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Call Sign : 26CT2192 Posts : 6 Times Thanked : 0 Join date : 2020-04-05 QTH or Location : Bedfordshire Equipment Used : SSB, FM Age : 58
Subject: Motorhome antenna Sun Sep 29, 2024 12:15 pm
Hello. A little advice please.... Taken my magmount from car and put it on van roof. Van roof is aluminium, so I have screwed a steel square plate to roof an attached magmount. Swr on car was great through all channels 27ukfm and great on 555 usb also. On van the best I can get is swr of 2.5 on ch 1 & 40 and 1.5 on ch20 on 27ukfm. Not tried the multi band radio as too scared. Contact between aluminium and steel is good. Tried different antennas and just as bad if not worse. This is a trial to see if it works well before making a hole in roof. Any help appreciated. Thanks Gary
VanRougeT4 Major contributor
Call Sign : G1DBS - F4WEY Posts : 238 Times Thanked : 18 Join date : 2024-02-17 QTH or Location : Montreuil sur Mer Equipment Used : XIEGU G90 + XIEGU XPA125B
Subject: Re: Motorhome antenna Sun Sep 29, 2024 1:04 pm
It could be that your magmount on the car wasn't electrically connected to the roof, but was achieving a low swr by means of capacitance.
Deb
Speidy New Member
Call Sign : 26CT2192 Posts : 6 Times Thanked : 0 Join date : 2020-04-05 QTH or Location : Bedfordshire Equipment Used : SSB, FM Age : 58
Subject: Re: Motorhome antenna Sun Sep 29, 2024 6:20 pm
Thanks for reply. The antenna on the car works a treat. Thinking outside the box, would the fact it's going from steel to aluminium make any difference? Thanks
VanRougeT4 Major contributor
Call Sign : G1DBS - F4WEY Posts : 238 Times Thanked : 18 Join date : 2024-02-17 QTH or Location : Montreuil sur Mer Equipment Used : XIEGU G90 + XIEGU XPA125B
Subject: Re: Motorhome antenna Mon Sep 30, 2024 12:55 am
Speidy wrote:
Thanks for reply. The antenna on the car works a treat. Thinking outside the box, would the fact it's going from steel to aluminium make any difference? Thanks
Probably not, but other reasons for a different match might be that the vehicle is the ground plane, the van roof is probably bigger than the car. If the antenna isn't electrically connected to the roof, then the way the coax is routed will also have an effect. To be honest, I'd forget about how the antenna worked on the car and adjust for lowest swr on the van. If you can't get a low swr on the van try grounding the rig to the van body. If all else fails, you could use an antenna analyser to see where the antenna is resonant. Also, check the coax, if it's been jammed in a door, it might be damaged.
Deb
Speidy New Member
Call Sign : 26CT2192 Posts : 6 Times Thanked : 0 Join date : 2020-04-05 QTH or Location : Bedfordshire Equipment Used : SSB, FM Age : 58