Charles A. Toupin

In all the cars equipped with a mobile Motorola radio systems I raced, communication has never been perfect. I have an Imsa radio system (motorola PM400).

A friend of mine races in the Imsa GT3Cup Challenge (Canada) and it was the same until the Alegra guys installed a brass antenna. He said that at the moment they did that, communication became instantly crystal clear all over the track.

Any idea where I could find that? I don't see any of this at Racing Radio. They only have the standard antennas, just like mine (shark fin)...

Thanks

c.

Izzone

Ditto for me

I have the same system and when I get to the back of the track it is not good at all

I've been looking for a better system

Charles A. Toupin

No one?

c.

GuyIncognito

I think when he said racing required "brass attachments" he was referring to something else

GuyIncognito

anyway, serious answer: I've seen people using antennas from Laird Technologies that use a lot of brass in their components, although I don't think the antennas themselves are brass. might be worth a look.

http://www.lairdtech.com/

also you may want to check with West Marine or other marine radio suppliers.

Bob Rouleau

The material makes no difference Charles. The size of the antenna does matter. Bigger is better. Height at your base station will also extend range since the radios you use are essentially line of site.

Charles A. Toupin

Hi Bob,

If I understand correctly, it would be preferable to put the mobile higher up in the car?

At mosport in 2010, I was in the 924 when Simon was in the 944, both on the same frequency. I was having the handheld radio strapped high on the roll cage. It was clearer than in his car with the mobile bolted on the transmission tunnel under the dash. I always wondered if the handheld unit was better...

So if I woubolo installthe radio higher it should give a better reception?

Thanks

Charles

J richard

I had a few discussions with racing radios trying to get a common setup between my cars. Most mfgrs have long and short range antenna kits. The chrome cap with 8-10" wire antenna is standard. The black plastic wound style are the updated style for longer tracks. The roof of the car makes a difference as it acts as a reflector and affects the focus of the signal. Most antennas need to be in the middle of a metal field to work which is why they want them dead center. If you have a plastic roof you need to have a grounding disk mounted under the roof to do the same thing as the roof panel or use the updated antennas only. And I did stay at a holiday inn last night.

dan212

Yes Bob... Size makes a difference.
(had to be said)

Charles A. Toupin

Yes, it's in the fibreglass roof but with a metal disc underneath. Still, I had better reception with the hand held unit tie-rapped to the roll cage than with the mobile bolted on the transmission tunnel.

I have the shark fin antenna made by Lairtech.

Maybe I should install the antenna on the metal part of the roof?

Thanks

c.

Surfbum

Charles, try a 8" circular piece of thin copper with a hole cut in the center on the underside of your roof, make sure there is direct metal to metal connection to your antenna base to the copper plate.
It did wonders for my reception.
Mine is installed in a carbon fiber roof.

Charles A. Toupin

Thanks! I'll try that! Now, I just need to find that copper sheet...

c.

J richard

^^^
This. The mounting recommendations were an 18" dia. disk but that seems crazy, the 8" seemed to work. I've seen DP cars with a 2' square of metal foil spray glued to the underside of the roof to do the same thing.

Interestingly they have a new rod antenna out now that says it can be mounted horizontally anywhere on the car...

Bob Rouleau

Charles,

IF the roof of the car is non metallic, the standard ground plane antenna will not work. It's designed to use the roof and body of the car as part of the antenna. That's probably why the handheld worked better. So the solutions are:

Mount the antenna to a part of the car which is made of metal:

Use an antenna which does not need a ground plane,i.e. a half wave antenna which will be 2X longer than a simple quarter wave whip.

Create a ground plane under your antenna such that the mounting stud of the roof mounted antenna is electrically fastened to the ground plane. The ground plane should be a copper disk having a diameter equal to the length of a quarter wave antenna for the frequency you are using. If you tell me the frequency, I'll give you the dimension.

Lastly it is the height of the antenna which counts, not the radio itself. Another hint, do not use thin coaxial cable to connect the antenna to the radio. Use RG 213 or equivalent. Cable loss is significant at UHF (450 MHZ).

Lastly, consider using your cell phone and a headset if all you need is base to one car communications.

J richard

This was mentioned as a common reason for poor performance, the coax will hook up but ruin your reception...