Different Kind Of 3 Meter Antenna

RFB also mentioned in another thread the idea of
an upside aluminum Christmas tree. So that has
been discussed, too.

So I guess we're down to what I mentioned above,
the cylinder of chicken wire, hardware cloth, or
something like that.

Thanks again,
Bruce, MICRO1690/1700

Hi Bruce. You have mentioned probably all the vertical possibilities ever considered, but I also think the tin foil might be hard to manage.

I will tell you this about the 4-element cage monopole I still have hanging on a bamboo tower for my FM.... it makes the signal in the room solid as a rock, and my walking around never causes multi-path distortion the way it did with a 1-wire antenna. But the increase seen on my FM S-meter, 2-rooms away, is very small.

Just to share another related matter.... I purchased a 10-foot roll of sheet aluminum that is 1-foot wide and rolled up in a shopping bag, which I plan to try for AM.

I am just now getting around to contemplating the top hat idea, which from what I gather, is very much experimental even with veteran ham operators. That is, I think everyone believes it adds capacitance in a good way, but the experimenting is to come up with a design that maximizes the effect.

There are many kinds of mesh wire in addition to chicken wire. Some of it has larger spaces some has smaller spaces. I think stucco wire even has little cup shaped wires designed to hold the plaster, and maybe that's good for grounding

Hi Carl!

I remember something else somebody said -
wider on top is better.

Best Wishes,
Bruce, MICRO1690/1700

Is why I mentioned to mount the aluminum Christmas tree upside-down. The width will be where it needs to be..at the top and compliment the wide diameter ground radials at the bottom.

Just make sure your aluminum Christmas tree is 6 foot or less in height, those have roughly about 4 foot diameter of limbs at the bottom. Thus your tree antenna will be in the length limits, plus or minus a few inches but enough to "trim" if your slightly beyond the limit.

Break out the tree trimming sheers!!

So how about a cylinder about 3 meters long (diameter to be
determined, I guess) made of window screen or hardware
cloth or aluminum foil

Well think of it this way..what would be the difference between a 3.5 meter solid satellite receiver dish and a 3.5 meter "mesh" dish???

Only one advantage here...the "mesh" dish has less wind loading than its solid counterpart....as to improving the signal it picks up...it does not. Only the LNA on the feed horn has anything to do with that part, as well as dish depth, the LNA focal point, and dish diameter.

You would get better results welding the oil barrels together and achieve a wide footprint. Remember, the signal rides on the surface of the antenna, so the wider it is..the bigger the footprint will be, and is why when the antenna is wider than a simple whip or piece of wire, it helps the AM audio response...same effect.

RFB

Wide or large diameter antennas will exhibit wider bandwidth resulting in better quality sounding AM. They will not make the signal stronger. Since the Rangemaster does not specify make and manufacturer of a whip antenna, though they do suggest Radio Shack, anyone's whip is OK as long (no pun) as the combined length of the ground lead if used and antenna does not exceed 3 meters. Now considering that not all CB whips are created equal with regard to diameter, the banter about compliance vs non-compliance, is just that banter. 🙂

Wide or large diameter antennas will exhibit wider bandwidth resulting in better quality sounding AM. They will not make the signal stronger. Since the Rangemaster does not specify make and manufacturer of a whip antenna, though they do suggest Radio Shack, anyone's whip is OK as long (no pun) as the combined length of the ground lead if used and antenna does not exceed 3 meters. Now considering that not all CB whips are created equal with regard to diameter, the banter about compliance vs non-compliance, is just that, banter. 🙂

No it wont make the signal stronger, it just makes the signal more clear at its furthest range. Antenna has nothing to do with TX power or making the signal stronger...tho this can be debatable when you talk about a poorly designed antenna vs a really good one, then yes obviously that signal will be stronger at the test point running the better built antenna than the poor one.

RFB

One thing common to part 15 types is that we think constantly about antennas. A new question popped in the head which fits the topic of this thread.

WHAT if a 3-meter antenna is placed right at the corner of a building? This has never been discussed. Previously there has been talk that placing the antenna against the side of a building will hamper its performance, but the corner of a house is the most minimum point of location next to a house.

Probably the most common reason for wanting the antenna close is to allow keeping the transmitter indoors.

Probably the most common reason for wanting the antenna close is to allow keeping the transmitter indoors.

Well 209 says nothing about length issue, just field strength....however that would not fly for those with them 600+ dollar certified units as those cant have any feedline of any useful length to seperate the guts from the stick to set up a separated system..would also void warranties and the certifications...but for other units...may work.

Still even with the antenna on stand-offs hanging on the corner of a building, that will seriously affect its performance...most likely to the un-favored direction, including shifting the omni-pattern in the direction of the corner point. That might not be where the signal needs to be going, as well as chances the building arrangement may not be positioned so that one of its corners are facing the direction of preferred signal coverage.

More of those real world variables to contend with...but that is what it is all about in this hobby! 🙂

RFB

pre·vail·ing (pr-v l ng) adj. 1. Most frequent or common; predominant. 2. Generally current; widespread. pre·vail ing·ly adv. pre·vail ing·ness n.

So, is it prevailing opinion that the diameter of the Top Hat rather than the radius of the Top Hat is part of the 3 meter antenna length limit?

Other forums have also discussed this and the general feeling was to use the radius in the calculation. One person went so far as to say a Field Inspector told them so.

Hey, RFB, call your Inspector buddy and see what he has to say.

Other forums have also discussed this and the general feeling was to use the radius in the calculation. One person went so far as to say a Field Inspector told them so.

Well hear say is like the ear socket holes...everyone has two of them. The only way that this person's assertion would be true is if your top hat was not a complete circle along the outer edge..ie splits like the @ sign. Then at that point yes it is the radius that counts as adding to the total length.

But a uniform circle attached at the center, it is the diameter that applies to the total length, counting from the center attach point to the outer edge anywhere along the diameter...not the combination of diameter in a left-right-forward-backward way.

If you mount 4 such top hats, and each were connected at their edges to form a clover leaf like configuration, then yes you account for edge to edge measurement of each attached top hat to the total length.

RFB

As to the top hat, my firm stand is that only the vertical height matters, and the other prevailing belief, that the diameter of the antenna isn't counted, also applies to top hats: the horizontal measurement does not count. I am willing to defend this position all the way in hand cuffs.

AND, to be the non-conformist that every website needs, I believe that a transmission line is NOT a lead in, and that part 15 does NOT disallow transmission line (my two NOTS).

Ankle bracelets.

Well life would be pretty darned boring if there were no varying ideas and styles. The trick is to sort through it all and find a common ground...HA! 😛

To me personally, I see no purpose to the so called 3 meter limit where as it must be comprised of everything under the sun. Here is why I say that.

In tests upon tests and more tests, having a coax feeding a 3 meter element with a loading coil anywhere on the element did not make any difference to the emitted signal measurement when hitting the field strength limit at the given distance and compensating TX power to overcome the coax losses and its length and hitting that field strength limit at the specified distance.

To me, makes more sense to run a coax than to be stringing lines out to a box filled with power and audio. This is especially true when the 3 meter stick is sitting above an elaborate ground radial system which does not have to have a radial length limit.

Field strength is what counts here. It is the thing that will determine if your signal is usable and not causing interference, or is causing interference at the measurement point.

A so called choke filter can be placed at the coax connector's ground just as easily as it can be attached to the ground lead before it leaves a TX box such as that of the Rangemaster and Procaster. So why not let us run a coax for pete's sake! And why not have a TX capable of more than 100mW to allow for compensating for coax losses and attach that choke to the fitting ground lug and meet the specified field strength limit at the specified distance point!!!!

REBEL I SAY!!! 😉

RFB

Thanks gentlemen. You have given me a lot
to think about.

I will probably be reading your comments and
thinking about them for a while.

I appreciate your input very much.

Bruce, MICRO1690/1700