gamma on a mobile ?

[BOOTY MONSTER]

anyone ever tried a gamma on a mobile antenna ? i realize a conventional 38x24 stud mount wouldn't work with it , but that's very easy to change . could it possibly help with noise issues ? would it have any benefits over a typical open circuit mobile antenna ?


just curious ............

 

[mackmobile43]

Shunt feed it and you have the same basic design like the rod of god.

 

[Captain Kilowatt]

A gamma match is used to match a low impedance to 50 ohms and has no effect whatsoever on noise rejection.

 

[6.0 Liter]

Shunt feed it and you have the same basic design like the rod of god.

Hey Mack, you talkin about this? Bout halfway down the page.
Antenna Coil Adjustment Procedure

 

[mackmobile43]

Hey Mack, you talkin about this? Bout halfway down the page.
Antenna Coil Adjustment Procedure

Yup that's one way to do it and can be done with simple capacitors for use at lower wattages.

 

[6.0 Liter]

I wonder if it makes a differance what size wire is used, depending how much power is being used............

 

[W5LZ]

As more power is fed to the antenna that shunt coil will have to be made with larger wire and more space between windings. The pictured coil is only one variation of shunt, the bug catcher type antennas typically used another that fits between the base of the bottom shaft and the mount. A ground lead is then taped to the coil. Those can handle more power than the shown coil. They can also be affected by weather and bugs, etc, if not covered (they typically aren't covered).
- 'Doc

 

[mackmobile43]

The shunt pictured appears to be installed inside the bed of a vehicle away from the elements so it should not be affected unless some snot nosed brat spills his sippi cup on it.

 

[Se7en]

A gamma match is used to match a low impedance to 50 ohms and has no effect whatsoever on noise rejection.

ding ding ding winner winner chicken dinner!

 

[mackmobile43]

ding ding ding winner winner chicken dinner!

Look Ma I'm a capacitor

 

[Captain Kilowatt]

Look Ma I'm a capacitor

Yep, two plates (ears) with a whole lot of nothing between them. He must be charged up as well to make the hair do that.

 

[Shockwave]

The gamma will not help with noise but it is one way to match the approximate 36 ohm 1/4 mobile whip to a perfect 50 ohm impedance. Another simple way is to use the shunt coil as pictured. Although, I would not do it exactly like this in high power applications. The coil is energized with RF an can create a pretty nasty RF field inside the vehicle at high power.

 

[6.0 Liter]

Would anyone have a suggestion how to do the shunt in a mobile app. like pictured, in a scenario where higher wattage is being fed to the antenna? Just for an example, say a couple kw?

 

[Shockwave]

Would anyone have a suggestion how to do the shunt in a mobile app. like pictured, in a scenario where higher wattage is being fed to the antenna? Just for an example, say a couple kw?

Just wind the coil from some small diameter copper tubing rather then wire. Then install the coil on the outside of the vehicle between the 3/8 stud and a ground screw.

 

[6.0 Liter]

On the KOGB website, he talks about using an enamled wire, is this important? Or say a piece of copper tubing like you suggested Shock, would it need to be coated someway? Or is there no need for worrying about arcing?