800Mhz Yagi

[dledinger]

Finally - after a decade or more of wanting to try - I built a yagi antenna today. I am hoping to pick up more of the 800Mhz trunked systems in the area. I used the calculator located at: Martin E. Meserve - K7MEM - VHF/UHF Yagi Antenna Design.



I have been running my new rig, a Pro-652, with a Radioshack discone in the attic. It's doing quite well across the board. No problem hearing 800Mhz signals out to 40km. Beyond that, nothing. I have it fed with 50' of RG-6 (I know it's 75 ohm, but even with an adaptor on each end it's light years ahead of RG58). I used elements bonded to the beam (and selected that option in the calc) except the driven element.

This yagi is centered on 854Mhz. It has a folded dipole driven element, a 300:75 Ohm TV balun, and 12' of RG6 quad shield. I have it set up only about 6' above grade.

Problem is, it doesn't seem to be directional. I have no idea if the s-meter on my scanner means much. But if it does, it indicates only a negligible and inconsistent difference between being pointed directly at the transmitter, directly away, and 90 degrees offset.

I feel like I just need to get this guy up in the attic and see what's up.

What's the consensus of the forum?

 

[dledinger]

I decided to stick it up in the attic and see what happened. Sure enough, I'm picking up the station I wanted with 3 s-units.

I'm happy!

 

[mmckenna]

That is pretty impressive. Nice job. How are the elements held in place?

Often, the coaxial cable feeds off the back. This is to prevent the cable from interfering with the function of the antenna. You might want to try rotating the balun around and feeding the coaxial cable off the back of the antenna.

 

[dledinger]

The elements go straight through the boom. They are 3/8 solid alum and they are tapped for a 6-32 screw which holds them in place.

More toying with the antenna this morning. I don't know why I was under the impression that it didn't seem directional...up off the ground it's VERY directional. I have it dialed in now so I have 4 s-units on a site I couldn't even hear before.

 

[mmckenna]

Nice. Aluminum is great to work with. Sounds like a really nice set up.

 

[WA4HHG]

Very nicely done. Your workmanship looks great.

Hope to hear more about the antenna as you get used to it.