I went for 500 plus ohms at 27mhz.
I don’t have a choke at the radio or amp however, only at the feedpoint.
I don’t have a choke at the radio or amp however, only at the feedpoint.
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Mobile Rigs - Static, interference, and thoughts on these issues...
- Thread starter Cutlass327
- Start date
FLAME_WALL=On.
Skip the SWR, your only working with a coax to attach to the antenna - you need the SWR thingy ok between both to allow the coax to transfer power to from the antenna and radio.
That's really what COAX is supposed to be used for - a simple conduit (SIC) so you can talk on (er, Excuse me - I meant USE ) the antenna without having to put you and your radio on the top of a tower or on the roof of your vehicle getting wind whacked at +55MPH while asking for a Smokey report....kinda keeps you cleaner too...
So, if the Coax does what it does - then why worry?
Once installed, you'll need to check it every now and then, or if you get a hiccup or two from the radio and it doesn't seem to want to work right and your friends are asking - Hey, WHERE DID YOU GO? - then you may need to check SWR - it's the QUICKEST indication of your systems performance.
Well, if you know what TRUE length of antenna you need to make 1/4 wave work - then skip worrying about the SWR part and build it...Some where's between 102" on up to 108" depending on where YOU POSITION the ANTENNA. over or on your Ground Plane - you should never ever have to worry about SWR, just buy that cable that meets the radios 50 ohm unbalanced and make it connect, properly - to the antenna to BALANCE that unbalanced load using that cable...
Oh! Wait - It's called COAX...
Oh geez...-Honey, get the Fire hose ready - I'll 'prolly get lamb-basted for this too...
Well, if you have the right length, and you are using the proper "cable" - then why would - or should I worry about SWR?
- Just make sure the antenna is CONNECTED to your radio thru that "Cable" ok?
Look into Resonance...
That is what a lot of people don't truly look for, they think SWR of 1:1 is where they need to be at, and as far as the radio goes, they'd be in the rights...
But, again, and this is where I bought the Farm before...(ahemn)
They don't think of RESONANCE - you have a frequency, you have the radiator - you connect the two using that Cable they call COAX - if the antenna is 1/4 wave Resonant - then SWR doesn't need to be 1:1 - if it's done right, whether it's 1:1 or even 1:1.7 - you will be ok, BECAUSE you use SWR to verify the antenna SYSTEM is ok, DOES not mean the coax needs to be adjusted...
Well, you "adjust coax" (you can't really - just play with it) by fixing it, by repairing connections, replacing it, preventing pinch points - routing it properly, everything you need to do, in making it work and transferr energy to and fro - with the least amount of ohmic/Reactive and Radiative problems...you do not fix coax by making it RESONATE to the antenna - where now you have an even bigger problem that you cannot solve for now the coax is part of the antennas system - your CMC (Common Mode Currents)
You can find that - https://www.dxengineering.com/techarticles/balunsandfeedlinechokes/balun-basics-common-mode-vs-differential-mode#:~:text=Common mode current is the portion of conductor,caused by improper feedline installation or antenna design.'] definition from DX Engineering here [/URL]
- Caution THE ABOVE may not be the last word, or even the best words, but you need to get your head around Resonance - then everything else will fall into place.
But when it comes to making things couple, as into the air and in kind, to reciprocate; from the air to get the signal to your radio...
The less losess - the better - that's where your efforts with Coax come into play.
The Antenna can be any design, you've heard of 1/4 Wave tuned, 1/2 wave tuned and even 5/8ths and above tuned - ok, stop here and rest a moment...deep breath...
Ok, you can put 50 ohm coax to them and get a pretty good SWR IF YOU PUT IT TOGETHER CORRECTLY - right? Well, they will sell you know (PUN) antenna - before you pay for it.
They leave that up to you - as to how to make it work.
Then why does Lil Wil, Realistic Base Loaded and others like Firestik work? Because although they may have properties of the whatever fractional wavelength they claim it to be - you still have to put it on the old clunker, or hot rod - or your go-kart - and still make the SWR tolerable for the radio to work it.
Their antennas are designed to tune to a specific range of frequencies based upon a simple design of an adequate ground plane to (or counterpoise) form an image to provide a 50 ohm loading appearance for LOW SWR - KEY WORD: Appearance - doesn't mean it's RESONATE - just it's providing a TUNED effort of loading for low SWR to 1:1 or thereabouts' AT The Frequency range it is tuned to - with you being the responsible party for placing all of this on a similar shape or design they originally tuned their antenna using whatever type or kind or shape of Ground Plane for their Counterpoise Imaging - washtub onto the stick framework of the Titanic. We don't know, only can guess - about the same as trying to really understand the ingredients for what inside a tube of Toothpaste.
If it don't provide a LOW SWR (see above) better reset and restart your approach and look for errors in your assembled piece of work; like - position of radiator - the connector assembly and the cable connectors for it and how it's placed on your "ground plane"
Doesn't mean you'll get out like a raped ape, banshee or even across the street - that claim is up to the antenna maker. You decide their fate...
If you Build it, they will come...
If you make it RESONATE - they will listen...
If it provides a low working SWR, they will Hear you...
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I had one of those made for 2 places in the coax, one for behind the radio, one for the antenna feed side at the amp. I ended up with only one behind the radio.
I have been told now, that this choke should be at the base of the antenna, not at the radio end.
Part of my issue is that book seems to be over my head, getting into technical speak I am not familiar with.
Once it was all hooked up, except power to amp, I am still picking up the pulses in the CB from the beat of the music, and it does increase a little when starting the vehicle.
Seems to be a little lower noise level, but still present.
Andy, I'm referring to tuning antennas for lowest X, not SWR.
And what I'm discussing in the post you quoted was looking at the R at the point X=zero to judge the effectiveness of the RF ground. The actual point of the post is discussing whether its worth pursuing a R of less than 50ohms, if that’s what you’ve got at X=0.
I don’t know the answer to that, but that’s how my truck is right now. Very close to 50ohms at X=0.
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Nah...not an intrusion. Just wanted to make sure my thoughts were clear. I very intently avoided the acronym “SWR” in that post, lol.
Still - I’ll tell you up front, I don’t think tuning for SWR or X amounts to a hill of beans for 99% of mobile installs.
I hope I’m wrong, as I’ve changed to tuning for X 100% of the time..and I’ll take any benefit I can get.
Usually the example that comes up to counter my thoughts is either a multiband ham antenna, or a 5/8 wave base CB antenna with multiple means to change impedance...and the topic gets dragged so far off course we can’t see the forest for the trees.
But...as far as my mobile, I definitely notice zero change in efficiency from lowest X, to lowest SWR, and well beyond.
So if CBers want to tune a mobile for lowest SWR - using easy to use and commonly available tools - I tend to doubt that they would be able to be able to observe better performance adjusting an antenna by the X.
So yeah, if we want to open the door into that discussion (been done here many times) then that’s cool as well.
So...my thoughts...a mobile 1/4 wave CB antenna, being monobanded, having very little bandwidth requirement, and already close to 50 ohms at resonance by design, mounted over an inherently imperfect ground...I don’t think the average “Joe” would see a difference tuning for X.
Anyway...I took it all in. Thanks for sharing.
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I just try to wrap my head around things, @Handy Andy . Discussion helps that along immensely...and especially when several folks with different viewpoints and experiences contribute...the “food for thought” gets tossed back and forth, and feeds my brain.
I actually went back to read my first post; the one you responded to. I actually intended to include a different quote, that was a better basis for my question and has come up several times:
That quote was more in line with what I was asking with respect to changing or attempting to change the feedpoint impedance at resonance on a mobile antenna. Like I was saying, ground plane antennas are typically designed with lowered radials to get to 50ohms...so why wouldn’t we be happy if our mobile antenna works out close to the same? Is it less efficient to drop the radials on a ground plane antenna and run 50ohms at X=0, as opposed to operating with 90 degree radials and a lower, closer to 36.8 ohm impedance? If so, is there enough difference that anyone would even know?
And if we aren’t happy with 50 ohms on a vehicle and chase 36.8, then short of changing the shape of a vehicle it may well not be possible to lower it. <- This is something I’d love to fully grasp.
But the other problem with my post is I’ve latched on to a separate side-topic (above)and strayed from the question in the original post.
With respect to the original topic of reducing noise through bonding, there is some useful info here, at least one account that vehicle noise was perceptibly lower after concerted effort to bond the vehicle.
But a lot of it doesn’t mean anything. To be RXd an S9 at 10 miles, without the full context, I feel is just an anecdote. I’ve been recorded from my mobile S9+20 at 5000 miles, and my story is just the same - it tells no one anything.
Same with regards to talking over base stations with a mobile. Plant your feet in the right spot and you can do that with an HT. But if one were told demonstrate that, what would it prove with respect to bonding? And of course, I have to be reminded that @Marconi has quoted directly from article where the author tells us we may not be able to observe a difference. That’s a pretty strong caveat, in my mind.
I actually went back to read my first post; the one you responded to. I actually intended to include a different quote, that was a better basis for my question and has come up several times:
That quote was more in line with what I was asking with respect to changing or attempting to change the feedpoint impedance at resonance on a mobile antenna. Like I was saying, ground plane antennas are typically designed with lowered radials to get to 50ohms...so why wouldn’t we be happy if our mobile antenna works out close to the same? Is it less efficient to drop the radials on a ground plane antenna and run 50ohms at X=0, as opposed to operating with 90 degree radials and a lower, closer to 36.8 ohm impedance? If so, is there enough difference that anyone would even know?
And if we aren’t happy with 50 ohms on a vehicle and chase 36.8, then short of changing the shape of a vehicle it may well not be possible to lower it. <- This is something I’d love to fully grasp.
But the other problem with my post is I’ve latched on to a separate side-topic (above)and strayed from the question in the original post.
With respect to the original topic of reducing noise through bonding, there is some useful info here, at least one account that vehicle noise was perceptibly lower after concerted effort to bond the vehicle.
But a lot of it doesn’t mean anything. To be RXd an S9 at 10 miles, without the full context, I feel is just an anecdote. I’ve been recorded from my mobile S9+20 at 5000 miles, and my story is just the same - it tells no one anything.
Same with regards to talking over base stations with a mobile. Plant your feet in the right spot and you can do that with an HT. But if one were told demonstrate that, what would it prove with respect to bonding? And of course, I have to be reminded that @Marconi has quoted directly from article where the author tells us we may not be able to observe a difference. That’s a pretty strong caveat, in my mind.
Sorry for taking your thread in another direction.
As I mentioned before, when I first set up my pickup I bonded the hood. That’s the only bonding I have done. I believe it made a perceptible difference...but sometimes I would hear engine noise again and I second guess that.
Then, most recently, I installed 5 1/2” split beads at the antenna feedpoint, right inside the headliner.
And that made a huge difference in the noise. I’m certain of it.
Not to pretend I understand it all, but I wanted to share what worked for my truck.
So in regards to the QSO range. This is no skip, just direct mobile to base between two towns. No doubt you've seen, know of or have experienced the fact that many mobiles struggle to make a few miles.
As in regards to not being able to observe a difference, yeah that's quite possible looking at it purely from a "what my eyes and ears tell me when I'm using my CB" and I won't argue it because I often get the same on my amateur gear when adding an RF choke to the antenna. However use a RF current meter on your coax to measure currents flowing on the outside of the braid or use the hack method of putting a flourescent tube near the coax as you key up and seeing how bright it is and you'll get an observable difference assuming of course you didn't already have a good ground.
You're hitting the nail...
But the board is breaking under the pressure...
You helped awaken the beast that many ignore.
At least they feel they could just "noise filter it away" - and yet by doing so, they are not addressing another problem with the durability and operability of the noisy device and how it screws up an otherwise quiet noise floor the vehicle can operate in and all sensors would communicate without having to scream at each other until they have no choice but to turn on the Check Engine - Service Engine Soon -Malfunction Indication Light. In fewer words, when is dependable - a failure? - only when a condition is ignored.
IF you have more time to delve into this - think of the ideal ground plane image - the antenna's counterpoise - able to provide it (your antenna) the ability to radiate - if the perfect world you'd have the only limitations of the "Q" for bandwidth and the loading itself to provide the 50 ohm loading "range" for the radio's unbalanced output.
Else just ignore the below ---
Bonding of the individual pieces (Panels) of a vehicle - even though it's bolted together as a unit, look at the perspective of why CMC and Coax seem to become intertwined. The coax now takes on the duty of the counterpoise the vehicle cannot provide.
The panels of the vehicle, wherever you mount the antenna - become part of the image because the panel is able to be part of the congruous (intact homogenous - singular) piece of the antennas' needed other half.
But if it can't utilize enough surface area nor does it have the ability to become a RESONATE half of the radiator - the coax becomes what...
Ok, stop there, we have some stuff others have talked - discussed, yelled - preached and otherwise emboldened themselves in saying...
Coax length matters...<--The Urban Myth still exists...
But in the reality of the situation - does it really matter?
Yes, because the antenna and it's image are not equal - either in phase, reactively in element or as an effective length in which to be tuned and show resonance - equal length - or greater - for the image the driven radiator is struggling with to generate.
No, because it's not designed to do that in a simple antenna system.
Why?
That is due to the fact of the FEEDPOINT is not conducive to the R = X = 0 - it's a CONJUGATE event - it has reactive elements - the capacitive effect of the shortened (Read this as Less Surface area) ground plane image onto the fact that the inductive effects of the antenna whether loaded or not - APPEARS AS to this new complex equation. within the coax connection at the antennas' mounting location.
Since the feed point is not "50 ohms" anymore, - the coax itself is no longer the simple conduit - it is part of the antennas' SYSTEM. The Coax is now a reactive element trying to pipe/contain RF power - but now it's performing the multiple duties of Shielding, Providing RF, accepting RF (Reflection) and BALUN (Nodal) effects at the same time - all because of the lack of surface area.
Which if the owner had done a simple bonding process of making the panels able to couple to the RF "skin effect" and radiate as one single piece - all the out of phase currents, shielding problems and radiational reactive Conjugate problems - would work themselves out.
The above is also why many Antenna makers that give you the whole antenna - Coax and all, tell you to always properly be mounting it and tune it. DO NOT CUT the COAX they provide and mount the loading system within -extending coax to its full length and MOUNT the antenna in a suitable location ON TOP OF YOUR VEHICLE - as simple or as complex as it is, it is a single unit.that Is supposed to work for MOST applications (ULP).
So if you come up short on length (The reference to the top of the tower or on the roof of your vehicle at 55) Because you can't reach the radio to the antenna - Ok, a Barrel connector or two later and the jumper - you add on length of coax - you're gong to find it changes it's tuning - why? because the antenna loading system is affected by the added length. You bought a package deal, now you've voided it's performance warranty because you can't find a suitable spot for the antenna on your vehicle that is suitable and close enough to connect the radio to it and tune it for (LOW SWR) Proper resonance (SIC) The antenna, loading and the coax - It's really making it meet 50 ohm reactive Conjugate meeting of the Capacitive and Inductive Reactance to leave you with the Radiation resistive element as big or as small as it is...Isotropic to Dummy Load as Dipole is to dBi
Add coax to something like the Lil Wil and you may wind up with an unworkable antenna. All because you've positioned the antenna mount on a spot that takes too long of coax run to make it back to the radio and now you have to add a coax jumper that isn't supposed to be reactive - but little did they tell you - that if you encounter problems - don't cut the coax and call them - they'll help you.
What do they do? Well, they used to offer advice and even different length of whips to help you - you had to pay for it but nowadays - you might want to just give up using the "Menu" system and being put on hold - for if you're on a minutes plan, you'll be out of them soon enough waiting for their endless loop of songs to end and a real operator to come on and check for breathing on the other end.
But the board is breaking under the pressure...
You helped awaken the beast that many ignore.
At least they feel they could just "noise filter it away" - and yet by doing so, they are not addressing another problem with the durability and operability of the noisy device and how it screws up an otherwise quiet noise floor the vehicle can operate in and all sensors would communicate without having to scream at each other until they have no choice but to turn on the Check Engine - Service Engine Soon -Malfunction Indication Light. In fewer words, when is dependable - a failure? - only when a condition is ignored.
IF you have more time to delve into this - think of the ideal ground plane image - the antenna's counterpoise - able to provide it (your antenna) the ability to radiate - if the perfect world you'd have the only limitations of the "Q" for bandwidth and the loading itself to provide the 50 ohm loading "range" for the radio's unbalanced output.
Else just ignore the below ---
Bonding of the individual pieces (Panels) of a vehicle - even though it's bolted together as a unit, look at the perspective of why CMC and Coax seem to become intertwined. The coax now takes on the duty of the counterpoise the vehicle cannot provide.
The panels of the vehicle, wherever you mount the antenna - become part of the image because the panel is able to be part of the congruous (intact homogenous - singular) piece of the antennas' needed other half.
But if it can't utilize enough surface area nor does it have the ability to become a RESONATE half of the radiator - the coax becomes what...
Ok, stop there, we have some stuff others have talked - discussed, yelled - preached and otherwise emboldened themselves in saying...
Coax length matters...<--The Urban Myth still exists...
But in the reality of the situation - does it really matter?
Yes, because the antenna and it's image are not equal - either in phase, reactively in element or as an effective length in which to be tuned and show resonance - equal length - or greater - for the image the driven radiator is struggling with to generate.
No, because it's not designed to do that in a simple antenna system.
Why?
That is due to the fact of the FEEDPOINT is not conducive to the R = X = 0 - it's a CONJUGATE event - it has reactive elements - the capacitive effect of the shortened (Read this as Less Surface area) ground plane image onto the fact that the inductive effects of the antenna whether loaded or not - APPEARS AS to this new complex equation. within the coax connection at the antennas' mounting location.
Since the feed point is not "50 ohms" anymore, - the coax itself is no longer the simple conduit - it is part of the antennas' SYSTEM. The Coax is now a reactive element trying to pipe/contain RF power - but now it's performing the multiple duties of Shielding, Providing RF, accepting RF (Reflection) and BALUN (Nodal) effects at the same time - all because of the lack of surface area.
Which if the owner had done a simple bonding process of making the panels able to couple to the RF "skin effect" and radiate as one single piece - all the out of phase currents, shielding problems and radiational reactive Conjugate problems - would work themselves out.
The above is also why many Antenna makers that give you the whole antenna - Coax and all, tell you to always properly be mounting it and tune it. DO NOT CUT the COAX they provide and mount the loading system within -extending coax to its full length and MOUNT the antenna in a suitable location ON TOP OF YOUR VEHICLE - as simple or as complex as it is, it is a single unit.that Is supposed to work for MOST applications (ULP).
So if you come up short on length (The reference to the top of the tower or on the roof of your vehicle at 55) Because you can't reach the radio to the antenna - Ok, a Barrel connector or two later and the jumper - you add on length of coax - you're gong to find it changes it's tuning - why? because the antenna loading system is affected by the added length. You bought a package deal, now you've voided it's performance warranty because you can't find a suitable spot for the antenna on your vehicle that is suitable and close enough to connect the radio to it and tune it for (LOW SWR) Proper resonance (SIC) The antenna, loading and the coax - It's really making it meet 50 ohm reactive Conjugate meeting of the Capacitive and Inductive Reactance to leave you with the Radiation resistive element as big or as small as it is...Isotropic to Dummy Load as Dipole is to dBi
Add coax to something like the Lil Wil and you may wind up with an unworkable antenna. All because you've positioned the antenna mount on a spot that takes too long of coax run to make it back to the radio and now you have to add a coax jumper that isn't supposed to be reactive - but little did they tell you - that if you encounter problems - don't cut the coax and call them - they'll help you.
What do they do? Well, they used to offer advice and even different length of whips to help you - you had to pay for it but nowadays - you might want to just give up using the "Menu" system and being put on hold - for if you're on a minutes plan, you'll be out of them soon enough waiting for their endless loop of songs to end and a real operator to come on and check for breathing on the other end.
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Yes, obviously not skywave propagation. I still don't think it tells us anything.
When I first started in the hobby, having no clue and a legal 4 watt radio and pretty short magnet mount antenna....I used to sit in the evenings and talk to all the locals in the next town on AM. Always excellent reports, I never worried about the details. It was around 15-18 miles from me to them, depending on specifically who I was talking to. Wasn't unusual at all that my radio could talk over someone else that was much closer.
One day one of the fellas and I discussed meeting up for coffee....turns out he had no clue I lived in a neighboring area, and didn't dream that I was a mobile. He always figured with my signal in the red every single day, that I was sitting right in the middle of his town and probably running power.
But there wasn't anything magical occurring - I just had a absolutely perfect line of sight to his antenna due to the terrain. My low power radio with a cheap magnetic antenna was enough to do the rest.
And as far as tearing for common mode currents - I know that I have that problem.
The antenna mounting arrangement and location is virtually identical to what I have used on two previous pick ups. Neither of those showed any symptoms at all. This one does.
If I can make an improvement to my set up then I’m all for it. It’s on the agenda...but working on my pickup in June in Eastern NC isn’t terribly high on the list of things that get me aroused. Still, a large roll of braid and some ancillaries sit here waiting for me.
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