BlueArmidillo, I tend to agree with your idea about radials pushing the signal up some. I don't know if we could tell the difference just using our radio to test the idea however. Even comparing a SD'r with one that has horizontal radials might be difficult to tell. For sure horizontal radials will ill-effect the antenna match somewhat and you may need a tuner or a matcher added to the antenna to handle the mismatch which will likely be well over 4.00:1 SWR.
I'm going to disagree with this premis based on models I made in the past. I have modeled a center fed vertical dipole and starduster design at the same feedpoint/tip heights a number of times and the angle of maximum radiation for both is always the same, at least to within the same indicated degree. If there is a difference, I don't see it being anywhere near enough for anyone to notice. Something that I didn't expect when I first modeled these designs is a Starduster design with radials 15 degrees off of vertical actually has some gain over a center fed vertical dipole, and its lobes were, in general, wider. It is also being reported by NEC2 as a more efficient antenna overall. Whatever the reason, it is not a change you will ever notice in the field.
this longer radial idea of mine stems from trying to match 1/4 wave antennas to a 50 ohm impedence , i tried many 90 degree radial variations and had no luck with good swr's my conclusion is that the angle is to accute to have a sign wave form ,,,,, and this theroy i want to apply to a larger scale example 1/2 or 5/8 wave ..but the hitch is this,,,,do such on a un gamma matched direct fed antenna/ (non dc grounded)....every antenna i know of that is on the market is as such gamma matched, inductance fed . ect..
When it comes to matching antennas, it takes much more than simply matching lengths to get a resonant 50 ohm match. For example, your 1/2 wavelength antenna with 1/2 wavelegnth radials example you may be able to find a resonant point, however, R will be a thousand ohms plus, and that is a very poor match to your 50 ohm feedline. With a 5/8 wavelength vertical, you won't have resonance for one, you will actually have capacitive reactance you will have to deal with, and R will be between 100 and 200, or perhaps even a little more.
But the gain differences at a local ground leval would be nice to know?
That would depend on the length of the vertical, the radials, and the angle of the radials.
I believe 6 foot radial's on a 24 or 23 or whatever length 5/8 wave antenna are only (semi effective) as compared to radials of = wave length.
Once upon a time in my early days of modeling I did such a test with a 5/8 wavelegnth vertical, and radials that were 5/8, 1/2, and 1/4 wavelength long and at multiple angles, namely every 15 degrees between vertical and horizontal. I can tell you than with a 5/8 wavelength antenna that 1/2 wavelegnth horizontal radials had the most gain, although only a small amount of additional gain over 1/4 wavelength horizontal radials. That being said, it also had a much higher feedpoint impedance that needed to be tuned out, and because of this the matching network to make it work would additional losses to some extent, in effect canceling some if not all of the benefits of the additional length. 5/8 wavelength horizontal radials shot the radiation angle sky high. If you want to use 5/8 wavelegnth radials they need to be about 15 degrees off of vertical.
Further, this design (4, 5/8 wavelentgh radials at 15 degrees off of vertical) seems to be more sensative to beign close to the earth than a horizontal radial design, as I recall you really needed to get the bottom of the radials up to a certain point, either a half or a full wavelenvgh high before it would really outperform the standard 5/8 wavelevngh design with four horizontal radials... So at CB frequencies, you are talking an antnena that is in the range of 60 feet tall that needs to be 20 to 35 feet off of the ground... Not a small structure by any sense of the imagination...
Maybe i am wrong,,,,,,but what is a half wave diapole?
It is 2 similar length antennas ? not one that is 18 feet long and another that is 9 feet
A 1/2 wavelength dipole is made up of two 1/4 wavelength section. The length of those sections is just as important as the fact that there are two of them. If you take a center fed dipole for, say, the 20 meter ham band, you will have two half wavelength sections and a very high impedance on the 10 meter ham band. There are a few general methods to get around this. One is to use parallel feedline, which is very low loss, even compared to the LMR-400 that so many swear by, and an antenna tuner to match out the impedance mismatch. One other method is to use multiple antennas fed at the same point, so you have a center fed 10 meter dipole, and a center fed 20 meter dipole, and perhaps others all fed from the same feedpoint. There are other methods as well, such as an OCF (off center fed) dipole, which can get you access to multiple ham bands. Yep, a dipole doesn't have to be fed in the center to still be considered a dipole...
I also believe that most old school aluminum antennas with a 90 degree radial angle to fed element are gamma fed and gamma fed as such to lose potential in rf signal due to not having the correct match, which i believe due to angle of radiation conflict between the two phases, (i am no scientist or antenna man) so correct me if i believe incorrect.
angle of radation counts for a lot when we are comparing skip, to local talk,,
There is an antenna design that is like a dipole and consists of two 5/8 wavelength sides. It is called an "extended double zepp", and is a horizontal antenna (although there isn't any reason it wouldn't work as a vertical antenna as well). If what you say you believe were true it would feed directly to a feedline, however, it doesn't. The sides of the extended double zepp are the same length, yet to match this antenna to a coax you must deal with a phase variance. The phase variance isn't between the two sides of the antenna, but the antenna feedpoint and the feedline. There is also an impedance variance that must be dealt with as well.
Just to point out, I have not seen a gamma match per say on a 5/8 wavelength antenna, however, all matching networks are based on the same set of principles. I'm not saying it is impossible, but gamma's are generally used when the feedpoint impedance needs to be raised to be matched. In the case of a 5/8 wavelevngh antenna the feedpoint impedance needs to be lowered to be matched. Many 5/8 wavelength antennas use a tapped ring, and in many cases a capacitor that is often hidden in the design.
I am really interested in doing some antenna mapping, field strength measurements, i have a home made rf signal detetcor, basically a couple transistors, hooked up to a very low scale analog volt meter, and a couple potentiometers to adjust the bias of the transistor feeding the volt meter./ i built this many years ago,,,it runs on 9 v bat and has a 60 inch teloscopic antenna.. one potentiometer controls bias to amplifer transistor (basically like gain on a radio),,the other throttles full scale on the meter eg..full throttle pegs meter with 6 volts....1/2 throttle only lets meter go half way.< anyways this a crude,,,,ide like to own one of these new remote rf power meters, the kind with a frequency counter ect...(anyone have one)?
So you built a field strength meter? Good job. I encourage you to use it often. You can learn as much with one of those as you can with many of the low end antenna analyzers that exist on the market (MFJ-259b and such).
The DB
