I come to ham radio from a broadcast background, I was a broadcast engineer long before I was a ham. At almost every AM station I've worked for or visited, there is a matching network at the tower base, often a PI network with parallel capacitors and a series inductor, even if the tower happens to be a quarter wave length naturally resonant antenna. OTOH, if the tower is not the correct height to be naturally resonant, the matching network cancels out the reactance to make the tower electrically resonant, so that the antenna current will oscillate at the carrier frequency. But the second function which the matching network performs is to convert the 50 ohm transmission line to the resistance of the antenna. At one station the antenna was inductive with a radiation resistance of 24 ohms. So, the network also converted from the 50 ohm transmission line to 24 ohms.
John really knows of what he speaks. I have used an SGC SG-239 tuner in a NEMA non metallic enclosure outside since about 2015 with only about 20 0r 25 feet of parallel feed line from it to the antenna. I float the tuner at RF so no balun needed. Tunes on all HF bands from 80 through10 meters except I have never tried 60 meters. I am 76 years old and have had a General license since I was 15 and up graded to Extra in 2015. 73 great video.
Really enjoyed your discussion on Non-Resonant Antennas and the use of Antenna Tuners (Couplers) at the Antenna. We employ this at home and on Field Days very effectively. Makes the best use of power and available antennas for field use. As a matter of Fact in my time as a Transmitter Engineer with CBC all our AM, LW, SW antennas were tuned (Coupled) at the antenna. By the Way so are all the VOA transmitters. Only way to ensure maximum power at the antenna. Note Al new Cellular antennas at least on the Telus and Bell networks the Transmitter fed by Fibre is sitting at the base of the antenna and the coupling again is at the antenna. The loses are as you know both on Receive and Transmit. Even on the old Sherman Tanks the coupler was essentially at the base of the Antenna (All be it on the inside of the steel hull.
Excellent video. I use the AH-4 with a 100' antenna and works very well. I was inspired by HF antennas on ships which all have a tall vertical with an antenna tuner at the base.
The best book I have ever read is called "Reflections" by M. Walter Maxwell, W2DU/W8HKK. You can find it on the web or the ARRL might have it. He goes into great detail what SWR is at the antenna and at the end of the transmission line and what the difference is between matching at the antenna or at the radio. He talks about transmission lines, coax vs. balance line. Your eyes will be opened after reading this book. Its a bit complicated but there are a few chapters without all the math that he explains SWR and where to correct the match with plus/minus of where the matching method goes.
Yeah the video missed out that the radio would put out maximum output with a tuner at the radio greatly reducing those loss figures, Walt Maxwell goes into great detail explaining this ,a must read 👍
@@paulm0hpd319 with a remote tuner the output should be close to 50 ohms. At that point there should be no or very little SWR on the coax and the only losses should be the coax itself. If the tuner is placed at the radio and the SWR on coax line is high you will have additional losses on the coax as the reflected wave travels up and down the coax. The tuner reflects the wave back to to the antenna so you have this back and forth action until all the RF minus the losses in the coax as it goes back and forth are absorbed by the antenna. This is why the old timers used balance line for the transmission line. The losses are so low it's almost insignificant and it doesn't matter if you put the antenna tuner in the shack or outside. Coax with high SWR is a problem and it's losses depended on the frequency and the quality of the coax at different frequencies. If you can get the losses of he coax very low at high SWR then it would work just like balance line but that is hard to do with coax.
Good to hear the correct information, Technically tuners that are placed at the feed point (out at the antenna) are couplers. Very efficient and does not waist RF energy "heating" the coax or feedline. TNX John.
Few people except hams want antennas to cover a wide range of frequencies. The military loves to match antennas that give them specific radiation patterns. The military wants their signal to go where they want them to go.
What was missed out with the swr loss charts was that the radio will be reducing its power to the various swr values, if a tuner was introduced at the radio allowing it to produce its maximum power at those swr figures then those loss figures would be greatly reduced, especially if lower loss feedlines where used
Very good video, as a newbie the information was clear. I am in an HOA and my antenna will need to be hidden or at least disguised. So non resonant antenna will most likely be my antenna.
All AM broadcast towers use a matching network or tuner at their base as they are usually not exactly resonant on the assigned frequency. Simetimes even shorter than a full quarter wavelength. But, even at resonance , a quarter wave tower is closer to 30-35 ohms, and requires matching network to the coaxial feeder, generally 50 ohms for best efficiency.
Thanks, John, for the great presentation. I do have to though take exception that there are no full legal limit auto tuners on the market as MFJ as the MFJ-998RT, Remote Auto Tuner, 1.5kW, 1.8-30 MHz. Like it's smaller brother it needs to be enclosed in a water tight container to keep the moisture from the inside. I personally have one that moisture got into and shorted out some traces around the relays and burned them off the board.
The Zepp is 1/2 wave "resonant" as is end fed dipole. It is simply an end fed resonant dipole. It is generally "matched" but not tuned with a quarter wave section of transmission line. And perhaps a balun to the coaxial feeder. The OCF dipole is just a half wave resonant dipole fed off center at usually 20-33 per cent off the end. All is needed is a broadband matching transformer generally 4:1 or 6:1 as needed. They just require a matching transformer to bring their impedance down to 50-75 ohms to match the radio at the antenna, but it is not a tuner. The ocf is also useful on it's even harmonics. Example an 80 meter ocf will be a good match at 40, 20 and 10 meters. Sometimes it's even decent on some of the WARC bands. (I use one at my station).
John, you are such an AWESOME man!! I am 69 and a BRAND NEW hammer... I bought the Lincoln PLUS II and I'm stuck in the middle of a condo, So I plan on buying the DOUBLE LOOP antenna made in England and does 8 BANDS 10m--40m I will let you know I make out .... Please, Please keep up the wonderful POD CASTS 👍 🌍🌎🌏
Excellent presentation. The only toes you may be stepping on ar those that THINK they know antennas and tuners and can't understand why their perfomance goes down the drain.
Great video for helping me understand. I'm looking at a flagpole antenna from zerofive antennas. The owner says to run a tunner in the shack with 100fy of coax between tuner and antenna. I figured remote at the antenna with minimal coax would be best
At 28:00 the ATU circuit diagram looks like the inductors are always in series and the capacitors are always in shunt but can be switched to toggle which is the first element. Meaning the ATU can only ever be in the first and third quadrant of the smith chart at 27:00. Maybe that is why ATUs can not match all loads?
Many resonant antennas are not 50 ohms, often there are advantages in polar diagram as well as reduced ground losses by avoiding some of the simpler designs. Also most antennas have limited bandwidth....
Great explanation. Could easily be cut to 20 minutes or less. Skip the first half hour. From about 30:00 to about 45:00 he actually explains things. The last 15-20 minutes are 80% old men trying to figure out how to un mute their microphones and 20% useful questions and answers.
It all boils down to matching the output impedance of the coax to the INPUT impedence of the antenna FEED POINT, matching Or transforming the I/O impedances of the Ant feed point & the Coax's output end characterestic impedance for Optimum Power transfer with minumum Loss as MUCH as possible.
