460mhz Antenna Mounted to Side of Steel Building

[kingshootr]

I want to put up an antenna for just 460mhz - there is a public safety channel I'd like to listen in on. I currently have a roof mounted antenna tuned to 150mhz, which gets all the analog signals in my area just fine. Frankly, the slick-as-snot steel roof - I do not want to go up there again. I mean it was sketch as heck getting the other antenna up there.

The signal I want to receive is from a tower 60 miles away. I can pick it up with my HH and and whip antenna, not great, but reachable. It is exactly due north of me, and the back wall of my steel building/shop is perpendicular/facing it. I'd like to mount the UHF antenna on a mount bolted to the building side.

My question(s): Is there any detriment to this mounting scenario? Possible benefit?

Does one design seem more advantageous than another? NMO, yagi, whip, etc? Making a ground plane for the antenna is no problem - half a pizza pan would seem workable.

 

[mmckenna]

My question(s): Is there any detriment to this mounting scenario? Possible benefit? Does one design seem more advantageous than another? NMO, yagi, whip, etc? Making a ground plane for the antenna is no problem - half a pizza pan would seem workable.

The metal siding will act like a reflector if you mount a vertical antenna 1/2 wavelength away from the side. On UHF, 1/2 wave is about 1 foot. You could fabricate a simple bracket with the NMO or other mount on it and it should work. If your hand held is having issues, you may see a ~slight~ improvement with a 1/4 wave antenna. A 1/2 wave or 5/8ths' wave antenna will give you some more gain.

If the signal is really weak, you can mount a Yagi out there and that should help quite a bit. Probably don't need a big one, just get a 3 or 4 element model. You can often find used Yagi's on eBay pretty cheap.

 

[prcguy]

Any vent pipes on that roof? Steep steel roofs are a b*tch but you can toss a safety rope across the roof and anchor it to something on the the other side then get up there and get it done. Then you can use a Yagi or anything you want.

 

[kingshootr]

Any vent pipes on that roof? Steep steel roofs are a b*tch but you can toss a safety rope across the roof and anchor it to something on the the other side then get up there and get it done. Then you can use a Yagi or anything you want.

No, no protrusions. I wound up digging my knees into the screw heads for traction. 4/12 pitch with steel is great for weather, stinks for traction.

 

[prcguy]

Check out this this roof I have to deal with. I end up tossing a rope over the roof and tying it to a tree then attach that to my climbing harness. I also place a door mat at the peak of the roof under the rope to keep it from tearing up the shingles at the peak. Its not fun working on such a steep incline but its easy to make it safe to work and I can get the antennas up high where they belong.

 

[mmckenna]

Did the same thing hanging a damned weather vane for my sister, but tied off to a tractor parked on the other side.

I still think mounting a Yagi down low is going to work and be a bit safer.

 

[kingshootr]

eBay Yagi Antenna



This looks about right, yes? Besides coax, I understand I will need a diplexer to properly connect the two antennas to a single radio? (And why in the heck do some sellers list them as duplexer?)

Question on diplexers: When it says it is 1-150mhz and 400-460 mhz. Are those hard cutoffs? Like does it block signals that are slightly higher (156mhz, 465mhz)? Or can I still hear those frequencies?

 

[mmckenna]

eBay Yagi Antenna
This looks about right, yes?

That should work. I'd be skeptical of those spec's across 70MHz. It's probably going to have some less gain/directionality near the fringes. That'll work, but if you can find one that has a bit tighter frequency range, that would be my choice.

Besides coax, I understand I will need a diplexer to properly connect the two antennas to a single radio? (And why in the heck do some sellers list them as duplexer?)

Yes. But keep in mind that the diplexer will split VHF and UHF totally. All your UHF coverage will come through the Yagi, so make sure this is what you want for UHF coverage. You might do better with a dual band vertical with some gain and skip the diplexer. Or run a VHF antenna and a UHF antenna with gain and use the diplexer if you need omnidirectional coverage on UHF.

Question on diplexers: When it says it is 1-150mhz and 400-460 mhz. Are those hard cutoffs? Like does it block signals that are slightly higher (156mhz, 465mhz)? Or can I still hear those frequencies?

It rolls off towards the edges. You would be fine up to 150 and then start to lose performance above that.

Sounds like you need to find a different diplexer with a more appropriate split if you need coverage higher up in the VHF band. Kind of sounds like you are looking at the amateur radio diplexers.

 

[Radiofantast]

I have similar obstacles, a sheet metal wall around the entire house up to the roof. I use a Sirio Boomerang 27W bass antenna and it works perfectly SWR 1.1 for 27MHz and 400-480MHz between 1.4-1.8. If you are only going to listen to 460MHz, I recommend this antenna. I run both RX-TX without problems on all bands.

 

[prcguy]

I have similar obstacles, a sheet metal wall around the entire house up to the roof. I use a Sirio Boomerang 27W bass antenna and it works perfectly SWR 1.1 for 27MHz and 400-480MHz between 1.4-1.8. If you are only going to listen to 460MHz, I recommend this antenna. I run both RX-TX without problems on all bands.

SWR has nothing to do with how well an antenna receives or transmits. The Sirio 27W is a horrible performing antenna on UHF and is in no way designed to work there. Its pure luck the SWR is low but a dummy load has a low SWR.

 

[kingshootr]

I found this one, seems to cover what I want with a little cushion on each end.

I thought my google-fu was strong - but I couldn't find a 460mhz yagi to save my life. Then, by chance, I found one that is 450-470mhz. That was the keywords - now I'm finding a ton of them. All I want the yagi to do is 460mhz +/- 1mhz.

Arizona DPS - The two line items for "Holbrook" are what I want, plus the state wide stuff. 460.xxx for all of them.

Everything else up here is in the 150mhz +/- 15mhz. The Sirio you turned me onto is doing great. GP-3-E. So ideally, I'd like to pump the yagi/450-470mhz and the Sirio 135/175mhz into a single coax attached to my SDR dongle.

Well, I am an amateur , and a cheapo to boot! I can get $100 +/- past the war department, any more and I risk scrutiny.

 

[prcguy]

I found this one, seems to cover what I want with a little cushion on each end.

I thought my google-fu was strong - but I couldn't find a 460mhz yagi to save my life. Then, by chance, I found one that is 450-470mhz. That was the keywords - now I'm finding a ton of them. All I want the yagi to do is 460mhz +/- 1mhz.

Arizona DPS - The two line items for "Holbrook" are what I want, plus the state wide stuff. 460.xxx for all of them.

Everything else up here is in the 150mhz +/- 15mhz. The Sirio you turned me onto is doing great. GP-3-E. So ideally, I'd like to pump the yagi/450-470mhz and the Sirio 135/175mhz into a single coax attached to my SDR dongle.

Well, I am an amateur , and a cheapo to boot! I can get $100 +/- past the war department, any more and I risk scrutiny.

There are version of that Comet diplexer with all female N connectors so you don't have to use goofy adapters.

 

[kingshootr]

Ahh, I hadn't gotten that far, but greatly appreciate the heads up!