HF End-Fed Multiband that works well

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KK4NSF, Aug 12, 2019.

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  1. KK4NSF

    KK4NSF Ham Member QRZ Page

    Oddly, none of the above "quotes" are relevent to the random length, end-fed antenna discussion of the original posting.... and appear to be nothing more than trolling BS, and the product of a curmudgeon.

    As far as my antenna goes, it follows the ARRL Antenna Book, section 10.1 (in the 22nd Edition) very closely, which describes using a good ground, and offers a counterpoise as an alternative. If you have a problem with what they say, or if you don't like tuners, there's not much I can do about that. Take it up with them..... and please stop being such a stick-in-the-mud.
     
  2. KK4NSF

    KK4NSF Ham Member QRZ Page

    Yes, that was added as a clarification in the earlier discussion, and tests..... and the counterpoises worked well under the condtions described. And that is how I built this particular antenna at first, but included a good ground to earth as well.

    From my experiences, and depending on the soil conditions, either a counterpoise or a good ground will work with the semi-random wire antenna. This coincides with the ARRL Antenna Book, section 10.1 perfectly.
     
  3. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Does this section recommend laying the counterpoise on the ground, or keeping it elevated?

    Unfortunately, I don't have a copy of the 22nd Edition. In my 18th Edition, the relevant passage is in 6-6, and reads as follows:

    "A counterpoise is most commonly a system of elevated radials (my emphasis - DZ)...the purpose of the elevated-radial system is to provide a return path for displacement currents...the idea is to minimize the current flowing through the ground itself, which is usually very lossy."

    (Yes, I understand your soil is less lossy than most. However, it seems obvious it will still be more lossy than wire. A quick comparison of admittance or conductance figures for common soil types, and conductivity numbers for copper wire, will demonstrate this beyond doubt.)

    Laying the counterpoise on the ground almost certainly greatly reduced its effectiveness as a return path. The current distribution in a counterpoise should build very high voltage at the end of the wire; placing the counterpoise directly on the ground greatly inhibits this. To counter this effect, if the radial is to rest in/on the ground, many of them must be used to provide an effective counterpoise/return path, not just one.

    No wonder you didn't notice any difference when you disconnected it! It was, in effect, a single in/on ground radial, which makes a notoriously poor counterpoise.

    Please try the experiment again, this time with one elevated 1/4 wave radial on any band where there are signals, connected to the shield of the coax section. It need not be very high, but keep the end free and in the clear and don't let anyone touch it! Listen to a station while alternately connecting and disconnecting the radial. If you notice a rise in signal levels with the radial, your system without the radial is almost certainly suffering from ground losses. The more pronounced the difference in noise levels, the higher the ground losses. (You will almost certainly also notice a rise in noise levels. Noise is composed of signals, also! Obviously, unless the noise levels rise higher than the desired signal levels, this is not really a problem and actually a good sign.)

    On other note: connecting such a radial as described will probably also cause your SWR numbers to go up. This is because excessive losses actually mask true SWR readings and give artificially low ones. It indicates the antenna has become more efficient, not less. This demonstrates that SWR numbers are not always the best way to evaluate antenna performance.

    I hope you understand that I am not attempting to troll or start an argument, but rather offer a more reasoned discussion of what your findings may mean.
     
    Last edited: Aug 13, 2019
    KK4NSF and NH7RO like this.
  4. AI3V

    AI3V Ham Member QRZ Page

    Well now gentelmen, when you add the "other half of the antenna, whether you call it radials, counterpoise, ground, or something else,

    Your antenna is no longer "end fed".

    Turns out, its center fed just like every other antenna.

    You might not believe it, but that's on you.

    Rege
     
    NH7RO likes this.
  5. KK4NSF

    KK4NSF Ham Member QRZ Page

    The section 10.1 in the 22nd edition does not mention whether or not the counterpoise is elevated, or on the ground, but other older sources put them on the ground, or elevated.... depending on who is writing the article.

    We've debated the raised vs on-the-ground subject before, and the consensus is that that while raised is theoretically better, the on-the-ground counterpoise is better than no counterpoise in most situations...... so yes, a longer, elevated counterpoise might improve my antenna. No question. The problem with elevated radials (which are effectivly the same thing) is mostly one of site conditions / constructability / simplicity / and so forth.

    The real question on the table is whether the Earth Ground can take the place of the counterpoise, if the soil conditions are good enough. The ARRL docs say that either can "be effective" and offers the counterpoise as an alternative to the ground, if conditions warrant.

    About the test you recommend: I've already thought about it.... and agree. A good test is in order. As soon as it stops raining, I will be outside setting some dowells and wire in place.

    Well now, Rege.... you are correct.
    A good antenna must be balanced somehow.... whether it is through a second leg , a good grounding system, a set of radials, or a counterpoise. I think we all agree on that. The only question is which is best. I am getting good results with an Earth Ground, as measured by SWR, the lack of RF problems in the shack, and signal reports from other Hams. Is it "optimum"? In theory, maybe, maybe not... but "optimum" in the real world varies greatly from the theoretical because of hundreds of unknown factors.

    Do we call it End-Fed or something else? It is irrelevant to the dicussion. If you want to call it Center Fed.... feel free. BUT rather than argue, let's discuss it like gentlemen.

    That is a good point, as we discovered with the ground plane vertical experiment. BUT that phenomenon can also be helpful in situations where re-tuning is impractical..... such as in field operations with limited gear.

    Dave
    KK4NSF
     
    WB5YUZ likes this.
  6. W0AEW

    W0AEW Ham Member QRZ Page

    As was mentioned earlier, why the tuner if the SWR is low?
     
  7. K0UO

    K0UO Subscriber QRZ Page

    I have three of these monster wire end fed-antennas up. They are on hundred foot wood poles, each having about 2500 foot wire and taking 6 or 7 Acres, they definitely work, and not using any tuner. The angles are optimized for 40 meters, as I go higher and frequency my gain goes up.
    I feed them at either end to change direction.

    The antenna is called a Rhombic
    See K0UO on QRZ
     
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  8. KK4NSF

    KK4NSF Ham Member QRZ Page

    I recommend you read the ARRL Antenna Book, section 10.1. It explains the antenna in detail.

    Essentially, by itself the random wire does not have a low SWR. The tuner is an integral part of the set-up.
     
  9. AF7TS

    AF7TS Ham Member QRZ Page

    As I have said in the past (and this is a semantics argument, not a physics argument) _center fed_ implies a symmetry that is not there.

    There are absolutely 2 sides of the antenna at the feedpoint. Even a 'Zepp' antenna has two sides of antenna the feedpoint, one being much longer than the other. You can _never_ feed an antenna right at the end, only close to the end.

    However you can most certainly have a non-symmetric antenna, two sides that are of different length.

    73
    Jon
    AF7TS
     
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  10. AI3V

    AI3V Ham Member QRZ Page

    The trouble with that is there are no pairs of different lengths of wire that are truly equal in impedance.

    As soon as you realize a amtenna is a pair of transducers, each acting with both the other wire and the space between them you will understand the issues with asymmetric designs.

    While these issues can be mostly overcome with a single band design, it is my opinion that the siren song of these types of antennas have led many a ham upon the rocks. :)

    Symmetric doublets are easy, inexpensive, and simply work.

    Rege
     
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