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 Subscriber 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 Subscriber 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.
     
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