumradio]

Thanks for the presentation. FYI it's not necessary to get the 2xM2.5 nuts. The provided nut, which is not M2.5, can work as a spacer right above the variable capacitor's lever (flat on two sides). The configuration that worked for me was (from top to bottom): M2.5 long screw>washer>(thread through the plastic knob)>washer>the provided nut (not M2.5 size)>screwed onto the variable capacitor. Tighten the M2.5 long screw and then the knobs turn the variable capacitors. 73!

[@kp4md]

Thanks for your solution!

[@stefanoranaldi2883]

Thanks for your video very clear endeed

[@ea6wu]

Thanks for the video!

[@bruceweight7319]

Very good. Thank you.

[@zaicevnn]

Спасибо Кэролл! Очень подробно и точно всё изложили, большой труд, спасибо! 73

[@kp4md]

Я рад, что помог тебе!

[@steveelectronics7819]

Given the argument about the placement of the 10 turn section of the inductor, why are the other taps at 1, 2, 2, 2, 4, 2, 3, 3, 2, 3, 2,10 Surely, following the same argument, taps at 1, 2, 2, 2, 2, 2, 3, 3, 3, 4,10 would provide the "finest" adjustment where it is required, gradually getting more and more coarse? Just for fun, I plan on making 2 of these, one with the documented taps and the other with the alternate taps that intuitively make sense to me.

[@kp4md]

Your suggestion makes sense.

[@twkolejofil]

I'm personalizing my kit now and I just thought the same. I use an aluminum case 10x10x5 cm (4x4x2 inches) with an additional switch for a general bypass and five others to switch between T/L/Π network

[@tmmlrd]

I built one without the coil reversal mod and in fact was not fully satisfied with the kit. Bought another kit and used the parts, including the box, to build a Z-match instead, which works very well. After the mod, can the T-match tune also high impedance antennas e.g. random wire or end fed or it can just tune antennas with, say,

[@kp4md]

Yes, the corrected T-match does tune high-impedance and end fed antennas.

[@dlabyer]

Will the swr indicator work at the one watt or less power range?

[@carolf.milazzo3103]

Yes, I have seen the LED light with as little as 0.1 watt.

[@bruceweight7319]

One question that the diagram didnt seem to show but you pointed out and i wanted to make sure of. Does the wiper terminal and the tail end of the ten turn section go to ground; that was a point i am a bit confused by? I figured the wiper went to ground as you showed and the 10 turn tail end went to terminl 12 of the rotary switch. Otherwise what was the second ground wire on the ground wire? And again thanks so much for the wonderful video. I think most of the builders are still getting the torroid and rotary switch wrong.

[@andyleatherbarrow7322]

I just asked the same question. Is the end, ground? Did you figure this out?

[@AdrieKooijman]

Having both the bottom end of the coil and the center contact of the switch to ground seems strange: you basically create a transformer with the secondary winding short circuited. The 4STUNER schematic reverses the connections, but also leaves one end of the coil open. I'm also not sure about if A having only one winding from signal to ground is any useful. 10 windings as minimum may be too much, only one seems very little even at 10 meter frequency. My gut feeling says: start with 3 or 4, and step up 2 windings per step until about D, make steps of 3 windings until H and increase the steps to 4 windings. This brings the total number of windings to 38, about the same as the original, but in my opinion with a more sensible distribution. (adding 4 windings to a coil of 20 or 2 windings to a coil of 6) update: I ended up to use 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4 windings (36 in total) windings and the first results look promising. More after I finish building my (tr)usdx.

[@bruceweight7319]

I did ground the tail end. Mine works well. If you look at what the multi position switch does it makes sense. It keeps as someone else pointed out parasitic problems at bay. You can wind it anyway you like that's the stuff hams do. I just needed it to work and it does quite well. The center knob was a challenge but I got it

[@bruceweight7319]

If you carefully watch the KP4MD Video you will discover that the diagram is backwards and the turn closest to the tee is somewhere around ten turns! That is wrong! It is something like one turn and then so on two ect. After the last turn of the ten turns it goes to ground. Each click gives you more and more inductance. If I had blindly followed the instructions it would not have worked and also the primary and secondary windings are backwards printed on the board. Many folks did not end up with a functioning LED if they followed the instructions that came with it. Again thanks KP4MD I think there were others who caught the LED mistake. I watched a number of videos before I built mine. I have been tempted to re-do the torroid again as I found a nice open non plastic rotary switch that won't melt when you solder it, also at one point I found brass extensions for the rotary capacitors that were made for just such a problem as the knobs. Mine cracked when I tightened them.

[@kp4md]

@@andyleatherbarrow7322 Yes, the tuner exhibits high losses above 14 MHz with the end floating off ground. See photos.app.goo.gl/zY3cQaQDLFs2QU7U8

[@TI3IES]

Great video, thank you. I built one with the diagram published by the seller, with regular results, I will make another one with your instructions. I have a doubt, what each letter of the knob refers to, I have always asked myself and I have not found that information. 73, TI3IES

[@kp4md]

Ignacio, the letters "A" through "L" in order represent the increasing or decreasing values of inductance, depending on how you wire the switch. The letters help you to reset the inductor for a particular frequency. I posted the calculated inductance values in my photo album at photos.app.goo.gl/zY3cQaQDLFs2QU7U8

[@Rob-ml7ps]

Thanks for this. I bought one and started putting it together, but then saw your reverse toroid winding, but after i wound the toroid in the original way. I have a few questions. Do i need to wind it again starting with the 1 turn and ending in 10 turns? Does the other end of the enamel wire go to ground or leave unconnected? Which turns go to which number on the 12 pos switch (there are numbers on the back of switch)?

[@kp4md]

Hi Rob. No need to rewind the toroid. Just connect the end with one turn to the capacitors. Then either position "A" or "L" would be minimum inductance depending on how you wound it. My position "A" corresponds to one turn, or minimum inductance. My schematic diagram shows the far end of the coil connected to ground. T-network tuners with air core inductors usually wire the switch that way to short the unused coil turns and avoid parasitic resonances in the free end. There is some evidence that shorting the unused turns of toroid core inductors may cause core heating and power loss. I plan to check this in my tuner by comparing its performance with and without that ground connection to the inductor. Lifting that connection off ground is a trivial matter.

[@Rob-ml7ps]

@@kp4md Thanks. I've soldered it up now. I just found out the LED and BNC nuts are missing from the kit, so i have to go off and source those. Another question; I have a 40M QRP transceiver. Once i have this built can i simply attach a length of wire for 40M band, like for EFHW 84' long end fed and a 17' long counterpoise, to a BNC plug and use this tuner to tune it (no unun or anything else needed)? If that's the case maybe i can replace the antenna BNC with another style that allows me to screw down wire.

[@kp4md]

If the coil end at switch position "L" is not connected to ground as in the original Chinese circuit diagram, the unused turns of the T network coil behave as an autotransformer. When the rotary switch selects few coil turns, a high voltage is induced at the free unused end of the coil. To test this effect, I temporarily connected a toggle switch between the unused end of the toroid coil and ground to compare the tuner insertion loss with it either grounded or floating. My observed results shows that tuner functions as desired over the 2-28 MHz frequency range when the lose end of the coil is grounded. When the unused end of the coil is disconnected from ground (floating), the tuner exhibits increasing insertion loss and fails to achieve an impedance match at frequencies above 14 MHz. For this reason, I connect the "bottom" of the T network inductor to ground to short out its unused turns.

[@kp4md]

@@Rob-ml7ps Yes, you can use the tuner that way and use any type connector on its output.

[@andyleatherbarrow7322]

Does the end of the inductor need to be grounded? some diagrams show it grounded, others not.

[@kp4md]

@andy leatherbarrow My schematic diagram shows the bottom end of the coil connected to ground. T-network tuners with air core inductors often short the unused coil turns that way to avoid undesired parasitic resonances in the free end of the coil. Some have reported that shorting the unused turns in this way may cause heating and power loss in toroid cores. When I disconnected the unused end of the coil from ground (floating), my tuner exhibited excessive insertion loss and failed to achieve an impedance match at frequencies above 14 MHz. See photos.app.goo.gl/zY3cQaQDLFs2QU7U8

[@andyleatherbarrow7322]

@@kp4md Thank you so much. I wound the toroid yesterday. My kit came with no documentation whatsoever, so your vid has been invaluable. 73 G8ZZF

[@kp4md]

These alternative knobs appear to be usable with the 223p polyvaricon capacitors: 11:46 Knob + screw for 223p Variable Capacitor www.aliexpress.us/item/2251832461267835.html and Extension and Knob for Variable Capacitor www.mikeselectronicparts.com/product/extknob/

[@georgealbertacanadaeh1038]

Thanks. Purchased last summer started build today Jan 18,22. Really don't understand the wiring for the T106-2? is it 23 turns or 35 turns? George

[@kp4md]

Hi, George. There are a total of 36 turns on the T106-2 core. The numbers on the switch diagram are the number of turns between adjacent taps. The one turn at the top of the coil is between the first switch contact and the junction of the two variable capacitors.

[@georgealbertacanadaeh1038]

@@kp4md Thank you Can I ask a favor? Could you re draw for me showing the turns and where the taps are? as the drawing that came with this is very confusing? Thanks George

[@kp4md]

@@georgealbertacanadaeh1038 See the photos on arkadiam.github.io/transmissionlines/atu/qrp-antenna-tuner/

[@kp4md]

@@georgealbertacanadaeh1038 Scrape the enamel insulation off the ends of the wire loops in order to solder the taps to the switch contacts. Use the minimum possible soldering time to avoid melting the plastic switch body.

[@MakeDoAndMend1]

Ps your circuit diagram is wrong on the chinese atu it doesn't have a ground connection at the bottom of the 10 turns. It's the centre of switch is ground only. George

[@kp4md]

George, you correctly noticed that change. Here is the reason: If the loose end of coil end at switch position "L" is not connected to ground as in the original Chinese circuit diagram, the unused turns of the T network coil behave as an autotransformer. When the rotary switch selects few coil turns, a high voltage is induced at the free unconnected end of the coil. To test this effect, I temporarily inserted a toggle switch between ground and the "bottom" end of the toroid coil at the "L" position switch contact 12 to compare the tuner insertion loss with it either grounded or floating above ground. The graph comparing the observed results shows that tuner functions as desired over the 2-28 MHz frequency range only when the loose end of the coil is grounded. When the unused end of the coil is disconnected from ground (floating), the tuner exhibits excessive insertion loss (>10 dB) and fails to achieve an impedance match at frequencies above 14 MHz. For this reason, I short the unused turns by connecting the "bottom" of the T network inductor to ground. My data is posted at photos.app.goo.gl/zY3cQaQDLFs2QU7U8 I would appreciate comparing with your findings. 73, Carol