High gain/very long range 850mhz reception

[jsncrso]

Hello,

I want to pick up a 850MHz NC VIPER site quite a ways from my house, and I'm not sure if it's feasible or not. I'm 54 miles direct line of site from the transmitter (no obstructions), which is 155ft high in elevation with 100w output /150w radiated power. My roofline where the antenna will be installed is at 30ft. I'd like to keep an omni antenna as I monitor other sites far away in the opposite direction, but I know I'll need something with high gain.

I get mixed results on some of the antenna calculator sites, so I just want to know is it doable? And does anyone know of some high gain omni 850MHz antennas over 6dB that aren't in the thousands? Thanks!

 

[merlin]

Receiving, there is no such thing as range. the best antenna in the world means nothing if a signal can't get to you.
Range is dictated by trnsmitter EIRP, antenna height, terrain and other habitus.
54 miles is doable, but very likely you will need a Yagi and as high as practical.
Personally, I get a site just over 50 miles. the EIRP is some over 150 watts at 9000 foot.
My antenna is a discone at approximately 48 foot AGL and line of site. The signal is weak, but usable for P25 monitoring.
Height is your friend, hills, buildings, trees, utility lines are not.

 

[mmckenna]

800MHz is pretty much line of sight.

If their antenna is at 155 feet, that gives them 15.3 miles to the horizon. That leaves 38+ miles that your antenna would need to overcome. To get line of sight, your antenna would need to be around 1000 feet above sea level.

Unless you can get your antenna up 1000 feet, no amount of antenna gain or low loss coax is going to overcome that. You've got too much distance in the way.

*disclaimer:
-sometimes radio waves will do funny things over salt water. Some very specific atmospheric conditions can duct radio waves longer distances than normal. That may make this work periodically, but it would be very periodically, as in rare and not reliable.

Options:
Save your money to cover all the permits, legal fees, lawyers and B.S. you'll have to go through to get a 1000 foot tower approved.
Save your money for the cost of said 1000 foot tower, obstruction lighting, periodic painting, foundation, coax and antenna.
-or-
Get someone to let you install your scanner closer to that tower and stream it to you over the internets.
-or-
Hope someone else will stream it for you.

 

[buddrousa]

The cheapest option is buy a scanner put it near the site you want with a PC and PROSCAN and control it remotely.
I have 2 setups that I will leave places with internet and log data from miles away.

 

[prcguy]

I live in Los Angeles about 100-135mi north of San Diego and I hear their 800 stuff just fine. It all depends on the height of the transmitter site, which can be very high here, the height above ground of your receive site and if the transmitter site has any antenna downtilt.

 

[sonm10]

The cheapest option is buy a scanner put it near the site you want with a PC and PROSCAN and control it remotely.
I have 2 setups that I will leave places with internet and log data from miles away.

Hey budd, can you elaborate more on your setup? Is it portable or mobile friendly?

 

[Ubbe]

My roofline where the antenna will be installed is at 30ft. I'd like to keep an omni antenna as I monitor other sites far away in the opposite direction, but I know I'll need something with high gain.

Go up on that roof with a scanner programmed with a couple of control channels from sites you would think you could receive and do that as analog only and open the squelch and listen. If you can hear a faint data signal then it might be possible to receive it using a higher gain antenna and more possible if it also can be installed a bit higher up above the roof. A LNA amplifier at the antenna would then probably be a good investment to overcome coax loss and any impedance mismatches.

A SDS scanner are not suited well for DXing weak signals as it will detect cellular transmitters as being too powerful and reduce it's gain, when not using blocking filters and a directional antenna. Viper seems to not use simulcast so another model of scanner than SDS would probably be more suitable.

/Ubbe

 

[buddrousa]

@sonm10
I use a Mini PC PROSCAN a 2 or 3 SCANNER Rack from Scanner Master a Stridesburg Magnetic Antenna and 2 or 3 Scanners and a Friends location with Internet.

 

[KC3ECJ]

I've had good results on 850 with an old cellular phone antenna in a mobile setup.

Not every such antenna is the same, but they're something to consider.

 

[jsncrso]

Thanks for all of the very knowledgeable replies! I took Ubbe's suggestion and went up on the roof with my Terrawave 806-960MHz 10dBi Yagi and my BCD996XT scanner and was able to pick up the control channel for the Buxton site (2 bars) 44 miles away. VERY strangely, I was only able to pick the site up with the Yagi pointing in the OPPOSITE direction. Strange behavior, although I was holding the antenna by hand, so I'm assuming my body was interfering somehow. This system is going Phase II next year which will render my 996XT silent and is why I bought two SDS200 scanners. They do have slightly less range, but the other system I monitor has extreme multipath distortion and I need LAN control, so SDS200 is my only real option. I will take the suggestion and add in a notch filter to block nearby cellular towers.

Considering I'm mostly interested in listening during storms, where there will be heavy rain induced attenuation (and no power or internet at my friend's house who lives near the tower), I don't expect great results since I'll be just over the horizon trying to receive some of these sites. Regardless, I'm going to install a 6dB omni antenna onto my existing LMR400 and I'll receive what I receive. If anyone knows of any omni antennas with more than 6dB of gain, please let me know!

 

[hazrat8990]

For an omni, you would need a collinear, which can be very expensive for a quality commercial grade unit. The ones I looked at were anywhere from 6dbi-12dbi gain. You'd be looking at a couple grand for a starting price, and a bit north from there!!

There is at least one cheap hobby grade option I found with a quick search: 800 MHz UHF Vertical Outdoor Base Antenna (851-869 MHz)

 

[prcguy]

For an omni, you would need a collinear, which can be very expensive for a quality commercial grade unit. The ones I looked at were anywhere from 6dbi-12dbi gain. You'd be looking at a couple grand for a starting price, and a bit north from there!!

There is at least one cheap hobby grade option I found with a quick search: 800 MHz UHF Vertical Outdoor Base Antenna (851-869 MHz)

There are a lot of surplus 800 high gain commercial grade antennas out there cheap, just look around.

 

[jsncrso]

Currently I'm looking at the Laird FG8066 which is 6dB (8.15dBi). Which would be better, that or the DPD unit at 7dBi? The Laird has slightly higher gain but a much larger 806-866MHZ bandwidth vs the DPD unit's 851-869. Considering I'm monitoring at 851MHz, which would get me better results? Or am I splitting hairs here? I can't find a loss chart for the Laird so it may have worse performance at my frequency.

I've looked for used units on eBay but haven't has much luck so far.

 

[scanmanmi]

I find it difficult to believe you will hear anything because you haven't mentioned coax which could be more important than the antenna. Without something like LMR400 you're going to be losing a lot of signal. You will need a beam to pick up anything that far. I've got a 15 element beam with LMR400 @30' and I can hear at least 60 miles.

700/800 MHz 15 Element Yagi, 698-890MHz, 13dBd

The YW15-6989 is a high gain yagi antenna which provides excellent point to point communications in RF control, short or long haul link, point to multipoint and other applications calling for highly directional antennas. This model particularly suits cellular 700MHz 4G and 800MHz 3G applications.

www.rfiamericas.com

 

[JustinWHT]

their antenna is at 155 feet, that gives them 15.3 miles to the horizon.

That's using the distance to physical horizon formula.
√h x 1.25 miles

Radio waves diffract (the 5/4 earth curvature rule).
So the correct formula is √h x 1.53 miles.

 

[JustinWHT]

Black Crow 1 to Black Crow 2, you copy?
Black Crow 2, loud and clear.
I found a lit roosting spot.
Does he park his car under it?
10-4, Roger that.
OMY, over and out.

 

[jsncrso]

I ended up ordering a 850MHz 9dBd custom tuned antenna from Childs Antenna. Haven't seen much online about their antennas, but what little I've seen says they are well built.