Hi Peter, on most of the mini-vans like Kangoo or Berlingo or Trafic, there are M8 holes on the roof to fix sturdy baggage carriers, because plummers, electricians etc like to put ladders and tubes on them. So i made a Z shaped fixing for normal Antenna foot or SO239 and only fix it once with an M8 x 15mm bolt and it has perfect chassis ground connection. The cable just passes between the rear doors rubber seal. Works fine for 18years.
As someone new to the hobby and who has been struggling to tune my HF antennas on the roof of my (steel) narrowboat, this has been really, really useful and a few things to try! Thanks very much!
I think Mr Waters has been stalking us on Facebook - a lot of this explanation was what I wrote on your (presumably yours!) thread on the UK amateur radio group. I was going to paste the link to this video as a further part of my explanation! :-)
I mostly use vhf /uhf so these mounts are practically all I use other than a rubber ducky. If I ever get around to getting a general license I will have to try hf mobile (14 years as a technician) Thanks for the info on the line isolation for a mag mount! I can only add - Don't pinch the coax going through the door jam or through the window... 😉
Have been a ham for over 40 years and have never used a choke however I decided to try your advice and put one on and all my dedicated whips for 20,17,10, 2m the swr was the highest I have ever known of 30 to 40 to 1, removed the choke and swr was fine on all antennas about 1.8 to 1 on all so my advice us no chokes
May I add some thoughts Peter, from years past and the use of many magnetic bases and various whip aerials. I used to put the base in the centre of the roof with coaxial cable across same and in through a door jam or tail lift hatchback. But beware, that if you leave it on for a period of time, you ran the risk of scratches under the coax caused by dust road grime accumulation. This only happened once for me and I had learnt my lesson, so after that I would mount the magnetic base on the offside of the roof and where the coax did not contact same. I have to admit that I never used a line isolator and I would be rather concerned at having one close to the magnetic base as you show and decribe so admirably, and which would not be advisable in my opinion if the aerial installation was used for any high speed mobile operation, fine if static /M of course. And one final point and which I experienced with the magnetic bases having rubber boots, was the black circle left on the paintwork if the base had been on for a period of time, I think I spotted this on your car Peter? Another excellent video and a really good watch for newcomers and old timers like me! Never too old to learn more about our diverse hobby. And in passing, I still have the FDK Multi U11, purchased from you over 40 years ago, £249, paid for on hire purchase ;-) 73, Martin GW3XJQ
Thank you for sharing , it's very interesting as always . A line isolator is not required if the transceiver is earthed to ground via an earth electrode stake ,the common mode current is then slugged straight to ground via the earth electrode stake . If a line isolator is used , the line isolator will reduce the RF power output from the transceiver . There are difficulties using transceivers mobile or portable as there's generally no ground , a simple earth stake tapped into the ground should suffice on mobile & portable radio use. The home base transceivers are generally grounded through the negative terminal that is connected to the power supply as the negative terminal on the 13.8v power supply will also relate to the earth connector on the 13 amp mains plug , so there is a direct negative earth connection from the home base set up to the outside of the SO239 connector on the rear of the transceiver & again a line isolator will serve no purpose , however if the transceiver has no earth whatsoever , then perhaps a line isolator may suffice ?.
Absolutely brilliant. It has been a long time mystery to me why/how a magnetic mounts works. I knew that it was capacitance coupling, but did not fully grasp the concept, or how the amount of capacitance played a role. And that Mat-50... had no clue that it existed. Also, does not the position/location of the mount affect the directionality of the radiation pattern, and it becomes more directional than omnidirectional... and it starts to work somewhat like a Yagi-Uda in that respect?
Thank you for taking time to cover this subject. I was having some real issues tuning my M1ECC Slidewinder on a mag mount on the roof of my van a couple of weekends ago. I put it down to poor grounding / counterpoise. I did coil the coax 4-5 times approx 5” diameter though , near the radio end to reduce common mode current. I was toying with the idea of using radials draped over the side of the van in conjunction with the inductive coupling of the mag mount. What would your thoughts be on that be please Peter?
Radials may prove that your mag mount is not large enough, but it is not my favourite cure. You don’t mention the bands or mag mount details. Try a ferrite core but make sure this is on the tcvr. side of the radials.
Thanks so much Peter for yet another great video ! My question is, do you think it is safe to use magmounts with HF antennas on the modern EV with their huge lithium batteries ? Any opinion on that ? Thank 73 de VK6 BLU, Johan, Perth, Australia.
one for truckers pulling an empty full size forestry trailer.... you could string a full size moxon rectangle for 21MHz between the uprights on the back.... so when someone comes on trying to impress you with an ATAS on a mag mount you can go back with "& I'm using a full size 2 element beam mobile" (OK it is a sod when you go around a corner & you lose them as they drop out of the beamwidth but there are plenty of straights on the motorway good enough for a quick qso). Going to the opposite extreme when I first started I had a friend who had a bright yellow little Fiat 126 with a Revco 2m 5/8 on a magmount on the roof so it looked more like a dodgem car than anything else (& had a xtal Pye Vanguard in the boot). Good call about the line choke (type 61 material may be better for vhf/uhf... or just an ugly balun).
There is also capacity between the body of the car and earth, I once read it's on the order of 50 pF. Therefore, if over a concrete parking area with embedded 'rebar' or metal reenforcement, there is better system ground effect. Bob KK5R
Thank you for this video, Peter. My question is do we need to keep the line isolator in the line to the antenna for normal use, I.e. after measurements are made, and one is ready to roll down the road?
I keep it really simple and have fantastic results. No antemna analyser,.no isolator. Just put my Ampro whip onto Sirio magmount, see what SWR is at top and bottom of band, adjust accordingly like in the olden days before people they had to have an amalyser. Always get decent match and always work some great DX! 73 M3KXZ
Hi Peter I think that the diameter of the torroid is measured in 1/100th inch segments. Therefor a 240-43 would be 240 hundredths of an inch. Or 2.4 inchs imperial.
Hi. Great vid. Can you let me have a link to the ferrite ring that you have used for your coax filter? I have an ATAS120A which presents a number of mobile tuning and FT8 operating challenges! Trying to resolve them. 73es
Excellent video. You hit most all of the important points that most people don’t think about. I will add that the Radio Handbooks contain formulas for calculating Capacitive Reactance from the value of capacitance and it is an inverse relationship. As the capacitance goes up the reactance in ohms goes down. Also there is a formula for calculating the capacitance in pf knowing the area of the plate ( area of the mag mount) and the spacing and also the dielectric constant if not an air gap. The capacitance of the mag mount can be calculated ( in reality I can only estimate mine due to some unknowns as the dielectric of the material covering of the magnet is also significant in the calculation). For example the dielectric of a capacitor with an air gap is 1 but if Teflon was used it would be about 2.0 and mica would be about 5. But with a conservative estimate you can come close to determining if the mag mount has a low impedance to the car roof! Again remembering that the reactance is inversely proportional to frequency and you need twice the capacitance on 40 as you do on 20 for the same low impedance.
Some commercial VHF/UHF sellers talk about quarter wave vs 1/2 wave and claim that 1/2 wave mobile antennas do not need a ground plane. Can you comment or include discussion of this in a future video?
@@watersstanton But what makes the 1/2 so unique that it does not require a ground plane? And, is it the same principle/reason why it is said that you don't need a ground plane/counter poise for a EFHW antenna? I, and probably many others, would really like to understand the why of it.
On this same subject. Installation of mobile antennas. What do you think about the installation on the rear doors of vehicles taking into account the hinges and on metal roof rails? Greetings from Argentina
Many of us drive pickup trucks with an aluminum tool box mounted on the bed. Would this make a good location to mount a HF antenna and would you recommend a bottom or middle load antenna?
I think we also need to consider whether we are using the mobile whip in position and driving the car or are we just having a drive out and parking up to work 20m for example? If the latter then i wonder if it would be better to simple fit the HF mobile whip to one of those L shaped mast brackets, fitting it to a 6ft pole and clipping a suitable length counterpoise on it effectively turning it into a vertical dipole. You could then include a 1:1 balun on the coax connector to the antenna bracket. I think this would solve a lot of issues such as thin car roofs, damage, RF and common mode currents and exposure to RF. The assembly could be placed any lenth from the car and perhaps temporarily lashed to a fence post or similar. Thoughts anyone? Or just hoist a wire on a fibreglass pole.
@@watersstanton Yes indeed peter , I was just thinking out loud as I’ve recently become inspired to fire up again after a long period of radio inactivity. Like a lot of people, I’m short on real estate for HF so it’s either dig out my am pro vertical ( very effective !) or fly a bit of wire from a fibreglass pole … all mobile of course !
I was more hoping that an installation video would tell me how to get the cable from outside the car to inside the car without compromising waterproofing or crushing the cable. Maybe “Installation Theory” would be a more apt title?
I think almost everybody “crushes” the cable through door or hatch jam. The rubber car inserts are softer than co@x. Never had a problem with this in over 60 years.
Hi Peter, on most of the mini-vans like Kangoo or Berlingo or Trafic, there are M8 holes on the roof to fix sturdy baggage carriers, because plummers, electricians etc like to put ladders and tubes on them. So i made a Z shaped fixing for normal Antenna foot or SO239 and only fix it once with an M8 x 15mm bolt and it has perfect chassis ground connection. The cable just passes between the rear doors rubber seal. Works fine for 18years.
many thanks for that information.
Brilliant video, Peter! Best explanation on this subject that I've seen yet. I wish Waters and Stanton had a shop on my side of the pond!
As someone new to the hobby and who has been struggling to tune my HF antennas on the roof of my (steel) narrowboat, this has been really, really useful and a few things to try!
Thanks very much!
I think Mr Waters has been stalking us on Facebook - a lot of this explanation was what I wrote on your (presumably yours!) thread on the UK amateur radio group. I was going to paste the link to this video as a further part of my explanation! :-)
And don't forget it is on the roof, then drive into a multi-storey park or under a height barrrier - it makes one heck of a racket! 🙂
Ah yes, been there!
I mostly use vhf /uhf so these mounts are practically all I use other than a rubber ducky. If I ever get around to getting a general license I will have to try hf mobile (14 years as a technician) Thanks for the info on the line isolation for a mag mount! I can only add - Don't pinch the coax going through the door jam or through the window... 😉
Nice explanation of use of mag mounts. Several things not considered before especially how it is an offset dipole! Thanks Peter, cheers!
Have been a ham for over 40 years and have never used a choke however I decided to try your advice and put one on and all my dedicated whips for 20,17,10, 2m the swr was the highest I have ever known of 30 to 40 to 1, removed the choke and swr was fine on all antennas about 1.8 to 1 on all so my advice us no chokes
Are you sure you were choking the outer sheath only? Correctly installed the result you report is just not possible.
May I add some thoughts Peter, from years past and the use of many magnetic bases and various whip aerials.
I used to put the base in the centre of the roof with coaxial cable across same and in through a door jam or tail lift hatchback. But beware, that if you leave it on for a period of time, you ran the risk of scratches under the coax caused by dust road grime accumulation. This only happened once for me and I had learnt my lesson, so after that I would mount the magnetic base on the offside of the roof and where the coax did not contact same.
I have to admit that I never used a line isolator and I would be rather concerned at having one close to the magnetic base as you show and decribe so admirably, and which would not be advisable in my opinion if the aerial installation was used for any high speed mobile operation, fine if static /M of course.
And one final point and which I experienced with the magnetic bases having rubber boots, was the black circle left on the paintwork if the base had been on for a period of time, I think I spotted this on your car Peter?
Another excellent video and a really good watch for newcomers and old timers like me!
Never too old to learn more about our diverse hobby.
And in passing, I still have the FDK Multi U11, purchased from you over 40 years ago, £249, paid for on hire purchase ;-)
73, Martin GW3XJQ
Some good points. Thanks.
Thank you for sharing , it's very interesting as always . A line isolator is not required if the transceiver is earthed to ground via an earth electrode stake ,the common mode current is then slugged straight to ground via the earth electrode stake .
If a line isolator is used , the line isolator will reduce the RF power output from the transceiver .
There are difficulties using transceivers mobile or portable as there's generally no ground , a simple earth stake tapped into the ground should suffice on mobile & portable radio use.
The home base transceivers are generally grounded through the negative terminal that is connected to the power supply as the negative terminal on the 13.8v power supply will also relate to the earth connector on the 13 amp mains plug , so there is a direct negative earth connection from the home base set up to the outside of the SO239 connector on the rear of the transceiver & again a line isolator will serve no purpose , however if the transceiver has no earth whatsoever , then perhaps a line isolator may suffice ?.
Great explanation. Thank you for the excellent explanation.
Absolutely brilliant. It has been a long time mystery to me why/how a magnetic mounts works. I knew that it was capacitance coupling, but did not fully grasp the concept, or how the amount of capacitance played a role. And that Mat-50... had no clue that it existed. Also, does not the position/location of the mount affect the directionality of the radiation pattern, and it becomes more directional than omnidirectional... and it starts to work somewhat like a Yagi-Uda in that respect?
Great video Peter,timing was perfect as im getting a cb magmount ready.Thank You.
Glad it helped
Thank you for taking time to cover this subject. I was having some real issues tuning my M1ECC Slidewinder on a mag mount on the roof of my van a couple of weekends ago. I put it down to poor grounding / counterpoise. I did coil the coax 4-5 times approx 5” diameter though , near the radio end to reduce common mode current. I was toying with the idea of using radials draped over the side of the van in conjunction with the inductive coupling of the mag mount. What would your thoughts be on that be please Peter?
Radials may prove that your mag mount is not large enough, but it is not my favourite cure. You don’t mention the bands or mag mount details. Try a ferrite core but make sure this is on the tcvr. side of the radials.
After various mag mounts I found that the tri-mag works the best in the center of the roof.
Yes usually the best option
Good gold wisdoms, from wise & practical man.TNX and stay well Peter. 73,S51X
You are very welcome.
Thanks so much Peter for yet another great video ! My question is, do you think it is safe to use magmounts with HF antennas on the modern EV with their huge lithium batteries ? Any opinion on that ? Thank 73 de VK6 BLU, Johan, Perth, Australia.
I have an EV and no problem. I cannot think of any extra caution needed.
one for truckers pulling an empty full size forestry trailer.... you could string a full size moxon rectangle for 21MHz between the uprights on the back.... so when someone comes on trying to impress you with an ATAS on a mag mount you can go back with "& I'm using a full size 2 element beam mobile" (OK it is a sod when you go around a corner & you lose them as they drop out of the beamwidth but there are plenty of straights on the motorway good enough for a quick qso).
Going to the opposite extreme when I first started I had a friend who had a bright yellow little Fiat 126 with a Revco 2m 5/8 on a magmount on the roof so it looked more like a dodgem car than anything else (& had a xtal Pye Vanguard in the boot).
Good call about the line choke (type 61 material may be better for vhf/uhf... or just an ugly balun).
I have an early ARRL book showing a 3 element 10m whip arrangement on the back of a car!
Question: Why is not a line isolator built in as default. If it is a must it should be there when you buy the mag mount.
It's generally not needed at VHF/UHF, but is good for HF.
There is also capacity between the body of the car and earth, I once read it's on the order of 50 pF. Therefore, if over a concrete parking area with embedded 'rebar' or metal reenforcement, there is better system ground effect.
Bob KK5R
Thank you for this video, Peter. My question is do we need to keep the line isolator in the line to the antenna for normal use, I.e. after measurements are made, and one is ready to roll down the road?
Yes.
Good explanation as ever. Much appreciated.
This was very helpful. Thank you my friend.
Glad it was helpful!
A very good Friday morning to you sir from Wellington Somerset
I have long wondered why moving the mag mount around the top of the car changed the sir. Thanks
The first time I have ever heard of a line isolator you should probably go into a lot more detail because you just blew me away with that one.
I have published a couple of videos on it in the past. There are also others on YouTubr.
@@watersstanton is the ring a product you stock and if so, could you share a link please? Thanks very much!
I wouldn't worry too much on VHF/UHF, but it would always be better to use one on HF. Look up FT240-43.
I keep it really simple and have fantastic results. No antemna analyser,.no isolator. Just put my Ampro whip onto Sirio magmount, see what SWR is at top and bottom of band, adjust accordingly like in the olden days before people they had to have an amalyser. Always get decent match and always work some great DX!
73 M3KXZ
Which band/bands?
@@paulsengupta971 generally 20, 17 are what I use most as I'm an early morning person. But no problems at all with 30 and 40.
Thank you!
Hi Peter I think that the diameter of the torroid is measured in 1/100th inch segments. Therefor a 240-43 would be 240 hundredths of an inch. Or 2.4 inchs imperial.
Yes you are right.
Thanks for an interesting informative video young man.
Hi. Great vid. Can you let me have a link to the ferrite ring that you have used for your coax filter? I have an ATAS120A which presents a number of mobile tuning and FT8 operating challenges! Trying to resolve them. 73es
Excellent video. You hit most all of the important points that most people don’t think about. I will add that the Radio Handbooks contain formulas for calculating Capacitive Reactance from the value of capacitance and it is an inverse relationship. As the capacitance goes up the reactance in ohms goes down. Also there is a formula for calculating the capacitance in pf knowing the area of the plate ( area of the mag mount) and the spacing and also the dielectric constant if not an air gap. The capacitance of the mag mount can be calculated ( in reality I can only estimate mine due to some unknowns as the dielectric of the material covering of the magnet is also significant in the calculation). For example the dielectric of a capacitor with an air gap is 1 but if Teflon was used it would be about 2.0 and mica would be about 5. But with a conservative estimate you can come close to determining if the mag mount has a low impedance to the car roof! Again remembering that the reactance is inversely proportional to frequency and you need twice the capacitance on 40 as you do on 20 for the same low impedance.
Thanks for sharing that.
Dear Sir,
What would work very effectively with icom v3500 ?!
I am looking for a magnetic antenna 😏!!
Some commercial VHF/UHF sellers talk about quarter wave vs 1/2 wave and claim that 1/2 wave mobile antennas do not need a ground plane. Can you comment or include discussion of this in a future video?
A half-wave does not rely on the car body, but is not practical on HF.
@@watersstanton But what makes the 1/2 so unique that it does not require a ground plane? And, is it the same principle/reason why it is said that you don't need a ground plane/counter poise for a EFHW antenna? I, and probably many others, would really like to understand the why of it.
Thanks for all the information
On this same subject. Installation of mobile antennas. What do you think about the installation on the rear doors of vehicles taking into account the hinges and on metal roof rails? Greetings from Argentina
It works. I have used thus method as an easy option.
@@watersstanton TK 73
Many of us drive pickup trucks with an aluminum tool box mounted on the bed. Would this make a good location to mount a HF antenna and would you recommend a bottom or middle load antenna?
Every days a learning day ta muchly.
I think we also need to consider whether we are using the mobile whip in position and driving the car or are we just having a drive out and parking up to work 20m for example? If the latter then i wonder if it would be better to simple fit the HF mobile whip to one of those L shaped mast brackets, fitting it to a 6ft pole and clipping a suitable length counterpoise on it effectively turning it into a vertical dipole. You could then include a 1:1 balun on the coax connector to the antenna bracket. I think this would solve a lot of issues such as thin car roofs, damage, RF and common mode currents and exposure to RF. The assembly could be placed any lenth from the car and perhaps temporarily lashed to a fence post or similar. Thoughts anyone? Or just hoist a wire on a fibreglass pole.
There are many options but the subject matter was the use of magnetic mounts. Appreciate you sharing your thoughts.
@@watersstanton Yes indeed peter , I was just thinking out loud as I’ve recently become inspired to fire up again after a long period of radio inactivity. Like a lot of people, I’m short on real estate for HF so it’s either dig out my am pro vertical ( very effective !) or fly a bit of wire from a fibreglass pole … all mobile of course !
The Diamond magmount with the thin membrane is which model number?
Very useful video!! You brought up some very interesting points, many thanks!! Robert K5TPC
Hi Peter, what is the model/ order number for the ferrite ring you use in the video. I can then order a couple. Best wishes David M0DUU
FT140-43 FERRITE CORE TOROID
@@Alan2E0KVRKing Thanks for the information.
Would a FT140-31 not be better??
@@Alan2E0KVRKing No, FT240-43. You can also use -31 for the lower bands. I tend to get mine from Digikey.
@@paulsengupta971 I meant 240 dunno why i said 140 I had to look it up myself!
You keep saying capacity are you referring to capacitance?
Yes same thing. Capacity, capacitor and capacitance And sometimes in the workshop, caps.
my car is 100% aluminium, will it work anyway if i just put the mag-mount on the roof? (car parking of course)? tks
Yes. A triple mag mount works even better, and you could put some makeshift sandbags to weight it down. Aluminum/aluminium is a good conductor. 73
@@Locksnut thank you sir!
Would this work on 11meters and 10meters?
Yes.
Peter would you recommend a Line Isolator even for VHF UHF? Thanks
Yes, although the problem seems to be far less at VHF and UHF..
@@watersstanton thanks for the advice
I was more hoping that an installation video would tell me how to get the cable from outside the car to inside the car without compromising waterproofing or crushing the cable. Maybe “Installation Theory” would be a more apt title?
I think almost everybody “crushes” the cable through door or hatch jam. The rubber car inserts are softer than co@x. Never had a problem with this in over 60 years.
Whats the store web site
hamradiostore.co.uk
Peter question please. i have female ant bases i neen 3/8 magmounts can the diamond 3/8 mag accomodate the mat 50 please? ty sir
oh ,i knew very well of cmc's but i forgot to apply it to mag mount,ill correct it immediately ,ty
Yes it can.
@@watersstanton How would you connect it? Would you have to go into the back of the mount or would you connect it at the radio end?
@@watersstanton ty sir