2m / 70cm -- 1/4 or 5/8+ wavelength antenna -- House surrounded by hills

[drew4392]

I am designing my base station, and realized that my house is surrounded by hills. Ugh.

They are not huge mountains. The hills are about 300-1,000 feet high, and about 1/2 - 2 miles away from me.

I was reading about antennas, and some suggested a smaller/lower wavelength antenna for higher radiating angles. Then again, I read where longer, lower radiating angles are okay because there is a type of diffraction over hilltops.

My roof is about 25 feet, and the antenna I was looking at (Jetstream) is about 10 feet.

Is there hard and fast rules about this, or is it more of a test-as-you-go-as-see-what-works-best sorta thing? Concerned about the latter, as I'm apart of an HOA and can't be up there multiple times... if I can help it.

Also... the link I pasted above for the Jetstream antenna... is that over a full wavelength??


Thanks, all!

-Andrew

 

[FeedForward]

At 2 meters and above, you better have some repeaters in those hills for usual communication purposes.

FF

 

[drew4392]

Yea, there are a handful of local repeaters that I will be able to hit. My concern, though, is which antenna type will be most effective and what are the most appropriate scenarios for each (shorter, higher angle... or longer, lower angle).


Thanks
Andrew

 

[exkalibur]

1/4 wave would be best if you're in hilly terrain. A gain antenna tends to make the signal more "flat" so it won't go over obstacles quite as well.

 

[mmckenna]

I'm roughly in the same position as you:
Single Story house, surrounded on 3 sides by 1000-1500 foot hills, Pacific Ocean on the 4th side. No need for high gain antennas.

I've run both UHF on a GMRS base, 440 and 2 meters. Never had any issues at all with the lower gain antennas. Actually, at the moment, I'm using an old discone I scored for free, and it works just fine. Coax is about 30 feet of LMR600. Current radio is a 25 watt CDM-750 on VHF, and we normally run simplex on 2 meters. On Saturday I was over the East hills, well out of direct sight from home, and about 25 miles away. Was able to talk to my wife simplex. While not reliable, it does happen.

I'd say save your money, go with the normally less expensive lower gain antennas, and put the money you save into better coax. The higher gain antennas won't provide any reliable "over the horizon" coverage, and the lower gain will work just fine. The antenna pattern really doesn't make that much difference in these cases.

 

[teufler]

I lived the the Las Vegas area for a while. Almost all th repeaters were up on the hill tops. Being a non local, I had gain antennas on my car while locals ran 1/4 wave for a high angle of radiation. I quickly found out when downtown amoung the buildings the 1/4 wave unity gain was a better radiator. Now when on the road traveling, I ran a Mahdol 5/8 wave colinear with a 150 watt amp. If you could hear the repeater, you could esily talk to the repeater. The antenna was not small. about 90" tall, and the mount on the car, was a ball mount, to handle the wind torque that the antenna produced.

 

[dksac2]

I'm surrounded by hills and mountains, with repeaters, one on the far side of a mountain that requires the signal to bounce off a mountain to hit the repeater.
I was just net control for a very large bicycle race. I have a gain type vertical at 42' at the base. I also put up a quarter wave at 40'.
In using both (with 2 different radios, 50 watts each), I found the 1/4 wave to be a little bit better overall, so were I you, I'd save the $$$ and use a 1/4 wave.
73's John KF7VXA

 

[drew4392]

Thanks everyone! Sounds like the 1/4 is the way to go.

Part of me thinks there is no replacement for gain and a bigger antenna would do better.... but I can't disregard all of your experience and dksac2's comparison between the two. Seems like higher angle is the way to go.


Thank you!!