Topband: More anecdotal "stories" to cause one to stop and....

[Ashton Lee]

When you use antenna modeling software to look at a low dipole on 160 you note three things: 1) They are extremely high angle radiators and 2) Raising the height from say 10 feet to say 100 feet has essentially no impact on the performance, and therefore 3) At any reasonable height the antenna lacks the directionality you tend to want from a horizontally polarized antenna.  So low horizontal antennas look pretty bad at first glance.

When you model an inverted L with say a 60 foot vertical section and 64 foot horizontal run you get an antenna where the pattern looks pretty nice. Lots of low angle radiation. A pretty big hole in the vertical pattern.

But then if you overlay the two models you see something very strange. The Total radiation of the horizontal antenna (against normal ground, not sea water) is so much better that its effective radiation at low angles is about the same as the vertical. At most it's down 6 dB at 5 or 10 degrees depending on ground conditions, radial fields etc. When I model it I actually see less than this difference in my location.

So the fact that you can be heard by DX on a low horizontal isn't all that amazing. You have to have a pretty ideal vertical set up to beat it by a lot.

The real problem is that the low horizontal may not hear DX very well because it favors high angle radiation and the low angle inputs are a lesser part of the total reception. Receiving antennas fix that.

I think the bigger problem with horizontal antennas on 160 is that next to no one really has the room for them.




On Sep 9, 2013, at 12:23 PM, Mike Armstrong <armstrmj at aol.com> wrote:

> Same here, guys.  Please do reply here and if someone "already knows everything," they need not even read the thread, right?  LOL.  I have heard, but don't know if it is a common mode of propagation or if it is very rare, like LDEs on 15...... They do happen, but it is as rare as hen's teeth.  I have heard it 3 times on 15 that I am aware.... But I digress, the mode I am wondering about, and it might explain why even I with a low horizontal on 160 have worked some decent DX (Chile, Japan, several Carib countries, and some pacific islands)..... Is "ducting" a common propagation mode on 160?  If it is, that could explain ALOT when it comes to high angle radiators working DX that they probably shouldn't even hear with such a setup.  
> 
> Any thoughts from those who would like to talk about the subject of high angle radiators (even NVIS), ducting and DX?  Quite honestly, during one particular 160 contest a couple of years ago, I worked 11 countries (all new for me) all over the place except europe...... As strange as it seems, those were the only countries that ANYONE in my area was hearing or working.  So here I was working the same DX stations that some guys with really decent 160 antennas were working, but MY antenna was anything but ideal........ 300 foot long OCFD (fed about 20 feet in from one side) and, this is the kicker, it is only up 50 feet in the air on one side and 40 feet on the other side (available trees, one of which is on my neighbor's property..... but she is my mother in law, so no legal issues there.... lol).  So how is it that I was working these stations with the same amount of effort as the guys who had "ideal" antennas, like full sized 1/4 wave verticals over an EXTENSIVE radial field.
>   It was a very pleasant surprise, but not expected at all.
> 
> On later dates,I would hear people in the same areas of the world, but no matter how hard I tried, not able to work them..... although I HEAR them quite well on that antenna (it seems to be fairly low noise).  Something has to be "up," but I will be darned if I can figure it out..... unless there is some prop mode that is common to 160  and isn't on other bands where this type of antenna "scaled" in length and height would suck 100 percent of the time...... LOL.  Well, maybe not 100, but often enough that EVERY antenna book would say "get it higher in the air....  ALOT higher"
> 
> Thoughts from experienced 160 folk?  Again, only those interested in talking about this subject need respond. :) :)
> 
> Mike AB7ZU
> 
> Kuhi no ka lima, hele no ka maka
> 
> On Sep 9, 2013, at 8:56, Bill Cromwell <wrcromwell at gmail.com> wrote:
> 
>> On 09/09/2013 10:33 AM, James Rodenkirch wrote:
>>> ...think that there's "more to understanding" horizontal and vertical antennas on Top Band.
>>> Listening to a fella on 80 SSB this morning about his experiences with a vertical 1/4 wave and a horizontal loop on Top Band.
>>> He said he had both up and used them over a 20+ year period and noticed that one would work better than the other for DX.  For five years or so the loop would outperform, for a couple of years the two would be equal and then for about five years the vertical would do better.
>>> One can easily point to the 12 year period as aligned with the Solar Cyclef BUT -- when I look at the radiation patterns for both I see the loop as a hugely efficient NVIS antenna with little low angle radiation.  Sooooo, I think there are some magnetic anomalies at play here but -- if the radiation angles don't change, how does one work "mo betta" than the other?
>>> I do have the ON4UN book and will start diving in to it more to see if John can shed some light on this topic AND I don't wanna start a cuss and discuss session here (I know many of you already understand what influences the above "observations" so I don't want to rekindle any previous "debates) but.....if someone can direct me to specific sections of John's book or lother papers/websites, I would appreciate it!!
>>> I consider myself a "newbie" re Top Band" propagation and "other 'influencers'" on antenna performance (I do understand gray line, the various ionized layers and all of that) but anxious to learn more - thank you, in advance, for any "direction" you can point to so I can learn.  Replies off line are probably mo betta - don't need to get any pissin' contests agoin'!  Hi Hi
>>> 72, Jim Rodenkirch                       
>>> _________________
>> Please reply on the list. I'm interested, too. My own suspicion is there are parts of propagation that are not very well understood if at all and those bits are pointed out by what happens with real antennas as opposed to theoretical antennas. That does not dismiss the theories.
>> 
>> I'm taking baby steps here and I am permanently limited by my postage stamp lot but we have all read testimony about success from small lots (and with low power). I'm cornering the parts to build a 'meter' that will give me information about the antennas I already have so that I might make them perform "mo bettah" - if I know whether to turn left or right when I get some 'numbers'.  Just like Jim, I am not interested in stirring up any pots. It's pretty easy with a 40 meter dipole antenna to just go outside and cut off all the parts that don't work. 160 meters (or 600 meters) doesn't lend itself to that simplicity - if nothing else because of size.
>> 
>> 73,
>> 
>> Bill  KU8H
>> _________________
>> Topband Reflector
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> Topband Reflector
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