Larsen NLA-150 Antenna & New Ham Q?s

[Hedge]

I recently purchased some used Larsen NLA-150 Antennas. I tried to find information about them, but to no avail. Is anyone here familiar with these antennas or the Larsen NLA mounts?
- Will they need to be tuned with an SWR meter, or are they pre-tuned for 2m ham from the factory?
- Do they require a ground plane to keep the SWR low enough to avoid damage to my 2m radio?
- Will they attach to the Larsen NMO mounts that are sold today?
- If I attach a spring to either this or a Larsen NMO 2/70B to add flexibility, should it go between the coil and the mount, or between the coil and the whip?

I'm hoping to use one as a mobile antenna on a mag mount and one as a base station antenna mounted in some fashion up in my attic. They would be used in both locations with a Yaesu FT-2500 mobile 2m. I'm a freshly coined ham, so any advice is appreciated.

Also, I am thinking about using a computer power supply as an inexpensive alternative to a purpose-built 12vdc power supply. Is this viable?

 

[AndrewP]

They make different versions of the 150 series, some are 1/2 wave and some are 5/8. The 1/2 wave will work ok without a ground plane and will be tunable even without much of a GP. It will give even better performance with a real GP. If you have a fiberglass roof, it's the one you want.

The 5/8 wave will give even better performance but requires a ground plane. Without, you won't be able to get your SWR low enough and may damage your radio. This is your best choice in general.

Larsen antennas are shipped long and will require tuning with an SWR meter. They come with a cut chart to get the first rough cut in the ballpark. If you run the spring at the base (I do that and it works great to keep the antenna and mount from being damaged) it comes with a cut chart to tell you how much antenna to clip off. That gets you close, and you still need to tune with an SWR meter.

I think the Larsen whip antennas are outstanding. They are tough, cheap, and the mast is replaceable for $12 if you damage it.

 

[Hedge]

Thanks for the help. I'll have to find my old SWR meter, it's around here somewhere...

 

[gary in ohio]

With the antennas being used you have no idea where they are cut for. May be anywhere from 140 to 170mhz. As suggested mount them and check the swr. cut the antenna, or lengthen with a spring as need to get a good resonate antenna.