Advice for setting up my mobile

[M0GVZ]

ok, well I wouldnt spend that kind of $ on a radio system in the car, however I was just trying to make a mobile setup with stuff I already have.
When you talk about the strap or connection for the lip mount, can you expand on that a little? is the idea to make the best possible eletrical connection between the mount of antenna and the ground in the car ( bare steel of the body) ? The mag mount junk antenna is gone, I have a k40 ss whip now mounted on the trunk lip

A picture paints a thousand words. First of all there's no point putting one directly to the lip mount because if its installed properly the securing screws should be cutting through the paint to the sheet metal anyway. Instead as you're putting the lip mount on the trunk do it to the trunk instead.

The idea is to maximise whatever ground plane the body of the car represents. So what you want to do is present as good a path for RF between the panels as you can. We do this with bonding. Here's what I did on mine on the tailgate and for the hood. It is done across the hinges both sides of the trunk and hood.

The reason the hood one is wider braid is because the longer the strap the wider it wants to be and it goes to a bolt on the hinge bracket on the underside of the hood. The short one for the tailgate is made from flattened braid taken from RG213 coax with a crimp/solder tag on like the image below. Under it is a serrated washer to cut through the paint to the metal below. On modern cars they use zinc rustproofing so you do not want to be sanding down to bare metal.

Here's another way to do the trunk

Concentrate on doing the horizontal panels, i.e hood/trunk and don't bother so much with the doors as there's little benefit from doing those.

You'll know if you've done it properly or its working as you should find that your antenna is no longer in tune when you've done it - higher SWR on the upper channels - and you need to shorten it a bit. This is because as you improve the grounding the resonant tuning point of the antenna lowers so we need to shorten the antenna a little to bring it back up to where we want it to be. I found mine lowered by 300kHz, equivalent to 30 CB channels, on the 10m band between starting and finishing.

For those reading this who mount by an antenna on the roof, whether it be fixed or magmount, you still want to be doing this for the very same reasons. Everyone with a CB installed in a vehicle should be doing it.

If you do the same on the exhaust as well to the underside of the car it'll help get rid of rf interference from the car if you do have any.

 

[cjruger]

cool, thanks ill try it. I also drilled a couple drill points where the 2 screws from the lip mount push on the under side of trunk, to get thru the paint. there are nice bare metal dimples that they seat into, I put some dielectric grease in them to help prevent oxidation

 

[222DBFL]

Not to rain on your party but I found that the k40 is not the greatest performing antenna IMO, a mag mounted sirio 5000 on the roof would probably perform better IMO. I know it's not a hard mount but being able to get on top of the roof and the added length of the sirio 5000 will make a difference. JMO

 

[hotrod]

Not to rain on your party but I found that the k40 is not the greatest performing antenna IMO, a mag mounted sirio 5000 on the roof would probably perform better IMO. I know it's not a hard mount but being able to get on top of the roof and the added length of the sirio 5000 will make a difference. JMO

while i agree with all this and find same to be true. imo the k40 is a ok starter antenna .but there is certainly better. look up a couple posts before this one i listed in order ones i found to work best on roof .the k40 did in fact rank last but ive also had worse

 

[David Waits]

I would suggest either the Wilson 1000 or the Tram 3500. Both excellent performers.

 

[222DBFL]

Yep saw your post hotrod, IMO I would hard mount a sirio 5000 with a breedlove or gunny puck mount or the sirio mount With the upgraded coax, or get some good lmr240 or lmr400 and the puck mount. The sirio performer and turbo 5000 seem to have performed the best for me. Never tried a full 102" whip with spring as my work van too sits at just shy of 9ft already! But for what's it's worth if you can take care of your setup some then a mag mount will work. Just don't push a bunch of power. Believe me if I could hard mount the work van it would have already been done lol. Maybe after 150,000 lol. God bless.

 

[M0GVZ]

One good thing about using the trunk as a mounting point if you decide to go with a fixed mount is that you can always get a replacement trunk from a breakers yard when you come to sell the car so it can be sold with no holes.