Net controller for the Denver Radio Club(DRC) Learning Net. IT professional, STEM/STEAM evangelist and advocate. This is an archive of older nets and meetings, newer one's can be found at ru-vid.com
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.
Hi. Great antenna. Do you have a formula to calculate the copper tape length for other bands please. Looking to build one for 4M (70mhz) 73 Steve M0UEH
One very interesting thing about using foil tape is that it has a much lower inductance per unit length than a round narrower wire. The wider the tape the lower the indictance per unit length. This can also be very useful depending on your antenna design. You can also use foil tape with a foam double sided tape as the dielectric (in between) as a balanced feeder with a low Charecteristic Impedence. This Paralel line has increased capacitiance and decreased inductance. I have created 50 OHm balanced feedlines with this concept. Great Video Mate & 73 from DownUnder 🇦🇺
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.
The PLDO component and its usage with an isolated/protected PDU in the shack was a component that I hadn't known about. I knew there was an issue there, and I'd even seen some descriptions of AC to DC power supplies that isolated, to an extent, the AC-side and chassis-ground separately from the DC-out to the radio, but this PLDO component was the missing link in how to make this work. Now the fun part comes in trying to figure out how to make all this apply to my house, including choice of desk location within the house relative to where I want to place the antenna and the SPGP, with relation to the electrical service ground.
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.
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.
I've heard W6NBC reject the idea of a flat conductor magnetic loop due to skin effect on the edges of the conductor, but here, he is promoting a fist conductor on the same bands for vertical dipoles. What am I missing?
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.
Wow! Looking through the questions leads me to think people either never actually watched this or never took in what was being said. It's very informative for the newbie.
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?
I have my 3 antennas connected to a 2 position MFJ switch, one position connects to the radio and the other directly to ground with 12ga copper wire. All antennas and equipment are connected to the same buss bar with that connected to a 12 cu ft galvanized window well and bonded to the house ground. Do you see a lightning problem with this setup when all switches are set to ground?
Hello Ward. I have a Grounding question. I have a copper pipe for grounding all my radios inside my Shack & all other Ham equipment. Then connecting it to my outside utility box to my copper bar where all my lightning arrestors are. From the Copper Bar inside the Utility Box connecting to my Ground Rod buried 9' on the ground. Is it safe to connect all my radios & equipment w/ the lightning arrestors? Some said it's wrong to put them all together. Was wondering about your opinion about this? Someone suggested that I need a separate Ground Rod for the Radios & Equipment. That it does not make any sense connecting the Radios & Equipment w/ the Lightning Arrestors for the Antennas? It is very expensive to put another Ground Rod because my Ground in the Property is Granite. I had to hire 3x Laborers to Sledgehammer the ground rod for 4 hours. Costing me around $400.00 in Labor per hour. Stay Safe. 73 Ruben Tiosejo KD6CWI
That's a big attic. 5 dipoles, 20m to 10m bent into my attic. 20m and 17m coiled at the ends round the roof beams to form large coils. I used a mag. loop in the bedroom shack to null out noise on receive from one direction. They work well considering their small size. For other h.f. bands I made a copy of a Joystick, if anybody remembers them, in the front bedroom. I have 26' of wire to it and an MFJ16010 tuner which I was given as not working, the system tunes 160m to 10m. The tuner had an intermittent fault easily solved by re-soldering a wire inside. For 2m I have a 2 element collinear in the shack. All aerials h/b. Many years ago I put a pallet wood walkway below the roof apex so I could walk around safely. G4GHB.
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.
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
@W1AL Some great info in this video. Unfortunately it is a myth to think that connecting a station ground to a ground rod outside the shack is a good idea. If lightning didn't exist, MAYBE. But lightning does exist. And if a strike is close enough, the voltage from the strike travels into the ground up the ground rod and its attached wire, and into your shack, likely frying everything connected to it. Ground is not equivalent to as place where lightning goes to die. The ground can and does get charged when struck by lightning, and connecting your radio and ham gear to it increases the danger dramatically. Lesson? Disconnect any buss bars that may be connected together inside the shack from the exterior "ground rod." Think of it this way: certain appliances come with a third wire (the green, for ground) so that it is properly grounded. In the olden days of ham radio, they weren't. What may have been necessary then (to eliminate charging the chassis of that old radio) is unnecessary today. Your ham rig IS grounded if it has a 3-prong plug. What is true for the garden variety appliance is equally true for the rig. Unless you know of an appliance that requires a ground rod being banged into the ground out the nearest window. I sure don't. If one thinks of the logic and physics of it, it really is simple. Now...RF grounding is another myth. BUT, none of these problems were ever solved (or could be) by running a ground wire from anything to an outside ground rod. First of, running a wire creates an antenna, therefore making any problem worse. Far better to put one's energy into ferrite chokes to resolve RFI than messing with "grounding." This old wive's tale needs to be put to bed. The mixup lies in the wording in the NEC code (that "equipment" must be grounded). That doesn't translate into running ground rods to everything that one plugs into an outlet. Why do ham rigs have a "grounding" post? It is for BONDING as you wisely point out. By the way......I live in FL. Lightning is not DIRECTABLE or CONTROLLABLE. Thanks again for your wisdom on this topic. 73 de Scott, W1AL
I have attended talks by Monty Bateman, WB5RZX -- he has a Ph.D. in Physics and works in lightning research for NASA at Huntsville. He advocates for single point grounding, including radio equipment. Also, Motorola wrote the industry standard practices for grounding at communications sites, and they advocate for it too. Where are you getting the information you're talking about?
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.
I can't believe that I have stumbled upon your exciting video, we have recently moved back to our home state of Idaho in retirement to an hoa neighborhood after living on 2 plus acres for 30 years, and now I am facing this Exact issue myself. Exact, and we too live in a tri plex with my Shack in the basement. Wow this will be so helpful over the next few months. My immediate issue is finding a path for coax and or ladder line from the attic down to the basement, as no room is directly over another lol, Thanks so much for taking the time to make this video,, !!! Merry Christmas and blessings to you from Idaho!
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.
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).
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.
Dont have them charging all the time. Li-ion batteries degrades faster when on full voltage ( same if it is depleted). Pouch batteries do swell because of gassing where cylindrical cells doesnt they can hold the pressure.
In the early 60's a good friend of mine worked for Decca in the UK.. He worked on the Decca navigator, specificly a base station and antenna in the South Atlantic.. The idea was to use one of the minor Falkland islands as a slot antenna...
