2e0edx
Full Member
QRP "It is vain to do with more what can be done with less" William of Occum, 1290-1350.
Posts: 109
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Post by 2e0edx on Dec 29, 2006 11:03:42 GMT
A question that has always nagged me is the best position to place a magmount and HF whip when operating static mobile from the car? I run the Landrover Discovery, a vehicle with a rather decent roof area in size. Normally I place the magmount at the front of the vehicle on the roof section between the driver and the passenger.However, I do realise that the location of the magmount is important and I have recently heard others stating that the best location is to place the magmount as far to the rear of the vehicle as possible on the boot lid or close to the rear gutter of the roof. This apparently will increase the groundplane in the direction the vehicle is pointing, just point the front of the car when parking up in the direction that you wish to direct your power and receive the signal. Can any forum member attest to this theory?
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Post by M0ZOE on Dec 29, 2006 13:44:43 GMT
Hi Ian, We have a Vauxhaul Zaphira Comfort... Having 6 children it comes in handy..lol. We were advised by a friend of ours who goes mobile all the time that we would be best suited placing the antenna at the rear of the car. So it's on the hatchback on a clip thingy...the antenna screws into it I think...not sure because Den sorted it out. Another friend also has his antenna in a similar place. Hope that helps a little.
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2e0edx
Full Member
QRP "It is vain to do with more what can be done with less" William of Occum, 1290-1350.
Posts: 109
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Post by 2e0edx on Dec 31, 2006 10:42:28 GMT
Hi Zo
Many thanks for coming back to the question asked.
Are you refering to 2m FM regarding the antennas and location you mention on your car? If thats the case 2M for example would give you no improvement because the optimum ground-plane size is 1/4 wavelength and a central roof location is more likely to give an "all round" 1/4 wavelength ground-plane than a location at the back of the vehicle as you suggest.
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Post by m0wow on Dec 31, 2006 13:15:25 GMT
Hi Ian, What Zo forgot to mention was, we have a roofbox on the car so a rear mount was the only practical option. Before we had the roofbox the aerial was magmounted in the middle of the car roof always the best place i.m.h.o. One idea would be to have 2 aerials mounted 1/4 wave apart on the roof, as when mobile i think the signal would be more directional towardsd the front and rear of the car (but i could be wrong ). 73's de Den.
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Post by M0ZOE on Dec 31, 2006 13:20:48 GMT
Oooops sorry I did forget to mention the roof box. I have a memory like a seive just lately. Thanks Den for pointing that out...much appreciated.
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g4owg
New Member
SOTA Addict
Posts: 26
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Post by g4owg on Dec 31, 2006 13:28:01 GMT
Magmounts are best avoided at HF - you could get away with 10m. The grounding of an HF aerial is very important. Even with gutter, hatch back and drilled mountains most operators would also use a thick earthing strap as well. The effect of using a magmount is at best a loss of signal due to losses, middle RF burns or worst interupting your engine management system.
Roger G4OWG
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2e0edx
Full Member
QRP "It is vain to do with more what can be done with less" William of Occum, 1290-1350.
Posts: 109
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Post by 2e0edx on Jan 1, 2007 12:23:04 GMT
Hi Roger
Thanks for this information. At this time I have yet to use HF mobile and I'm very keen to learn all.......
Hopefully antennas will be purchased or homebrewed in the near future that can be used close to the vehicle. Take your point regarding earthing......... thanks for that.
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Post by M0ZOE on Jan 1, 2007 15:51:59 GMT
Point taken here also regarding earthing Roger Thanks from me too. We had a problem with our Engine Management around August last year and I never gave thought to it being possibly connected to the Mag Mount that we were using at the time. It cost me £80 to have the car hooked up to a computer and an update added...Sheeeesh! costly!!
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