Thank you Peter. Only yesterday I set up the exact antenna and had the same problem, not only with this antenna but with my ampro. Easy fix that I forgot about...
That is so crazy. I just started to think about using my car to mount an HF antenna. Just went to the store for help and they were nothing like this video. It's crazy how I've learned so much from you. I don't understand why those who sell this equipment really can't critically think what is going on - as if collectively they haven't put a mobil system up.
Great video Peter, I was having all manner of problems trying to tune the TXCR. Fitted some clip on ferrites I had in the junk box and managed to get 1:1 VSWR 😊 . I also noted that the ferrites have to be at the TX end not the antenna end otherwise you cannot get resonance to the wanted frequency. Guess the coax braid is acting as a counterpoise before the CMC.
Fantastic video Peter. These real life examples are so powerful when you use your knowledge, a good antenna analyser and the power of the video. Thanks for a wonderful presentation, 73, Jamie VK2YCJ, Newcastle, NSW, Australia.
Thanks for these videos Peter! I spend a lot of time in my work vehicle on job locations and hope to be upgrading from a 10m monoband rig to a multiband rig to do voice and js8call when parked at the job. These videos on mobile setups are giving me good insight. Thanks and 73. N2SCD
Sorry Peter. I feel I must point out that I feel your assertion that the Ampros have a narrower bandwidth than the diamond equivalent is fanciful. My Ampro 20 covers all the ssb portion of the band well within 1.5:1 and with a single mag mount. I also think if you had used a reasonable sized mag mount (the one you used looked like one for a 2/70) and located the antenna on the roof you would have been able to tune it in anyway. 73
i never mentioned bandwidth - I said matching - somerhing quite different. I also said the mag mount was smaller than I would like but it proved the point I was making - use an RF chike.
@@timg5tm941 I've have both these antennas and use mounts drilled straight through roof of my van, there is little difference between the two in performance if any, I find mounting the antennas this way plays the biggest part in reducing loss and increasing efficiency
A very helpful and simple explanation regards swr problems and cures, always find your videos top class and more to the point easy to understand and follow...73s Peter
My Ducato-based Hymer has even less metal than yours, so mag-mounts are out. I've had one heck of a game trying to find a decent ground plane and SWR and I'm still struggling to get rid of electrical interference. I'm going to experiment with your ferrite ring idea.
I have pretty well the same set up, campervan, diamond whip and mag base. Poor swr EXCACTLY as shown in your video caused me to shelve the idea. Time to revisit. THANKS so much. 👍 DARYL - de VK3AWA
Peter! what a well-delivered video. Please would it be possible to stop associating low VSWR with resonance though? It muddies the water for newcomers and can cause confusion. The AA230 will show resonance with ease, as you know, be good to see where the antenna is really resonant and not at lowest VSWR. I'd be running an earthing wire from the magmount to the chassis/bonnet (hood, for our US friends) where it connects to vehicle body to help the antenna also. Keep up the great work and easy to watch videos.
A snap-on ferrite near the antenna helps keep RF outside of your cab and *another* at the feed point and maybe a few along the length but not at regular intervals. The idea is to prevent standing waves from forming along the length of the coax.
An rf choke /ferrites stop common mode current on braid of coax that may be interfering with swr, an rf choke has nothing to do with stopping standing waves along the length of coax
@@Pioneer936 "stop common mode current on braid of coax that may be interfering with swr" The "S" of SWR is "standing", how can it be both a current and standing? If it is standing, it is not a current. It is standing. Common mode is a feature of a pair of wires that are supposed to be balanced; one wire has a current going one way and the other wire has exactly the same current but going the other way. Their magnetic fields thus cancel and such an arrangment neither radiates nor accepts electromagnetic energy. Coax is unbalanced and the term "common mode" isn't exactly appropriate because of that. You might achieve magnetic cancellation but not electrostatic cancellation because the inner wire is shielded but the outer wire (the braid) is not shielded. TRIAX shields the braid of Coax. Ferrite on the coax can *provoke* standing waves by suppressing RF current on the outside, creating a high impedance point. If you space the ferrites 1/2 wavelength apart on the coax, you'll get a doozy of a standing wave between the ferrites and it can dramatically alter your antenna radiation pattern. Vertical antennas that use guys tend to have irregular spacing of guy wire insulators to prevent this phenomenon. "an rf choke has nothing to do with stopping standing waves along the length of coax" Stopping the standing waves is a side effect of their actual function. Obviously they impede RF current, but without RF current there cannot be a standing wave. What exactly IS a standing wave? It is the peak VOLTAGE that you would measure along the length of the braid where the outgoing wave passes through the reflected wave. At specific distances from the antenna or radio, the peak voltage of the outgoing wave happens to align with the peak voltage of the reflection and consequently that's where you get a peak voltage. 1/4 wave along the reflection is now out of phase and when the transmitter goes positive, the reflection goes negative and with infinite SWR, you would measure ZERO volts at that location. Now, insert some ferrites, and suddenly that node where you had zero volts now has the expected transmit voltage. If you happen to put your SWR meter at that zero volt node, its reading is going to be seriously in error. Not completely wrong, but certainly not reliable. That is why I have ferrites next to the SWR meter to break up the standing waves. By themselves, standing waves are relatively harmless. The danger to the transmitter is that in worst case it can double the voltage on your final amplifier (tube, transisistor or MOSFET) and destroy it. A tuner simply reflects the reflection back to the antenna giving that wave another shot at being radiated (more or less). Ferrites are an inductor and become part of a tuned circuit with the coax. They won't always stop RF current IF you happen to choose values of inductance and spacing of ferrites that just happen to be resonant at the frequency being used. In that case the ferrites might as well not be there and might even augment the phenomenon.
@@thomasmaughan4798 think you have misunderstood what I've said, you said that the idea of an rf choke is to stop standing waves forming along the length of coax,,, this is not what an rf choke does, it has nothing to do with stopping standing waves forming at all its to stop common mode current on braid of coax due to an antenna imbalance, nothing to do with a feedpoint impedance mismatch, you can have common mode currunt issues with a 1.1 swr perfect match
@@Pioneer936 "you can have common mode currunt issues with a 1.1 swr perfect match" While rare, I suppose it is possible. I don't use the phrase "common mode" since it simply is not common mode. It's just RF on the outside of the coax. Usually from unbalanced antenna feed point but can also be induced by the radiating elements of the antenna into everything metal nearby, which includes the feed line. This is particularly true for people using mag-loop antennas (me). www.arrl.org/files/media/Group/antenna_myths.pdf
Thank you 4 sharing. Would it not be better to install the choke at the antenna instead of the at the radio end? I am having this exact problem and just found your video. I am trying to work 40 meters in my RV connected to an ICOM IC-7300 and I am trying to use an MFJ-2289 Big Ear antenna system. I can't get the VSWR below 18:1. I am using a recently purchased RigExpert AA-650 ZOOM. Any ideas? Cheers, Jay N6WIP
Hi Jay. The advantage of the choke at the radio end is that any RF pickup on the outside of the coax is choked off. Getting VSWR down can sometimes mean juggling with antenna position. But I assume you are using a choke just before the antenna enters the Rig Expert. Also, on 40m you really need a three legged mag mount. A single mag mount does not have enough capacity. Try a 20m whip. If that works out, then it is likely the mag moint needs tipo be larger. 73 Peter.
I had the same problem with the 17m version. I did try a commercial HF choke in series at the feed end but still no joy. Couldn't get a good match at all.
Any time the antenna itself is not perfectly balanced (certainly the case for mobile antennas) the coax is going to radiate and develop standing waves of its own, depending on many factors. It is important to prevent that from happening. So, if the antenna is not a perfect dipole, you must use some sort of RF "choke" on the coax. It can be as simple as some turns of the coax even without a ferrite. IF you use a ferrite, you must choose carefully the KIND of ferrite since they have vastly different responses at different frequencies and might not work at all at 14 MHz and above. UPDATE: Even with a perfect dipole you still need a "balun" to achieve balance and not have the coax radiating.
If you have more than one HF mobile whip do you have to vary the turns around the ferrite ring for each band or do you add a few turns and adjust each HF whip to give good SWR? Thanks.
Hello, Tnx for sharing this video.. For information, what is reference of Ferrite Ring Pse ? 73's for F-15413 Bernard From France in JN38IT. See You Soon...
I've found that the biggest improvement you can do with the Atas is mount it will a drilled mount straight through roof of vehicle, this with illiminate any common mode currunt issues and also reduce loss within the system increasing performance
@@Pioneer936 I don't want to drill through the roof of a very expensive car HI! I know the AT120 works on a three magnet mount on 20 to 10. I'll dip into my ferrite core stock and see what happens.
@@watersstanton you say you cured the problem with a ferrite core and if you have problems matching you must start with this ferrite core, you still have a problem you have just stopped cmc on braid of coax, you still haven't got an adequate counterpoise or ground plane the reason cmc was present in the first place, a low swr doesn't prove that your antenna is radiating as it should, As you can see in other comments the video has created some misunderstanding about this subject
Thank you Peter. Only yesterday I set up the exact antenna and had the same problem, not only with this antenna but with my ampro. Easy fix that I forgot about...
Glad it helped
Very good tips must say thanks I've been working on the radio for over 35 years now we just never stop learning. Great video.
That is so crazy. I just started to think about using my car to mount an HF antenna. Just went to the store for help and they were nothing like this video. It's crazy how I've learned so much from you. I don't understand why those who sell this equipment really can't critically think what is going on - as if collectively they haven't put a mobil system up.
Great video Peter, I was having all manner of problems trying to tune the TXCR. Fitted some clip on ferrites I had in the junk box and managed to get 1:1 VSWR 😊 . I also noted that the ferrites have to be at the TX end not the antenna end otherwise you cannot get resonance to the wanted frequency. Guess the coax braid is acting as a counterpoise before the CMC.
Fantastic video Peter. These real life examples are so powerful when you use your knowledge, a good antenna analyser and the power of the video. Thanks for a wonderful presentation, 73, Jamie VK2YCJ, Newcastle, NSW, Australia.
Good presentation format there Peter. Great advice and well delivered!
Thank you kindly
Thanks for these videos Peter! I spend a lot of time in my work vehicle on job locations and hope to be upgrading from a 10m monoband rig to a multiband rig to do voice and js8call when parked at the job. These videos on mobile setups are giving me good insight. Thanks and 73. N2SCD
The best radio channel on UA-cam. Thank you!
Wow, thanks!
Sorry Peter. I feel I must point out that I feel your assertion that the Ampros have a narrower bandwidth than the diamond equivalent is fanciful. My Ampro 20 covers all the ssb portion of the band well within 1.5:1 and with a single mag mount. I also think if you had used a reasonable sized mag mount (the one you used looked like one for a 2/70) and located the antenna on the roof you would have been able to tune it in anyway. 73
i never mentioned bandwidth - I said matching - somerhing quite different. I also said the mag mount was smaller than I would like but it proved the point I was making - use an RF chike.
@@watersstanton ok on bandwidth. You did say that you get a much better VSWR resonance compared with the Ampros. This I find very surprising indeed
Remember guys loss increases bandwidth
@@Pioneer936 agree. It’s the assertion that for some reason that a shorter antenna that is 3 times more expensive should automatically match better.
@@timg5tm941 I've have both these antennas and use mounts drilled straight through roof of my van, there is little difference between the two in performance if any, I find mounting the antennas this way plays the biggest part in reducing loss and increasing efficiency
A very helpful and simple explanation regards swr problems and cures, always find your videos top class and more to the point easy to understand and follow...73s Peter
Another great video Peter, every day is a learning day! Thank you! 🙂
Thanks for the very helpful and enlightening video Peter! 👍⚡️📻
My pleasure!
Good catch on that choke. Thanks for the idea.
My Ducato-based Hymer has even less metal than yours, so mag-mounts are out. I've had one heck of a game trying to find a decent ground plane and SWR and I'm still struggling to get rid of electrical interference. I'm going to experiment with your ferrite ring idea.
Great advice and when you are a seasoned ham like we are we’ve chased a lot of these Rabbits 🐰 down those wholes❗️🤔
Always very interesting material...
Great advice, as always.
Excellent advice!
Really surprising to learn! Tnx & 73 de WA4ELW in TN 🇺🇸
I have pretty well the same set up, campervan, diamond whip and mag base. Poor swr EXCACTLY as shown in your video caused me to shelve the idea. Time to revisit. THANKS so much. 👍 DARYL - de VK3AWA
Glad we may havesolved your problem. 73 Peter
Nice video.
Thanks!
Great trick! Thanks!
Very helpful!
Peter! what a well-delivered video. Please would it be possible to stop associating low VSWR with resonance though? It muddies the water for newcomers and can cause confusion. The AA230 will show resonance with ease, as you know, be good to see where the antenna is really resonant and not at lowest VSWR. I'd be running an earthing wire from the magmount to the chassis/bonnet (hood, for our US friends) where it connects to vehicle body to help the antenna also. Keep up the great work and easy to watch videos.
Hi would the , principal work with a Cb as I have problems with SWR with mag Mount on my lorry
👍
Cool! Thanks 👍
What a nice number plate :-)
Groovy music!
A snap-on ferrite near the antenna helps keep RF outside of your cab and *another* at the feed point and maybe a few along the length but not at regular intervals. The idea is to prevent standing waves from forming along the length of the coax.
An rf choke /ferrites stop common mode current on braid of coax that may be interfering with swr, an rf choke has nothing to do with stopping standing waves along the length of coax
@@Pioneer936 "stop common mode current on braid of coax that may be interfering with swr"
The "S" of SWR is "standing", how can it be both a current and standing? If it is standing, it is not a current. It is standing.
Common mode is a feature of a pair of wires that are supposed to be balanced; one wire has a current going one way and the other wire has exactly the same current but going the other way. Their magnetic fields thus cancel and such an arrangment neither radiates nor accepts electromagnetic energy.
Coax is unbalanced and the term "common mode" isn't exactly appropriate because of that. You might achieve magnetic cancellation but not electrostatic cancellation because the inner wire is shielded but the outer wire (the braid) is not shielded. TRIAX shields the braid of Coax.
Ferrite on the coax can *provoke* standing waves by suppressing RF current on the outside, creating a high impedance point. If you space the ferrites 1/2 wavelength apart on the coax, you'll get a doozy of a standing wave between the ferrites and it can dramatically alter your antenna radiation pattern.
Vertical antennas that use guys tend to have irregular spacing of guy wire insulators to prevent this phenomenon.
"an rf choke has nothing to do with stopping standing waves along the length of coax"
Stopping the standing waves is a side effect of their actual function. Obviously they impede RF current, but without RF current there cannot be a standing wave.
What exactly IS a standing wave? It is the peak VOLTAGE that you would measure along the length of the braid where the outgoing wave passes through the reflected wave. At specific distances from the antenna or radio, the peak voltage of the outgoing wave happens to align with the peak voltage of the reflection and consequently that's where you get a peak voltage. 1/4 wave along the reflection is now out of phase and when the transmitter goes positive, the reflection goes negative and with infinite SWR, you would measure ZERO volts at that location.
Now, insert some ferrites, and suddenly that node where you had zero volts now has the expected transmit voltage.
If you happen to put your SWR meter at that zero volt node, its reading is going to be seriously in error. Not completely wrong, but certainly not reliable. That is why I have ferrites next to the SWR meter to break up the standing waves.
By themselves, standing waves are relatively harmless. The danger to the transmitter is that in worst case it can double the voltage on your final amplifier (tube, transisistor or MOSFET) and destroy it. A tuner simply reflects the reflection back to the antenna giving that wave another shot at being radiated (more or less).
Ferrites are an inductor and become part of a tuned circuit with the coax. They won't always stop RF current IF you happen to choose values of inductance and spacing of ferrites that just happen to be resonant at the frequency being used. In that case the ferrites might as well not be there and might even augment the phenomenon.
@@thomasmaughan4798 think you have misunderstood what I've said, you said that the idea of an rf choke is to stop standing waves forming along the length of coax,,, this is not what an rf choke does, it has nothing to do with stopping standing waves forming at all its to stop common mode current on braid of coax due to an antenna imbalance, nothing to do with a feedpoint impedance mismatch, you can have common mode currunt issues with a 1.1 swr perfect match
@@Pioneer936 "you can have common mode currunt issues with a 1.1 swr perfect match" While rare, I suppose it is possible. I don't use the phrase "common mode" since it simply is not common mode. It's just RF on the outside of the coax. Usually from unbalanced antenna feed point but can also be induced by the radiating elements of the antenna into everything metal nearby, which includes the feed line. This is particularly true for people using mag-loop antennas (me).
www.arrl.org/files/media/Group/antenna_myths.pdf
www.w8ji.com/common_mode_current.htm
Very useful advice in an entertaining
manner, thank you Peter
73 Rob G3RCE
Your 'solution' will decrease the power getting back to your radio, but it won't increase your output efficiency.
er….wromg! A 3:1 VSWR will certainly decrease the output from the transceiver. Peter
It stops common mode current causing havoc with you system, it does not reduce power
Thank you 4 sharing.
Would it not be better to install the choke at the antenna instead of the at the radio end? I am having this exact problem and just found your video. I am trying to work 40 meters in my RV connected to an ICOM IC-7300 and I am trying to use an MFJ-2289 Big Ear antenna system. I can't get the VSWR below 18:1. I am using a recently purchased RigExpert AA-650 ZOOM.
Any ideas?
Cheers,
Jay N6WIP
Hi Jay. The advantage of the choke at the radio end is that any RF pickup on the outside of the coax is choked off. Getting VSWR down can sometimes mean juggling with antenna position. But I assume you are using a choke just before the antenna enters the Rig Expert. Also, on 40m you really need a three legged mag mount. A single mag mount does not have enough capacity. Try a 20m whip. If that works out, then it is likely the mag moint needs tipo be larger. 73 Peter.
very good video.
Thank you very much! 73 Peter
Hi Peter, any tips on mounting a Little Tarheel 2 to a motorhome.
Is this in essence same as using a 1:1 balun?
standard... RF choke also needed by an HF magnetic loop antenna?
I had the same problem with the 17m version. I did try a commercial HF choke in series at the feed end but still no joy. Couldn't get a good match at all.
Update, got a suitable ferrite today just as you used in the video and voila ! Problem solved, thanks Peter.
Great Vid & Advice , Sold on idea to Keep 2 or 3 FRs Handy
Any Freq any Band inc other than Ham ?
Any time the antenna itself is not perfectly balanced (certainly the case for mobile antennas) the coax is going to radiate and develop standing waves of its own, depending on many factors. It is important to prevent that from happening. So, if the antenna is not a perfect dipole, you must use some sort of RF "choke" on the coax. It can be as simple as some turns of the coax even without a ferrite.
IF you use a ferrite, you must choose carefully the KIND of ferrite since they have vastly different responses at different frequencies and might not work at all at 14 MHz and above.
UPDATE: Even with a perfect dipole you still need a "balun" to achieve balance and not have the coax radiating.
Will the same apply to a CB Radio antenna??
If you have more than one HF mobile whip do you have to vary the turns around the ferrite ring for each band or do you add a few turns and adjust each HF whip to give good SWR? Thanks.
Generally speaking if the number of turns work tk for the lowest band, they will work for higher bands. 73 Peter
Thanks Peter, great video. 73 de ok8msw.
Hello,
Tnx for sharing this video.. For information, what is reference of Ferrite Ring Pse ?
73's for F-15413 Bernard From France in JN38IT.
See You Soon...
I wonder if this will help with some of the ATAS 120A on a magmount problems? Thanks for another useful video Peter. 73 G3WNR
I've found that the biggest improvement you can do with the Atas is mount it will a drilled mount straight through roof of vehicle, this with illiminate any common mode currunt issues and also reduce loss within the system increasing performance
@@Pioneer936 I don't want to drill through the roof of a very expensive car HI! I know the AT120 works on a three magnet mount on 20 to 10. I'll dip into my ferrite core stock and see what happens.
@@kengrey7263 that's never stopped me lol. No worries, but it does eliminate those mag mount problems and is more efficient
Not really magic you've stopped common mode current on braid of coax with an rf choke that's interfering with swr readings
er…….I actually said that in the video!
@@watersstanton you say you cured the problem with a ferrite core and if you have problems matching you must start with this ferrite core, you still have a problem you have just stopped cmc on braid of coax, you still haven't got an adequate counterpoise or ground plane the reason cmc was present in the first place, a low swr doesn't prove that your antenna is radiating as it should,
As you can see in other comments the video has created some misunderstanding about this subject
2M Directional Antenna
Yaesu ft5d
Fantastic thanks very much 🙂 de 2E0FNM