MURS Base Antenna Question

[JeepZJ]

We are in the process of setting up a new MURS communication network with our community in a heavily forested and hilly area. We need a couple base antennas for the two cabins that are the furthest apart. My cabin is the highest up the hill but it is also on the other side of the hill from our furthest neighbor. We currently have to go outside to talk to them on the FRS radios. This is a pain when it is -20F.

Can someone recommend a good yet inexpensive unidirectional MURS antenna that we could mount on the roof. We need unidirectional because the MURS will also be used during hunting season.

I've found the Centerfire dedicated MURS antennas CENTERFIRE VHF Antenna Menu Page
and the Firestick Base antenna M.U.R.S. BASE ANTENNA

I'm sure there are others. Just not sure which antenna would work best for our conditions.

Thanks for your guidance....

 

[wyomingmedic]

I personally do not like Firestick brand antennas. Never had luck with them. The 1/4 wave groundplane from Centerfire is what I would shoot for. It is cheap and looks sturdy.

I DO like antennas made by the Arrow folks. They are based in Wyoming and really do make good antennas that are quite literally tough as nails. I have seen some take a serious beating, high in the mountains of Wyoming. Give their website a look http://www.arrowantennas.com/gp/gp146.html

Mount that up on a pole 20ish feet up and give it a go. There is no telling exactly how far you will be able to communicate, but you should get some decent miles. Don't forget good quality coax and connectors. Take your time assembling everything as minor imperfections can degrade performance.

WM

 

[ramal121]

Both antennas mentioned should work well. The 5/8 wave will give you a little more gain. I'll also throw in a Larsen BSA150, same general purpose VHF antenna.

What you will find, being in the trees and such, VHF MURS with a base antenna up on the roof will just run rings around a handheld FRS radio. Not knowing the terrain and the actual range of the FRS radios, if you could only get say a half mile on FRS, then I would think you could two or three miles easily with a base antenna on MURS.

 

[JeepZJ]

What coax would you recommend? Aprox 50 ft run.

 

[jhooten]

The very best you can afford. I would suggest 1/2" heliax but it ain't cheap. LMR400 would be the best bang for the buck.

 

[wyomingmedic]

1/2 inch heliax would be nice!!! But it is rather expensive and complicated to assemble. LMR400 is where I would go. It can be had for cheap and the connectors are only a few dollars a piece.

I use LMR400 in runs up to 100 feet and have had good success. It is tough and withstands mountain weather well.

Remember that with MURS, the power is very low. 2 watts legally. If you use a coax with a high loss, you may only be radiating 1/2 a watt from the antenna. But it also affects receive. Signal to the antenna is attenuated in its trip down the coax and into the receiver. It is certainly worth spending the extra time and money to get it right.

WM

 

[JeepZJ]

Just did a quick Google search on the recommended coax. Well needless to say the 1/2" heliax is waaaay out of our budget. I did find a 50' roll w/ends of the LMR-400 for $55 delivered. Is this a good price or do you have a recommended vendor with better prices?

 

[JeepZJ]

Do I need to borrow a tuner after I install the antenna and coax if I purchase a frequency specific antenna like the Centerfire 150-156 MHz 1/4 Wave Base Antenna?

I have read about checking continuity on the cable and the importance of waterproofing the cable.

I plan on running my antenna on a 21ft 1-1/2" galvanized pipe which will be attached to the end of the house and penetrate through the overhang of the roof near the peak. Should I run a ground wire from the pole to the metal roof or from the pole to a earth ground?

Or should I just mount this antenna with LMR-400 cable, plug it into my radio and enjoy?

I'm obviously a rookie and appreciate your patience....

 

[wyomingmedic]

I personally would get LMR400 without ends so you can get the exact length you need. You don't want 15 extra feet or to be short 3 feet. The connectors are easy to put on.

I like the idea of putting the antenna up on a pole. I did that for many years and had good coverage. Ground the pole to earth and put a lightning arrestor in the coax line and ground it. Very basic but should go a long way.

Once the antenna is up and BEFORE you waterproof it, make sure the SWR is good. Borrow a meter from somebody and check it. It is easy. Easier to make adjustments BEFORE you seal it Once you are happy with the setup AND it is working properly, take your time and seal it well. If you don't you can get degredation over time. Water will get into the coax and slowly ruin the setup.

WM

 

[JeepZJ]

If the SWR is off how do I correct it on the mentioned Centerfire antenna?

 

[cmdrwill]

You would need a good antenna analyzer to check the tuning.
Your local ham may have a MFJ analyzer and could help you check it out.

Here is a better Commercial antenna that you will not have any problems with:

Comtelco BS150U-B 150-156MHz

 

[wyomingmedic]

It probably won't need any adjustment truthfully. The SWR checking is mainly to make sure you don't have a coax or antenna problem.

WM

 

[JeepZJ]

Last questions on the subject....I hope.

I want the option of connecting one of our hand held radios to the base station antenna on occasion. It takes a female SMA connection. Can I just use a short jumper with the appropriate ends? Will the thinner, more flexible wire on the jumper degrade my transmit and receiving capabilities significantly?

http://shtfinfo.com/images/sma female to s0239.jpg

 

[davidgcet]

a short jumper is fine, and is the recommended method of connection since the LMR is not real flexible.

back to the grounding, bond your ground to the building electrical ground rod. if you just drive a rod in the ground and don't tie it in then you create a possible ground potential which is actually worse than not grounding at all.

 

[JeepZJ]

The house doesn't have an earth ground because it is off the grid. Lights, fans, TV, frig and inverters run off 12 volts. I do have an earth ground connected to the generator, would that work? Also the roof is metal....should I bond the antenna pole to the metal roof???

 

[benbenrf]

Yes - earthing is a good practise.

Stick a steel pole into the ground and connect to the antenna with a woven steel/copper/copper plated strap) - and stay away from the gennie (they can introduce all sorts of noise into rf systems - and they offer no grounding protection in any case if they stand as isolated ac power sources).

Regards earthing a tower/antenna there are a whole bunch of standards and good practise rules regards size of pole to use/depth to sink pole/diameter of pole/strap dimensions etc etc ...... not withstanding whichever standard you decide to adopt (if any) a good practise has to be: as large a diameter steel pole and as deep as you guys can practicaly sink it. The strap?: nice big earthing strap from a mechanical horse/earth moving plant ... something along those lines - and you guys will be good to go.

Keep in mind: you can earth an antenna up to the eyeballs - it ain't no garuntee: lightening is unpredictable - its all about reduction, never elimination. I've seen antenna systems earthed to accepted European standards and in the States, earthed to USA practise standards - didn't save them from vaporisation, and I've seen systems earthed with little more than a rebar and earthing strap - and they have survived!

You can never tell with lightening.

 

[Thayne]

Last questions on the subject....I hope.

I want the option of connecting one of our hand held radios to the base station antenna on occasion. It takes a female SMA connection. Can I just use a short jumper with the appropriate ends? Will the thinner, more flexible wire on the jumper degrade my transmit and receiving capabilities significantly?

http://shtfinfo.com/images/sma female to s0239.jpg

You could also make a jumper to connect a 110 watt Motorola Syntor to the base Ant and probably talk to every Sams club & Wal-Mart in Wyoming---:wink:

 

[W2NJS]

JeepZJ,

Clear up one point for us. You wrote, "We need unidirectional because the MURS will also be used during hunting season." Do you mean OMNIdirectional (all directions) or UNIdirectional (one direction)?

 

[JeepZJ]

JeepZJ,

Clear up one point for us. You wrote, "We need unidirectional because the MURS will also be used during hunting season." Do you mean OMNIdirectional (all directions) or UNIdirectional (one direction)?

Yes Omni is what I meant....sorry for the confusion....greenhorn mistake LOL

 

[newsphotog]

You could also make a jumper to connect a 110 watt Motorola Syntor to the base Ant and probably talk to every Sams club & Wal-Mart in Wyoming---:wink:

:lol: