I have an antron 99 and would like to use some aluminum tubing for ground radials but am not sure what the length needs to be or what angle I want to have 4 radials someone told me to build it straight out and another person told me either 45 or 90 degree angle for better takeoff what is the best way? thanks.
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Ground Radials?
- Thread starter sanjosebay21
- Start date
First things first, what is the goal you are trying to accomplish with the addition of radials? Improve the transmit/receive of the antenna? Help cut back on TVI? Lower the amount of static you are receiving? Some combination of the above? Or perhaps something else entirely?
There are many people who add radials to these antennas and report a world of difference, and many others that add radials and report no difference at all. Your results may vary.
If possible I would stick with 8.5 to 9 feet in length for radials, that being said any size is better then nothing, so long as you can still tune the antenna with them on.
As far as straight out or angled down, yes there is a slight difference in the take off angle, but in reality it isn't nearly as large as many people seem to think. If memory serves, we are talking in the range of one degree or so.
The DB
thank you! I was looking to gain possibly a little more receive? but anygain of anysort would also be improvement lol thanks
You can just buy the radial kit for it; or find out the dimensions of the radials and their downward angle and build your own.
yes Robb you are certainly right I could buy one... but I like to learn about antennas and find it interesting to build they are fun ive just not done anything with ground radials yet....
21, I can only add that in my real world experiences I could tell very little to NO differences using my A99, with or without radials. IMO, this end fed 1/2 wave antenna does not need radials due to the design of the matching network used.
At some point I've real world tested radials that were horizontal 6' and 9' feet long. I also tested the A99 with three and four radials GPK hubs and the same lengths noted above at 45* degrees and about 30*, and I never was able to really tell an obvious difference in local or DX work.
A while back I made Eznec models for these same setup options using a 4 radial hub only, and a 17.5' x .125" wire radiator at 18' feet high. I found minor differences in gain, and no differences at all in the angle for the maximum lobe close to the horizon. So, I'm not sure anyone could detect such differences just using a radio.
I have the models, but here are the results for each model. As a note, the high SWR, R, X values are due to no matching included in these models, and these results show the physical antenna's natural match.
Gain = dbi, H = horizontal, S = Slanted as noted in this report.
R = Resistance, X = Reactance, * = degrees.
View attachment A99 Radials.pdf
Marconi thanks for the reply I was hoping to use radials for receive and tunning,
ok my antenna mast is 40ft then have my rotor and another 6ft mast ontop 4ft on the 6ft pole is my beam and my a99 on top cant get a good match on my a99 when I take it off my beam gets perfect match when I put back on both antennas match are off if I run just my a99 on a separate mast perfect match ive tried insulater between the a99 and the mast and cant get swr lower than 2 but then my beam will match perfect ive even tried runnin a separate ground strap to gnd 6ft copper stk in ground... match goes off on both again ive bought new coax RG8 and LMR400 no change. that's y I was hoping to use radials for tunning possibly, and better receive thanks again
ok my antenna mast is 40ft then have my rotor and another 6ft mast ontop 4ft on the 6ft pole is my beam and my a99 on top cant get a good match on my a99 when I take it off my beam gets perfect match when I put back on both antennas match are off if I run just my a99 on a separate mast perfect match ive tried insulater between the a99 and the mast and cant get swr lower than 2 but then my beam will match perfect ive even tried runnin a separate ground strap to gnd 6ft copper stk in ground... match goes off on both again ive bought new coax RG8 and LMR400 no change. that's y I was hoping to use radials for tunning possibly, and better receive thanks again
As far as tuning is concerned I don't see radials of any kind making much of a difference at all. The natural impedance of the half wavelength antenna is high enough that a set of quarter wavelength radials is likely not noticeable (at least much) when it comes to tuning. That isn't to say that there aren't other benefits that you might get from them, but tuning wise I doubt they will make any real difference.
The problem with the two antennas being that close together is they interfere with each other. Adding a set of radials may help tune the a99 but not directly. The radials will help decouple what is happening below them from the rest of that antenna. However, they will still detune and further interfere with the beam likely, making the issues on that antenna worse. The best suggestion I can make is more space between the antennas if possible.
The DB
Isn't a A99 a dipole of sorts? Wouldn't placing ground radials on the ground/dirt surface do better than ground radials at the base of the antenna?
End fed half wave dipole? Like a big stick?
http://www.copper.com/discus4/messages/34/94243.html?1160878683
Fire-Up section for A99?
http://www.firestik.com/Catalog/FS99-W.htm
http://www.bellscb.com/products/antennas/Firestik/new/Firestik_FS99W_fire-up_99.htm
http://www.worldwidedx.com/cb-antennas/20018-how-should-i-refurb-save-my-antron-99-a.html
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No; not a dipole. An end fed is end fed and a dipole is center fed. A big stick is an end fed half wave also. IIRC, end fed half wave ('EFHW') antennas are resonant; but the impedance they present to the radio is not 50 ohms; it is much higher. So, at the base of the A99 and the Big Stick is a coil and capacitor to balance out the impedance back to 50 ohms and still allow for the length to be resonant.
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Every antenna tries to act like a dipole. What happens with antennas such as the a99 is they will use whatever they can find to make up the "other half", be it a metallic mast, the coax shielding, whatever, the antenna will find something. Something always plays the part, weather the person who put it up realizes it or not, and weather or not what the antenna finds to use is any good for that purpose (and sometimes what the antenna finds is actually detrimental).
All antennas work as two parts. If there is nothing to play the part of that "other half" the antenna simply cannot act like an antenna.
The DB
All antennas work as two parts. If there is nothing to play the part of that "other half" the antenna simply cannot act like an antenna.
The DB
I've heard mixed results in the past, but nothing on it recently. Do they still sell that conversion?
I don't know that it is something that I would actually pay for, if I wanted a 5/8 wavelength antenna it would be better to simply get an antenna designed to be an actual 5/8 wavelength antenna, and not try and force something else to act like one.
The DB