Okay, here is the challenge: what is the most efficient antenna for QRP portable. Why? How? For me, a resonant doublet that has no common mode gets the signal out. This has meant getting the feedline length right. I optimize height for the frequency, 32-33'. What do you say? If you use coax, how do you determine feedline length if you use an antenna analyzer, or, do you use a balun or a 1:1 common mode balun and call it good?
that is a good question... At the moment, I'm studying and experimenting with just that issue, and haven't reached any firm conclusions yet. It is important when discussing "most efficient" to work with objective measurements of some sort, like SWR, Field Strength, Published Data, and so forth.... so we have an objective way to compare our results and avoid basing our future antenna set-ups on opinions that may or may not be substantiated in fact. One thing I'm seeing is a strong reliance on the number of QSOs as a measure of an antenna's quality. While that may be an indicator of sorts, it also may not be. A few weeks ago I made 20+ QRP QSOs in two hours using a Hamstick duct-taped to a camera tripod. While it did make good QSOs on that day, I really doubt it was a very efficient radiator.... it was just a good radio day. The other thing I'm curious about is the often-stated comment that Antenna Tuners cause a loss of signal strength. While it does seem to be a reasonable idea, I haven't been able to find any published data supporting it. If it DOES cause a loss.... which we as QRPers can't afford, how MUCH of a loss does it cause? A little or a lot? Dave KK4NSF
ahoy what band low or high, what i would use for 40 meter rag chew is not the same as what would use when 10 is hot and the DX is rolling in when, car camping or backpack hiking in camping, can you just take it out of the trunk and use it near the picknick table or are you going to carry it in 18 miles where, by the sea shore, in a forest with lots of tall trees or on a mountain top sea shore go for a vertical, in the woods use the trees, on mountain top lots of people go for metal self supporting jobs most efficient antenna for QRP is the same as the most efficient antenna for QRO well made and used antenna tuner causes negligible loss i use a tuner most all the time home and in the field have used most back pack camping end fed wire either as a bottom feed sloper, inverted L, inverted V, inverted U (depending on trees) with one or two wire counterpose on the ground beneath it to a simple tuner have also used a St. Louis vertical look it up it is a tried and tested QRP HB vertical last used it camp cruising a sailing dinghy with a tuner and IC-703 have played with dipoles, all kinds of verticals, a few store bought lashups and a kite antenna the kite antenna worked great it can be lots more work, often the wind and place is not right for kite work ( was a avid kite flyer still own a few dozen big kites ) keep going back to simple wire and tuner read book sellers need the business still in the stacks mac
are you sure we're not long-lost brothers? I've got several replica Weather Service kites that I've used to hoist up instruments and antennas. One of them even has an APRS system to relay it's altitude. Kite make great antenna supports when the wind is blowing.... until they get ~400 ft up or so. Then they get sort of static-y BbbbzzzzzzzzzAAAP
Antenna tuners just add inductance and/or capacitance in series and/or parallel with the antenna. An ideal inductor or capacitor can't produce any loss -- it dissipates no energy. Unfortunately, real antenna tuners are made of real inductors and real capacitors, and those things always have at least a little bit of real resistance associated with them. The amount of loss will have to do with the amount of resistance added. How much will it be? It's very hard to say, and the answer will depend on which inductors and/or capacitors are switched in the circuit for the particular antenna and band we're talking about. It may be negligible, or it may be enormous. The only thing we can say for certain is that it won't be zero. The losses in a tuner will be lower if the tuner doesn't have to switch in large inductance, nor high ESR capacitors. It'll be lower if the inductors are made with heavy gauge wire. It'll be lower if the inductors keep their cores well below saturation. If you can tune the antenna directly, by lengthening/shortening the elements, that's probably going to be more efficient than adding a tuner. That's often fairly practical for a temporary single-band operation. But a well-made tuner used well isn't necessarily going to add much loss, and it can provide greater flexibility.
ahoy i forgot were the weather service kites like the French military style kite a box shape with wings always need to ground the antenna use a big old RF choke from antenna to ground keeps the static charge from building up many years ago learned the hard way blew out the front end of a 509 Argonaut lucky the 509 Argo is very very easy to work on years ago was a member of the AKA nearly wore out a sewing machine making kites yours truly mac
oh on kites and antennas years and years ago Ozona Bob W5PY and a T (SK) a famed big time old buzzard AM OP some times used a kite antenna he lived outside Ozona Texas which is out in West nowhere by gosh Texas the wind would be steady for days on end one night all the receive signals dropped off the map and his transmitter went screwy the antenna and kite had broken loose dragging the antenna wire for a mile or so to a power sub station knocked out the power to Ozona Texas they never found out who did it Bob never used a kite antenna again dit dit mac
..some antenna tuners have a bypass. Is there a radio amateur that doesn't know great propagation or even good or fair propagation makes a fine day for amateur radio, and has very little to do with the "best" antenna, or not. Least loss. Most current at the feedpoint. I have heard these things. I am interested in objective and quantifiable knowledge, as well. Not only loss, but gain.
ahoy your question is not so much a QRP question but a antenna question your question may get more reply's posted in the antenna forum dit dit mac
Been there, done that. I was told to read a book. I think no one had an answer. However, QRP levels output makes the point doesn't it. I want to see straightforward answers online, anyone can get with an online search, rather than purchase books, CD's, DVD's and website memberships at the antenna websites like Cebik or antennaX.
