1.3.10

Mobile Antenna Efficiency (Grounding Issues)

Each day I have a 45 minute journey from home into work and spend a lot of time scanning around the 20m band, I have never been very happy with the initial installation, but had more pressing matters to deal with (such as the kitchen refit) so had settled on just listening to stations.

I had a number of problems when I tried to use the radio:
  • RF in the radio head unit, causing the display to
  • Intermitant high SWR depending on if it is raining or not (Better SWR when wet)
  • Intermitant rebooting of the radio.
 Whilst I had some free time this weekend I decided to have a go at providing a better ground for the antenna to work against. The car is a 56 plate Renault Megane hatchback with a Comet fixed 20m antenna on a Maldol adjustable mount. I suspected that the electrical contact in two obvious places was a little less that what was needed. So I stripped the outer cover from some RG213 I had stored in the shed and then proceeded to remove the outer braid from the remaining cable (This was much easier than I had anticipated).
I then proceed to cut 4 x 1ft lengths of the braiding, put two pieces together and krimped a ring connector to end one.

FIX 1: I then connected this to the Maldol adjustable mount and drilled a hole in the tailgate (Inside & out of view) crimped another Ring connector and screwed it to hatch lid.

FIX2: Same double strap of RG213 Braid across the hatch back lid hinge, making a solid RF contact between the main car body and the hatch back lid.

Results: 95% of the RF issues have disappeared, I still need to put some ferites on the cable between the head and the transciever. On air results have been much more impressive. Talked to a number of stations whilst out and about over the weekend and cannot believe the difference on received signal reports, whilst talking to a UT5 station this morning I got a 5.9+20db and he almost accused me of not being mobile at all. The main thing I am pleased about is home much more I can hear. Now mobile operating is a pleasure and I will endeavour to take some pictures later today and post them to hopefully make my description above clearer.

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