What's the best method to use to tune a manual ATU? Let's find out... NOTE: If you are tuning using RF from a radio remember to release the PTT before you rotate the inductor selector switch.
K4KID here... Typically you have to double your power (3db) for someone at the receiving end to tell the difference so the needle's breadth of increase is negligible. Thanks for the lesson though. As for reflected power... I would prefer 10 or 20% less power out w/ ZERO reflected power to keep my finals happy. I have a 31 year old Kenwood TS130 w/ the original finals that still produce full rated power and I think that's because of the "LOVE" I've shown them. Happy airwaves to all. K4KID
I want to say a big thanks to you for taking the time to explain to the new amateurs how to use a manual tuner. I started off with the old Military style variometer, ie. crank it up to get an antenna current reading showing on the meter and usually adjust a capacitor to tweak for maximum. This was done at a rate of knots so you were spending minimum time sending out a carrier. Totally crazy has you then spent ages on that frequency banging away on the key passing all the required traffic that needed sending. 73 de John - G0WXU.
The slightly more forward power is a myth. What is actually going is that there is a phase variant between reflected and forward power. So you are measuring more forward power but this can not be true since your transmitter is only a certain power. Say 1 Watt. Make your SWR slightly higher and you see more forward power. If you really want to measure what the best tuning position is, get a field srength meter and try to find the 1:1 position that gives you the highest field strength. That is the position you need.
I've been quiet for many years. Trying to get back to speed and get back on HF again. This vid is a great help. Well done. I spent over 20 years developing technical training programs so please understand that I appreciate your succinct delivery. Too many put too much unnecessary "stuff" in their vids. WA4OKO
I have just bought the MFJ 945e, lively piece of kit, hopefully I chose wisely 🙂 as I am new to tuners & HF Radios, so always good to see tutorials on use, 73's 26-CT-4078 Mcr. 🇬🇧
Great tutorial video i always use the first method and have done for years i was told to do it this way by a dear friend G3MRP now silent key set the caps mid way point listen to the band you wont to tune and move the inductor you will hear the signal come right up you now know your in the right place to start tuning .Thanks for posting i know its an old post but i just stumbled across it cheers from across the pond.
I use to do it that way and then I would move down maybe 1 step on the inductance and add a little more capacitance. I use to be able to tune it with out a SWR meter by using a receiver and turning down the RF gain very low and turning up the audio high. You can really hear it when it is peaked.
The MFJ manuals differ on that point. The MFJ-949E manual advises you to set the maximum capacitance and minimum capacitance possible for a good SWR. I've followed those instructions and got nice results when using my 11 meters T2LT antenna. I was able to tune and get signal out from 10 to 30 meters. Anyway, the more inductance, the more fiddly the tuning is.
You appear to get more power but what is happening is the reflected is added to the out put appearing to have more out. Cross needle meters always add in the swr !
Great Video, Thank You very much ! I have had my license sense the mid 90's and I am confined to the 2 meter band, it wouldn't be so bad but I live in a small town, everybody knows everybody. I bought a brand new Base radio with HF&6 meter four years ago, and it still sits in the box, never used. I got into this hobby to talk around the world, not around the block. I am one of those people that put down the Ham radio, and went to C.B. !
Very interesting concept. I have always gone by the method recommended by MFJ. The other way may have tweaked out 1-2% more power, but NOT worth all the time and trouble. I really like that small sized antenna analyzer!
Thanks for the video. I discovered that the reason I couldn't tune my homebrew 40 meter dipole wasn't a problem with my antenna but the procedure I was using for the tuner. I now have a 1:1.1 match with 0 reflected power.
I used an Ericsson auto AMU many years ago that tuned under low power. It started with min L and min C, then increased L until max fwd power, then increased C for min refl power. As the refl power dropped, the fwd increased. Further fine adjustment could be done after the auto had run to obtain the best match.
I found his video to be very educational and interesting. I don't post many comments, but this one was worth a mention. Will look at some of your other videos. Great video!
Thank you very much for your videos. I'm just getting started after a 28 year absence from radio, and I'm very happy that you posted these. Actually, now that I've seen your videos, I'm contemplating buying the FG-01 Antenna analyzer. Seems to be the missing link between your transmitter, swr meter, and antenna. Makes tuning a breeze. A little salty on the price, but it's probably worth the money. Again, thanks for posting these, and keep up the good work.
the higher power reading with max cap is due to circulating currents and is Not adding to the forward power despite the reading, just to heating. You significantly reduce the max power handling before arc-over of the tuner with this tune as you have to use both more XC and XL Should always tune with least inductance even thought other combinations are possible Least inductance will give you the widest tuned bandwidth and is much less touchy and fussy - less coupling to your hands while operating the knobs and ensures highest max power handling before an arc over
I, too, found that model a bit 'fiddly', as you said. Even when I was not transmitting, if my hand got near the meter that made the meter move.made it move. I didn't like that excessive meter sensitivity and I returned it to the vendor.
I worked VK from London in 1987 when I got my UK 'A' licence. Just 100W and a bit of wire down the garden. You can work the world on next to nothing when the sunspot cycle is generating lots of spots.
Thank you for those kind words Andrew. Yorkist, Yourkits... it's You-Kits Andrew, You-Kits! You won't regret picking up one of these if you love playing around with HF antennas, traps and tuners.
Good question... for the application I bought it for, yes I would. I bought it for portable/mobile use so I didn't need an internal balun, or a wire antenna connection post. When portable, a wire antenna terminated with a banana plug will plug nice and snugly into the SO239 antenna socket. And when mobile the coax terminated with a PL259 plug will plug directly into the SO239 antenna socket. It works well from 1.8 to 60MHz and I thought the 6m capability was useful. I wouldn't buy one of these as a base station tuner, but as a budget entry level portable/mobile play-around tuner they're ideal. I have heard you should rate any MFJ tuner at half the power it's rated at, and looking at the internal components that's probably about right. This one is rated at 300W, I wanted to use it at 100W, so I should have 50W of 'headroom'. Tuning it with the antenna analyser eliminates the risk of high voltage arcing on the inductor selector switch and flash-over on the rather small variable capacitors. So far I have not had any problems with arcing or flash-over tuning it with my FT950 and FT857 at 100W in FM mode.(Tuning it in FM mode allows me to see the SWR more easily). The important thing to remember is to release the PTT when you rotate the inductor selector switch if you're tuning with a radio and not an antenna anlyser. When it's correctly tuned, running 100W SSB through it will be fine. If you're looking at getting a good quality ATU for your base station, take a look at LAMCO and Palstar.
Nice video. I wonder if the difficulty encountered in method 2 has to do with the choice of the physical position of the taps. They were factory set with the method 1 in mind. To best set it up for method 2, I guess one can change the tap positions on the coil. Likely a fools errand from a practical point of view.
Bought first manual ATU this week and struggled so far :( Found this very informative and practical thanks - just need to go and put it into practice. I'll be back to say how I got on !
Hi, I bought the Comet CAT-300. The unit is fine but the instructions useless. I think it would be in the bin by now if I hadn't found your youtube tutorial . cheers Mark 2E0XCZ
There's a couple of videos on that tuner here on You Tube... it looks pretty good. What's a bit less confusing with the MFJ is the inductor is labelled A to L, not 1.8 to 50MHz, so if you choose an inductance that works it doesn't look wrong if it has the the wrong frequency band written on it. I'm glad you found my video useful, thanks for the feedback.
Nice demonstration, may I add another quick reference point to start with is tuning for noise first, capacity half way then find more noise with induction, most occasionally you are near a reasonable matching point. 😁
With my own t-match I used to start with both capacitors half meshed and then find the inductance for best match before making final adjustments to the capacitors. I don’t think that it was the optimum, efficiency was not my problem but flashover at high power was. I know this video has been up a long time, the behaviour of the forward power meter is normal, it does not prove the power to the load is increased. Just a suggestion, put a 100w lightbulb in a box and use an exposure meter or LDR to determine maximum brightness as you tune the atu, many rigs can produce more power into loads that are not exactly 50 ohms with zero reactance. Found your channel via your GS35B experiments, great stuff.
The user learns their antenna set up. For example if you are on 40 and want to go to 80 and you've done it before you pretty know where to put the settings.
Well actually I played around last night. With your method I lost around 2W from my 5W on 80m. Using the MFJ's method I was at my full 5 Watts. Although MFJs method needs more efforts, it pays off.
a lot of you still seem confused about this there is ONLY ONE proper combination of inductance and capacitance for the (most efficient) True Tune there are multiple ways to find it and there are plenty of settings that are just good enough but still ultimately only one is correct only the one True Tune allows for tuner's full rated power handling without an arc
I wish you could have tuned without that contraption on the right, I doubt most people have one of those things. I am always refining my HF signal on a screwdriver which takes considerable time with every frequency change.
I'm new to hobby, so thanks for this. I haven't got my license yet but have built a 20m doublet (open wire fed) and have just bought the MFJ 949e. Because I'm only listening for now, is there a way of using an ATU to increase receive noise? Do you set it for max reflected?
Thanks for that, really appreciate the quick response. One other question, if I use Bypass, will that permit LW, MW, VHF, UHF through to my SDR? again thanks very much, 73 Adrian.
When I tune around I have my tuner in bypass mode because peaking it on one frequency will put attenuation in on others... especially if they are MHz away. In bypass mode it's a lot like connecting the antenna directly to the radio. LW and MW would be ok but there is stray capacitance in HF tuners that may adversely affect VHF and UHF signals. It wouldn't hurt to just try it.
Just want to thank you again for these tuner vids, and all your other output. I sat my exam there before Christmas (we only have one class here - all or nothin'!) . Your videos were of great help and added to my understanding of theory elements etc. So thanks again. 73 Adrian EI9HAB
No, the only way to bypass the tuner is to press the 'bypass' switch or take the tuner out of circuit. The bypass switch is the top one of the three to the right of the meters. All commercial ATUs have a bypass switch, the auto-ATUs will bypass if you remove power to them.
I was wanting to purhase this but I dont understand where to put the balancing wires? Do they go on the antenna or what? I dont want to hack into my jpole.
This is designed for feeding coax, it's designed for tweaking mobile whip antennas. It does have the tuning range to match wire antennas that are quite long though. If you want to connect it to a balanced feeder you'll have to put a balun on the output. Something like this: www.ebay.com.au/itm/MFJ-911-4-1-Balun-UnBal-300-Watts-/111802128383?hash=item1a07ed17ff:g:uY4AAOSwQTVV-JVZ Then just have a coax lead to connect the antenna port on the tuner to the coax input of the balun. You would probably be better off getting a tuner with a balanced output.
WD4ED is quite correct. A tuner, or any tuned input or antenna for that matter, is matched with either capacitive reactance or inductive reactance assuming that the feed point is not 50+/-J0. The efficiency of the radiator (antenna) is a function of the ratio of forward to reflected. But, we all know that. So an antenna tuner matches the output of the RF output to look perfect to the transmitter. So, the VSWR meter on the tuner shows the result of that match. However, the tuner is not adding to the efficiency of the antenna. As to another question: where is the loss in RF going? Well, back into the antenna tuner. The reflected power has to go somewhere. Do antenna tuners get hot? You bet and so do tuned stubs. 73 WA6VWY
No T piece. Take the coax out of the radio and connect it to the antenna analyser. Set the frequency of interest on the antenna analyser and adjust the controls on the ATU for a good 50 Ohm match. Then take the coax off the analyser and connect it to the radio.
The antenna port on the ATU is connected to the antenna, the antenna analyser is connected to the TX port on the ATU. So when the ATU has been tuned for a match the lead on the ATU TX port is taken off the analyser and connected to the radio.
Am I the only one who noticed your mistake with method 2? Rather than starting at max capacitance, you started at min capacitance. It no wonder why you could not lower the swr, it need lower capacitance. That said, I agree the recommended method is better.
Yes, ATU = Antenna Tuning Unit. Antenna matching unit is a more accurate description as they don't actually 'tune' the antenna, they just transform the mismatch impedance to 50 Ohms to keep the radio happy.
If you are transmitting 1W from a rig capable of transmitting more than a watt, then there is some sort of control loop inside the rig keeping the power at 1W. A couple of methods of doing this are to monitor the current in the PA or detect some of the forward power using a directional coupler. In any case the assumption of the designers will have been that the transmitter will be working into the nominal impedance i.e. 50 ohms, and all the development work of the power control loop will have been done into a 50 ohm load. If you mismatch it, the power control loop will move to a different point. It may produce more power, it could be be less power - nobody knows because you have moved to a condition where the behaviour is not specified. All you are doing is looking at the behaviour of this control loop under the changed conditions, and you have not proved anything general at all.
Any time you go below the ZERO, or past the 10, you are using the same amount of capacitance that you would be using, about 90 degrees in the other direction!!! Don't believe me? Take the damn cover off! :)
Method 2 was a waste. You got about 50mW more forward power. To get one more s unit at the receiving end you'd have to have 6dB more power. That means going from one watt up to four watts.
