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Best Moblie Antenna for OTR Truck
- Thread starter ctvanover
- Start date
I'm a truck driver here in the UK and do over 450 miles per day including commuting to and from work (56 mile round trip). Since I started truck driving in the early 1990s I worked out I'd logged over 2 million miles Truckers in the USA can drive at higher speeds and have less overall traffic congestion to deal with than we do here so I can quite believe that a US trucker could rack up 4 million miles in 31 years.
No it doesn't. The feedpoint impedance of the antenna and the ratio of the diameter of the outside of the inner conductor to the inside diameter of the braid of the coax and the antenna socket impedance on the radio sets the feedline SWR. The antenna socket impedance does not change between TX and RX. I understand the thinking you're applying but it is wrong. You're thinking in terms of DC, RF isn't DC.
Because it is longer than a full wave. As you get longer than a full wave you start to form lobes with high gain. The number of lobes increases, their gain increases but they get narrower with more and more nulls as you get longer from a full wave length. I used an inverted L antenna that was 85ft long for amateur radio. On 10m that had several lobes than had more than 10dBi gain. Downside is you also get nulls and they can be as severe as -30dBi.
The EDZ does not have higher gain in all directions or elevations depending on vertical/horizontal mounting. Mounted horizontally you may find you can no longer hear signals from certain directions that were around a S5 whereas signals from other directions that were a S5 may now be a S7/9.
It is a good radiator because the directors are used to concentrate the signal into a beam pattern thus increasing the intensity of the RF field in the direction the antenna is pointing.
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There are a lot of people here making silly pie in the sky claims. They probably get away with it in CB forums because some people like to argue nonsense, and other just don't know when it is nonsense.
I don't have a lot of time for this, but let's look at just two of the many extremes of nonsense:
One person claimed there could be "several dB" change from tuning for "resonance" vs. lowest SWR. Reactances are not dissipative. They simply change phase angle between voltage and current. Any loss increase would have to come from either an increase of a dissipative resistance in the system, or from an increase in current. This is why we can change the height of an AM tower all over the place with very little field strength change. Any field strength change pretty much comes from a pattern change, NOT an efficiency change. So we are expected that if someone tunes an antenna for 35 j5 ohms we will suddenly see "several dB" difference than if he tunes the antenna for 35 j0 ohms at the feed point. That's pretty silly.
Then we have a fellow who thinks size means gain. Why he is talking about gain is beyond me, because I spoke ONLY of efficiency. Efficiency is not gain. Gain is a product of directivity and efficiency. I was not speaking of directivity or gain, I was only speaking of **efficiency**. Since gain was brought up, antenna gain is not a direct result of size. Antenna gain actually comes from squeezing radiation into a smaller area of space by introducing destructive wave interference in some directions. That forms a null, and since we apply a constant power, the field strength in directions without a null increases (as long as we don't hurt efficiency more than we increase pattern directivity). It is much like filling a balloon with air and squeezing it. The balloon extends out in the directions where it is not squeezed, as long as it does not lose air from the squeezing.
As for receiving, let's not be silly. We all know, or we **should know**, the load and feedline surge impedance (or characteristic impedance if you prefer that term) determines the feedline SWR. When transmitting, the transmitter is the energy source and the antenna is the load. The antenna and feedline impedances would determine SWR...not the transmitter. When receiving, the antenna is the energy source. The receiver is the load. Thus the receiver sets the SWR on a given feedline when receiving.
The point of this is if the feedline is long and so lossy that a few ohms reactance radically changes system efficiency (please pay attention I said efficiency and not gain), then you also better be sure the receiver is matched to the feedline. Because if, while transmitting, a few ohms of reactance changes efficiency enough to cause several dB of magical system efficiency change, then you damn sure better make the receiver matches the feeder or you get the same result!
Most receivers are not even 50 ohms. I've measured them between 20 ohms and 100 ohms or more on 50 ohm inputs, and no one notices. As a matter of fact optimum noise figure is almost NEVER when the input device is matched perfectly to the feedline!
This is a very strange world. In the real world, reactances are by definition....lossless. In this world, a few ohms reactance magically causes huge loss. In this world efficiency is gain, not efficiency, and antenna size makes gain, not directivity and efficiency. If commercial stuff worked like CB stuff, none of it would be working. LOL
I don't have a lot of time for this, but let's look at just two of the many extremes of nonsense:
One person claimed there could be "several dB" change from tuning for "resonance" vs. lowest SWR. Reactances are not dissipative. They simply change phase angle between voltage and current. Any loss increase would have to come from either an increase of a dissipative resistance in the system, or from an increase in current. This is why we can change the height of an AM tower all over the place with very little field strength change. Any field strength change pretty much comes from a pattern change, NOT an efficiency change. So we are expected that if someone tunes an antenna for 35 j5 ohms we will suddenly see "several dB" difference than if he tunes the antenna for 35 j0 ohms at the feed point. That's pretty silly.
Then we have a fellow who thinks size means gain. Why he is talking about gain is beyond me, because I spoke ONLY of efficiency. Efficiency is not gain. Gain is a product of directivity and efficiency. I was not speaking of directivity or gain, I was only speaking of **efficiency**. Since gain was brought up, antenna gain is not a direct result of size. Antenna gain actually comes from squeezing radiation into a smaller area of space by introducing destructive wave interference in some directions. That forms a null, and since we apply a constant power, the field strength in directions without a null increases (as long as we don't hurt efficiency more than we increase pattern directivity). It is much like filling a balloon with air and squeezing it. The balloon extends out in the directions where it is not squeezed, as long as it does not lose air from the squeezing.
As for receiving, let's not be silly. We all know, or we **should know**, the load and feedline surge impedance (or characteristic impedance if you prefer that term) determines the feedline SWR. When transmitting, the transmitter is the energy source and the antenna is the load. The antenna and feedline impedances would determine SWR...not the transmitter. When receiving, the antenna is the energy source. The receiver is the load. Thus the receiver sets the SWR on a given feedline when receiving.
The point of this is if the feedline is long and so lossy that a few ohms reactance radically changes system efficiency (please pay attention I said efficiency and not gain), then you also better be sure the receiver is matched to the feedline. Because if, while transmitting, a few ohms of reactance changes efficiency enough to cause several dB of magical system efficiency change, then you damn sure better make the receiver matches the feeder or you get the same result!
Most receivers are not even 50 ohms. I've measured them between 20 ohms and 100 ohms or more on 50 ohm inputs, and no one notices. As a matter of fact optimum noise figure is almost NEVER when the input device is matched perfectly to the feedline!
This is a very strange world. In the real world, reactances are by definition....lossless. In this world, a few ohms reactance magically causes huge loss. In this world efficiency is gain, not efficiency, and antenna size makes gain, not directivity and efficiency. If commercial stuff worked like CB stuff, none of it would be working. LOL
When someone on the Internet finishes their sentence with the word period.............their eyes are usually brown but not from genetics.
I remembered someone mentioning receiving SWR before so I looked at previous posts until I found it...
Have you ever heard of reciprocacy? It is usually used when discussing radiation patterns, but it applies here as well. If you are measuring an SWR mismatch through the system in one direction, a signal that begins its life at the far end of the system and travels through the system in the opposite direction will have the exact same amount of mismatch when it gets to the radio. This makes sense actually, as the signal is traveling through and being affected by all of the same equipment. It is also a requirement for something like a smith chart to work, and speaking from experience, smith charts work very well.
Then these words caught me...
Are you using a noise bridge? That would be cool in my book as many people quickly jump to more expensive and far more complex tools that they don't really understand, and skip over other cheaper tools like this, which for them would be just as useful and perhaps less confusing. That being said, I, personally, prefer my grid dip meter over my noise bridge for various reasons. Still, the fact that someone might have mentioned using a noise bridge really made my day.
If you are using a noise bridge, what you are measuring is not actually the input circuit of the radio. A noise bridge does not measure a circuit, it measures a point in a circuit, and that point is where the noise bridge is in the circuit. Unlike a modern day antenna analyzer, it can't even measure the actual reflected SWR signal. It is literally limited to where in the system it is attached, and if you move it along a coax to a different part of the circuit, if you don't have a perfect SWR match, you will notice that the results it reads will change. Further, as the signal itself has not yet traveled through the receiving circuit of the radio (as far as the signal is concerned this is after the noise bridge) before it gets to the noise bridge, there is no way that the noise bridge could logically measure said circuit and apply it to its output. Further complicating that problem today is the widespread use of AGT circuits in radios, which modify the input signal before you ever get a chance to hear it, making said noise bridge harder to use, and potentially less accurate. This really is unfortunate, but it is a fact of modern life.
Unless of course you are saying that you used something other than a noise bridge. If that is the case, please explain further, I would love to hear how exactly you did said testing...
The DB
Lol..... nothing like some humor.
I think its best you and i sit back and Listen.
CTR wrote the book on this stuff.
Problem is he has very limited time.
The Db has the knowledge to ask the correct questions , especially for LEARNING.
That should be the Key here.
I can see we are talking past each other.
Noise figure has nothing to do with a noise bridge. Noise figure is a way of expressing weak signal receiving capability by using noise temperature.
Analyzers, even very good analyzers, are more accurate for SWR than reactance. Most important the claim or notion tuning antenna or antenna system for resonance is better than tuning for low SWR is completely without merit. In a properly calibrated meter, reactance always shows as an increase in SWR. Some people think 30 ohms resistance and 20 ohms reactance is 50 ohms, and can make a false 1:1 SWR. It cannot.
Reactances do not absorb power.
The only loss in system efficiency when off resonance either comes from increased feedline current (because the feeder has higher SWR) or a loss of transmitter energy transfer to the feeder (caused by increased SWR).
If someone measures SWR it is just fine, and because bridges are much easier to calibrate and maintain accuracy for SWR, and since SWR is what ultimately matters for loss and power transfer, it is a preferable method.
Any claim a small reactance change causes greatly increased loss without a significant SWR change is simply untrue. If someone can give a specific example where the antenna system is unaltered except for increased reactance at some defined point without an accompanying increase in SWR, I'm all ears. No arm waving and wild several dB claims.....just explain the loss mechanism that changes without violating electrical laws. Someplace there would have to be loss or the signal source would have to not transfer the same energy, and we all know (or should know) reactance is by definition lossless. If we have an inductor with a series equivalent impedance of 10 ohms 100j it has a Q of ten and only the 10 ohms is dissipative. If we changed it to 10 ohms 200j, twice then reactance, Q would be 20. If it had the same current loss would be exactly the same. If it had less current, loss would be less by the square of the current level change.
This is why, with low loss feeders, tuning can be done far from an antenna without significant loss increase. This is why an off resonance antenna like an extended double zepp with a good low loss feeder has nearly 100% efficiency, even though current and voltage are not in phase (reactive) at the antenna feed terminal. Please note I said efficiency, which has nothing to do with gain.
Noise figure has nothing to do with a noise bridge. Noise figure is a way of expressing weak signal receiving capability by using noise temperature.
Analyzers, even very good analyzers, are more accurate for SWR than reactance. Most important the claim or notion tuning antenna or antenna system for resonance is better than tuning for low SWR is completely without merit. In a properly calibrated meter, reactance always shows as an increase in SWR. Some people think 30 ohms resistance and 20 ohms reactance is 50 ohms, and can make a false 1:1 SWR. It cannot.
Reactances do not absorb power.
The only loss in system efficiency when off resonance either comes from increased feedline current (because the feeder has higher SWR) or a loss of transmitter energy transfer to the feeder (caused by increased SWR).
If someone measures SWR it is just fine, and because bridges are much easier to calibrate and maintain accuracy for SWR, and since SWR is what ultimately matters for loss and power transfer, it is a preferable method.
Any claim a small reactance change causes greatly increased loss without a significant SWR change is simply untrue. If someone can give a specific example where the antenna system is unaltered except for increased reactance at some defined point without an accompanying increase in SWR, I'm all ears. No arm waving and wild several dB claims.....just explain the loss mechanism that changes without violating electrical laws. Someplace there would have to be loss or the signal source would have to not transfer the same energy, and we all know (or should know) reactance is by definition lossless. If we have an inductor with a series equivalent impedance of 10 ohms 100j it has a Q of ten and only the 10 ohms is dissipative. If we changed it to 10 ohms 200j, twice then reactance, Q would be 20. If it had the same current loss would be exactly the same. If it had less current, loss would be less by the square of the current level change.
This is why, with low loss feeders, tuning can be done far from an antenna without significant loss increase. This is why an off resonance antenna like an extended double zepp with a good low loss feeder has nearly 100% efficiency, even though current and voltage are not in phase (reactive) at the antenna feed terminal. Please note I said efficiency, which has nothing to do with gain.
I would agree with this.
Noise temperature, wow, that is something you don't hear every day, especially when referring to antennas... You did mention noise factor, but this isn't something I expected to hear from anyone really ever, especially on a CB antenna forum. I bet that aside from the two of us there are maybe five (if we are lucky) other people on this forum that has any idea what noise temperature is without having to go look it up first. When it is talked about, it is generally not referred to in this environment, which brings up a convenient problem, I have no way to measure or factor in anything that has to do with this at this point. I cannot say for sure that it can be used in this way or not (haven't had a chance to verify it) but even if it is, the use of this will make a perfect example for ssomething I want to discuss with you below.
Analyzers, even very good analyzers, are more accurate for SWR than reactance. Most important the claim or notion tuning antenna or antenna system for resonance is better than tuning for low SWR is completely without merit. In a properly calibrated meter, reactance always shows as an increase in SWR. Some people think 30 ohms resistance and 20 ohms reactance is 50 ohms, and can make a false 1:1 SWR. It cannot.
Reactances do not absorb power.
The only loss in system efficiency when off resonance either comes from increased feedline current (because the feeder has higher SWR) or a loss of transmitter energy transfer to the feeder (caused by increased SWR).
If someone measures SWR it is just fine, and because bridges are much easier to calibrate and maintain accuracy for SWR, and since SWR is what ultimately matters for loss and power transfer, it is a preferable method.
Any claim a small reactance change causes greatly increased loss without a significant SWR change is simply untrue. If someone can give a specific example where the antenna system is unaltered except for increased reactance at some defined point without an accompanying increase in SWR, I'm all ears. No arm waving and wild several dB claims.....just explain the loss mechanism that changes without violating electrical laws. Someplace there would have to be loss or the signal source would have to not transfer the same energy, and we all know (or should know) reactance is by definition lossless. If we have an inductor with a series equivalent impedance of 10 ohms 100j it has a Q of ten and only the 10 ohms is dissipative. If we changed it to 10 ohms 200j, twice then reactance, Q would be 20. If it had the same current loss would be exactly the same. If it had less current, loss would be less by the square of the current level change.
This is why, with low loss feeders, tuning can be done far from an antenna without significant loss increase. This is why an off resonance antenna like an extended double zepp with a good low loss feeder has nearly 100% efficiency, even though current and voltage are not in phase (reactive) at the antenna feed terminal. Please note I said efficiency, which has nothing to do with gain.
Let me be clear about something, there is nothing in this quote that I don't already know. (You will have to click the quoted text to see it all, but it is everything that I didn't previously quote from your message above) If you think you are teaching me in particular something with the information in this quote, then you are mistaken. That being said, I didn't use any wild dB claims either. Actually I suggested a source above (which has a freely available version) that tells anyone who is willing to read the exact same thing, and if anything is far more readable than how you are writing it.
Reactance, in and of itself, does not cause loss, and neither does SWR. It is neither of these, but the reflected wave form as it travels back (and forth) over a lossy feed line that causes additional losses within the antenna system. As a matter of fact, I have, in the past, demonstrated with modeling that reactance and resonance have nothing to do with efficiency and gain, although the study at the time focused primarily on gain. There is no peak in gain or efficiency just because you are near/at resonance, and I have never once claimed that there was. I have also talked about the earlier days of radio when SWR was first discovered, and even readings at and above an SWR of 5:1 was found to make so little difference that it was treated as a curiosity more than anything. That was before the step backwards (my opinion) with the advent and wide use of coax.
Now I want to go back to your reference to noise temperature. Luckily I knew what you were referring to when you mentioned noise temperature. although noise factor eluded me. In all fairness I wasn't really expecting to have anyone refer to this much less actually use either of those terms. Something to think about is what if I had no idea of what you were referring to? There really isn't much on it out there, and much of the information that is out there is beyond the understanding of most hobbyists, which, lets be clear about this, is who you are talking to here. I also have no way of confirming/denying what you are saying, at the very least not easily (you can trust that I will, one way or another, get an independent verification, it is how I learn), and many people even here would have brushed off your attempt to dazzle with brilliance as an attempt to baffle with bullshit.
When explaining something to someone, its not about what you know as much as it is about what they know and can understand. For example, the guy that just got that fancy antenna analyzer, the way you are presenting it, the device is completely useless, and the guy that tried to learn more would go back to, and likely be stuck in, the CB equivalent of the dark ages (aka stuck on SWR). When you say something like "may as well just use SWR" you reinforce in their minds the importance of SWR and more often than not their perception of its connection to gain. In my opinion it is better to let them think that resonance is better and let go of the hold SWR has on the average newbie/beginner as they now have precedence to build on when it comes time to let go of resonance being directly tied to gain/efficiency. Further, experience with an antenna analyzer will help them get the building blocks to potentially get to that point while an SWR meter generally will not. By your own admittance, it doesn't matter one way or the other, so as it makes little difference I choose to recommend the device that will give the person trying to learn the tools they need to do so, or at least the experience they need to ask the right questions.
Talking beyond not only what someone can understand, but also beyond what they are willing to consider will do them no good, and more often than not will turn them off to listening to what you have to say. You have to remember, most people here are not engineers, talking to someone who doesn't understand what you are trying to say, and doesn't know enough to get from where they are to what you are saying, doesn't help them at all.
The DB
Gain is a way of describing how much of an increase/decrease there is in a way that can be easily translated to improvements on S meters as both use dB. On shortened antennas doubling the length of the whip will give you gain over the shorter whip and as it works as a function of the square it will give you 6dB gain. That doesn't mean its efficient, it just means it is more efficient than the shorter antenna. It is far easier to quantify gain in dB than it is to quantify efficiency because the difference in signal strength is easily measurable and a figure for gain over a reference point can be given that can then be used by a third party as a point of measure. If I tell you X antenna is 34.6% more efficient than Y what does that translate to in S meter readings? Would you say an antenna that is 34.6% more efficient than Y is better than one that has 3dB gain over Y? What gain does an efficiency improvement of 34.6% translate into? And that is the entire point and why we use gain as a reference.
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