You need to install and tune a SINGLE BAND RESONANT ANTENNA.
Something like a coax fed 1/2 wave dipole, cut for 20Meters.
No balun,stub,extra wires,changing line lengths,coils,traps or any thing but a length of coax long enough to reach between the transmitter and the antenna, and 1/2 wavelength of center fed wire.
A simple, classic, dipole.
After you master a simple antenna, can you hope to have any success, or to know when you have obtained that success, with a multi-band, or compromise antenna.
Rege
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Much has been written, both pro and con, about the G5RV antenna. Research it to cut through hype & myth, and you'll find that it does the task it was designed for if installed as intended.
Just to make sure we're on the same page, I would define "the task it was designed for" as: "providing usable performance on the bands from 40m through 10m." Assuming you agree, how would you define "installed correctly?"
The reason I ask is that I am aiming for a more or less invisible antenna, and if both the Q5RV and the Shorty can provide "usable performance on multiple bands" then I could conceivable eliminate the bundle of interchangeable feed-line outside my window. Also, the distance from the feedpoint to my window is on the order of 15ft, so any additional twin-lead will have to be packaged in some way to keep it off the ground and I imagine simply folding or rolling it into a coil is probably counterproductive. I'm not actively trying to move away from the Shorty, but the extra 15ft of wire and even more feed-line are going to be quite hard to fit.
Quote:
Originally Posted by AI3V
You need to install and tune a SINGLE BAND RESONANT ANTENNA.
After you master a simple antenna, can you hope to have any success, or to know when you have obtained that success, with a multi-band, or compromise antenna.
Rege
Rege,
I completely understand your point about starting out with a simple, highly effective single band antenna and working my way up from there. However as this will be my first endeavor into HF, I am willing to compromise some degree of simplicity and performance in exchange for the ability to experiment with the different bands. Sure, my operating capacity will probably fall short of "If I can hear it I can work it," but only after I fumble around for a while to get my bearings will I be able to pick and choose the bands that I really want to hone. After that, I fully anticipate revamping whatever I decide on now (besides, building is half the fun).
Quote:
Originally Posted by AI3V
There is some incredibly bad info in this thread about changing the length of your transmission line to enable a transmitter to tune up.
This is obviously not my area of expertise so I'll leave this open for verification.
J I would define "the task it was designed for" as: "providing usable performance on the bands from 40m through 10m." Assuming you agree, how would you define "installed correctly?"
Part One: Disagree. The original design was about 102' and intended to provide gain on 20 meters. The characteristic balanced line matching section performed an impedance transformation that allowed direct connection to coax. The G5RV worked as intended on 20 meters (with about 2.5:1 SWR on the coax); all other bands had higher SWR, some bands much higher. It was subsequently discovered that the G5RV could be made to load on some bands other than 20 meters (multi-band, by definition).
Unfortunately, one crowd of "believers" misinterpreted multi-band to mean "all-band", so there's been a spate of whining that this multi-band antenna doesn't work on all bands like they expected. In contrast, another crowd judged it great because they "could work everything they could hear".
That situation brewed for a while, begging for a swarm of G5RV antenna modifications, and so it came to pass. Most of the mods still carried the G5RV moniker, no matter how far they departed from the original concept and dimensions. Enter the G5RV Jr. See this interesting link about the G5RV antenna for a more detailed explanation of what it is, and what it isn't.
Part Two: The G5RV (and G5RV Jr) should be installed high enough to permit the balanced line section to fall down & away from the antenna perpendicular to the antenna wire. That right angle should be maintained as the transmission line is drawn toward the building with just enough tension to keep the line out of reach from the ground. The same link I gave you earlier provides some specifics of G5RV feed line routing. For general guidance about feed line routing, you can google up a bushel full.
Part Three: I noted that Rege brought up a common misconception. He is totally correct that varying the length of transmission line does not alter the SWR on the line. Although I've read and re-read the posts in this thread, I can't find any statement or insinuation that changing transmission line length can change the SWR. Not before Rege's post, anyway; he was the first to mention it. Otherwise, cutting was always about impedance transformation except for one mention of trimming the antenna length to bring the SWR down.
Quote:
Originally Posted by AI3V
A VERY FEW antenna impedances- resistive only, no reactance allowed- can be corrected with lengths of line to 50+j0
If the added line is a different impedance than the existing line.
Well, I can't dispute Rege there; I can't even spell 50+j0 without copying it directly. I have, however, cut (and extended) mucho balanced line in search of an impedance that my transmatch(es) could handle. I have no idea what impedance I ultimately achieved; it worked so I used it. I was recommending the same to you because your TS-440SAT has an antenna tuner, meaning you probably won't need an impedance of 50+j0 - just get it close enough for the internal tuner to do its thing. No doubt Rege is right on the money, and that would be critical if the objective was to match that feed line to the output of a solid state transceiver with no tuner whatsoever.
Oddly enough, I have read some fine articles that outright say you can adjust the length of a balanced transmission line to match the impedance at the shack-end to the transmitter. Tuner not mentioned. Here's one article worth studying. It was published originally in the QRP Quarterly, July 2001 issue, and even cites Cecil's switched segments of balanced transmission line as an example.
It would be interesting to read a critical analysis of the assertions in that article, but my google search didn't turn up any rebuttals. Rege?
Regarding the dangling portion of Rege's comment quoted above: I don't think anyone spoke of correcting impedance by adding a different impedance than the existing line. I know my discussion was about adding segments of same-impedance balanced line (although I didn't specifically say so). 73
I completely understand your point about starting out with a simple, highly effective single band antenna and working my way up from there. However as this will be my first endeavor into HF, I am willing to compromise some degree of simplicity and performance in exchange for the ability to experiment with the different bands. Sure, my operating capacity will probably fall short of "If I can hear it I can work it," but only after I fumble around for a while to get my bearings will I be able to pick and choose the bands that I really want to hone. After that, I fully anticipate revamping whatever I decide on now (besides, building is half the fun).
Thatcher
And here is the problem.
You have no experience in HF, therefore you have no experience knowing when a antenna works, or not.
Good luck to you.
Rege
__________________
Now my mistakes travel at the speed of light!
I have, however, cut (and extended) mucho balanced line in search of an impedance that my transmatch(es) could handle. I have no idea what impedance I ultimately achieved;
So yo have at least 3 random variables here that you can adjust.
1-antenna impedance
2-length of feedline
3-antenna tuner.
And a whole bunch more variables you cannot:
Antenna impedance.
Impedance of the transmission line
Loss in said line due to VSWR
Tuning range of ATU
Loss in ATU
I put antenna impedance in both lists, because while you CAN change the antenna to go from the Oak tree to the Maple tree, You CANNOT really adjust it for any particular impedance.
Especially compromise, multi-band antennas.
You can either poke-and-hope (cut and try), or you can MEASURE the impedance, and DESIGN a matching solution.
Some of the solutions obtained by poke-and-hope will work, sorta kinda, if you mean turning the typical 100watt rig into a 2 watt radiated power rig. Very easy to do with a high VSWR on a long length of transmission line.
Quote:
it worked so I used it. I was recommending the same to you because your TS-440SAT has an antenna tuner, meaning you probably won't need an impedance of 50+j0 - just get it close enough for the internal tuner to do its thing. No doubt Rege is right on the money, and that would be critical if the objective was to match that feed line to the output of a solid state transceiver with no tuner whatsoever.
Oddly enough, I have read some fine articles that outright say you can adjust the length of a balanced transmission line to match the impedance at the shack-end to the transmitter. Tuner not mentioned. Here's one article worth studying. It was published originally in the QRP Quarterly, July 2001 issue, and even cites Cecil's switched segments of balanced transmission line as an example.
It would be interesting to read a critical analysis of the assertions in that article, but my google search didn't turn up any rebuttals. Rege?
Cecil did a fine job with that article, but he really glosses over how incredibly lucky he is in having an antenna that can be tuned with only a change in feedline length.
To oversimplify the matching issue, There are a infinite number of possible antenna impedances, that is the combination of resistance, and either inductive or capacitive reactance.
In order to be able transform any of the possible impedances to on that your transmitter is happy with requires at LEAST 2 variable elements .
That assumes that you are willing to re-arrange the 2 elements for some of the required solutions.
Think of a "L" network with a single coil and single capacitor, the coil and capacitor will have to be rewired depending on which 1/2 of the possible combinations of antenna impedance you have.
To match ANY possible impedance, WITHOUT having to rearrange the components in the ATU requires a MINIMUM of 3 variable elements.
You can use a change in transmission line length for 1 of the elements. as long as there is a standing wave on the line.
Anyway, it's well beyond the scope of a newbie who has never installed and used a simple Marconi (1/4 wave vertical) or a Hertz (1/2 wave dipole) to master all the numerous technical subtlety's of antenna impedance matching, and expect him to stumble on the correct combination of transmitter/ATU/Feedline/ and antenna. that works with reasonable efficiency.
Again, I urge the new guy to install a SIMPLE, BASIC, antenna for his first project.
Quote:
Gary, K9ZMD/6
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Now my mistakes travel at the speed of light!
Last edited by AI3V; 11-10-2009 at 03:45 PM.
Reason: pushed wrong button
It sounds like you can get a nice resonant 20m or even 30m dipole in there, or you can experiment and try other antennas and see what works. A buddy of mine is limited in the antenna he can put up at his location so all he has is a 20 meter dipole. He works plenty of stateside and DX with it. It doesn't get you on other bands, but hey, something is better than nothing.
There were other antennas suggested here as well. Try them if you like, and see what works! A 20m dipole will be the least expensive - no tuner needed and simple to put together. I started out a long time ago with a 40 meter resonant dipole, it also worked on 15. I've had inverted L's, 80m dipoles fed with ladder line, and my latest is as much wire as I could get into a loop in my attic fed with ladder line. I don't have the option of an outdoor antenna. Heck, I didn't even measure how much is up there in the attic - I just fed it into the tuner. I have a QSL card from VQ9LA from that and nearly 100 other countries - it must be working? It sounds like you have some options to experiment with.
It sounds like you can get a nice resonant 20m or even 30m dipole in there, or you can experiment and try other antennas and see what works. A buddy of mine is limited in the antenna he can put up at his location so all he has is a 20 meter dipole. He works plenty of stateside and DX with it. It doesn't get you on other bands, but hey, something is better than nothing.
There were other antennas suggested here as well. Try them if you like, and see what works! A 20m dipole will be the least expensive - no tuner needed and simple to put together. I started out a long time ago with a 40 meter resonant dipole, it also worked on 15. I've had inverted L's, 80m dipoles fed with ladder line, and my latest is as much wire as I could get into a loop in my attic fed with ladder line. I don't have the option of an outdoor antenna. Heck, I didn't even measure how much is up there in the attic - I just fed it into the tuner. I have a QSL card from VQ9LA from that and nearly 100 other countries - it must be working? It sounds like you have some options to experiment with.
Nice DX catch, I was VQ9AA from 1980-1981.
I was there to maintain the NAVY HF relay transmitters and antennas on the island.
Antenna included rhombics pointed at Alice Springs, Australia, rotateable log periodic Yagi's for 4-30 mhz, and a couple hundred acres of assorted wire antennas, mostly inverted discones for tx and various sector LPA's for receive.
Ham station was a little peanut whistle, just a pair of 3-500's and a little 4-el Yagi at 50'.
Rege
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Now my mistakes travel at the speed of light!
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