Wich is the best 160m antenna ?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by CU3AK, Aug 20, 2010.

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  1. N9AAT

    N9AAT Ham Member QRZ Page

    I'm pondering the same thing ... getting on 160. One of the problematic things about 160 is that you usually only get a small portion of the band on a wire antenna unless you use a remote antenna tuner at the terminals.

    So, I'm also pondering a very "controversial" antenna, the TFD (terminated folded dipole). Lotsa people have loaded lots of criticism on the TFD because it has a terminating resistor that absorbs the load when you're off frequency, BUT it makes your rig run nice and cool AND it only needs one center support AND you don't need a tuner.

    Interstingly, Rohde and Schwarz, a company I've had a long history with in the military, usually sells very good stuff. Check out http://www2.rohde-schwarz.com/en/products/radiomonitoring/antennas/HD420.html

    Not that I would BUY one of these babies, it's a portable anyway, but it looks like a great design and there are lots of web postings with formulas, suggestions for making your own, which is what I'm planning to do.

    Apparently, the non-reactive resistor where the loop joins together has a lot to do with performance, and how much power you can feed the thing. I'm going to put mine up with a pulley system so I can play around with resistors easily.
     
  2. K9STH

    K9STH Ham Member Staff Member QRZ Page

    A T2FD antenna will have very little efficiency on 160 meters. How much power the antenna can "handle" is dependent on the wattage of the load resistor.

    The military uses T2FD antennas a lot. However, they are also usually operating on frequencies where there is little interference and they also run power levels that "make up for" the poor efficiency of the antenna.

    Glen, K9STH
     
  3. N9AAT

    N9AAT Ham Member QRZ Page

    Agreed. The TFD is inefficient away from the cut resonant frequency. But how about if I use it where I cut it? I know that off-frequency the thing is nothing but a big resistor in the air, but at least the PA is happy. I know it's not the holy grail, but then ... what is?
     
  4. K9STH

    K9STH Ham Member Staff Member QRZ Page

    If you use it on the frequency for which it is cut then you don't need the resistor! It is just no more than a regular folded dipole which will have a feed point impedance somewhere near 300 ohms. You can use a 4:1 balun and feed the antenna with 75 ohm coaxial cable. Or, you can use 300 ohm balanced feed line and then use a "tuner" at the transmitter end.

    If you use 14 gauge or heavier wire then the antenna can definitely take full legal power. Probably could use 16 gauge and possibly 18 gauge wire and still be able to run full legal power.

    Glen, K9STH
     
  5. PA1ZP

    PA1ZP Ham Member QRZ Page

    Hi Everybody

    this question is not so easely answered as it seams.
    W8JI says vertical.
    But I think that a proper rotary dipole on 1 wavelength high or higher even will perform better, a 5 elements yagi even will do better as the dipole.

    That was just kidding I know that those antenne's are not affordable for most of us.

    I think that a vertical antenne of at least 1/8 wave with toploading or inverted-L or full size vertical will do nicely for TX.
    On RX you could concider all other antenne's you allready have.
    K9YA RX loop could be a fine RX antenna.

    For TX antennas the rule is very simpel use that antenna that will produce the strongest possible signal at the station that you want to work.

    Fer RX The demands are very different, you want use the antenna that will give you the greatest signal to noise ratio.

    On some occasions that can be any of the other antenna's you have or can switch to.


    RX performance also will be greatly influenced by your living area.
    I live in a city and here in PA almost everybody has ADSL LED lights switching power supply's plasma TV's LCD TV's with cheap switching power supplies etc.
    Every thing that can destroy the RX of a radio amateur.

    There is one thing I always do since a few years, I always look at radiation patterns produced by the antenne in simulation.
    I used to do that with MMANA-GAL, but I found that MMANA-GAL made enormes foults in patterns when were trying to develope and buil and use half wave vertical phased arrays fed and phased with open wire only.
    These portable vertical arrays were both tried and tested on 20 mtr and 40 mtr.

    Since then I use another program and that is called 4NEC2(x) , it is aldo freeware and doesn't make the trouble that MMANA-GAL gave me.
    But I have to say that MMANA-GAL is much more easy to learn and use.
     
    Last edited: Aug 21, 2010
    PS7MW and K8PG like this.
  6. K8JD

    K8JD Ham Member QRZ Page

    I have made more contacts and had better signal reports with a 160M half wave dipole I finally put up a few years ago than with any shortened inv "L" or any thing I have tried in all the years before. (Back to the late '60s)
     
  7. N9AAT

    N9AAT Ham Member QRZ Page

    I guess it all depends on what you want to do.

    Have heard some good reviews lately on skywave loop antennas being used in noisy areas, especially with balanced tuners and fed with window line. In limited space, just put up as much wire as you can as high as you can and hope for the best. Coax cable also works if you have a remote tuner that can live up at the feed-point. Of course any horizontal wire antenna however can be problematic in areas prone to lots of ice build-up, and you certainly don't want the thing to be able to come down across a power line.

    Glen, not to belabor the point but the point of having the resistor on a TFD (to me at least) is just to keep my finals happy. And yes, I hate tuners. I'm like King Arthur who told his Knights of the Skywave Loop not to come back without an antenna that can tune DC to daylight with a low SWR. Who cares if it radiates a signal or burns it up in a big-ole resistor. I just don't want it coming back down into my rig.

    Hi.
     
  8. W0BTU

    W0BTU Ham Member QRZ Page

    This question IS easily answered, and W8JI answered it right on. Lots of others suggested using dipoles and other horizontally polarized antennas as transmit antennas. However, if a horizontal antenna produced the best signal, then AM broadcast stations -- which are just below the 160 meter band and have the same requirements and propagation characteristics as 160 -- would be using them.

    For a transmitting antenna on 160 meters, a quarter-wave vertical (or an array of them, properly phased) is best, but a very good and far less expensive alternative is an inverted-L. Make the vertical portion of the inverted-L as high as possible, and absolutely put down a good array of radial wires on the ground. (But don't use it for receiving; instead, use a Beverage, a loop [such as the K9AY loop], or dipole, in that order.)
     
  9. W8JI

    W8JI Ham Member QRZ Page

    We have to stay in the real world of how antennas work. :)

    Any low horizontal wire has high earth losses. The longer it is the greater earth losses are.

    Conductor losses also come in play on 160, because the antenna is so long. The longer the conductor path, the greater the losses.

    Rhombic antennas, the favorite of many people because they are so large, are really very low efficiency on lower bands. This is because of the conductor losses, earth losses below the antenna, termination losses, and because the pattern splits into many wasteful minor lobes. You can see some analysis of Rhombics here: http://www.w8ji.com/rhombic_antennas.htm

    Note the gain analysis I did agree with multiple other sources, and with engineering data from antenna test ranges, so I am not cooking any data.

    A Beverage, while it can transmit, generally has a gain of -10 dBi. It is comparable to a good mobile antenna or a Gap Vertical on 160. I have worked Europe on 160 SSB from my mobile, and Japan and Australia (10,000 miles) many times with either a mobile on the other end, or me in my mobile.

    The fact DX is worked does not mean the antenna is high efficiency, or even reasonable efficiency. Some extremely poor antennas will work DX.

    Then we have that T2FD dipole, that if normal size is about -20 db gain on 160. If optimized to 250 feet long, it would probably be 0 dBi gain or less.

    Or someone can put up an 1/8th wave tall Inverted L vertical, cover nearly the whole band, and be S-units ahead of any low dipole or makeshift antenna for any distance local groundwave, or over a few hundred miles. It does require a GOOD ground system, but once installed a good ground system is a lifetime investment for better performance of any future antennas.

    We used to spend hours on 160 horse-racing, and my friend's 70 foot tall Inverted L would nearly tie my 130 foot tower with 100 radials at any distance. His 70 foot high L would beat another friend's 70 foot high dipole by a few S units at 2500 miles, and equal or beat the dipole anyplace else. there almost never was a case where the dipole beat anything except at about 50-100 miles distance.

    At my own QTH, I have a dipole 300 feet high. I have a 220 foot tall vertical, and a four square. In hundreds of tests, the 300 foot high dipole very rarely beats my vertical. It rarely beats an Inverted L 80 feet tall.

    This type of behavior is well known among serious 160 ops, and what nearly all serious ops use a good Inverted L or vertical antenna for transmitting.

    As for receiving, gain does not matter much at all. Only pattern matters. A beverage has a good pattern,even though it has very low gain (negative gain).
    That is why a Beverage, with very high loss, works so well for receiving.

    Anyone serious should get Low-Band DXing by ON4UN.

    73 Tom
     
  10. W8JI

    W8JI Ham Member QRZ Page

    that's true.

    Then transmit on all your antennas with a dummy load in parallel with the antennas. After all, that's all a T2FD is. It's a somewhat close equal of a dummy load in parallel with a dipole antenna.

    :)

    73 Tom
     
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