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Antenna Tuners....Yea or Nay?
- Thread starter Eastside
- Start date
I dont think having it on wood is that big a deal. I had a vertical dipole hanging from the side of my 2nd story roof, not 2 feet from the house used with a midland 80 watt radio and it did alright(YES THATS RIGHT A 2 METER DIPOLE, HELPS TO HAVE A FLAT RADIATION ANGLE WHEN YOU LIVE UP ON TOP A MOUNTAIN). I got the SWR down to 1.3:1 although it was terrible before I finally got a friend to bring his MFJ out, alot better than a CB SWR meter used backwards.
I got a wire up a tree for CB right now, its all in the branches with the top about 80' up, installed with a crossbow and fishing line to pull rope to pull wire. SWR was at 1.5:1 but I plan to trim it a bit to get the center freq closer to the center of the band.
You can also make a dipole reflected, although not sure how far back the reflector should be, I just copied what I have seen on commercial antennas up on the tower. Very unscientific but it would hit knoxville 90 miles away even in the worst conditions like it was next door.
I got a wire up a tree for CB right now, its all in the branches with the top about 80' up, installed with a crossbow and fishing line to pull rope to pull wire. SWR was at 1.5:1 but I plan to trim it a bit to get the center freq closer to the center of the band.
You can also make a dipole reflected, although not sure how far back the reflector should be, I just copied what I have seen on commercial antennas up on the tower. Very unscientific but it would hit knoxville 90 miles away even in the worst conditions like it was next door.
Capacitive coupling:
In electronics, capacitive coupling is the transfer of energy within an electrical network by means of the capacitance between circuit nodes. This coupling can have an intentional or accidental effect. .
Sooo . . . having an object too close (building, tree, dog, etc) to the end of a dipole or vertical antenna can allow a capacitive effect and detune any antenna that would otherwise be resonantly tuned if not influenced by said objects.
Open for debate . . .
In electronics, capacitive coupling is the transfer of energy within an electrical network by means of the capacitance between circuit nodes. This coupling can have an intentional or accidental effect. .
Sooo . . . having an object too close (building, tree, dog, etc) to the end of a dipole or vertical antenna can allow a capacitive effect and detune any antenna that would otherwise be resonantly tuned if not influenced by said objects.
Open for debate . . .
A very limited factor as conductor diameter is related to wavelength.
I doubt it would be a real factor at all at HF frequencies.
Stranded vs solid is only important due to availability and durability as RF travels only on the surface, not in the core.
Tuning the home brew can be a little bit of a pain. As I found, the dipole likes to be strung out and away from any object. I didnt have such a place so it was frustrating. I finally got it but I had to keep putting it up and taking it down to get to the high end for trimming. I use my dipole in a vertical set up though and most put them horizontal (which would be easier). Tuners have their use, but I think just trimming the antenna is the route to go. If I was going to use an antenna tuner, it would be to match different banded radios for use on one antenna.
Wire antennas can be fun, as long as you realize that that wire antenna is not a yagi nor will it perform like a yagi in multiple directions.
It is a fixed antenna so depending on what you build it will be bi directional.
Do they work? Like gang busters in the direction of the main lobe.
Some antennas to research, google is your friend here.
Double extended Zep, Lasy H, Sterba curtain, all those except the extended Zep are arrays, they require some real estate to build and get there gain from the length of the array.
Also N4GG array for phased verticals, it has a 50 ohm impedance.
If you are real estate challenged, then an inverted L may be something to play with.
Wires are fun, they are in expensive to play with and most of all they work.
If you are thinking of playing with some wires, then a antenna coupler and ladder line is a must, saves all the headache of building a matching network at the feed point for each antenna, and the ladder line is basically loss less for all considerations at the HF freq no matter what the feed point impedance of the antenna is.
Someone mentioned a antenna coupler produces heat and reduces the output of the transmitter? Maybe they need to do some more research as to how an antenna coupler actually works, also research how VSWR works and how an antenna coupler will combine any, ANY reflected power in phase with the transmitted power and send it to the antenna to be radiated Yes you ACTUALLY GET MORE TRANSMITTED POWER OUT THAN THE TRANSMITTER PRODUCES DUE TO REFLECTED POWER BEING COMBINED IN PHASE WITH THE TRANSMITED POWER AND REDIDIRECTED TO THE ANTENNA TO BE TRANSMITTED.
Someone also mentioned using an antenna coupler to extend the frequency usage of an antenna. If the dipole is made for 40 meters then it will work for 40 meters and up in frequency, feed it with ladder line and have some fun.
An good antenna coupler can match the 40 meter antenna, 7mhz antenna to 3.9 mhz but then the antenna coupler is adding inductance and capacitance, it gets warm when used for something it is not designed for. The radiated signal is far inferior than an 75 meter dipole would be. If an antenna coupler is used as it is designed to be it is a very efficient piece of equipment and a noteworthy addition to any shack.
The same principal as a 108" 1/4 wl whip being compared to a base loaded shortened mobile antenna, the 1/4 wl will out perform it every time.
Playing with wire antennas is a step forward in understanding how antennas and transmission lines actually work. Armchair experts can talk about it all day long, repeat what they have been told without actually getting their hands dirty and building anything.
It is a fixed antenna so depending on what you build it will be bi directional.
Do they work? Like gang busters in the direction of the main lobe.
Some antennas to research, google is your friend here.
Double extended Zep, Lasy H, Sterba curtain, all those except the extended Zep are arrays, they require some real estate to build and get there gain from the length of the array.
Also N4GG array for phased verticals, it has a 50 ohm impedance.
If you are real estate challenged, then an inverted L may be something to play with.
Wires are fun, they are in expensive to play with and most of all they work.
If you are thinking of playing with some wires, then a antenna coupler and ladder line is a must, saves all the headache of building a matching network at the feed point for each antenna, and the ladder line is basically loss less for all considerations at the HF freq no matter what the feed point impedance of the antenna is.
Someone mentioned a antenna coupler produces heat and reduces the output of the transmitter? Maybe they need to do some more research as to how an antenna coupler actually works, also research how VSWR works and how an antenna coupler will combine any, ANY reflected power in phase with the transmitted power and send it to the antenna to be radiated
Yes you ACTUALLY GET MORE TRANSMITTED POWER OUT THAN THE TRANSMITTER PRODUCES DUE TO REFLECTED POWER BEING COMBINED IN PHASE WITH THE TRANSMITED POWER AND REDIDIRECTED TO THE ANTENNA TO BE TRANSMITTED.Someone also mentioned using an antenna coupler to extend the frequency usage of an antenna. If the dipole is made for 40 meters then it will work for 40 meters and up in frequency, feed it with ladder line and have some fun.
An good antenna coupler can match the 40 meter antenna, 7mhz antenna to 3.9 mhz but then the antenna coupler is adding inductance and capacitance, it gets warm when used for something it is not designed for. The radiated signal is far inferior than an 75 meter dipole would be. If an antenna coupler is used as it is designed to be it is a very efficient piece of equipment and a noteworthy addition to any shack.
The same principal as a 108" 1/4 wl whip being compared to a base loaded shortened mobile antenna, the 1/4 wl will out perform it every time.
Playing with wire antennas is a step forward in understanding how antennas and transmission lines actually work. Armchair experts can talk about it all day long, repeat what they have been told without actually getting their hands dirty and building anything.
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Wavrider your right. I always smile when op's bash antenna tuners.
"it just makes the radio happy" "your reflected power goes up as heat"
In most cases using a properly applied matching network improves the radiated signal.
Most do not realize unless you are using a quarter wave vertical and tuned radials...you have a matching network(tuner) built on the antenna.
A 5/8ths wave vertical ground plane must have an LC circuit at the feed point to "match" to 50 ohm coax...So does an A99/Imax/1/2 wave ground plane...etc...Even a Gamma match is an "antenna tuner"
Even the 1/2 wave dipoles true impedance is 72 ohms when cut for a true electrical 1/4 wave on each leg. You must shorten the legs or change the feedpoint angle from 180 degrees to match it to 50 ohm feedline coax.
Coax feed dipoles cut for 40m will work very well on it's 3rd harmonic(15m) it is effectively a 3/4 wave antenna...like wise and 80m dipole will work on 10m. However neither will radiate as effectively on 20m due to the mismatch of the 50 ohm coax.
However feed the 80m dipole antenna with 300/450 or 600 ohm feedline with a double "L" or link coupled tuner and the loss on 40 through 10m is almost negligible.
The 5/8ths wave ground plane at 2:1 vswr radiates 95% of the power impressed upon it...at 1.5:1/ 98%...All your doing below 2:1 vswr in making the output impedance circuit of the "radio happy" your effectively not improving your signal squat!
OK boys flame on!
All the Best
BJ
"it just makes the radio happy" "your reflected power goes up as heat"
In most cases using a properly applied matching network improves the radiated signal.
Most do not realize unless you are using a quarter wave vertical and tuned radials...you have a matching network(tuner) built on the antenna.
A 5/8ths wave vertical ground plane must have an LC circuit at the feed point to "match" to 50 ohm coax...So does an A99/Imax/1/2 wave ground plane...etc...Even a Gamma match is an "antenna tuner"
Even the 1/2 wave dipoles true impedance is 72 ohms when cut for a true electrical 1/4 wave on each leg. You must shorten the legs or change the feedpoint angle from 180 degrees to match it to 50 ohm feedline coax.
Coax feed dipoles cut for 40m will work very well on it's 3rd harmonic(15m) it is effectively a 3/4 wave antenna...like wise and 80m dipole will work on 10m. However neither will radiate as effectively on 20m due to the mismatch of the 50 ohm coax.
However feed the 80m dipole antenna with 300/450 or 600 ohm feedline with a double "L" or link coupled tuner and the loss on 40 through 10m is almost negligible.
The 5/8ths wave ground plane at 2:1 vswr radiates 95% of the power impressed upon it...at 1.5:1/ 98%...All your doing below 2:1 vswr in making the output impedance circuit of the "radio happy" your effectively not improving your signal squat!
OK boys flame on!
All the Best
BJ
Resonant antennas are always desrable for the best power transfer but sometimes the situation calls for a tuner. I used to have a 40' tower and a Force 12 C-3SS and no tuner was needed. I build, put up and take down resonant dipoles all the time just for fun. Now I use an OCD and use an LDG-600AT Pro auto tuner to touch up the slight mismatch on 40 meters. No biggie.
I don't think I'd ever use a tuner to fix big mismatch issues or to load a rain gutter...but folks with antenna restrictions probably do and that's ok to. Whatever it takes to get a signal out there.
If your antenna SWR is in the 1.X:1 range, you're wasting money on a tuner.
I don't think I'd ever use a tuner to fix big mismatch issues or to load a rain gutter...but folks with antenna restrictions probably do and that's ok to. Whatever it takes to get a signal out there.
If your antenna SWR is in the 1.X:1 range, you're wasting money on a tuner.
Yes resonant antennas are desirable for the impedance matching.
I will respectfully disagree on the "best power transfer".
A dipole IE 1/2 wl antenna is the basis for all antenna comparisons.
a 3/2 dipole is a resonant antenna, 15 meters on the 40 meter dipole shows that. Provides more gain in the favored direction of the lobes than the 1/2 wl dipole.
If the 1/2 wl resonant antenna is the "best antenna" for power transfer then why are the commercial manufactures producing and selling in great quantities the .625 and .64 WL antennas?
Why are all the ARRL antenna handbooks full of antennas designs that produce more gain than our standard 1/2 wl best power transfer antennas?
Not a one of those antennas are the standard 1/2 wl dipole, they are extended Zep, double extended zep, on and on and on to curtain arrays phased dipoles etc etc.
I will agree that the standard 1/2 wl dipole is the simple and easy way to achieve a resonant antenna, but it is definitely not the "best" antenna for power transfer, just the easiest to build and make work.
I will respectfully disagree on the "best power transfer".
A dipole IE 1/2 wl antenna is the basis for all antenna comparisons.
a 3/2 dipole is a resonant antenna, 15 meters on the 40 meter dipole shows that. Provides more gain in the favored direction of the lobes than the 1/2 wl dipole.
If the 1/2 wl resonant antenna is the "best antenna" for power transfer then why are the commercial manufactures producing and selling in great quantities the .625 and .64 WL antennas?
Why are all the ARRL antenna handbooks full of antennas designs that produce more gain than our standard 1/2 wl best power transfer antennas?
Not a one of those antennas are the standard 1/2 wl dipole, they are extended Zep, double extended zep, on and on and on to curtain arrays phased dipoles etc etc.
I will agree that the standard 1/2 wl dipole is the simple and easy way to achieve a resonant antenna, but it is definitely not the "best" antenna for power transfer, just the easiest to build and make work.
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Resonance can be equated with efficiency. But that's with the efficiency of that one resonant antenna. It says nothing about comparing that antenna with another antenna's efficiency.
Why would a resonant antenna be more efficient than a non-resonant antenna? Because reactances, un-neutralized reactances do not radiate. So if there's un-neutralized reactance present in an antenna it isn't as efficient as it could be. Adding the equal and opposite reactance to the reactance already in an antenna neutralizes that reactance (z + (-z) = 0), it ain't there no more. The antenna is resonant by definition, and is as efficient as it can be. It radiates all the power presented to it. The key phrase in that last sentence is -presented to it-, which deals with the most efficient transfer of power to that antenna. Or, matching impedances of the transmitter and feed line to that antenna. The input of a resonant antenna doesn't mean that it's 50 ohms, it can be almost anything. So, start matching impedances -AT- the feed point of the antenna since that's where the mismatch is most likely to be. (Shades or beta/gamma/delta/etc. matches!)
Ain't nothing as simple as it might seem...
- 'Doc
Why would a resonant antenna be more efficient than a non-resonant antenna? Because reactances, un-neutralized reactances do not radiate. So if there's un-neutralized reactance present in an antenna it isn't as efficient as it could be. Adding the equal and opposite reactance to the reactance already in an antenna neutralizes that reactance (z + (-z) = 0), it ain't there no more. The antenna is resonant by definition, and is as efficient as it can be. It radiates all the power presented to it. The key phrase in that last sentence is -presented to it-, which deals with the most efficient transfer of power to that antenna. Or, matching impedances of the transmitter and feed line to that antenna. The input of a resonant antenna doesn't mean that it's 50 ohms, it can be almost anything. So, start matching impedances -AT- the feed point of the antenna since that's where the mismatch is most likely to be. (Shades or beta/gamma/delta/etc. matches!)
Ain't nothing as simple as it might seem...
- 'Doc
Someone mentioned a antenna coupler produces heat and reduces the output of the transmitter? Maybe they need to do some more research as to how an antenna coupler actually works, also research how VSWR works and how an antenna coupler will combine any, ANY reflected power in phase with the transmitted power and send it to the antenna to be radiated
Ummmmmm............speaking of the need to do some more research as to how an antenna coupler actually works, they DO indeed produce heat. It may not be apparent and ideally that is the case but they DO generate heat in the inductor due to current flow through the coil. The more current there is the greater the heat. That is VERY apparent when matching very low impedances where the current will be high.Coil forms have been melted due to excessive heat buildup. .You also can't get more power out than the transmitter produces. Sorry but unless you have found a way around the basic law of energy conservation it just won't happen. What it DOES do is allow the transmitter's SWR protection circuitry to see a good match and allow full transmitter power output in the case of a solid state transmitter. It does not combine the for and ref powers in phase and then redirect it to the antenna. The SWR is still messed up between the coupler and the antenna and as such the for and ref will be of whatever phase relationship the reactance present on the transmission the line dictates.
I believe L.B. Cebik and M. Walt Maxwell allready did the research, and published it. For your reading pleasure.
The Real SWR Page - Explained by WC7I - Will high SWR burn up my radio?
Been there and done that. While both Cebik and Maxwell are authorities on the subject both have been proven to be wrong on the odd occasion as well.I have actually engaged W2DU on several occassions on this subject on amphone.net. My comments were directed at what YOU posted,not what Cebik or Maxwell said. YOU said tuners do not generate heat. I said false. While they do not generate heat of their own accord they do in fact heat up due to losses in the inductor therefore tuners do produce heat.That is a fact. ask almost any ham that runs high power and uses a tuner.Moleculoe deformed the coil in his tuner due to heat.YOU also said that you will actually get more power out to the antenna than the transmitter produces. I don't know how to break it to you but that is an impossibility. You cannot create energy from nothing. Combining forward and reflected power does not equal more power than the transmitter produces.
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