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Dipoles and the rig's RF ground...
I realize that dipoles are balanced antennas, but does the rig
itself still need an RF ground too? (I know the radio always needs a DC ground, of course). How about if the dipole is being used as a non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER LINE--DIPOLE) -- would this affect the need for an RF ground on the rig for operation in the dipole's non-resonant bands? Or is no RF ground _at all_ required with a dipole; unlike when using random wires or verticals, and other such un-balanced antennas? Thanks! Bill |
Dipoles and the rig's RF ground...
"billcalley" wrote in message oups.com... I realize that dipoles are balanced antennas, but does the rig itself still need an RF ground too? (I know the radio always needs a DC ground, of course). How about if the dipole is being used as a non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER LINE--DIPOLE) -- would this affect the need for an RF ground on the rig for operation in the dipole's non-resonant bands? Or is no RF ground _at all_ required with a dipole; unlike when using random wires or verticals, and other such un-balanced antennas? With ladder line it is best to use a balun between the antenna tuner and the transmission line. An RF ground on the rig is then not required (you won't have RF voltages on the rig's chassis). The thing about an RF ground is that due to the length of the ground circuit, the rig is often not grounded anyway. |
Dipoles and the rig's RF ground...
billcalley wrote:
I realize that dipoles are balanced antennas, but does the rig itself still need an RF ground too? If your feedline is balanced, that is it has equal and opposite currents on the two conductors, then there's no current left over to flow to or from ground and no need for an RF ground connection. All the current from one conductor goes back on the other. Feedlines can be balanced even if they're coax and/or the antenna is unsymmetrical; they can be unbalanced even if the antenna and feedline are symmetrical. If the feedline isn't balanced, the difference current (that is, the difference between the currents on the two feedline conductors) will find its way to ground however it can. This often creates undesirable effects. But if you can't avoid it, it's better to provide a low impedance path for the ground current if possible. And that can sometimes be difficult to do. (I know the radio always needs a DC ground, of course). No, it doesn't. It needs an AC safety ground if connected to the mains, and a lightning ground if that's a possible hazard. But DC isn't important. How about if the dipole is being used as a non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER LINE--DIPOLE) -- would this affect the need for an RF ground on the rig for operation in the dipole's non-resonant bands? Or is no RF ground _at all_ required with a dipole; unlike when using random wires or verticals, and other such un-balanced antennas? The trick is to get the feedline balanced on all bands. That requires either a truly balanced tuner, or a combination of a good balun and impedances on all bands at the balun which the balun can handle. Roy Lewallen, W7EL |
Dipoles and the rig's RF ground...
ORIGINAL MESSAGE: On 1 Jan 2006 12:47:43 -0800, "billcalley" wrote: Or is no RF ground _at all_ required with a dipole; unlike when using random wires or verticals, and other such un-balanced antennas? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Any antenna which requires a connection to ground should be shown the trash can immediately. Ground (earth) is a lousy conductor and does nothing to help your signal. RF belongs up in the air, not down in the dirt. If you find that connecting a ground wire actually improves your signal, you have a SERIOUS problem in your antenna. 73, Bill W6WRT |
Dipoles and the rig's RF ground...
Charles Schuler wrote:
"billcalley" wrote in message oups.com... I realize that dipoles are balanced antennas, but does the rig itself still need an RF ground too? (I know the radio always needs a DC ground, of course). How about if the dipole is being used as a non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER LINE--DIPOLE) -- would this affect the need for an RF ground on the rig for operation in the dipole's non-resonant bands? Or is no RF ground _at all_ required with a dipole; unlike when using random wires or verticals, and other such un-balanced antennas? With ladder line it is best to use a balun between the antenna tuner and the transmission line. An RF ground on the rig is then not required (you won't have RF voltages on the rig's chassis). The thing about an RF ground is that due to the length of the ground circuit, the rig is often not grounded anyway. Most modern shacks have to long distance between the rig and ground. It's not equal to an ungrounded rig but you might experience hf in your shack. This is best solved by a short ground cable to a proper ground rod. The next best thing is to buy or build an artificial ground. It's very simple and can be made to cover all ham bands easily and will always give you a perfect length of the earth cable... By cheating of course - but it works! Cheers M0DFI |
Dipoles and the rig's RF ground...
billcalley wrote:
I realize that dipoles are balanced antennas, but does the rig itself still need an RF ground too? (I know the radio always needs a DC ground, of course). How about if the dipole is being used as a non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER LINE--DIPOLE) -- would this affect the need for an RF ground on the rig for operation in the dipole's non-resonant bands? Or is no RF ground _at all_ required with a dipole; unlike when using random wires or verticals, and other such un-balanced antennas? Thanks! Bill Get a virtual earth! They are easy to build for all ham bands! It's basically a phasing unit for the earth connection which can null the voltage on the earth at the RF Rig! Cheers M0DFI |
Dipoles and the rig's RF ground...
ORIGINAL MESSAGE: On Mon, 02 Jan 2006 00:12:21 +0000, Dan Andersson wrote: This is best solved by a short ground cable to a proper ground rod. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No it isn't. It's best solved by keeping the RF out of the shack in the first place. Even if you could "ground" your RF, why would you want to run your RF through dirt? Is dirt a good antenna? 73, Bill W6WRT |
Dipoles and the rig's RF ground...
"billcalley" wrote in news:1136148463.132269.164130
@g49g2000cwa.googlegroups.com: I realize that dipoles are balanced antennas, but does the rig itself still need an RF ground too? (I know the radio always needs a DC ground, of course). How about if the dipole is being used as a non-loaded "all band" antenna (IE: RIG--TRANSMATCH--LADDER LINE--DIPOLE) -- would this affect the need for an RF ground on the rig for operation in the dipole's non-resonant bands? Or is no RF ground _at all_ required with a dipole; unlike when using random wires or verticals, and other such un-balanced antennas? If the antenna is TRULY balanced and the feedline dressed well away from it at right angles you should have no common-mode currents on the feedline. That's the ideal case and in that ideal case you need no RF ground at the radio. The ideal case, however, rarely ever exists in practice. And end-fed wires can be a whole different ball game. I had to use a 16 foot counterpoise once to "ground" a rig in a 2nd story location when I end-fed a very long wire with it. -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
Thanks Guys -- I really appreciate the clarifications on grounding! It sometimes gets a bit confusing for me. Best Regards, Bill |
Dipoles and the rig's RF ground...
Dave Oldridge wrote:
If the antenna is TRULY balanced and the feedline dressed well away from it at right angles you should have no common-mode currents on the feedline. . . . That only prevents one of the two ways common mode current can be created, by coupling. It can also be created by conduction. A common example is a coax-fed dipole, where the current in the outer feedline conductor splits between the antenna conductor and the outside of the coax. An equivalent problem can occur when a dipole is fed with symmetrical line such as ladder line, and one conductor of the line is connected to the rig's chassis at the rig end. The current on the inside of the chassis is equal to the current from the "hot" conductor, and this splits between the transmission line conductor and the outside of the chassis. A detailed explanation of conducted common mode current can be found at http://eznec.com/Amateur/Articles/Baluns.pdf. Roy Lewallen, W7EL |
Dipoles and the rig's RF ground...
Roy Lewallen wrote in
: Dave Oldridge wrote: If the antenna is TRULY balanced and the feedline dressed well away from it at right angles you should have no common-mode currents on the feedline. . . . That only prevents one of the two ways common mode current can be created, by coupling. It can also be created by conduction. A common example is a coax-fed dipole, where the current in the outer feedline conductor splits between the antenna conductor and the outside of the coax. An equivalent problem can occur when a dipole is fed with symmetrical line such as ladder line, and one conductor of the line is connected to the rig's chassis at the rig end. The current on the inside of the chassis is equal to the current from the "hot" conductor, and this splits between the transmission line conductor and the outside of the chassis. A detailed explanation of conducted common mode current can be found at http://eznec.com/Amateur/Articles/Baluns.pdf. Roy Lewallen, W7EL Still, if the antenna is TRULY balanced (a situation that only rarely actually happens), you won't get common-mode currents. I've never had a problem with them with well-grounded (from an RF standpoint) ground- mounted verticals either. Essentially this is why I recommend using open wire or twinlead and feeding it through a proper balanced-line tuner. Years ago, I built an amplifier that literally had a balanced line output and fed a 600-ohm feeder direct off two taps on its output coil. That feedline was only ten feet long and I worked a TON of 80m DX an the inverted vee that it connected to. And I could always tap the coil so as to have ZERO RF in the shack (though my landlady's little 7.5 watt light bulbs used to light on some frequencies when the house wiring picked up direct from the antenna). -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
Is it not true that if the currents on the transmission line are unbalanced
(i.e., unequal on the two conductors) then the transmitter must already be connected to ground? If not, what is the path of the differential current? Chuck Dave Oldridge wrote: Roy Lewallen wrote in : Dave Oldridge wrote: If the antenna is TRULY balanced and the feedline dressed well away from it at right angles you should have no common-mode currents on the feedline. . . . That only prevents one of the two ways common mode current can be created, by coupling. It can also be created by conduction. A common example is a coax-fed dipole, where the current in the outer feedline conductor splits between the antenna conductor and the outside of the coax. An equivalent problem can occur when a dipole is fed with symmetrical line such as ladder line, and one conductor of the line is connected to the rig's chassis at the rig end. The current on the inside of the chassis is equal to the current from the "hot" conductor, and this splits between the transmission line conductor and the outside of the chassis. A detailed explanation of conducted common mode current can be found at http://eznec.com/Amateur/Articles/Baluns.pdf. Roy Lewallen, W7EL Still, if the antenna is TRULY balanced (a situation that only rarely actually happens), you won't get common-mode currents. I've never had a problem with them with well-grounded (from an RF standpoint) ground- mounted verticals either. Essentially this is why I recommend using open wire or twinlead and feeding it through a proper balanced-line tuner. Years ago, I built an amplifier that literally had a balanced line output and fed a 600-ohm feeder direct off two taps on its output coil. That feedline was only ten feet long and I worked a TON of 80m DX an the inverted vee that it connected to. And I could always tap the coil so as to have ZERO RF in the shack (though my landlady's little 7.5 watt light bulbs used to light on some frequencies when the house wiring picked up direct from the antenna). |
Dipoles and the rig's RF ground...
On Tue, 03 Jan 2006 16:24:01 GMT, chuck wrote:
Is it not true that if the currents on the transmission line are unbalanced (i.e., unequal on the two conductors) then the transmitter must already be connected to ground? If not, what is the path of the differential current? Chuck Think about it. If there is no path there would be no current! Danny, K6MHE email: k6mheatarrldotnet http://www.k6mhe.com/ |
Dipoles and the rig's RF ground...
Dave Oldridge wrote:
Still, if the antenna is TRULY balanced (a situation that only rarely actually happens), you won't get common-mode currents. That's true only if by "balanced" you mean that the two feedline conductors carry equal and opposite currents. In that case, common mode current is zero by definition. But if you really mean symmetrical, as most amateurs do when they say "balanced", you certainly can have common mode current. A detailed explanation of how that happens is in the article at http://eznec.com/Amateur/Articles/Baluns.pdf, and the article by Walt Maxwell, W2DU at http://www.w2du/r2ch21.pdf which is referenced at the end of the first article? Note particularly figures 3 and 4 of the Baluns.pdf article. I've never had a problem with them with well-grounded (from an RF standpoint) ground- mounted verticals either. The reason this provides balanced feedline currents is that the impedance to ground at the base of the antenna is much less than the impedance looking back from the feedpoint down along the outside of the feedline. Consequently, the large majority of the current from the inside of the coax shield flows to ground rather than down the outside of the coax. And laying the coax on the ground keeps coupled common mode current down. Essentially this is why I recommend using open wire or twinlead and feeding it through a proper balanced-line tuner. That combination will produce a truly balanced system with no common mode current. But it's not the only way. . . . Years ago, I built an amplifier that literally had a balanced line output and fed a 600-ohm feeder direct off two taps on its output coil. That feedline was only ten feet long and I worked a TON of 80m DX an the inverted vee that it connected to. And I could always tap the coil so as to have ZERO RF in the shack (though my landlady's little 7.5 watt light bulbs used to light on some frequencies when the house wiring picked up direct from the antenna). |
Dipoles and the rig's RF ground...
chuck wrote:
Is it not true that if the currents on the transmission line are unbalanced (i.e., unequal on the two conductors) then the transmitter must already be connected to ground? If not, what is the path of the differential current? Your thinking is correct. If you had a small, battery operated rig, you could theoretically force current balance by completely isolating it from ground. You might burn yourself when you touch it, though. In practice, differential current can flow to ground via capacitive coupling from the rig to ground, or by flowing onto any connecting wires such as power supply, speaker, or key leads, which will radiate. Common mode feedline current is generally sinusoidally distributed. So you can have a relatively small common mode current at the rig but a much larger one at places on the feedline, if the rig happens to fall at a common mode current node. When the current is due to coupling, a single balun will be ineffective if placed at a natural current node, or in some other cases will only change the distribution by moving the node, rather than reducing the overall current. In those cases, two baluns placed about a quarter wavelength apart are effective. Roy Lewallen, W7EL |
Dipoles and the rig's RF ground...
chuck wrote in
nk.net: Is it not true that if the currents on the transmission line are unbalanced (i.e., unequal on the two conductors) then the transmitter must already be connected to ground? If not, what is the path of the differential current? There's the rub, you see. It's RF and, on some frequencies, standing waves don't NEED to feed current to a ground for there to be common mode currents on the line. But yes, whatever current is required at the end of the transmission line will seek to ground itself through the radio. My amp had the output coil center-tapped to RF ground and the feedlines were tapped off it an equal amount on either side. -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
Roy Lewallen wrote in
: Dave Oldridge wrote: Still, if the antenna is TRULY balanced (a situation that only rarely actually happens), you won't get common-mode currents. That's true only if by "balanced" you mean that the two feedline conductors carry equal and opposite currents. In that case, common mode current is zero by definition. But if you really mean symmetrical, as most amateurs do when they say "balanced", you certainly can have common mode current. No, I mean ELECTRICALLY balanced. And with the feedline at right angles to the antenna so that it doesn't pick up anything by induction. It's a tricky thing to do, yet back in the old days hams used to feed dipoles or extended double zepp antennas with open wire line and not get much RF in the shack. I know mine didn't. I was putting nearly 700 watts into the antenna and you could touch the amp chassis without any RF burns. Didn't have the fancy tools I have now for testing things, but still managed a good, clean and loud CW signal from an angled dipole. Worked a lot of DX on 75 with that antenna, including a nightly sked with Midway Is. for traffic (from Vancouver, BC.). -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
No, I mean ELECTRICALLY balanced. And with the feedline at right angles to the antenna so that it doesn't pick up anything by induction. It's a tricky thing to do, yet back in the old days hams used to feed dipoles or extended double zepp antennas with open wire line and not get much RF in the shack. I know mine didn't. Ran a Windom in Texas in 1965 (WA5KBO) with only 150W and burned a hole in my lip (no joke) with the RF on the metal ring around the microphone! The Windom was a good performer, but I could not effectively ground the rig. I was in student housing (College Station) and was not allowed antennas but improvised! |
Dipoles and the rig's RF ground...
rf 'ground' is a real misunderstood thing. and things like this point out
just how poorly understood it is. there is really no need for a radio to be 'grounded' to prevent rf burns or to have an antenna work properly... the important thing is to remember that at that point where the rf leaves the radio on the center conductor of the coax connector the current there must be exactly balanced by a current going the opposite direction the inside of the shield of the coax connector. looking at the worst possible case, just stick a random wire in the coax connector and run the rig off a battery with a short cable and no other 'ground' wire. current flows out the center conductor of the connector into the exposed wire and somehow has to get back to the inside of the connector shell to balance it out... well, the only place for that current to come from is coupling from the antenna wire back onto the case of the radio and from there it flows back into the connector. now, put your hand on a metal part of the radio, or your lip if you are unlucky, and what happens?? you are much bigger than the case of the radio and you are fairly conductive, so now you provide a bigger collector for the current from the antenna so lots of it flows through you to get back to the radio connector... hence rf burns. how to stop it?? provide a lower impedance path for the rf to get back to the connector than through you. that can be a counterpoise wire, a 'ground' wire that collects current from the soil under the antenna, connect the case of the radio to your car and the car becomes the collector... OR add an equal sized second wire that 'balances' the current from the wire in the center conductor... the critical point is that it mut be very nearly identical to the first one so the current in it is the same... a dipole that is symetric with respect to the feed point will work, but you have to watch out because the case of the radio is connected to the coax connector also, which tends to unbalance the equation since there is no equivalent lump of metal on the center conductor part of the antenna. to make this job of balancing the currents easier we normally add a length of coax (to get the antenna farther away from the radio) then add a balun to help force the currents in the two halves of the dipoles to be equal so there is no need for current to flow from the radio back into the inside of the shield. a choke on the outside of the feedline also can help, but the reason is different... a choke on the coax creates a very high impedance so that current has a hard time flowing from the case of the radio or outside of the coax back to the inside of the coax. enough rambling, just remember, rf ground is a myth, all you need to do is get those currents equal while preventing the path where they flow from being through you or something else that could be damaged by them. "Charles Schuler" wrote in message . .. No, I mean ELECTRICALLY balanced. And with the feedline at right angles to the antenna so that it doesn't pick up anything by induction. It's a tricky thing to do, yet back in the old days hams used to feed dipoles or extended double zepp antennas with open wire line and not get much RF in the shack. I know mine didn't. Ran a Windom in Texas in 1965 (WA5KBO) with only 150W and burned a hole in my lip (no joke) with the RF on the metal ring around the microphone! The Windom was a good performer, but I could not effectively ground the rig. I was in student housing (College Station) and was not allowed antennas but improvised! |
Dipoles and the rig's RF ground...
Charles Schuler wrote:
Ran a Windom in Texas in 1965 (WA5KBO) with only 150W and burned a hole in my lip (no joke) with the RF on the metal ring around the microphone! The Windom was a good performer, but I could not effectively ground the rig. I was in student housing (College Station) and was not allowed antennas but improvised! Dang Charles, I did exactly the same thing in 1957. If you had asked me, I would have told you to watch out for those metal microphones when using a Windom. -- 73, Cecil http://www.qsl.net/w5dxp |
Dipoles and the rig's RF ground...
Dang Charles, I did exactly the same thing in 1957. If you had asked me, I would have told you to watch out for those metal microphones when using a Windom. I only made that mistake once! That burn was very slow to heal, by the way. I clearly understood several principles after that. Close-talking the mic and over-modulation was the least of them. |
Dipoles and the rig's RF ground...
"Charles Schuler" wrote in
: No, I mean ELECTRICALLY balanced. And with the feedline at right angles to the antenna so that it doesn't pick up anything by induction. It's a tricky thing to do, yet back in the old days hams used to feed dipoles or extended double zepp antennas with open wire line and not get much RF in the shack. I know mine didn't. Ran a Windom in Texas in 1965 (WA5KBO) with only 150W and burned a hole in my lip (no joke) with the RF on the metal ring around the microphone! The Windom was a good performer, but I could not effectively ground the rig. I was in student housing (College Station) and was not allowed antennas but improvised! A true windom with a single wire feed, or one of the latter-day kind with twinlead? -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
"Charles Schuler" wrote in
: Dang Charles, I did exactly the same thing in 1957. If you had asked me, I would have told you to watch out for those metal microphones when using a Windom. I only made that mistake once! That burn was very slow to heal, by the way. I clearly understood several principles after that. Close-talking the mic and over-modulation was the least of them. This is where those artificial ground things come in handy. But the end of the counterpoise needs to be where it can do no harm, as that's where the artificial ground sticks the voltage. -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
A true windom with a single wire feed, or one of the latter-day kind with twinlead? Single wire feed. I was a student (living off of my wife) and used what I could get my hands on. |
Dipoles and the rig's RF ground...
Single wire feed. I was a student (living off of my wife) and used
what I could get my hands on. ======================================= A true radio amateur! Just get a random, bent wire into the air. A single-wire feed helps a lot. With a modest ground and a simple tuner you have an efficient, multi-band, go-anywhere antenna system you can be proud of. Anybody who boasts about his G5RV has never tried anything else. ---- Reg. |
Dipoles and the rig's RF ground...
On Mon, 9 Jan 2006 22:29:58 +0000 (UTC), "Reg Edwards"
wrote: Anybody who boasts about his G5RV has never tried anything else. Sounds like the text for a bumper sticker! Owen -- |
Dipoles and the rig's RF ground...
"Reg Edwards" wrote Single wire feed. I was a student (living off of my wife) and used what I could get my hands on. ======================================= A true radio amateur! Just get a random, bent wire into the air. A single-wire feed helps a lot. With a modest ground and a simple tuner you have an efficient, multi-band, go-anywhere antenna system you can be proud of. Anybody who boasts about his G5RV has never tried anything else. Right.....you should hear the bands open up when you launch a kite antenna. There's nothing like a few hundred feet of random long wire up in the air. ;-) WARNING: No one should ever do such a thing for what should be very obvious safety reasons. I'm a big fan of cubical quads, but you need allot of room for them. I'd take one over a yagi any day. I built a two element quad for 10 meters using bamboo fishing poles for the spreaders. The boom was made from cedar. It lasted about three years before a flying tree limb took it out. I also made an 8 element quad for 2 meters using 1/2" poplar dowel rod spreaders and a wooden boom as well. Man was that thing hard to tune. Weird things happen after the fifth element is added for some reason. Might explain why most have only 4 elements. ;-) Seriously, it really kicked ass but the tornadic storm took it out too. I'll not be making another with that many elements, too fussy but extremely narrow beam w/incredible back side rejection. |
Dipoles and the rig's RF ground...
Reg Edwards wrote:
Anybody who boasts about his G5RV has never tried anything else. Reg, I replaced my 130 ft. dipole with a G5RV so I could experiment with it. Given my modifications, Nobody can tell it from the 130 ft. dipole so there's no reason to return to the 130 ft. dipole. My G5RV has an SWR of less than 2:1 on all eight HF bands. -- 73, Cecil http://www.qsl.net/w5dxp |
Dipoles and the rig's RF ground...
"Cecil Moore" wrote My G5RV has an SWR of less than 2:1 on all eight HF bands. ========================================= The CIA W.M.D. department must have told you that naughty fib. The SWR on your 380-ohm transmission line to the antenna is umpteen times greater than that! Isn't it time you changed the name of your SWR meter? ---- Reg. |
Dipoles and the rig's RF ground...
Reg Edwards wrote:
"Cecil Moore" wrote My G5RV has an SWR of less than 2:1 on all eight HF bands. The SWR on your 380-ohm transmission line to the antenna is umpteen times greater than that! I'm not talking about SWR on the series section transformer, Reg, I'm talking about on the 50 feet of RG-213. And it's not "umpteen times", rather limited to about ten times. Isn't it time you changed the name of your SWR meter? Nope, for a G5RV with the nominal 70 feet of 50 ohm coax, the SWR meter is indeed reading the SWR on the coax. Remember, I'm not using a tuner. The coax from the G5RV goes directly to the transceiver through the SWR meter. I actually use my SWR meter to display the SWR. -- 73, Cecil http://www.qsl.net/w5dxp |
Dipoles and the rig's RF ground...
I have both a 130 foot dipole and a G5RV, I can switch between the two and
the reports are exactly the same on 75. With 100 watts on the G5RV I have worked well over 100 countries on SSB 75 meters. The day I received the Olivia for my mix w, worked Russia on it with 5 watts on 20 meters. I use it nightly on my Navy Mars nets in the 3 Mhz area. Like the 130 foot dipole I vary the feed line length to tune. Both feedlines are fed from the rig to the ladderline with coax covered with ferrite beads at the junction end. "Cecil Moore" wrote in message et... Reg Edwards wrote: Anybody who boasts about his G5RV has never tried anything else. Reg, I replaced my 130 ft. dipole with a G5RV so I could experiment with it. Given my modifications, Nobody can tell it from the 130 ft. dipole so there's no reason to return to the 130 ft. dipole. My G5RV has an SWR of less than 2:1 on all eight HF bands. -- 73, Cecil http://www.qsl.net/w5dxp |
Dipoles and the rig's RF ground...
"Cecil Moore" wrote in message om... Reg Edwards wrote: "Cecil Moore" wrote My G5RV has an SWR of less than 2:1 on all eight HF bands. The SWR on your 380-ohm transmission line to the antenna is umpteen times greater than that! I'm not talking about SWR on the series section transformer, Reg, I'm talking about on the 50 feet of RG-213. And it's not "umpteen times", rather limited to about ten times. Isn't it time you changed the name of your SWR meter? Nope, for a G5RV with the nominal 70 feet of 50 ohm coax, the SWR meter is indeed reading the SWR on the coax. Remember, I'm not using a tuner. The coax from the G5RV goes directly to the transceiver through the SWR meter. I actually use my SWR meter to display the SWR. -- 73, Cecil http://www.qsl.net/w5dxp ======================================= I see you are happy to change names when in a tight corner. The name "Transmission line" has been conveniently changed to "Series Section Transformer". But it still has standing waves on it far higher than what you claim for all bands. And don't standing waves increase loss on SST's just as much as they do on transmission lines? Louis is turning over in his grave - yet again. But what the heck? A G5RV will work even if you havn't got one. I once set up an 80 feet dipole without a series section transformer. Unsurprisingly - it worked. ;o) ---- Reg. |
Dipoles and the rig's RF ground...
Reg Edwards wrote:
The name "Transmission line" has been conveniently changed to "Series Section Transformer". But it still has standing waves on it far higher than what you claim for all bands. And don't standing waves increase loss on SST's just as much as they do on transmission lines? As you know, standing waves increase loss on SST's just as much as they do on transmission lines *OF THE SAME LENGTH*. For instance, on 3.8 MHz, that 300 ohm series section transformer on a G5RV has an SWR of about 20:1 and a line loss of about 0.7 dB, about 12% of one S-unit. That's a small price to pay for multi-band operation. And using Wireman #554 (like I do) instead of 300 ohm twinlead will cut those SST losses down to 0.37 dB, about 6% of an S-unit. I once set up an 80 feet dipole without a series section transformer. Unsurprisingly - it worked. ;o) If you fed it with ladder-line, you fed it with a long series section transformer. :-) -- 73, Cecil http://www.qsl.net/w5dxp |
Dipoles and the rig's RF ground...
"Cecil Moore" wrote If you fed it with ladder-line, you fed it with a long series section transformer. :-) ========================================= .. . . . and your SWR meter is not an SWR meter - it is a transmitter loading indicator. ;o) Go on then - call me a copy cat! ---- Reg. |
Dipoles and the rig's RF ground...
I have both a 130 foot dipole and a G5RV, I can switch between the two and
the reports are exactly the same on 75. With 100 watts on the G5RV I have worked well over 100 countries on SSB 75 meters. The day I received the Olivia for my mix w, worked Russia on it with 5 watts on 20 meters. I use it nightly on my Navy Mars nets in the 3 Mhz area. Like the 130 foot dipole I vary the feed line length to tune. Hummmmm.......... :/ Both feedlines are fed from the rig to the ladderline with coax covered with ferrite beads at the junction end. Try the 130 ft dipole fed with straight coax and see if you don't see a difference then. Sure, it won't be huge, but it should be there, and be quite noticable too on a receiver. I think this why you are seeing no difference. . You are "clutter" feeding both antennas. :/ Seriously. Coax to ladderline...yuk...:/ But saying that, it's obvious it works well nuff I suppose.. I just like to stir it. It's been too slow around here lately. But...I am serious about what I say.. If you want the vurry best 80m dipole, feed it with nuttin but coax. MK |
Dipoles and the rig's RF ground...
On Sat, 07 Jan 2006 23:51:47 +0000, Dave wrote:
rf 'ground' is a real misunderstood thing. and things like this point out just how poorly understood it is. [snip] Broken shift key, huh? -- Flap! The Pig Bladder from Uranus, still waiting for that hot babe to ask what my favorite planet is. ;-j |
Dipoles and the rig's RF ground...
"Reg Edwards" wrote in news:dpuo55$isc$1
@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com: Single wire feed. I was a student (living off of my wife) and used what I could get my hands on. ======================================= A true radio amateur! Just get a random, bent wire into the air. A single-wire feed helps a lot. With a modest ground and a simple tuner you have an efficient, multi-band, go-anywhere antenna system you can be proud of. Anybody who boasts about his G5RV has never tried anything else. Well, I'll put the system I started to design last night up against most other 80m antennas. But it won't be cheap to build. Needs 8 165-foot towers, and a bunch of phase delay networks and some power dividers. :-P But the gain over ordinary ground works to between 9.5 and 10.5 dbi depending on the direction favoured by the phasing networks. -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
"Anthony Fremont" wrote in news:FZBwf.39022$9e.30720
@tornado.texas.rr.com: "Reg Edwards" wrote Single wire feed. I was a student (living off of my wife) and used what I could get my hands on. ======================================= A true radio amateur! Just get a random, bent wire into the air. A single-wire feed helps a lot. With a modest ground and a simple tuner you have an efficient, multi-band, go-anywhere antenna system you can be proud of. Anybody who boasts about his G5RV has never tried anything else. Right.....you should hear the bands open up when you launch a kite antenna. There's nothing like a few hundred feet of random long wire up in the air. ;-) WARNING: No one should ever do such a thing for what should be very obvious safety reasons. I'm a big fan of cubical quads, but you need allot of room for them. I swear OH8OS used to MAKE his own band openings or 15 back in 65 when I used to work him from VE8ML. He had a huge quad, 15 elements, I think, pointed right in my direction. -- Dave Oldridge+ ICQ 1800667 |
Dipoles and the rig's RF ground...
"Fred W4JLE" wrote in
: I have both a 130 foot dipole and a G5RV, I can switch between the two and the reports are exactly the same on 75. With 100 watts on the G5RV I have worked well over 100 countries on SSB 75 meters. The day I received the Olivia for my mix w, worked Russia on it with 5 watts on 20 meters. I use it nightly on my Navy Mars nets in the 3 Mhz area. Like the 130 foot dipole I vary the feed line length to tune. Both feedlines are fed from the rig to the ladderline with coax covered with ferrite beads at the junction end. "Cecil Moore" wrote in message et... Reg Edwards wrote: Anybody who boasts about his G5RV has never tried anything else. Reg, I replaced my 130 ft. dipole with a G5RV so I could experiment with it. Given my modifications, Nobody can tell it from the 130 ft. dipole so there's no reason to return to the 130 ft. dipole. My G5RV has an SWR of less than 2:1 on all eight HF bands. There's nothing wrong with a G5RV if you couple power to its radiating element efficiently. I usually just don't bother with the coax part of the feed system and prefer to just run 300 ohm (or better yet 450 ohm) line right to the shack and feed it through a tuner. -- Dave Oldridge+ ICQ 1800667 |
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