[Antennas] 1/2 wave & 5/8 wave 144 mhz mobile antenna

Mon May 8 16:41:14 EDT 2006

Over the past few weeks I have been involved with installing a antenna and a 
2 meter rig in my car - Finally finished today - on my shake-down-cruise I 
noticed the following:
5/8 wave antenna gives me a better receive sig.
1/2 wave is shorter with lower sig level but less prone to hitting tree 
branches - so this I can live with.
I notice that with either ant (5/8 or 1/2 wave) I get deep nulls in signal 
level as I drive along.
I did not notice this effect in my previous car - I used the same two 
antennas - only difference was the mount. In my old set-up I had a lip mount 
on the trunk and the mount was grounded via the set screws.
In my new set-up I am using a Diamond (HRKS) mount on the roof - it is a 
stick-on non ground mount. From what I have read a 1/2 wave or 5/8 wave 
antenna can operate with out a ground or a ground plain - is this a fact, or 
would I be better served if I grounded the mount ?
I should be able to remove some paint from a hinge bolt on my rear tailgate 
and run a short strap to the 259 connector on the mount. I would like to 
hear some comments on grounding first - the bolt and paint deal is not an 
easy project.
Antennas: The 5/8 is a Larson the 1/2 wave is a Diamond NR770HA (144/440)
Questions are:
Should a 1/2 wave and a 5/8 wave mobile antenna be grounded ?
The deep nulls as I drive along (slow speed) in traffic - is this an 
indication of a poor install or no ground?
I have not measured the SWR ( do not have a meter for 144mhz) will grounding 
alter it ?
This should be the last of my problems installing a rig in a 2005 VW Passat 
wagon.
Thanks for reading this
Myles - W1IKO 