January 24, 2021

Mounting mobile antennas for better performance

#1 The DB…

When we talk about a db rating, what is really being expressed?

dB is an abbreviation for “decibel“. One decibel is one tenth of a Bel, named for Alexander Graham Bell. The measurement quoted in dB describes the ratio (10 log power difference, 20 log voltage difference, etc.) between the quantity of two levels, the level being measured and a reference.

From a loss standpoint, if a measurement is deemed to be -3db between to levels, then that indicates a measurement of 1/2 or 50% lower signal level.

(You will see this described when looking at antenna feedline losses at a certain frequency limit on lengths of 100 ft or more).

A measurement level of +6db would indicate a signal level approximately 4 times the originating signal level on the reference antenna.

NOTE – It has stated that the energy level losses from an HT inside of a vehicle is at times -11.3db or greater than the same signal level radiating from a center mounted 1/4  wave whip in the center of the vehicle’s roof.

That means that a 5 watt HT will be radiating a signal approximately equal to  .3125 watts out of the vehicle. (Conditions in the car vary)

#2 Some examples…Loss visualization.

#3 Where to put the antenna


#4 Propagation between a 1/4 wave and 5/8 wave gainGain_plot_70cm_vehicle

#5 Beam Width


#6 Feedline losses


#7 Antenna Types






#9 Drilling a hole in my car will reduce the value.

As the manager of a Motorola Mobile Telephone Service shop in San Diego, Ca., I was asked that question very often by customers having mobile telephone antennas installed on their new vehicles.

Over the years I have questioned car dealerships, if a vehicle had a mobile telephone antenna (it was easier for them to understand why there was antenna on the vehicle) installed, would that affect the vehicle’s resale value when it was removed and a proper rubber flat antenna plug used to cover the hole.

My answer from the Mercedes, BMW, Chevrolet and Ford dealerships in San Diego, Ca. at the time all responded with no.

So….is it worth the trouble to install an antenna properly…absolutely.

Will it cost me money down the road at trade-in time?….absolutely not (if removed and plugged properly).

Will it make a difference in performance, again… absolutely!

Antenna mounting holes can be as small as 3/8″ to 3/4″, all have plugs available.

CONCLUSION – Put a charge on that cordless drill and get ready to make your mobile radio talk and receive better than it ever has.

If you are a person who uses your HT inside your vehicle instead of a mobile radio, at least consider putting a good quality magnet mount antenna on the center roof of your vehicle to improve  your mobile signal.

Everyone will be glad you did.

This Tek Net audio stream is provided by Dave W3QQQ