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I built a 40m vertical using the W8AMZ design https://www.amateurradiosupplies.com/v/vspfiles/assets/images/40m_vertical_monopole_-_manual.pdf

Seems to be working for the most part. But I'm not sure if it's really exhibiting a 22 degree takeoff angle. I have it about 8 feet off the ground.

I get really strong signals from closer QTHs.. like +20 or +40 over S9. I'm in western NY state and i get the strongest signals from NJ, WV, MI. TX is pretty solid, but it really starts to fade around AZ and CA as well as NV.

It's hard to tell if it's just a propagation thing or a distance thing. The fact that the closer stations are booming makes me think it's a combination of distance and high takeoff angle.

Do you think lowering or raising the antenna would change anything? I have the radials as close to 180 degrees and level as possible. How critical is that?

EDIT: as far as dealing with common mode current is concerned, I have 8 turns of the RG8X feedline going through one of these at both the feedpoint and shack entrance: http://palomar-engineers.com/ferrite-application-experts-2#!/FSB31-1-ID=1-RFI-Range-1-300-MHz/p/74532157/category=21480229

After that, the feedline goes througha T connector which is attached to a round rod. The bottom part of the "T" has a PL-259 connector with a bleeder resistor across it: http://palomar-engineers.com/antenna-products/antenna-static-bleeders/Coax-Static-Bleeder-p74882773

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    $\begingroup$ What time of day? $\endgroup$
    – Phil Frost - W8II
    Aug 15, 2018 at 18:55
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    $\begingroup$ @PhilFrost-W8II I wanna say 8 or 9 pm EST $\endgroup$
    – user3191449
    Aug 15, 2018 at 19:03
  • $\begingroup$ 8 PM EST is 5 PM PST. Try it a few hours later when the path is better. $\endgroup$
    – Mike Waters
    Aug 15, 2018 at 20:50
  • $\begingroup$ Which directions are your radials pointing? You will probably have a lower takeoff angle in those directions, and worse in the perpendicular directions. $\endgroup$
    – rclocher3
    Aug 15, 2018 at 21:10

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If you model this antenna, it does predict a 22° takeoff with the radials 8 feet off the ground. Doubling the height would change the take off to perhaps 21°.

You may wish to consider a good current mode balun at the feedpoint and another one prior to entering the shack in order to reduce common mode current which will alter the directional characteristics of the antenna. If you can bury the coax in a couple of feet of ground immediately below the antenna, this will also help reduce common mode currents.

If you have an antenna analyzer, you may also wish to experiment with adding additional radials. While this will not have any significant effect on the takeoff angle, it may improve the efficiency of the antenna. Keep adding radials until the feedpoint impedance of the antenna no longer changes to any significant degree.

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  • $\begingroup$ I do have 8 loops of RG-8X going through a 1" OD mix 31 clamp on ferrite (big 20 to 30 dollar one from palomar) at the feed point, and then again just before entering the shack. Would that suffice for choking common mode currents? $\endgroup$
    – user3191449
    Aug 16, 2018 at 15:13
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    $\begingroup$ @Paul That sounds like it would work. $\endgroup$
    – Glenn W9IQ
    Aug 16, 2018 at 16:13
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Your description isn't too far off from predictive models, like VOACAP.

enter image description here

40m works very much better when the entire path is in darkness. At 8 or 9 PM in western NY, at this time of year (August), it is still light for the Western US. As such you won't have great results in that direction.

And in the other direction to the East, you get a whole lot of ocean, with marginal coverage of Western Europe and Northwest Africa.

It's hard to definitively say without qualitative measurements with a field strength meter, but I'd guess your antenna is just fine. Radial orientation isn't critical.

My suggestion: wait until later in the night (here's 0900 UTC):

enter image description here

or try a different band, like 20m at 0000 UTC:

enter image description here

or 30m at 0000 UTC (SSB isn't allowed on 30m, though this model is for SSB anyway for consistency):

enter image description here

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  • $\begingroup$ updated my post about handling common mode current. is that solution adequate? $\endgroup$
    – user3191449
    Aug 16, 2018 at 15:19
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    $\begingroup$ @Paul Sounds like it's probably adequate, yes. A lot of times people will operate with no choke at all, so you're much better than that. $\endgroup$
    – Phil Frost - W8II
    Aug 16, 2018 at 15:56

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