No Homer, I definitely agree that an antenna 90 degrees is equal to a 1/4 wave. Also the current on the Yagi element is maximum at it's feed point. It's the voltage that is at minimum here. The same condition occurs at the feed point of the end fed 1/4 wave.
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Capacitance Hat's Don't add Audio
- Thread starter MrSuburban
- Start date
No Homer, I definitely agree that an antenna 90 degrees is equal to a 1/4 wave. Also the current on the Yagi element is maximum at it's feed point. It's the voltage that is at minimum here. The same condition occurs at the feed point of the end fed 1/4 wave.
Coily,
I am completely neutral on this debate. I have no beef with you. I've always taken the view on most anything that a person's experience is never the servant to another's argument.
In fact, I heard the story of a fellow who, when walking by the fields of a farmer proceeded to tell the farmer of everything that was wrong with his fields. The rows went contrary to drainage, they were crooked, not tilled deeply enough, and generally everything the books told him was out of kilter.
The farmer asked the stranger where his farm was located, to which the critic answered, "I don't have a farm"
Well then, the farmer says, neither do you have an argument.
That said, in one non-scientific test of several antennas I had put together i found at least one that had a reported, and observed superior performance to the none loaded whip I tested in the group. I did not take it as a final report on all performance parameters for those antennas, but it did show me that from/to the same two stations, my mobile, and a 10 mile distant base, there was a circumstance in which the loaded antenna out performed the whip. Of 6 antennas tested only one of the loaded out did the whip, but all of them showed to be doing as well and nearly as well.
I'm not trying to educate you. I'm trying to educate me. I am just trying to learn while looking at data that seems to say more then is apparent in the thread by casual reading.
I've no beef with you, nor anyone. and I have no doubt your antennas prevailed in the shootouts. I'm trying to learn why for each case of differing antenna performances.
Respectfully,
Homer
I am completely neutral on this debate. I have no beef with you. I've always taken the view on most anything that a person's experience is never the servant to another's argument.
In fact, I heard the story of a fellow who, when walking by the fields of a farmer proceeded to tell the farmer of everything that was wrong with his fields. The rows went contrary to drainage, they were crooked, not tilled deeply enough, and generally everything the books told him was out of kilter.
The farmer asked the stranger where his farm was located, to which the critic answered, "I don't have a farm"
Well then, the farmer says, neither do you have an argument.
That said, in one non-scientific test of several antennas I had put together i found at least one that had a reported, and observed superior performance to the none loaded whip I tested in the group. I did not take it as a final report on all performance parameters for those antennas, but it did show me that from/to the same two stations, my mobile, and a 10 mile distant base, there was a circumstance in which the loaded antenna out performed the whip. Of 6 antennas tested only one of the loaded out did the whip, but all of them showed to be doing as well and nearly as well.
I'm not trying to educate you. I'm trying to educate me. I am just trying to learn while looking at data that seems to say more then is apparent in the thread by casual reading.
I've no beef with you, nor anyone. and I have no doubt your antennas prevailed in the shootouts. I'm trying to learn why for each case of differing antenna performances.
Respectfully,
Homer
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It's comments like this that imply the books were written before the experts experimented with thousands of antenna designs. Stop assuming the carriage has been put in front of the horse on this one.
Thanks again. I told you I'm trying to sort this out.
SO the voltage is greatest at the end of the Yagi/dipole elements, and the ARRL Handbook say the properly made coil forces more current into the upper 15° of the loaded antenna because of the high voltage that occurs at the top of the coil. I read this as an apparent change from the normal occurrence in the non-loaded 1/4 wave whip.
Why does the ARRL book seem to disagree that the voltage is maximum at the ends of the 1/4 wave? Or if it doesn't, why is the ARRL Handbook saying that a coil increases the voltage, as in steps it up to higher voltages, and this not improve performance?
If this idea really worked we would also see AM radio stations adding a second insulator on the tower so they could load the top half of the radiator. No antenna has it base lower to the ground then the standard broadcast Marconi. It makes more sense to me that the effect has more to do with direct blockage from the vehicle body then actual antenna height above ground.
Homer, can you provide the exact quote from the handbook that is leading you to believe that voltage is not highest at the end of the 1/4 wave or at the two ends of the dipole? If it says something like this, we need to report the error to the ARRL. Google search current / voltage distribution on either the 1/4 wave or dipole and it will return many images that confirm this.
Two things can be done to improve this distribution and make the current more uniform. One would be to increase the capacitance of the top of the antenna to ground through the use of top loading or a capacitance hat, . . . The other method is to place the loading coil farther up the whip, as shown in Fig 7, rather than at the base. If the coil is resonant (or nearly so) with the capacitance to ground of the section above the coil, the current distribution is improved as also shown in Fig 7.
The result with both top loading and center loading is that the radiation resistance is increased, offsetting the effect of losses and making matching easier."
ARRL Antenna Handbook ch.16
I think a key point was overlooked in the quoted material (see underlined above). The ease of matching an antenna is only a portion of what's necessary for it to perform efficiently. A dummy load will provide an excellent match, but is a terrible radiator. Resonance and TOA play a major role in performance. From everything I have read, studied and applied this is where the 1/4 wave has an advantage over any type of antenna that utilizes a coil to reduce overall physical length. I have no doubt that field strength may be strong at close range with a coiled antenna, but far field - and how my signal arrives at the horizon - is more important to me.
No. Thanks again. Once again had a brain fart. It says it has high voltage at the top of the coil which increase current at the upper end of the antenna which increases radiation in the upper 15° of the antenna which supports the idea that a coil improves the performance of the upper 15° of the loaded antenna over the upper 15° of a full 90° whip.
I accepted your reply regarding voltages and current on the dipole. I meant to ask whether the increased current that the coil adds does or does not lead to superior performance potential for the loaded antenna in circumstances where it is mounted on a lower vehicle. ARRL handbook does say it increases radiation, which I read as improves performance.
I wish I had reread more carefully what I was writing. I am trying to learn this stuff more completely.
It does make me wonder about whether or not there are high voltages at that point on the antenna where the coil is if the coil weren't there.
I had hoped someone would cite that piece of the quote and reply to it. I left it in because of the honesty of my inquiry, but I wanted someone to speak to it without me feeding them that dimension of the discourse. I am also persuaded that there is more to the antenna than meets the eye, and like a diamond, it has to be viewed for hte full effect of all it facets.
That is why my mobile antenna tests of my home mades will not be complete until I can test them over a longer distance than the 10 miles i used. It is too limited a test to tell the whole story of those antennas with different sized, placed, height, etc loaded coils.
B
BOOTY MONSTER
Guest
how much is the radiation increased in the upper %15 of the antenna ? more is more , but how much more ? from my own experience increasing power %100 or decreasing %50 didnt seem to effect my contact success . if %100 more signal/power (?) on a full length 1/4 wave vertical (speaker wire and pvc) didn't have much effect , how much more radiation does the upper %15 of the coil loaded antenna to achieve a detectable signal difference ?
Makes sense.
I have read where it was said that some of the work of a GP at the base of a vertical antenna was there to decouple the antenna from the earth while doing other things like improving the TOA and decoupling the feedline to improve CMC issues.
If the GP reintroduces the earth . . . never mind. The vehicle is part of the mobile antenna system, but the real GP is the earth over which the automobile sits. Not the same. The vehicle does not replace the earth . . . yes/no?
Now I may have a new blank to fill in . . .
Can you tell me why the AM stations set up as you've said/asked?
Would this suggest that capacitance higher on the antenna could reduce signal on the horizon where the commercial radio station must put its signal to service it customers/listeners effectively? Or is it something else?
And could this apply to mobiles?
Bingo, and this is what happens when guys who don't understand what they are reading and what it pertain's to they try to craft it to there situation or think it is an answer to what they are doing.
A good question, but I haven't found the answer yet in the ARRL Handbook. I'm just trying to get some understanding from the forum for the questions reading the handbook has raised for me.
Maybe it's about improving TOA, more of the entire signal to horizon.
May not help much in these hills, but I would think it might out on the prairie.
And I'm not sure it's a discussion of wattage out. Someone may help us here.
i love you guys...if it was not for you guys and your massively thick books how would i ever get along HOw ould we all get along with out you supreme being of knowledge...lol....oh dear oh my i think i may have to run and hide.I would like to thank all you for the kind words and i would like to ask that you please keep it up..my hit counter just quivered.