rack201
Member
- Joined
- Jan 27, 2005
- Messages
- 6
Installing a 477mhz collinear antenna on the bull bar of my 4wd - opposite side to my 2m/70cm dual band. Testing off the car in the open it gives close to 1.1:1 Swr, but mounted on the car I can’t get better than ~2:1.
My SWR readings differ based on the length of the patch cable I’m using from the meter (AV400) to the radio, so I’m assuming I have common mode current on the coax and RF is coupling to parts of the vehicle and re-radiating to the coax.
I tried some mix31 ferrites which made no difference - believe I need mix61 for UHF. If it’s caused by re-radiated RF (and the feed point is 50ohms) would they be better placed closer to the radio?
Does it sound like I’m on the right track? Also tested with the 2/70 antenna removed - no change - it’s over a wavelength away.
My SWR readings differ based on the length of the patch cable I’m using from the meter (AV400) to the radio, so I’m assuming I have common mode current on the coax and RF is coupling to parts of the vehicle and re-radiating to the coax.
I tried some mix31 ferrites which made no difference - believe I need mix61 for UHF. If it’s caused by re-radiated RF (and the feed point is 50ohms) would they be better placed closer to the radio?
Does it sound like I’m on the right track? Also tested with the 2/70 antenna removed - no change - it’s over a wavelength away.