Best shortest mobile CB antenna??

[fourstringburn]

Not lossy at all, at ~12 miles it beats the 1/4 wave whip!

If you say so! I guess the Verizon test is absolute science. ( Can you hear me now?)

Wide bandwidth and high efficiency power radiation don't go hand in hand when talking about shortened antennas less than a 1/4 wave length. You have great bandwidth because you have a high value of inductive reactance which means big losses in the coil. I called your antenna comparable to a leaking dummy load because a 50 ohm dummy load has the best bandwidth anyone could ask for.

A full 1/4 wave whip isn't perfect but it does have better radiation efficiency over coil loaded antennas since it uses no loading coils That's a fact most everyone here knows. However there is a current loss at the feed-point being near 37 ohms instead of a perfect 52 ohms, so that's why it isn't perfect either.

I believe you know this but I'll say it anyway because it seems you don't grasp it very good. Loading coils are inductive and cause losses since inductance is energy stored ( and wasted in this case ) in a magnetic field. The shorter the antenna or poor design, the more inductance is needed to bring the feed point to 50 ohms. The more inductance needed, the bigger the losses. Eventually with enough inductance, you will have either a leaking dummy load or a full on dummy load but at least that will give you all the bandwidth you would ever want.

The only way to effectively counter the inductive losses and and improve some efficiency with shortened mobile antennas is to use a capacity hat. This adds capacitance to cancel out some of the coil losses and also adds to the antenna mass that equivalates similar to extending it's length. But you will have to redesign the antenna by removing some coil turns. I would say that a 4 ft antenna with just the right amount of coil loading and a 24 inch diameter 8 radial cap-hat would be inline to effectively radiate efficiency power like a 1/4 wave whip would, possibly even better. But the real test would be with a field strength meter not the Verizon test.

It required several days of calcs & trial/error in building. Bringing calculations to life in the real world is sometimes a daunting task when it comes to fashioning materials to make them do what you want.

Antenna building is a good learning experience and something everyone should attempt at least once. What testing equipment did you use to determine the antennas resonance and inductive values?

Looks like Sirio did a fine job on that trucker. What length & type of coax did you use to connect it to the analyzer?

The coax is irrelevant here except for using a 50 ohm coax to test the feed point of a 50 ohm antenna. A short jumper is all you need measured at the antenna feed point. It can be a piece of 9913 or rg-58, it doesn't really matter. You don't tune mobile antennas like these with specific coax or coax lengths.

 

[fourstringburn]

This is a good example of a shortened mobile antenna that should have good efficiency. I would redesign it without the upper 2nd coil and add a couple more cap-hat radials. That would eliminate a lot of inductive loss by minimizing the loading coils. Some inductance is needed to be able to get the antenna feed point to 50 ohms. Contrary to what The DB said on earlier posts, capacitance alone doesn't effectively tune an antenna like inductance does or a combination of the both. Maybe that's why antenna tuners are either the Inductive type or both capacitance and inductance, Gee I wonder Mr. DB?

 

[The DB]

Contrary to what The DB said on earlier posts,

Bringing my name up in a post, that can be a double edged sword to begin with, but you also said I was wrong when I wasn't... Actually, your the only person I know who has direct experience with capacity hats and still believes as you do... Anyway, when I get some time I will build a short CB antenna and tune it with nothing but a capacity hat, proving one of us is correct, I will document it as post it up as well, including pictures, and maybe even a video if warranted. Until then this discussion is tabled, and you can believe as you wish. However, like I just said, be careful about invoking my name, that in and of itself can be a double edged sword...

Maybe that's why antenna tuners are either the Inductive type or both capacitance and inductance, Gee I wonder Mr. DB?

When it comes to antenna tuners and matching circuits found on many antennas, in a vast majority of cases a combination of both inductors and capacitors are included. When this is the case, the inductors are in series and the capacitors are in parallel, or vice versa. They are never both in series or both in parallel, always one type in series and one type in parallel. Perhaps you are willing to explain to me why, careful, I already know the answer...

When it comes to using just inductors or just capacitors, both layouts will work, and both have been done. In fact, there is a method of tuning a dual band antenna with two different L matching networks one right after the other, the higher frequency uses two capacitors one in series and one in parallel, while the other band is tuned with two inductors. (NOTE: It has been a while since I studied this, I might have inductors and capacitors which which frequency range mixed up.)

An odd note about using inductors and capacitors for antenna tuning, you can actually use a series inductor to simulate the matching network effects of a series capacitor and a series capacitor to simulate the matching network effects of a series inductor. The same works for the parallel inductance and capacitance as well.

Their is a reason that at HF all capacitors are used more often than all inductors, perhaps you are willing to explain to everyone why this is? Hint: It has nothing to do with their loss characteristics, and the answer is really far simpler than that.

I know, long and offtopic, but I was asked, even if only rhetorically...

Going to your post that starts with a Verison joke (the same guy is actually advertising with another cell phone company now...).

A full 1/4 wave whip isn't perfect but it does have better radiation efficiency over coil loaded antennas since it uses no loading coils That's a fact most everyone here knows. However there is a current loss at the feed-point being near 37 ohms instead of a perfect 52 ohms, so that's why it isn't perfect either.

This statement taken from a certain point of view isn't necessarily wrong, what I would be worried about is someone misunderstanding a certain aspect so it does require a bit more of an explanation. The difference in impedance is, in and of itself, not directly where the loss the occurs. This impedance mismatch simply causes a reflection that travels back up the coax, and if the radio/amplifier was built properly, bounces off of the matching circuit (all of the reflection) and travels back towards the antenna and actually adds to the forward power of the transmitted signal. This is shown in the real world by measuring power while tuning an antenna. As antenna SWR goes down, the total power read on a power meter inline in the coax also goes down, this is true even if you are using a directional watt meter reading only forward power. Where the losses come in is when the signal travels over coax. There is no such thing as lossless coax, so a signal traveling back and forth over the coax is where the loss happens. The losses that happen are directly related to that quality and length of the coax in question.

Now I have a question for you...

Loading coils are inductive and cause losses since inductance is energy stored ( and wasted in this case ) in a magnetic field.

I can't tell if you are saying that all of the power stored in the magnetic field is, in this case, lost or not. By the way it is worded, I would assume you are saying it is, but I am not sure. Perhaps a further explanation on how you see this working, even if it is only for my benefit?

Unless I missed something, I agree with the rest of what was written in said post.

Now to Needle Bender...

My favorite mobile antenna "creation" which I made from odds & ends in the shop, has about a 3MHz bandwidth @ 2:1, and outperforms a 102" whip (and all other antennas tested against it - all of which were also mounted atop the center of the roof) - to a local internet-linked receiver approximately 12 miles away.

A few things on this...

1) Pics or it never happened, vids of the testing are even better.
2) Extraordinary claims require extraordinary evidence, and sating a shorter mobile antenna outperformed a longer one is such a claim.

Not lossy at all, at ~12 miles it beats the 1/4 wave whip!

Actually, to both of you, it is possible for an antenna that has more losses than another to outperform said antenna under certain conditions. Losses, while important, especially in the very high loss mobile environment, are not the end all and be all of antenna performance.

It required several days of calcs & trial/error in building. Bringing calculations to life in the real world is sometimes a daunting task when it comes to fashioning materials to make them do what you want.

Post up the calculations, I would love to see them.

I also note the method you used to test said antenna is flawed. S-meters are notoriously inaccurate to begin with, and to add to that the ALC circuit found on modern radios throws this off even further. With modern radios, a weaker signal may actually appear stronger than an actual stronger signal. I know you know this. So I have to ask, what other methods of testing have you done?

Unlike a lot of people, I am leaving the door open that a shorter antenna, under certain circumstances (that take more than just loading/matching losses into account) might actually be able to outperform a slightly longer antenna, however, I don't see it making so much of a difference that you would notice...

As I said above, extraordinary claims...


The DB

Edit note: I removed a sentence and corrected grammer and spelling. I normally do that before posting, unfortunately time did not allow for that this morning.

 

[fourstringburn]

. Anyway, when I get some time I will build a short CB antenna and tune it with nothing but a capacity hat

Be my guest...

That's what I been criticizing you on, you have no direct hands on experience but you argue anyway.

I can't tell if you are saying that all of the power stored in the magnetic field is, in this case, lost or not. By the way it is worded, I would assume you are saying it is, but I am not sure. Perhaps a further explanation on how you see this working, even if it is only for my benefit?

That's another part of your problem is you can't interpret a simple sentence. I gave a basic definition on what Inductance is and how it is relevant to shortened coil loaded antennas. If it stored all the energy then it would be a dead circuit at the coil wouldn't it? Geeeeeeezzz isn't that obvious!

I guess you have to have every sentence you read carefully worded like a politically correct liberal or else you will jump on them at first opportunity.

I would say get a life and ignore what I say and I will happily ignore what you say and all will be well.

But of course it is in your nature to always get the last word in so I leave this opportunity to you....Take it away!

 

[fourstringburn]

Actually, to both of you, it is possible for an antenna that has more losses than another to outperform said antenna under certain conditions. Losses, while important, especially in the very high loss mobile environment, are not the end all and be all of antenna performance.

I forgot to quote this one because it is utter ridiculous. I thought you were knowledgeable on things until I read this. You must have been visiting the state of Colo-weed-o when you were doing field test shoot outs on lossy mobile antennas.

But more than likely, it is another assumption based on your modeling program with no real hands testing to back up your claim.

 

[Mudduckmobile]

Be my guest...

That's what I been criticizing you on, you have no direct hands on experience but you argue anyway.



That's another part of your problem is you can't interpret a simple sentence. I gave a basic definition on what Inductance is and how it is relevant to shortened coil loaded antennas. If it stored all the energy then it would be a dead circuit at the coil wouldn't it? Geeeeeeezzz isn't that obvious!

I guess you have to have every sentence you read carefully worded like a politically correct liberal or else you will jump on them at first opportunity.

I would say get a life and ignore what I say and I will happily ignore what you say and all will be well.

But of course it is in your nature to always get the last word in so I leave this opportunity to you....Take it away!

4 stringburn, I whould like to know about useing a "matching box" over the home made coil inductor. I'm still working on all this. One step at atime to make all beter on my mobile.
Thank you.

 

[The DB]

Be my guest...

That's what I been criticizing you on, you have no direct hands on experience but you argue anyway.

And you don't have the knowledge to put your experience of what is happening into proper perspective. Your essentially telling me that your misunderstanding of what is going on is more accurate than what broadcast engineers, who also have experience with cap hats, tell me different. With all due respect, why should I believe you over actual broadcast engineers that have both knowledge of theory and experience in the field.

That's another part of your problem is you can't interpret a simple sentence. I gave a basic definition on what Inductance is and how it is relevant to shortened coil loaded antennas. If it stored all the energy then it would be a dead circuit at the coil wouldn't it? Geeeeeeezzz isn't that obvious!

Perhaps the problem was I was giving you to much credit and assumed that what was written at face value was just poorly written. OK, lets take your sentence at face value, you clearly don't know how an inductor works as not all of the power stored in the magnetic field is lost, actually very little of said power is lost.

I guess you have to have every sentence you read carefully worded like a politically correct liberal or else you will jump on them at first opportunity.

Or you expect me to read the world into your poorly worded sentences as well as say the same thing over and over the exact same way when what you said was understood the first time, "like a politically correct liberal".

I would say get a life and ignore what I say and I will happily ignore what you say and all will be well.

But of course it is in your nature to always get the last word in so I leave this opportunity to you....Take it away!

I don't hate you. You are, however, acting like a child. Because of this, the advice you give to me about ignoring you I give to everyone who would listen to you.

And about me always having the last word, sounds a lot like you, actually. Remember, you called me into this part of the discussion. I was perfectly happy letting the matter rest and sitting this out, even with Needle Bender's extraordinary claims, so you only have yourself to blame for me posting here to begin with.

I forgot to quote this one because it is utter ridiculous. I thought you were knowledgeable on things until I read this. You must have been visiting the state of Colo-weed-o when you were doing field test shoot outs on lossy mobile antennas.

But more than likely, it is another assumption based on your modeling program with no real hands testing to back up your claim.

So you honestly think losses are the end all and be all of an antenna's performance? There is nothing else in any way, shape, or form that matters? I didn't say losses were not a big part of the equation, and am definately not saying that they aren't an important part of what matters (and for the record, never have), but to say that they are all that matters shows just how much you don't know... You didn't even bother to ask what I was thinking or talking about to see if it was plausible, you just assumed. You criticize me because you think I am assuming something and then do the same yourself? There is a word for that...


The DB

 

[Global Mobile 357]

(Quote)

A full 1/4 wave whip isn't perfect but it does have better radiation efficiency over coil loaded antennas since it uses no loading coils That's a fact most everyone here knows. However there is a current loss at the feed-point being near 37 ohms instead of a perfect 52 ohms, so that's why it isn't perfect either.

So if there is a current loss will this mean a lower watt output at the meter?

 

[Captain Kilowatt]

Actually, to both of you, it is possible for an antenna that has more losses than another to outperform said antenna under certain conditions. Losses, while important, especially in the very high loss mobile environment, are not the end all and be all of antenna performance.

I forgot to quote this one because it is utter ridiculous. I thought you were knowledgeable on things until I read this. You must have been visiting the state of Colo-weed-o when you were doing field test shoot outs on lossy mobile antennas.

But more than likely, it is another assumption based on your modeling program with no real hands testing to back up your claim.

I'm late to the party but I just caught this one and would like to say that I have seen many times a simply lossy 1/4 wave has outperformed a 7/8 wave gain type antenna on VHF/UHF and it was due to take off angle versus elevation of the other station.Happens all the time when there is a great difference in elevations like mountain top versus valley or even with satellite communications. In this case a lower gain antenna does indeed outperform an antenna with higher gain since gain is measured at the angle of peak signal strength.

Now back to the party but lets keep it under control.

 

[fourstringburn]

I'm late to the party but I just caught this one and would like to say that I have seen many times a simply lossy 1/4 wave has outperformed a 7/8 wave gain type antenna on VHF/UHF and it was due to take off angle versus elevation of the other station.Happens all the time when there is a great difference in elevations like mountain top versus valley or even with satellite communications. In this case a lower gain antenna does indeed outperform an antenna with higher gain since gain is measured at the angle of peak signal strength.

Now back to the party but lets keep it under control.

And a 7/8 wave antenna is considered good?

We are talking comparing a 1/4 wave whip to a shortened CB antenna. A lossy shortened CB antenna against a 1/4 wave whip, which will be better???

 

[Captain Kilowatt]

And a 7/8 wave antenna is considered good?

It sure is considered good. I ran one for several years on 2m. Worked like a charm on the wide open spaces. It sucked getting into high hill-top repeaters when I was fairly close to them due to the low angle of radiation. My 1/4 wave worked better when working AO-27 satellite too.

We are talking comparing a 1/4 wave whip to a shortened CB antenna. A lossy shortened CB antenna against a 1/4 wave whip, which will be better???

Referencing my post above, see I told you I was late to the party. I didn't read every post. I suppose based on the same thing regarding TOA it would apply to CB as well although I would suspect the incidents of a shortened antenna outperforming a full sized 1/4 wave would be far fewer, not nonexistent just less often, and less dramatic in the difference..............if measurable.

 

[fourstringburn]

It sure is considered good. I ran one for several years on 2m. Worked like a charm on the wide open spaces. It sucked getting into high hill-top repeaters when I was fairly close to them due to the low angle of radiation. My 1/4 wave worked better when working AO-27 satellite too.



Referencing my post above, see I told you I was late to the party. I didn't read every post. I suppose based on the same thing regarding TOA it would apply to CB as well although I would suspect the incidents of a shortened antenna outperforming a full sized 1/4 wave would be far fewer, not nonexistent just less often, and less dramatic in the difference..............if measurable.

Never used a 7/8 and don't mess around much with VHF/UHF. But What about a 7/8 on 11 meters or even 80 ?

I would suspect the incidents of a shortened antenna outperforming a full sized 1/4 wave would be far fewer, not nonexistent just less often, and less dramatic in the difference..............if measurable.

You are not saying yes or no, just a vague answer because I think you don't want to take sides or you really don't know.

No need to go back and read the same old same old...

 

[Captain Kilowatt]

Never used a 7/8 and don't mess around much with VHF/UHF. But What about a 7/8 on 11 meters or even 80 ?

You are not saying yes or no, just a vague answer because I think you don't want to take sides or you really don't know.

No need to go back and read the same old same old...

A 7/8 is a little impractical on 11m and COMPLETELY impractical on 80m. Once you start getting into any type of skywave such as on the lower bands there will always be cases where a specific TOA will outperform another. Sometimes it is the lower gain high angle antenna that will be the better. Distance to target plays a role there. Far too many variables to make a definite YES or NO thus my answer is what it is. As for actually using such an antenna on 11m, it would again depend on elevation differences and distance to target whether skywave or direct. Variables are just that. Variable. This precludes anyone from making a definitive YES or NO answer that is all encompassing to all situations. In general the answer is NO but given the right specifics it could be YES. This is what makes experimenting educational as well as necessary.

 

[The DB]

Actually, to both of you, it is possible for an antenna that has more losses than another to outperform said antenna under certain conditions.

All this over a statement that says something *might* be possible under certain limited circumstances. The circumstances were neither mentioned, nor inquired about. The absoluteness in the response before even inquiring as to why I might leave the door open to such a possibility like that is amazing to me.

Wow, just wow.

So something is possible, that means it might happen some of the time under very limited conditions, or it might not happen at all, yet it is taken as if I said something like "all shortened antennas with always outperform full length antennas no matter what".

Seriously.

Because I leave the door open to something that you cannot imagine does not make what I said:

utter ridiculous

OK, my eyes have be been opened, the "lossy coil" rules all when it comes to antenna performance. It doesn't matter that the losses in the coil I am talking about will, in and of itself, make no noticeable difference between the near full length shortened antenna and a full length antenna (to the point that if you noticed I would ask you what is wrong with one of the antennas). It doesn't matter that the antenna is mounted so close to the earth the ground losses dwarf the losses from the coil by several orders of magnitude (you know every mobile installation on the CB band on the planet). It also doesn't matter that the coils main intended use is to elevate more of the higher current areas of the antenna further away from the very lossy earth below, thus potentially giving a net efficiency increase to the antenna system (something modeling predicts and parts of have been demonstrated in the real world). What also doesn't matter is the possible small change in the angle of radiation, and by extension its benefits to local communications that modeling also predicts and an effect that has also been shown to exist in the real world. None of this matters because there is a "lossy coil" included in the antenna design, and the "lossy coil" is the only thing that matters. Praise the antenna gods, my eyes have been opened and I now see the light...

Or not.

It is entirely within the realm of possibility that the concept I am using is simply not feasible in the real world, I understand this, but if it is the case, it is not because there is a "lossy coil" in the equation.

Its not like I'm not talking about something so inefficient as running 40 meter ham radio on a five foot whip mounted on a vehicle, I am talking a coil that will have much less effect, orders of magnitude less in fact, than this major loss in efficiency.

Actually, the real question is why am I bothering to try and explain any of this to someone who clearly doesn't understand the basic concepts of what I am talking about, isn't willing to even try to understand said basic concepts, and is hung up on something that has not only been factored in, but has far more limited effect in this situation than he seems to be able to understand?

That is a very good question, I think I'll sleep on it, literally.


The DB

 

[Road Squawker]

I can answer that question in one word