Does the Volvo "in the mirror" antenna mount typically have a good ground?

Be careful with the Volvo CB antenna system. Do you still have the stock antennas? My Volvo has what is called a Multiplexer.

Here is a copy and paste from the Volvo Owners Manual

Communications signals that travel to and from the antennas go through the antenna multiplexer.

Coaxial cables for the cellular phone, CB radio and radio are included in the multiplexer system ' all using the same set of antennas.

The multiplexer is accessed through the lower dash panels. Cable routing is as shown in the illustration above.

Use only genuine Volvo replacement parts for this multiplexer system; standard antennas will give unsatisfactory performance.

The windings in the antennas are specific to this system: different sections of the antenna are used for the cellular phone, radio and CB.

So the thing is, you may have to bypass that multiplexer if you are wanting to use different antennas.

If you already replaced the stock Volvo antenna, that may be the reason for a high SWR.

If you bypass the multiplexer, you may lose your receive in the stereo and if the truck has a connection point for an external cell phone antenna from Volvo, you will lose that as well.

It is a crappy set up if you ask me

Check your owners manual, if you cannot find it you can get it online from the Volvo Truck website.

The bird perch set up is a good option but only works well on the drivers side, the passenger side will "unscrew" as the wind pushes back on the antenna.

eBay search volvo antenna perch or Google search it and you will find one for about $20

The bird perch has you unscrew one of the mirror mount bolts from the body and replace it with the threaded bird perch. Then you have to run your own coax. Do not fall in to the "certain length" coax myth, get the length you need from your radio to the antenna. You should get a good ground because the perch is going directly to the body/chassis of the truck.

Good luck and keep us posted

 

Here is a picture of the bird perch
View attachment 45110

 

try this
take off both antennas and see if your stereo still receives????

 

I have been driving a company volvo for several years now and right or wrong this how I do it.
I get a mirror mount (has to be one big enough to fit around the large mirror brackets volvo uses) I mount it on the passenger side on the top part of the mirror bracket, I also make a heavy guage ground wire and go from the bracket to the mirror bolt that holds the bracket to the door, I then mount my wilson 5000 and route the coax along the mirror bracket to the door, open the door and run coax under the rubber insulation to the inside of the cab and plug it into my radio.
I get a new truck every couple years and when I do the install, the only thing I use that is not new is the radio. Right now I am running a 2012 volvo with 239k miles on it and my trusty 4300hp and showing 1.1to1 swr.
Good luck to ya

p.s. forgot to mention that I remove the factory antenna from the right side mirror and leave the left one on.

 

.... And a dummy load at the end of the feedline will show a 1:1 SWR but will be horribly inefficient as a radiator (which is why they make dummy loads in the first place.)

If you've got a "plastic cab", my suggestion for installing a decent ground plane (remember, an RF ground plane for an antenna is different from a frame or battery DC ground), get yourself some self-adhesive thin copper foil. Places like Georgia Copper sell it, but I usually just pick up some at the local stained glass supply house. Drop the headliner in your vehicle (I know: easier said than done), and make several runs of the sticky copper foil across the inside of the cab roof, fanning out from a point close to where the perch mount is, or or near where the part of the door that holds the hinge is. Remember, tape rather than wire; you want maximum surface area for RF grounds to work. Solder the edges of all the tapes together where they converge, and then run a piece of braid or something flexible like that to where the perch mount attaches to the door. If that point is inside the door, run a braid forward to the edge of the door that has the hinges on it, and fasten the inside braid jumper to the one from the fastening point of the perch (inside the door, where it'll be concealed.) The closer you can get those two braid ends together, the shorter piece of braid you'll have that has to flex every time you open & close the door.

The spans of sticky foil (I use 1" or 1.5", whatever I can find at the store) just run as far across the inside of the roof as you can reach. They won't be 9 ft, of course, which would be close to ideal, but even the 5 or 6 ft across the roof to the other door will be better than nothing. And if you can get a span down the A- and B-pillars, so much the better, as they can be longer.

It won't really matter if your newly built ground plane is on the inside or the outside of the roof; 1/4" or 3/8" won't make any difference. But the closer to the side of the door that you can place your mount on the perch will help with the coupling to the ground plane.

And keep in mind what MsJamie said: a half-wave dipole doesn't have a 50-ohm impedance at the feedpoint, nor does a quarter wave vertical over even a perfect ground plane. Sorta like a two-stroke engine: from what I'm told, having no muffler for back pressure is similar to having no radiation resistance for a transmitter, and efficiency drops.

Either that, or something else. <------- Handlebar's Universal Disclaimer (® Handlebar Services Int'l, 1981)

73

 

Mikeee,
I've got no solution for that one -- and it's an all-too-common problem, from what I hear.

73

 

What should be done:

If you are in a company truck, then what should be done to get better performance from your radio is: Run your own coax and antenna with a ground wire from the antenna to a "chassis" ground (not the cab that is aluminum...but to the actual frame) if possible run the power lines from the fuse panel by using an empty fuse socket. The thing about the antennas and the coax that Volvo, Freightliner, Mack, Peterbuilt, International and the rest use is all Motorola connectors and very low grade coax. In the new Prostars there is 7 connections from the radio to the antenna, with causes a significant amount of line loss and chance for interference. By running all your own gear you can eliminate all that crap and headache and have a lot better "gain" by just installing quality grade coax/antenna/grounded braket and only have a radio that has been lightly tuned.