Larsen NLA-150 Antenna & New Ham Q?s

[psfpilot]

I recently purchased some used Larsen NLA-150 Antennas. I tried to find web information about them, but to no avail. I figured I'd post here just in case somebody is familiar with these older antennas.
- 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?

 

[pappy]

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

Can't help you with the antennas. With the power supply, probably not. If I remember correctly the PC supplies put out an even 12 volts. You need 14v to power the FT-2500. I learned this first hand. I have an old Motorola radio power supply that a buddy gave me. It has two output terminals, 12v and 14v. My FT-2500 had issues with the 12v side on transmit. On 14v I have no issues.

 

[psfpilot]

Thanks, it's good to hear an answer from a fellow FT-2500 user on that question.

 

[pappy]

Opps, my bad. I have a FT-2800, not FT-2500. Still, probably the same.

 

[psfpilot]

Probably so. After posting that query, it occurred to me that I may be able dig up an old inherited PS from a dusty corner of a barn, so I think I'll be set to start transmitting before too long. I can always use a battery in the home office until then.

 

[Kofoed]

You need to know the wavelength of the antenna. If the whip is about 40 inches long, it is likely a 1/2 wavelength antenna, and no ground is *needed*. Any other non 1/2 wave multiple will need a counterpoise (aka ground plane=metal vehicle roof) for mobile, and radials for a base station application to get the SWR down. A commercially available base antenna, or home brew
(search here for J-pole) may be better for base use. Certainly more gain can be had.

My guess is it is a 5/8 mave antenna (whip about 51 inches long)

 

[FJ40_owner]

I recently purchased some used Larsen NLA-150 Antennas. I tried to find web information about them, but to no avail. I figured I'd post here just in case somebody is familiar with these older antennas.
- 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?

NLA 150 may be cut for the commercial bands, not the 144-148 Ham bands. Google it

How long is it? Don't they teach anything about antennas in the new appliance operators class?

 

[psfpilot]

I think it may be 5/8. It is ~51 inches long. I have a 1/2 wave Larsen NMO 2/70 that just showed up today, so I should be able to get on the air without frying my transmitter until I learn how to construct my own ground plane for these NLA 150s.

 

[Miescha]

How long is it? Don't they teach anything about antennas in the new appliance operators class?

Harsh perhaps, but true. As a fellow fresh ham, I must say I was disappointed by what little I was required to learn in order to get my license. I basically read through the questions once the week before the exam, then went to a local club's prep course (where they read through the questions again, but I could at least ask questions about why the answer was whatever it was). I took the tests and passed, and was immediately somewhat embarrased, albeit happy.

I did however immediately order the extra class study book, the ARRL Antenna Book, the ARRL operators book, the ARRL RFI manual and went to work trying to learn as much as I could - but only b/c I was angry that I didn't understand sh*t about antennas, image planes, dc ground loops, RFI, or just about anything else.

On the good side, I lucked into a great local ham club and I've learned a ton just by showing up at events and asking questions - including quite a few on the air.

Keep reading, order a few books, find a local club - hell, ask us some more questions. You'll figure it out eventually if you want to.

Welcome to the ham world - and good luck!

 

[spressomon]

There were a number of us pals here in Reno area that took a class sponsored by the local school district and HAM club that was very valuable to me. And he spent a good deal of time on the antenna portion. Does it make me an antenna expert: Hell no. But it did add clarity compared to what I read in the book.


Ok...I've decided to drill the roof! Ordered the NMO mount and this Larsen antenna and its going in the roof of my '99 LC. I'll have to bribe Rusty to help me with tuning to 2M...hmmm...maybe a little Zaya in a snifter after its all done might do it .

 

[psfpilot]

...
I tried to find web information about them, but to no avail.
...

...
NLA 150 may be cut for the commercial bands, not the 144-148 Ham bands. Google it
...
Don't they teach anything about antennas in the new appliance operators class?

Actually, no class is required.



If anyone has some constructive suggestions for self-directed education, I would appreciate it. Unfortunately I do not presently have a schedule that permits regular class and meeting attendance. I am curious as to what others have personally found to be useful, educational and readable references. I think I will start by trying to get the ARRL books that Miescha mentioned through inter-library loan. Right now I'm most interested in antenna design and usage for mobile and base station 2m operations, but thoughts about anything about ham that you have found to be interesting to read would be welcome.

 

[Miescha]

Ok...I've decided to drill the roof! Ordered the NMO mount and this Larsen antenna and its going in the roof of my '99 LC. I'll have to bribe Rusty to help me with tuning to 2M....

If you're using one of the current Larsen 2m NMO antennas like the popular NMO 2/70 then no tuning is required (or recommended). Just mount and go!

You can still bribe Rusty though

 

[Miescha]

Actually, no class is required.



If anyone has some constructive suggestions for self-directed education, I would appreciate it. Unfortunately I do not presently have a schedule that permits regular class and meeting attendance. I am curious as to what others have personally found to be useful, educational and readable references. I think I will start by trying to get the ARRL books that Miescha mentioned through inter-library loan. Right now I'm most interested in antenna design and usage for mobile and base station 2m operations, but thoughts about anything about ham that you have found to be interesting to read would be welcome.

The ARRL Antenna Book is great and the RFI book is also very informative for all things RFI. I know there is another post floating around about a good beginner book, but I can't seem to find it right now.

Good Luck!

 

[spressomon]

Andy,

Ok...bought the Larsen so I guess I'll figure this out shortly anyway: But since its soooo flexible don't you have transmission efficiency issues when travelling down the road at highway speeds (I would think wind would bend the antenna backwards reducing its effectiveness)?

 

[Cruiserdrew]

Andy,

Ok...bought the Larsen so I guess I'll figure this out shortly anyway: But since its soooo flexible don't you have transmission efficiency issues when travelling down the road at highway speeds (I would think wind would bend the antenna backwards reducing its effectiveness)?

I have not had a problem with this, at least not one I could detect. Even on my FJ40, I have the same antenna on a spring, and no issues at all. I can't hear anything in the 40 at highway speed anyway, in fact I wear ear plugs. No issues on the trail as Rusty Dan can attest.

Since you'll have that in the center of your roof, I would mount yours on a spring too. The antenna is very long-I think I cut close to 6 inches off of it when tuning. Use the Larsen cut chart, then snip 1/8 at a time untill you reach the SWR low point.

Regarding learning cool radio stuff-the most instructive thing I did was study hamtestonline for my general lic. That seemed to me what the tech license should have been. The tech is just an overview to keep you out of trouble. Also, the ARRL antenna book is chock full of great info, virtually none of it applicable to mobile use. It does make me want to home brew some antennas when I have more time in my life. I reaaly want to brew up a J-pole out of 300 ohm antenna lead for a high gain antenna you can roll up and put in your pocket. That plus a hand held would get out a long way, and be totally portable.

 

[psfpilot]

One of the gentlemen over at QRZ scanned his old NLA cutting chart. These were in fact cut for 2m so I put one on the equally old NLA MMO and it seems to radiate a slightly stronger signal than the new 2/70B on a NMO MMO. Both worked well for the local ARC net the other night.

I cleaned the mud dauber nests out of an old Astron power supply that was sitting in a corner of a barn and it is working well for base station power, but I think I need to install a j-pole in the attic or on the roof to make transmissions from inside the house, as the mobile antennas on the filing cabinet ground plane don't seem to be working for the repeaters further than 7 miles away, even at the 50 watt setting.

Spressomon, did you go with the NMO-150?

 

[spressomon]

One of the gentlemen over at QRZ scanned his old NLA cutting chart. These were in fact cut for 2m so I put one on the equally old NLA MMO and it seems to radiate a slightly stronger signal than the new 2/70B on a NMO MMO. Both worked well for the local ARC net the other night.

I cleaned the mud dauber nests out of an old Astron power supply that was sitting in a corner of a barn and it is working well for base station power, but I think I need to install a j-pole in the attic or on the roof to make transmissions from inside the house, as the mobile antennas on the filing cabinet ground plane don't seem to be working for the repeaters further than 7 miles away, even at the 50 watt setting.

Spressomon, did you go with the NMO-150?

Its sitting in the garage along with other stuff I have to fix/add on/to the LC. Its seen its share of overlanding/exploring/hunting trips this year and its showing it! Hopefully I'll get on it in the next couple weeks...