Inverted L antenna - compared to G5RV, multi-band vertical

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AE7F, Apr 12, 2011.

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  1. AE7F

    AE7F Ham Member QRZ Page

    I have no experience with an inverted L. I was able to find some information by using Google to search QRZ by entering this query: inverted l antenna site:qrz.com

    I have a more general thread going on here:
    http://forums.qrz.com/showthread.php?292278-Using-a-QTH-diagram-help-me-evaluate-antenna-feasibility...

    In that thread, I ask a few questions about the inverted L antenna, which may have been more appropriate for a specific thread about inverted L antennas:
    1. If I use a metal mast with an inverted L, won't the metal mast interfere with the vertical section?
    2. If one has to put down a bunch of radials under the antenna, why not just use a multiband vertical antenna instead?
    3. Will a well-designed inverted L antenna outperform a well-designed multiband vertical antenna?
    4. Will a well-designed inverted L antenna outperform a well-designed G5RV antenna?
     
  2. KB4QAA

    KB4QAA XML Subscriber QRZ Page

     
  3. EI4GMB

    EI4GMB Ham Member QRZ Page

    1. If I use a metal mast with an inverted L, won't the metal mast interfere with the vertical section? Yes
    2. If one has to put down a bunch of radials under the antenna, why not just use a multiband vertical antenna instead? Good Point
    3. Will a well-designed inverted L antenna outperform a well-designed multiband vertical antenna? On 80m,20m,17m,15m it will. On 40m,12m &10m they would be the same
    4. Will a well-designed inverted L antenna outperform a well-designed G5RV antenna? Not a lot of difference

    Hope this helps.

    73

    Fred EI4GMB
     
    Last edited: Apr 12, 2011
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Sure, mostly changing resonance. But you can adjust that by changing the wire length of the horizontal portion, and a lot of inverted-Ls are intentionally non-resonant, anyway.

    An inverted-L has the advantage of being "longer" due to the horizontal part of the antenna. This is very helpful on the lower bands like 80m and 160m. On the higher bands, they tend to work like top-loaded verticals, with the horizontal wire being the top loading.

    It might. To make a vertical load on 80m or 160m usually the vertical is "loaded" by coils that can introduce loss; and since the antennas are physically shorter than they should be, their bandwidth can be very restricted. By making an inverted-L "full sized" (no loading, no shortening), you eliminate any possible coil loss and enjoy wider bandwidth.

    On 20m and 12m, probably not. On 40m, maybe. On 80m, probably. Depends on the inverted-L: How long is the vertical portion (which also establishes how high is the horizontal portion)? My "standard" inverted-L is non resonant purposely so it's pretty easy to match on 80 and 160: I make them 165' long overall, with 40' being vertical, and 125' being horizontal. This is more than 1/2-WL on 80 and more than 1/4-WL on 160 and matches pretty easily on both bands. It also matches well on 40m, where it's more than 1-WL. I would never want to "hit" 1/2-WL or 1-WL or any integer of 1/2-WL as the feedpoint impedance becomes so high that matching can be difficult, stuff starts breaking down (arcing), etc. I don't bother with the inverted-L on the "higher bands," because those are easy to install far better antennas.
     
  5. N1CZZ

    N1CZZ Ham Member QRZ Page

    I think on 160, 80 and 40 meters the Inverted will probably be better than the multiband vert or the G5RV.
    I have just set up one antenna when I moved here a few months ago. It was 170' Inv L, vertical part goes up around 65'. I use it in on all bands. It excels on 160, 80 and 40, it works on the others. It works good enough on all bands that I will probably improve it some and move it like I want to before I put up something for the higher bands. As mentioned earlier by someone, it is easy enough to put up dipoles for the higher freqs, so if I was serious or needed to improve communications on those bands I would add some antennas, but for now it works well enough that more antennas are low on the priority list.
     
  6. W0BTU

    W0BTU Ham Member QRZ Page

    Absolutely it will, unless the other stations that you want to work are fairly close. However, it needs radials.

    The inverted-L is possibly one of the most under-rated antennas there is. Look at the EZNEC plot comparing short verticals to full-size quarter-wave verticals at http://www.w0btu.com/160_meters.html. It doesn't include an inverted-L, but to make a long story short, the results are not that different.

    ON4UN's Low Band DXing has some good info about, and high praise for, the inverted-L. And so do a lot of well-known 160 and 80 meter DXers, who DON'T successfully use any kind of low dipole (including the G5RV) to transmit on. At a distance, an inverted-L with a good radial system will simply blow away any dipole at the same height! It's all about the angle of radiation for distance work.

    The vertical portion should be has high as possible. The vertical portion of my 160 meter inverted-L was only about 50 feet high, but I (and many other people using it on 160) worked the far reaches of the earth with it.
     
    Last edited: Apr 12, 2011
  7. N0AZZ

    N0AZZ Ham Member QRZ Page

    Is there any advantage to increasing the length of the horizontal portion of the antenna past 1 wave length on 160m? Also how many radials are required and what is the layout under the wire?
     
  8. W5DXP

    W5DXP Ham Member QRZ Page

    It will in some directions, not in others. For a 33'v+33'h inv-L used on 20m over mininec ground, the maximum gain is 5.4 dBi at TOA=28 deg. A g5rv over mininec ground has a maximum gain of 7.7 dBi at TOA=23 deg, 2.3 dB more gain and a 5 deg lower TOA..
     
  9. K9FV

    K9FV Ham Member QRZ Page

    Steve, you wrote:
    Do you use coax or ladder (window) line with this antenna? Does the internal tuner on your rig tune? Or is an external tuner required?

    I've not considered an inverted L because 40 ft was the max I could get - close to shack anyway. I do have one tree that would get me up about 50 ft, but that would give at least 150 ft run of coax to get back to shack - is that too much for the extra 10 ft?

    Thanks to all for comments and help.

    73 de Ken H>
     
  10. W0BTU

    W0BTU Ham Member QRZ Page

    Cecil, why do you model using a Mininec rather than a High Accuracy ground? Just curious. I just switched between the two grounds in a ground plane model in EZNEC+, and there wasn't a whole lot of difference. Slightly more difference with a dipole.
     
  11. W0BTU

    W0BTU Ham Member QRZ Page

    Fred, did you mean 1/4 wave? An inverted-L is usually that length, bent to fit.

    Mine was about 160' long (~3/8 wave). I did that so that I could resonate it with a series capacitor. (But I wish I wouldn't have done that, because it narrowed the bandwidth.)

    Check out http://www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html and the links there to N6LF's excellent information on grounds.

    I would like to expand that table there someday, perhaps showing 8, 4, and 2 radials. It only goes down to 16.

    I used two elevated radials under mine, about 8' off the ground. (You can use far fewer radials if you elevate them). However, I think the inverted-L would have worked even better with 60 radials laying on the ground as per the chart.

    Typically, centered around the vertical portion. I forget the details, but the idea of favoring the horizontal portion was discussed before. Just put down the radials as if it were a vertical.
     
  12. W5DXP

    W5DXP Ham Member QRZ Page

    I used W7EL's VERT1.EZ to build the inverted-L and it uses mininec ground. I just modeled the inv-L with 8 elevated radials over high-accuracy ground and the G5RV over high-accuracy ground. The inv-L comes in at 5 dBi at 27 deg on 20m. The G5RV is 7.9 dBi at 23 deg on 20m. Not much difference when the ground is changed from mininec to high-accuracy. On 20m, the G5RV is still 2.9 dB higher gain and 5 degree lower TOA. Here's the comparison according to EZNEC. The inv-L has a maximum height of 35 feet. The G5RV is at 40 feet.
     

    Attached Files:

    Last edited: Apr 12, 2011
  13. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I'm not using an inverted-L at all today, but have several times in the past and a couple of times for Field Days and such. Just used a short length of coax with a tuner in the shack, as the 165' overall length isn't a terrible match so the coax won't have much loss. Lots of radials (similar to what would be used for a vertical), of course.

    I don't really know. But 40' vertically is what I've mostly used. I had an "elevated inverted L" at my NJ shore QTH back in the mid-to-late 1980s. It was fed about 20' above ground, right at the edge of the roof of my 2-1/2 story home there. The radials went over the roof in one direction, and out to trees in the backyard in the other direction; it only went "up" about 25 feet where it made a right angle at an insulator tied to a rope that was in turn tied to my tower; then it bent to horizontal about 140 feet to a tall tree in the backyard (with another insulator and rope over a limb). That actually worked "great."

    Of course, I really had nothing else to compare it to at the time (for 80/160m), so "great" was an impression. But I found myself working all the same stuff locals with more serious setups were working, and jumped into pileups on DXpeditions and worked most of them pretty easily, so that was "great" for me.
     
  14. W0BTU

    W0BTU Ham Member QRZ Page

    Thanks. Trouble is, the VERT1.EZ that comes with EZNEC doesn't have radials, and I think the gain that EZNEC shows reflects that. I have some .ez files of verticals with good radial systems at http://www.w0btu.com/files/antenna/EZNEC/, that are more accurate. Help yourself. :)
     
  15. W5DXP

    W5DXP Ham Member QRZ Page

    Mike, the G5RV doesn't need radials. :) You didn't read far enough. I re-ran the inv-L simulations with 8 elevated radials over high-accuracy ground. The results didn't change appreciably.

    Ground, Inv-L, G5RV
    mininec, 5.4 dBi@28 deg, 7.7 dBi@23 deg
    high-accuracy, 5.0 dBi@27 deg, 7.9 dBi@23 deg

    With the high-accuracy ground, the G5RV advantage is greater than it was with mininec ground.

    Actually, when the G5RV is lowered to the same height as the inv-L horizontal section, the take-off-angles are equal but the G5RV still has the inv-L beat by about 2 dB of maximum gain.
     
  16. AE7F

    AE7F Ham Member QRZ Page

    Great discussion and thank you.

    I haven't even tried to work on 160m. Just figured it wasn't worth it for whatever reason. I really only use 80m for rag chews or NVIS. I have worked some considerable amount on 40m and lately, a lot on 20m as well. What I am getting at is that if the inverted L is going to be an improvement on 160 and 80 but maybe not so much on the other bands, it may not be the solution I am looking for.

    I am not going to be pouring a lot of resources into DX hunting but when I am able to work DX, it isn't on 160 and most often isn't on 80m either. If 40-10 gives me the best DX, maybe the L isn't worth the trouble?

    Here is an example of some of my contacts with my current inverted V G5RV:
    -6 contacts on 10m
    -15 contacts on 15m
    -1 on 17m
    -32 on 20m
    -3 on 30m
    -158 on 40m
    -33 on 80m

    Most of my DX stuff is on 40/20 and most of my work is in the CW portion of the bands. How is the inverted L going to play considering a sample of my operating frequencies and mode?

    The antenna really tunes easily on 40m. Maybe I'm just making a case for aiming toward antenna resonance. If I had 7 resonant antennas, maybe I'd have just as many contacts on each band....

    Maybe someone else can post some data examples of contacts made using an inverted L antenna.
     
    Last edited: Apr 12, 2011
  17. N5YPJ

    N5YPJ QRZ Moderator QRZ Page

    Remember that the G5RV isn't an all band antenna and is a pretty bad performer on 30, 17 and 10 meters yet you've made contacts and will make more when conditions are good.
     
  18. EI4GMB

    EI4GMB Ham Member QRZ Page

    Hi Ben,

    40m/20m are 2 of the principle bands of use for the G5RV. The others are 80m & 12m. So you would be hard pressed to beat the G5RV with an inverted L on these bands. If you want to use the higher frequencies like 17m,15m & 10m it might be better to use resonant dipoles or perhaps a good vertical. Best of luck.

    Kind Regards

    Fred EI4GMB
     
    Last edited: Apr 12, 2011
  19. AE7F

    AE7F Ham Member QRZ Page

    Thanks Fred. Makes sense to me.
     
  20. AE7F

    AE7F Ham Member QRZ Page

    Agree.

    Interesting that my data seem to correlate with the design of the G5RV. I would love to see data like this for other types of antennas.

    Granted, there are a million other variables that can skew the data, but it does give a quick glance look at how you can use a particular antenna....
     
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