Topband: beverage lobes

[Larry Molitor]

answers/comments below>>>

Tom Rauch <w8ji at contesting.com> wrote:I wonder if you had both antennas up at the same time and 
did A B comparisons, or if this is by feeling or memory?

>>>A/B/C comparisons. Had a number of different lengths up at the same time last season and the season before.

Are you really saying for every foot added you saw an actual 
improvement? 

>>> A slight distortion of reality for illustrative purposes, forgive me! I can indeed tell the difference between a 360 foot and a 410 foot that are currently in service. But it's admittedly not much.

I barely notice a difference between 600 feet 
and 800 feet and almost never see a difference between 800 
feet and 1000 feet 

>>> The difference I saw between a 500 footer and an 800 footer was quite pronounced. The difference between 800 and 1100 not quite as much but still very much worth the extra effort.

Well, in my case a 500 foot Beverage is about 6-10dB better 
S/N than my transmit vertical and I am in a very quiet 
location. Assuming 6dB, are you really saying doubling the 
length gives you an additional 6dB S/N ratio? 

>>>I have no way of measuring the actual S/N of topband received signals. Do you? Signals which are detectable but not copyable on the TX vertical are easily copyable on the 500 footers and outstanding on the 1100 footers. How many dB is that?


The perfect 
case is only 3dB S/N change for double the length, and this 
assumes a perfect situation that we really can't obtain in 
the real world.

>>> In the real world 3dB can mean the difference between a log entry and not. A QSO in the log is worth what, 100db?? More? Less? Ask any EME'er what he would give for 3 dB!

Did you have them all up at the same time?

>>> Yes.


I'm having a 
difficult time understanding why a  ~ 1/3 length decrease 
translates to "very much inferior".  

>>>If you can copy a station on one and not copy on the other, the one you cannot copy on is "very much inferior". 


I spend a lot of time 
comparing multiple systems at the same time and have 
discarded inferior antennas. 

>>> Same here, different results, YMMV

Length, once over about 700 feet or so, just doesn't do 
much.

>>>Maybe in GA. I can say for certain here in the WA desert it does a lot!

In an ideal perfect-phase lossless world ........I'm not going to argue theory. I happen to agree with the theoretical case as you presented it. However that does not account for the fact that I can really see a dramatic difference in performance with the longer Beverages installed here. Since I make the observations on real topband signals and A/B switch around the various wires I can only assume that there is a difference between the theoretical case and my practical installation that has not yet been accounted for. When the model does not agree with the measured results, either the model is wrong or the measurement is wrong. Since the measurement is copy/no copy and is repeatable, there must be an inconsistency in the model.

The results have been consistent for the several years I have been up here in WA with many acres to play with. The differences are way more than enough to make the extra effort of installing long wires worth it. I guarantee that I would not be walking all those extra miles across plowed fields unless I was getting something out of it. I agree that phased wires would probably be better but in my particular situation I cannot keep the phasing coax's intact for sufficient time  to make good observations. What little I have done with phased systems was promising but pointless if I can't keep coax on them.

All of my wires are 8 foot high maximum and most are 30 inches high. All are terminated identically with 8 ea. 6 foot long wires on the surface or buried about 1 inch with a single 3 foot ground rod in the center. Most of the wires have to be removed periodically for farming activities hence the minimal grounds. I use galvanized 17 gauge fence wire. I tried good copper once and could not measure any difference at all nor see any difference in on-the-air performance. This season I was limited to two short wires due to the farm stuff. With a little luck, I'll be able to put up 8 or 10 more next season. I plan on running out at least one 2000 footer. At this point I have no idea if it will be worth the effort but it will be fun to try.

73,

Larry - W7IUV
DN07dg - central WA
http://w7iuv.com


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