ad: elecraft

I need stealth, low noise, and gain in the same antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD7VEA, May 3, 2012.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-assoc
ad: l-rl
ad: l-gcopper
ad: Subscribe
ad: l-innov
ad: l-Waters
ad: L-rfparts
  1. KD7VEA

    KD7VEA Ham Member QRZ Page

    OK, I have had it with my G5RV. The G5RV is an Okay antenna, but its just not cutting it for me. for the last 2 months, I have been scanning the bands and hearing pile ups, I cant hear the calling station, so I will look up the frequency on a dx cluster board, and see who is calling and where they are. there have been some stations in Yemen, Kuwait, India... but I am not hearing the DX stations. this has been on 20, 17, and 15 meters, and a couple of times on 40 meters. I am most concerned with 10-20. I am running an MFJ 1778 G5RV set up as an inverted sloper as I call it. basically, the top of my antenna is supported with a 30 foot mast, this is the center of the antenna at the feed point. from there, the antenna ends point toward the east, and west. the mast is centered width wise in the backyard, and as the legs go down toward the ground, they angle north slightly so that they stay in the yard. the ends are about 6 feet off of the ground. I am wondering if anyone can give me some tips on how to get a better signal. I don't have a ton of room, and it has to be somewhat stealthy. I dont think I have room for a beam, but was wondering if something like the MFJ rotatable dipole might let me get a little more directive gain by turning it? has anyone done a side by side comparison of a rotatable dipole and a full size wire dipole? does it help that much by rotating it? I am willing to spend a few hundred $$$ if I can actually get on my radio and talk, and hear other stations. also, starting at 10 meters, I have a noise floor of less than 1 S unit, 12 meters 1-2 S units, 15 meters 1-2 S units, 18 meters 3 S units, 14 meters 7 S units, 30 meters 9+ s units, 40 meters 10 over 9 to 15 over 9 noise floor, 80 meers10 over 9 to 20 over 9 noise floor. I do live in the middle of the city, but what can I do to get the noise down, and the signal up, am I just out of options? I love ham radio, but all I can say at this point is that I own radios, I can even use the radios with the conditions. any helpful input is greatly appreciated.
  2. W9GB

    W9GB Ham Member QRZ Page

    Can you get any higher than 30 feet?
    The DX stations you are listing are East, SouthEast of your QTH --
    ideally a dipole would need to be perpendicular to that line (N-S alignment).

    The noise floor is due to local RFI sources (e.g. leaky power insulators)

  3. KM3F

    KM3F Ham Member QRZ Page

    I agree. Your anterna is not high enough and without any gain.
    What your missing is antenna takeoff and receive angle is not good at 30 feet.
    Height it'self is not the sole issue but what the angle response of your antenna is at that height.
    I suspect your 'angle' is too high for long distances.
    Said another way, DX angle is usually quite low to the horizon.
    If your antenna angle for example is at 45 degrees it will be low responding the low angle signals.
    I run my beam at about 45 feet and do very well but it's still lower than I would like to have it for 10 and 15 m..
    Good luck.
  4. G4LNA

    G4LNA Ham Member QRZ Page

    To be honest, unless you can get the antenna up and in the clear you are onto a loser, it's the price us city dwellers have to put up with. The antenna you have there is a real cloud warmer, you will probably find the lobe is straight up on most of the lower bands, there is some advantage to that because you'll probably find that there is a fair amount of gain straight up which you can put to advantage.

    In my situation I have a very small garden 40 feet long by 18 feet wide but I've got a 40 Mtr doublet up in that space, one leg winds its way around the loft and the other leg goes out down the garden, the result is an omni directional cloud warmer. This hasn't stopped me working DX, you have to remember the layers are not always level, but are constantly changing, especially in the mornings and evenings this is where we can take advantage of it. I hear lots of pile ups where I can't hear the DX station, on the other hand I work a lot of DX after the first or second call, quite often I work DX that is calling CQ then no one else seems to work them afterwards.

    It sounds like you problem might be more down to high noise level, the worst band for me is 160/80 where the noise level is around S8-9 which I think is pretty good if you look on Google maps my location.

    Also, you have to be patient, conditions at the moment are not the best, so you have to be a bit more patient with the DX.
  5. K4SAV

    K4SAV Ham Member QRZ Page

    As others have already said, a low antenna is not very good for DX. Also with a G5RV on the high bands there are lobes and nulls. If a DX station happens to be in one of those nulls, you may have a difficult time working him, even if the antenna is raised to a good height.

    You have a large amount of noise, almost certainly form local noise sources. For the high bands I would recommend a horizontal antenna as high as you can get it. Also use a very narrow bandwidth on your receiver, no wider than 500 Hz, preferably less. That will improve the signal to noise ratio a lot.

    Utah to Yemen is a difficult path. You have to go over the polar region which makes it more difficult. Also notice that there are no times of common darkness between these two locations, so it's not likely you will be able to work them on 160, 80, or 40, even with a good antenna. (40 might be possible but you will only have a few minutes to do it.) Long path might be possible at times, but they haven't been pointing their antennas in that direction. 7O6T does have a very strong signal but there are a lot of stations you have to compete with, so even if you are able to hear them it will not be easy. They have been over S9 at my location on all bands 40 thru 15 meters (S9 on 80 too but so is the noise lately due to the thunderstorms), however I am listening to them on a 4 element SteppIR and I am a little closer than you are, and I don't have to go over the polar region. All US stations have to compete with Europe to work him. We have to go right over Europe and beyond to reach Yemen. So you are up against some difficult competition. Work on that antenna and just wait until they work most of the big guns, which should be starting about now.

    More info:

    I decided to look at your antenna on EZNEC (including about 75 ft of coax). As expected, you have a nulls in the direction of 7O6T. The bearing to 7O6T is about 11 degrees for you. The gain of your antenna on 20 meters at that bearing and at 10 degrees elevation is about -9 dBi. 15 meters isn't any better. It's also -9 dBi gain. 17 meters is a little better, -5 dBi. You hit nulls on the antenna on 20, 17, and 15 meters. It's no wonder you can't hear them.

    Jerry, K4SAV
  6. WA1FOK

    WA1FOK Ham Member QRZ Page

    When you hear these pileups are other stations in your general area hearing the dx? Just because someone is working the dx does not mean you should be able to hear the dx. I have a tribander and see dx on the cluster all the time that I cannot hear. When I check the stations that are reporting they are usually in europe which means that I do not have propagation to the dx.
  7. NY3V

    NY3V Ham Member QRZ Page

    I suggest you try operating digital mode JT65A.


    It is low power and you can use this site to find out what other worldwide JT65A stations hear your signal and how strong it is.
  8. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    If it's a "classic G5RV" (102' doublet center fed with about 31' of ladder line, and then coax to the station), don't expect much from it on 17, 15 or 10 meters because it's a lousy design for those bands. It should be okay on 80-40-20-12 meters, although on 12m it has large peaks and nulls and of course if a station is in a null you probably won't hear them even if your noise level was very low.

    High noise levels aren't always the case in "the City." I live in a slightly larger town than yours (I'm in Los Angeles, in the city itself) and my noise levels are normally very low. It's a matter of finding the noise sources and eliminating them one by one, until you find all the local noise is coming from power lines or neighbors. I worked with the electric company to virtually eliminate my power line noise (which was all coming from old hardware and insulators, which they replaced), so that leaves only the neighbors. I even worked with them the best I could and eliminated two major noise sources at two neighbors' homes (a sodium vapor lamp at one, and aquarium heater at the other). There are still some, but the noise is way down from what it was originally.

    "Most" of the noise is usually generated in your own home, from various appliances including computers, monitors, chargers, plasma TVs, and lots of other things.

    A rotary dipole that's a good design and actually works on 20-17-15-12-10 meters, and installed on a rotator at 30' above ground will slam-dunk outperform your G5RV, period. The only band where the G5RV might work just as well as the rotary dipole is 20 meters. It will never work as well as a rotary dipole on 15 or 10m, and not on 17m, either.

    But the rotary dipole really needs the rotator to be effective; otherwise you have an antenna that works in two directions and is lousy elsewhere.

    The Yemen operation, for example, was S9 at my home in L.A. last evening on 17m SSB (18.145), really quite strong and often stronger than all the guys in the pileup calling them up the band on .150-.155. They peak at about 15-20 degrees (NNE) from me, and that would be about your beam heading also. It's the other side of the world from here and the short path is nearly over the magnetic north pole, so it can be fluttery -- although last night, signals were actually quite clear and not much flutter.
  9. K4SAV

    K4SAV Ham Member QRZ Page

    WIK is correct. The bearing for you is about 17 degrees. I inadvertently put the cursor on Idaho instead of Utah the first time. So your antenna gain is a little more than what I quoted, but not by a lot.

    Compare that to my bearing for 7O6T, which is 46 degrees and you can see a significant difference in path.

    Jerry, K4SAV
  10. K7MH

    K7MH Ham Member QRZ Page

    Also, just because you can hear the pileup, it doesn't mean that you should be able to hear the DX.
    That area of the world is not all that easy to get into from the west coast, or close to it. Much easier from the east coast and of course most of 4-land. I think you are expecting too much from a simple wire antenna that is a few feet off the ground.
    I can hear 7O6T on 17 CW quite well most of the time I have listened there but not on SSB and not very well on 20 either mode. Other than 17 and 20, I don't really expect to hear them well at all. I have a 2 element quad at 45 ft. and I am about 400 ft above sea level with a pretty good shot to the north and east.
    I'd look at getting a junior beam up at least. A rotatable dipole would work better than what you have and is easier to get it up high sometimes. I made one for 15 meters from the handbook as a novice and used an armstrong rotor. Making one for 15 or 20 (single band) is cheap and easy.

    for beam headings and distances you can plug in your grid locator here;
    Last edited: May 3, 2012
  11. KD7VEA

    KD7VEA Ham Member QRZ Page

    Thanks for all of the input everybody. to answer the questions that I am getting, I really cant do much more than 30 feet in height, I don't have a tower setup (that will happen in the next couple of years once I buy a house). I just have a push up mast clamped to the house. I cant run the antenna in any other configurations other than the inverted/sloping V due to the size of the yard. yes the antenna is the classic design of 102 feet center feed, 31 feet of 450 ohm ladder line, and 50 feet of coax with a 10 turn 6 inch choke. so here is the big question, would I get a better signal out of a rotatable dipole like the MFJ 40-2 meter version, mounted on my 30 foot mast, or would I be better off with a vertical stuck in the ground in the corner of the yard. I had a butternut vertical a few years back, it worked Okay on the ground, but on top of the mast (with no radials) it was horrible. What do you all think would give me the best performance? I know I kind of focused on 7O6T because it was fresh in all of our heads, but I do want good all around performance not just DX, I still want to be able to work stateside.
  12. WD4OOZ

    WD4OOZ Ham Member QRZ Page

    What about a horizontal loop antenna....a 40 meter loop would be about 36 ft square and at 30 to 35 ft in the air would work better than the G5RV. With 14 ga insulated wire and 450 ohm ladder line to an antenna tuner would be a good antenna for most of the bands.

  13. WA4FNG

    WA4FNG Ham Member QRZ Page

    I would venture to say the rotating dipole would have to be better. And at 30' the take off angle on 20m and up should be lower than your current antenna. I woud try this before a vertical, at least on the upper bands. Verticals are great for the low bands, with good radial fields, but not so much for DX on the upper bands. If you can get a rotating dipole up 30' then you should be able to put up a moxon or hex beam.
  14. KJ3N

    KJ3N Ham Member QRZ Page

    That's because you only put up half the antenna. Don't blame the antenna for a faulty installation.

    Anyone who says you can get good performance out of a Butternut vertical without radials, is an idiot, IMHO.

    The rotatable dipole sounds like a better plan as far as not having to worry about nulls in your antenna pattern.
  15. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    This is the real question, and I doubt anyone could answer it. The MFJ model MFJ-1775 is only 14' long and very heavily loaded; they claim its operating bandwidth is 60 kHz on 20 meters and 40 kHz on 40 meters, so it really only covers a small portion of each of those bands. It also has no coverage at all on 12-17-30 meters. I don't have this antenna, but am a bit skeptical about it. Surely better than nothing, but it's not a "real" rotary dipole -- it's way too short.

    The Cushcraft model D-4 is a far better performer on 40-20-15-10 meters, and I have used these lots of times. Of course, it's also bigger (longer) and heavier. But it's "full sized" and "full bandwidth" on 20-15-10 meters, and about 3/4-sized and "nearly" full bandwidth on 40.

    Another very good rotary dipole is the Hy-Gain TH1:
    That is also "full size" and "full bandwidth" on 20-15-10m (it also covers 6m) but no coverage on 40m.

    The Mosley TA-31M is another very good rotary dipole for 20-15-10m (only): It's very strong, works well, and will last a lifetime.

    With any of these, you'd need a rotator or it's kind of a waste of time. But at 30' above ground, any of these "larger" rotary dipoles should work quite well and definitely outperform the G5RV.
  16. AD4J

    AD4J Ham Member QRZ Page

    An addition to WIK's list of trapped rotatable dipoles is the Cushcraft D-3 covering 20-15-10 meters. If you don't care about the 17 and 12 meters, a trapped dipole is probably the easiest solution. It might even be acceptable to you on the WARC bands with a tuner and reduced efficiency due the loss in the mismatched coax.

    I made my own 34' rotatable dipole from tapered aluminum (DXEngineering and Texas Towers are good sources). I modeled it with different lengths of 300 ohm ladder line feed and found I could cover 20-17-15-12-10 meters with just 2 lengths using my rig's internal tuner. I ended up with a basic feed line length of 52' for 15 and 10 meters plus an extension of 8' for 20-17-12 meters. The SWR ranges on each band are:

    20M 1.6-2.3:1
    17M 2.8-3.4:1
    15M 1.5-2.6:1
    12M 2.8-3.4:1
    10M 1.1-3.8:1 (28.0 - 28.6 MHz, all I care about)

    I put locking connectors on the feed line so I can add or remove the 8' extension in about 90 seconds. My shack is on the second floor, so the extension just makes the feed line hang a little lower between the antenna and shack window.

    The idea for my antenna came from W5DXP who modeled and built a very similar one.

  17. K8JD

    K8JD Ham Member QRZ Page

    A small , stealthy antenna with gain and DX launch angle? Not very likely.
    The closest thing would be a full size multiband vertical (including radials) Not very stealthy !
    . I have a Butternut HF6v vertical here and worked a fair amount of DX on 40/30 and 20M with it.
    I also have a full sized 3 element Yagi for 10M and have worked down under (VK/ZL) , Japan and pacific islands that I had to look up on a big map to find, with 25-100W from Detroit.
    Working a lot of "GOOD" DX usually involves a tower and Yagi or Cubical Quad you can rotate.
    Anything smaller (low dipole, vertical) and you will need a lot more time and luck to get the rare ones.
    Have fun...

  18. M0GVZ

    M0GVZ XML Subscriber QRZ Page

    Google the G3TPW Cobweb antenna. Five fullsize dipoles for 20-10m in an 8ft square. Almost omnidirectional with a slight 3dB variation between the ends and sides which gives a slightly oval pattern. At 30ft up it'll do quite well.

    Quite easy to homebrew - look at the G3TXQ variant which is easier to tune though.
  19. KD8FYI

    KD8FYI Ham Member QRZ Page

    Hey, anybody think that a magnetic loop might work for him? I never ran one myself, so I can't really make a suggestion.

  20. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Not really.

    Besides lacking real performance (compared with a full-sized dipole) they are also expensive to build, especiall for a mult-band design. The variable capacitor alone, for 100W operation, can easily cost well over $100 and that's just one component.
Thread Status:
Not open for further replies.

Share This Page

ad: k1jek