Ham Radio - Build your own L network antenna tuner

They're really very simple to build. I over-built this one to make it clear for the video, but you could make it smaller, put it in a nice box with labels and paint. ;-) I did just that in a newer video.
• Ham Radio Antennas - R...
The antenna I had connected for the demo is an external 98 foot end fed wire.

[@markw.schumann297]

This video made me gleeful, that's the word. Busting out the PVC pipe and the AM radio salvage part and making something _actually work_ was so much fun to watch.

[@yuudai1400]

One of the best vids on tuners and homebrew on KZbin. Thanks! K7SAK, 73

[@danlscan]

I've been looking at my junk pile for a while now (several weeks). This has given me the impetus to get my junky antenna tuned up. Thanks!

[@GeezerDust]

I learn something from every video of yours. Putting the moving plate/shaft side to ground to help prevent hand capacitance. Never thought of that - thanks.

[@kchoudri]

superb,,, first easy antenna tuner making video I found in ages. Thank you for sharing.

[@Migueldeservantes]

Great and awesome work! Thank for the education.. I just found out that that can be done with Vhf... Have a set of antennas that come with this circuit on them,,, and after a few hours of search found out that they where tuners..thanks you very much for posting.

[@TheCrunchbird]

Great video. I made one of these when I was first licensed back in the 1970's. I was living in a three tory brownstone building in NYC. I ran a wire to the roof of the building next door that was much higher and worked a lot of countries. N2SN.

[@RevGunn-jq3cq]

The best antenna tuner tutorial I've seen! Thank You!

[@sandraabarca6029]

Rev. Gunn yes ty very much for being a patient teaching Elmer . There are many of us out there . Plz keep up the great work we are listening🤠📡👍

[@CharlieTechie]

Great learning video, very simple design to get the point across.

[@MoTown44240]

Thanks for this video. You explain everything in a non-technical manner for this non-technical ham. This will be an ideal tuner for portable and home with my FT817. 73

[@loughkb]

Thanks for watching.

[@bradenglettkd8zm69]

Good tutorial Kevin, as usual. The clearest tute I've ever seen on this subject. Go order "two dogs and a Dew" at the Coney Island and send me the bill! 73, Brady, KD8ZM

[@USMCDAD47]

Kevin...you are an Elmer's elmer! This is a great video and you do such a good job of explaining things.

[@loughkb]

Thanks, I try to help. and thanks for watching.

[@patmb2011]

but even QRP, a bone-E-fied Elmer would ID his transmissions would he not?

[@southernexposure123]

Cool project. Some decades ago I was poor. Still am. lol I made my tuner with thin radio shack test lead alligator clip jumpers. My capacitor was from a pocket size transistor AM radio and the coil was still holding together a school 5 subject spiral notebook. The rig was an old tube radio that belonged to my local radio club. The coil and capacitor wren't mounted to anything. I tapped the coil while still using the notebook for my log and I just pushed the cap out of the way once I got the inverted v antenna tuned. I don't remember how the parts were configured.

[@graplingurty]

Thank you Kevin from KC0ZQB the Video was very Informative with hands on useful knowledge that will give you a very nice antenna tuner in the end. And you will know how and why it works....

[@loughkb]

You're welcome. Thanks for watching.

[@samuellourenco1050]

That is just what I need. Thanks for sharing this great piece of knowledge!

[@OldSweetTed]

Very good, as usual, Kevin!

[@Tetley02]

What a great video. Loved this. Will try building my own for sure!!!

[@arthurhunt642]

What a great little way to spend Saturday. Very good. .

[@loughkb]

Check out the follow up video where I rebuilt it into a small case. It's nice and portable now.

[@southjersey10]

This was a great video. A nice project for 2021.

[@peterarmitage5357]

Your right kevin, fantastic project, i was just about to order one from ebay, when i saw your youtube video, i have an old am vc so i will experiment with that, thanks very much for your excellent video, i enjoy them and are very informative. best regards.

[@pudiful]

Nice proyect and good video.

[@StrummerDave]

Great video. I get it now. Love the diy coil.

[@davidshermanlittle919]

On trying to use a 5/8th wave 2 meter antenna - remember there is a tapped coil in the antennas base. This presents a very low impedance on HF in the order of problems less than 10 ohms. That's why it won't tune to a low VSWR.

[@dl08in]

Awesome video. Thank you!

[@loughkb]

You're welcome. Thanks for watching.

[@draghiciciprian4002]

A very good video. Thank you! I built one, and it works amazing. My 2 x 10m dipole, I can use it in 4 bands with its help, 3.5mhz, 7mhz, 18mhz and 21mhz.

[@joeplante8551]

Licensed 1981 age 15, my first antenna end fed 80m half wave coupled thru an "L Network" alligator clip tap & var cap mounted on pine board ... worked WAS cw and the world :) KA1HSP

[@ScientistPrepper]

Pretty cool. Good job. Thanks for the video.

[@petek1pml746]

Awesome project, i think even i could do this. Ty for doing this video

[@johnedwinsnyder5082]

Best video on this topic. Thanks.

[@DMckee-pb7jr]

I'll have to try this. It looks like something I could build with one of my kids. Come to think of it, it would be a good group/club build for an evening. Thanks.

[@robincross4625]

When designing an antenna tuner, the first few taps should be ONE turn just like you made. After that additional turns should be added between taps. I don't think it is logarithmic. I think it more linear. By example, your tuner ran out of inductance and you were not able to tune the 2M antenna on the lower bands. Also, your design was very good in one aspect, It was configured as a Low Pass Filter [LPF]. If the capacitor and inductor are swapped in position, It becomes a High Pass Filter [HPF]. Most commercial antenna tuners a of the HPF configuration. I have seen it said that the HPF type is wider range but do not know if that is fact. The Ten-Tec 'tuners' were of the reversible type. That allowed low and high impedences to be matched. I'm not trying to be a wise ****. Just additional information.

[@daveengstrom9250]

You sound a little pompous.

[@robincross4625]

@@daveengstrom9250 Thank you for the compliment. Not all Amateurs have the same background. You know nothing of mine.

[@chriscutting5773]

simple and effective ideal for field days in a smaller package of course

[@c-mediagroup8311]

Great Tuner !

[@paulschmolke188]

Great demo…easy build, well explained a good first project for any receiver user and worthwhile for the QRP crowd as a transmit tuner. I’m wondering how much inductance you’ve created with the dead simple coil…

[@algiskara]

Very useful video, thanks!

[@jkbish1]

going to definitely build this "Loughin L Network antenna tuner".

[@buffplums]

Love this really inspiring

[@nasian4641]

Excellent tutorial.

[@jopplehead]

Thanks so much... Now I understand better what my mfj 949e does.... 73

[@easyeagle2]

T built mine many years ago in a similar manner but you should enclose the whole unit and when building the coil use a heavier wire and at least 20 closer spaced turns. I also used an old radio type variable cap. and never had a flashover. Its also a good idea to include a swr meter.

[@loughkb]

As I said in the video, I was over building it to make it more visually clear. If you watch the follow up video, you'll see I rebuilt it into a case with a more proper construction.

[@edbeckerich3737]

Kevin, when I need a tuner, I know where to go. I've got solid core bell wire, and PVC ready to go, will have one soon. Great video!!

[@kb3svj]

Thank you Kevin. Can that tuner be used for open feed line such as twin lead, 300-400 window or 600-ohm ladder line? I suspect you would have to add binding posts.

[@randyhamme6477]

Great Video! Thanks so much!

[@jps99]

Great video, thanks!

[@JamesP6084]

Thanks this will be my project 73's

[@BennyCFD]

Great video, thanks. But what is the capacitance range of the capacitor you're using. If you have only one capacitor what would you suggest

[@uniquedata9460]

Great explanation, Kevin. What (if anything) would need to be changed to build an L Network Antenna Tuner for 2 Meters and 70 cm? I want to experiment with open wire feedline (ladder line) on these frequencies with a homebrew yagi and a couple of other antennas. I want to try several different modes on these bands other than FM to see what I am able to have ready for Field Day.

[@1883GotDown]

Ive been working FT8 for about a year now with WAS on every band except 12 and 10(cause of openings) and 160. Why? cause my 80m Dipole WILL not tune for this band. Weirdly enough it will not tune for 60m but even with the radios output dropping to 5w cause of the SWR on my Yaesu I have have got enough radation out to WAS on 60. 160m though, everyone gets just enough signal to even hear me rather then work me. Now i think I have found the solution. If i can build my self an L-Match following your instructions I can finally Trick my radio into putting out some PWR now so I can get a better signal out there. Thank you sir!!!!

[@BarefootBeekeeper]

Is there any magic to the diameter of the coil, or the spacing between turns?

[@jcmcclain57]

Thank you for the education!

[@cw.only.channel]

Thank you for sharing videos. Best wishes for you

[@maikerumine]

Nice build! Add a diode for an insta crystal radio. :)

[@alalan3735]

Nice project! Hard to find variable capacitors nowdays, so what size do you recommend I purchase? Thanks!

[@tommiehinman1349]

Reminds me of my old MFJ travel tuner. I run the Tesla design random wire w/17ft counterpose

[@neira.francisco]

Great video and explanation. Which will be the approximate inductance of that coil? I want to try with a toroidal core inductor with tabs but need to have a reference. 73 de OA4CKN

[@hubercats]

Great video, thank you!

[@michaellum2211]

Where do you place your mfj tuner, ahead or after your L/C tuner? Thanks.

[@acestudioscouk-Ace-G0ACE]

This was useful and I'm building one,

[@weirdsciencetv4999]

Regarding the schematic on the thumbnail- Does the shorted part of the variable inductor act as a shorted set of turns in an autotransformer? Is it a negligible effect?

[@W4EMB]

thanks Kevin . i hope all is well. i really enjoy your videos. i would love to see a home brew Z match tuner if you are able. Thanks! DE W4EMB

[@TheMrKrause]

Thank you for sharing

[@margaqrt]

Great demo of a simple antenna tuner. I have that exact same dual variable cap with the same wheel that I pulled from an old tube AM radio. One clarification though on this video. Was the input of the swr meter connected to the output of the radio and then the output of the swr meter was connected to the input of the antenna tuner. Then the output of the antenna tuner was connected to the different antennas you were matching by adjusting inductance and capacitance?

[@loughkb]

Yes, that's correct, the wiring goes, Radio > SWR meter > Tuner > Antenna. The meter would be useless on the other side of the tuner. You need to know what SWR the radio is seeing when you tune the tuner.

[@RC-Heli835]

Hi Kevin! If I understand correctly the inductor is in series to the center pin of the radio and after the inductor coil the capacitor is tapped into the center pin and the other side goes to ground? Apparently in this setup the coax can be lengthened or shortened a bit by the inductor? I'm still having trouble figuring out what capacitance does. I know on an oscilloscope capacitance increase will roll the corners off a square wave.

[@DoRC]

great video. im sure you get this question all the time but is there a kind of inexpensive way to get into the ham hobby? i dont live in a big city so i probably need a least a moderate range. i hope this question isnt too annoying theres just sooo much info online its hard for a noob to weed through it all.

[@loughkb]

Not annoying at all. Test up to at least General class so you can get on the lower HF bands. There are often nice HF transceivers showing up on ebay in the 300 to 400 dollar price range. You don't need much power, I've talked to Europe on my little 5 watt yaesu FT-817. It's all about the antenna. Resonant dipoles are best if you've got the room and trees.

[@hubercats]

Very nice. Thank you!

[@WaterWhiteTuber]

Newbie Question: The video is interesting. I heard what you said about wanting a variable capacitor with greater spacing for higher power. Out of curiosity, say your pushing out 50 watts. What sort of voltage would be coming out of the radio? I'm a little confused as to how you determined wire awg and component ratings. Thank you.

[@loughkb]

Mostly just from experience. As far as the RF voltage, that varies depending on load impedence match and standing waves. Reflected power can add voltage depending on it's phase. That's one way a high SWR can kill finals in a radio. The reflected power brings the voltage up across the transistors and can exceed the breakdown voltage rating of their junction. I've read that into a good match, RF RMS voltage at 100 Watts will be in the arena of 800 volts.

[@juanjocastillo]

the coil... it has to be air-core?? Can i use a PC Power Suply toroid for the coil?

[@gortnewton4765]

Nice job. Simple, easy, low cost. Would a nylon strip connector work instead of the bolted-on wire taps? Thanks for showing us.

[@loughkb]

Any method of tapping the wires would work. You want to try to avoid compromising the integrity of the wire though. Mechanical connections can become noisy over time and RF doesn't like that.

[@PhiberOptik1979]

Great video! Thanks for posting!! I have a question though. I have not been able to get a specific answer in any of the videos i have watched on antenna builds. I should mention I am new to this hobby and electronics in general. I am teaching myself essentially.. What is the role of magnets in an antenna? Probably a stupid question, but I understand the need bu what I do not get is why magnets? Magnetic wire, ferrite bars (especially since I am trying to build a loop or dipole. Also, What would happen, or is it just nonsensical to combine 2 or more ferrite bars, Such as bundling them and wrapping them with wire? I would greatly appreciate that info. Thank you in advance. Tom.

[@loughkb]

No, not magnets.. You might be getting confused by the use of magnet wire and ferrite torroids. In most cases, when you see a ferrite core wound with wire in an antenna feed point, you're seeing a transformer or choke of some type. A transformer may be needed to match the impedance of the balanced antenna wires to the unbalanced feedline. Take the first three letters of 'balanced' and the first two of 'unbalanced' and you get "balun". A term I'm sure you've heard. So what you're seeing is a transformer. And although transformers do operate with induced magnetic fields, they are not magnets themselves.

[@kb3svj]

I see you are using a coax (unbalanced feed). Would that tuner configuration you built/demonstrated work with a balanced feed line such as 300 or 400 ladder line? Thx

[@loughkb]

It should work, since it's matching a low impedance at the TX side to a higher impedance. The ladder line should appear as a 450 ohm load at the antennas resonance and higher when out of resonance. You could also use a 4:1 balun at the ladder line and reverse the connections on the tuner. The L network tuner really shines with end fed wires though.

[@jeromegrzelak8236]

this beats my 40 d roller coil and half the time gettin low swr fellow hams u got to build this one kg6mn

[@noncounterproductive4596]

Your schematic seems to show a RHEOSTAT rather than a tapped inductor. If I recall correctly, that connection between the tap and one end of the coil should make a big difference in how the inductance varies as you move the tap. Have you tried it without that connection?

[@RosssRoyce]

Fantastic! So if i materialize this do i have to connect the "ground"(on transmitter side) to the outside barrel of the plug? Then do the "grounds" of the capacitor and antenna all connect to that? And the antenna's ground i guess is just unconnected to the antenna? Thanks a lot!!

[@loughkb]

If you look at the schematic, you'll see ground symbols. Those are all connected together. Yes, the cable coming from the radio and SWR meter needs to have it's ground connected. Usually, these are built into a metal box and all grounds are connected to the metal. The exception is the antenna side. The L network tuner will work very well with just a single end fed wire on the output side and no ground. Of course, it will radiate, so you get RF in the shack that can interfere with things or feed back through your microphone cable and mess up your audio.

[@RosssRoyce]

thanks enormous! i was used to all metal shells and casings to be effectively ground as in all audio equipment but was asking because it seemed to me that some radio guy was advising creating special ground connections to radiator heaters or pipes planted into the ground etc, which to me is useless since on of the terminals in the power socket is aniway connected to ground... best to you!

[@raykiii]

That was a great build. I enjoy it when hams make their own equipment. This build has so much in common with building a crystal radio set, it's as if all those skills lead to this build. Now for a question. In order to stop the impedance from your hand on the variable capacitor, would a simple rubber band work or would you just use electrical tape? Thank you in advance.

[@loughkb]

I'd use a large plastic knob. Just getting your hand close can affect it a bit.

[@raykiii]

I just watched the video where you put this in a box. When I saw it had a d-shaft I knew immediately that a knob was coming. Very cool project. I hope thousands are built. Thank you again.

[@loughkb]

If you build it, be sure to keep all of your wire runs as short and direct as possible. That limits stray capacitance between the wires that can make the tuner act strangely.

[@raykiii]

Good advice.

[@humaxf1]

very well explained. can you connect the shield of the SO239's and the ground lug of the capacitor to a common connection point?

[@loughkb]

They are tied together. Every point on the schematic with a ground symbol are connected together electrically. Usually to the metal chassis that it would be built in.

[@humaxf1]

Understood. Was your 98ft wire fed with coax or plugged direct into the SO239?

[@loughkb]

This type of tuner will work well in many different ways. You could connect the end of the wire directly to the center of the so-239 right at the tuner. You could use a coax and run the wire off it's end, with or without any couterpoise off the shield. (although it will work better with one.) My antenna during the test was coax out to a feed point that had a 9:1 UNUN and four counterpoise wires. I have used this kind of a tuner with only a center wire literally clipped to an unused electric fence before. It's very flexible.

[@mattharvey8712]

Bravo......... does the tuner need to be close to antenna.....bigger coil 80m......get driver ....run some brushes .....cheerz

[@donaldjeske5200]

I am thinking of building a 2 meter antenna tuner and was wondering how many turns it will take on the inductor . I am just getting into this stuff. And also how much capacitance do you think I will need. I am trying to tune a copper J poll antenna. KK7CZD DON JESKE

[@loughkb]

You want to tune the J-pole by moving the tap point of the coax up or down the J very very slightly. Using a transmatch at the radio would keep the radio happy, but do nothing about the efficiency loss of the detuned antenna.

[@petercane6376]

Would this be suitable for short wave listening please?

[@stevec5000]

Have you tried to calculate what values of L & C you need for a certain frequency? I'd like to be able to tune my G5RV antenna to receive WWV on 60 kHz, wonder what values I'd need for that?

[@loughkb]

In that case, the impedance match between the radio and the antenna isn't the problem. The short wire antenna isn't going to capture much signal to start with. You'll need a longer antenna. Over on teh HamAndShortwaveRadio channel, Greg did an extensive test with using a tuner to try to improve performance for shotwave listening. His results were clear. A tuner doesn't get you more signal out of an antenna than what the antenna can deliver. At best, a tuner will act like a pre-selector, allowing for rejection of signals outside of the intended frequency.

[@mohinderkaur6671]

Tapped coil normally uses a large enamelled copper wire like 14awg enamelled or regular 14awg spaced by its diameter wound on 1 1/2 to 3 inch dia pipe. will have much better Q. Terminals NOT needed for contacts

[@loughkb]

Yes, that's all correct. As I mentioned in the video, I built it this way to better illustrate the design visually.

[@samuelvillaver3479]

Can I used this one for a 2m vhf?

[@davidbyrd5065]

I really liked this video very useful. David Byrd KN4BHS

[@W1ZY]

You want to use as little inductance as possible to achieve the match, as you have done in the video. This maximizes efficiency.

[@TheDgdimick]

Great video. Could you put an analog VOM on the speaker and measure the voltage to get the best "tune"?

[@loughkb]

If you had a very steady local carrier to receive. Like a signal generator feeding some external wire your antenna could pick up. Kind of a convoluted way to do it and it wouldn't be very precise.

[@TheDgdimick]

@@loughkb I see the error in my logic..

[@germanjohn5626]

add 2 switches and another cap and it becomes a Pi, LC or CL tuner totally universal over a huge range

[@paulbaker9277]

I like this idea but I was wondering, would ceramic capacitors help in reducing the statics back ground

[@loughkb]

That atmospheric static noise is coming almost entirely from the antenna. The caps won't change that.

[@PhilLeith]

Would more winds on a smaller diameter pvc do the trick? THough that means more screws :-/ but ...

[@willwasson8113]

Did your 98Ft end fed work at 160M? I need an antenna system for my new FT857D that covers 6M-160M. I was thinking End Fed for 40-160M and a cobweb for 30-6M. But I'm getting paralysis by analysis with all the antenna options. A Hamfest is coming up this weekend and I'll keep a lookout for a variable cap.

[@loughkb]

Yes, and I'll tell you exactly what I did because it is the best multi-band compromise antenna I have ever made. The feed point is an UNUN that I made. The common design is the 9:1 UNUN, which is well documented with plenty of pictures showing how to wind it. By experimentation, I found that around 6.5:1 was a better ratio for this antenna. So, find the 9:1 design and instead of 9 turns on the torroid, do 6 turns. Then keep the feedpoint near the ground and run out two or three 9 foot radials. The antenna will tune very well on 160, 60, 40, 30, 20, 17, 15, 12, and 10 meters. It's a bit finicky on 80, but I can get it to tune down to about 1.8:1 on the low end and 1.5:1 on the high end of 80.

[@willwasson8113]

So you keep the UNUN at ground level near a ground point, and then run the radials out from there? Does the direction on the radials make any difference? I assume you then run the end fed wire up from the ground to some height and then horizontally off to somewhere.

[@loughkb]

The wire goes up and off at an angle, the couterpoise wires go in the opposite direction mostly.

[@ronaldjorgensen6839]

measure calibrate scope it math graph it there is no confusion thank you long time since built one, resonance has its peak also just like the rf then isolate static filter it to ground?

[@recumbentogiro26]

Amazing video. What type of calculations did you use to build this and what would be a good substitute for that capacitor?

[@loughkb]

I didn't use any math. The L configuration will provide a range of tuning for most common antennas. The more inductance and capacitance just extends the range. There are resources for calculating values if you know the range of loads you're going to hit it with. But you can just throw one together and it will work for many cases. I pick up air variable caps at hamfests. You always find some guy with a box of them cheap.

[@recumbentogiro26]

Kevin Loughin Thank You

[@jeromegrzelak8236]

Interesting swr mtr have u built the moxon antennas for 2 or 70 cm ??? kg6mn

[@loughkb]

Nope, never have tried the moxon design. Read about it though.

[@ERICtheLATE]

Any chance it can tune a large random loop? Maybe after adding a 1:1 or 4:1 balun? Mag loops are great, but walking over and tweaking the varicap is kinda annoying and encourages having the antenna right by the radio. A mathematic merger of 9:1 unun and mag loop needs to be discovered and proven. Random wire is nice, but it transmits from the tuner, right by the radio.

[@USMCDAD47]

kevin...was curious about the coil...what's the over all inductance and roughly how much inductance does each tap remove?

[@loughkb]

I haven't measured it. The nice thing about the L tuner is anything will work. I can try to hook it up to my RLC bridge I suppose, if you really want me to. I'll have to take it apart.

[@ameynikam44]

Can dis be used for 40m 20m fan dipole ? What is ground here , is it a earth ground or a chasis ground ?

[@loughkb]

Yes, and chassis ground.

[@CanJam8]

Nice video kevin. I've read other projects with higher number of turns like 40 to 60 on similar Dia form and taps at more specific and odd spots on the coil. Eg 1 3 8 11 15 etc. I guess trial and error. Any thoughts on these other approaches? Also could I pull the swr meter out of an old cb or Sw radio and make a stand alone swr meter? Thanks VA3RLF

[@loughkb]

You could use math to calculate the inductance and matching range of the circuit, then adjust your taps and turns to provide a desired range and linear steps. My point with this video is that the basic mechanics of the circuit will work well enough to be useful in many cases. And I've seen old CB SWR meters at hamfests for $5 regularly. But yes, you could hack one out of an old radio if you want. It should just be a little sense board, a variable resistor and a meter.

[@CanJam8]

Kevin Loughin Thanks for your reply. Your goal with your video is accomplished well. Keep it up😀

[@sleeve8651]

I must say, once you hooked up the 5/8 2 meter antenna, I was hoping you would try Six meters ? As if memory serves me, that antenna is around a quarter wave on Six ! So I was thinking maybe it would have been an easy match ? But perhaps outside your parameters of HF ? Still a nicely done tutorial ! Congratulations, and thank you for the down to Earth explanation ! If I could be critical, it was difficult for me to see the SWR Bridge ! Perhaps something to consider in the future ? '73 !

[@loughkb]

I had a magmount 5/8 wave 2 m antenna then I would also use for 6 m because it was a good quarter wave on six. Didn't even need a tuner at the low end of 6 m

[@kerron_]

That simple. Adding capacitance & inductance.

[@vincebiano190]

Would I be able to connect this setup to a longwire?

[@loughkb]

Yes, they work great with random wires.

[@dalemyers5096]

hello again. could you add a smaller inductor and bigger cap for a vhf tunner? i see adding a switch at the input so239 diverting the signal to the required section. and hook up the output combined to the output so239.

[@loughkb]

You would need a smaller cap I suppose, to bring it up to 6 meters, you could just tap the coil closer to the end for less inductance. However, long radiators don't work well at and above 50Mhz. You could make the radio happy, but the antenna would just not perform well.

[@USMCDAD47]

Excellent point...just because you can match the radio to the antenna...doesn't mean the antenna will radiate well.

[@skyl4rk]

If you don't have a tone function on your radio, do you have to make noise in it when tuning?

[@loughkb]

It would be a little harder to tune since the power would be bouncing around, but you really just watch reflected power and tune it to the lowest. Most radio's have a key input for a code key in CW mode. You could also switch to AM mode and key the mic to generate a carrier. You want to turn the power down on the radio though, don't hurt the finals when it's initially out of tune.