Scanner Antenna For A TV Station

[clintonfoxtv]

Hi all,

The news operation where I work is trying to upgrade it's scanner setup. We've got a 150ft tower out back we're going to mount the antenna to, but I could use some feedback on the antenna. We're looking for a wide band, but focused on the 800 range, and omnidirectional.

Would one of these Watson WBD-40s work for us?

WBD-40 Discone Base Antenna | Scanner Master

Thanks!

 

[ladn]

That would be one option, but I don't think it would the best for 800.

Of equal (if not greater) importance is the feedline from the antenna to the scanner--especially at higher frequencies like 800 MHz. If your antenna is going to be even halfway up the 150' tower, that represents a long and potentially lossy cable run. Definitely consider using hardline with "N" connectors for most of the run and using a short run of quality flexible cable from the antenna to the hardline and from the hardline to the scanner. If the tower also supports your transmitting antenna, you will probably also need some isolation filters to keep the high power tv signal out of the scanner.

 

[mmckenna]

If this antenna is going to be a critical part of the business operations, then I'd invest more than $150.00 on it.
Add in the cost of installation, coax cable (a very important factor as ladn mentioned), and you'd be spending a few hundred or few thousand on installation of a $150.00 antenna.

Going cheap on antennas is rarely a good plan, especially if you want it to last.
Not sure where you are located, but I would not recommend installing a hobby grade antenna on a tall tower and expect it to be a reliable system.

And, as stated, Discone antennas are a compromise antenna. They perform across a wide slice of the RF spectrum, but they do it at the cost of antenna gain. They are suitable for scanning, but if you really are trying to focus on 800MHz, you'll do better by getting a frequency/band specific antenna.

If you plan on having more than one scanner, as in one for each agency, city, etc. you might do better to have individual antennas dedicated for each radio, especially if the agencies are on different bands. By going with dedicated antennas, you can install either a higher gain omni directional, band specific antenna, or you could install a yagi antenna pointed at the system you want to monitor.
Either of these solutions would outperform a discone.
The benefit of higher gain antennas is that you increase the amount of received RF to send down the coax. As an example:
If you have a 0dB gain Discone and a coax run with 6 dB of loss, your received signal will be 6dB down by the time it reaches your radio.
If you have a 6dB gain omni and a coax run with 6db of loss, your antenna gain would offset the feed line losses.

If a discone really is what you want, and you are going to go through the effort of mounting this on a 150 foot tower, then go with a higher grade antenna. I'm running a Telewave ANT280S at work at one of my sites. It normally functions as a remote monitoring system to check my gear, however I can press it into use as a back up antenna for the VHF or 800MHz systems.
It's a $1400 antenna, but it'll last a lifetime. Again, if you are going to go through the trouble of mounting this on a 150 foot tower, then make it worth the effort.

As for coaxial cable, 150 foot run at 800MHz is going to have a lot of loss, unless you use some high grade coaxial cable. You won't want to be running RG-8, RG-6 or LMR-400 grade cables. No hobby/amateur grade stuff here. You'll need to look at 7/8" Heliax at minimum, maybe bigger if your radio is far away from the tower. You need to get as much of that signal to the radio, not lost in the coax cable. Since all coaxial cable has some loss, using cheap stuff will result in poor performance.

Good antennas and high grade coaxial cable will always pay off in the long run.

 

[Golay]

Maybe not as tall

You say your primary interest is 800 meg. That makes me think your primary interest is trunked or other repeaters systems. As the first two responses indicated, a long coax run equates to a lot of loss.

My query without knowing specifics is: Do you really need the height?

Why not start by seeing if you can receive what you want on an antenna on the radio indoors.
If it's mostly adequate reception, consider an outside antenna on the roof of the building. You may find you can receive the systems you want without going halfway up the tower. Much shorter coax run means much less loss, especially at 800.

 

[RFI-EMI-GUY]

Lets assume you have no transmitters on that tower or nearby. If so, that is important to consider.

Lets assume the scanners will be pre-programmed to a specific set of channels and monitored 24/7 for alerts. The users will monitor the scanners for alerts not be tuning around seeking stuff, like a hobbyist might.

Normally you don't need 150 ft height for a scanner unless you are scanning systems two counties away. I would start with building a list of what systems you need to scan and then from that decide if you need directional antennas for the more distant ones. Those antennas could be placed at a higher level of the tower. Your local scanning can be accomplished at 30 feet or above local obstructions, whichever are higher.

You may need filters and multicouplers depending upon the situation.



I would probably avoid the discone except for scanners that will be for utility, that is not just monitored but operated for special circumstances. The discone will be susceptible to VHF paging and weather transmitter intermod.

 

[KC3ECJ]

Does the station not have an engineer?

 

[DJ11DLN]

Two days after the initial post and still no clarification from the OP about what system(s) they are wanting to target, so I am starting to wonder about this one. Smells a bit fishy.

I think I'd start with a quarter-wave ground plane on the roof feeding some LMR-400 (or even -- gasp! -- some cheap RG-6) before putting something up 150' with all of the co-ax expense and hassle involved in getting meaningful signal that far. It may very well serve the OP's needs quite well. If the system(s) they are looking at are anything like the statewide TSYS here, all putting something up that high is going to accomplish will be to render the scanner(s) deaf due to massive front-end overload. I hear 8 counties and 2 ISP districts with RS ducks on the back of my scanners in the house.

 

[N5TWB]

Two days after the initial post and still no clarification from the OP about what system(s) they are wanting to target, so I am starting to wonder about this one. Smells a bit fishy.

I think I'd start with a quarter-wave ground plane on the roof feeding some LMR-400 (or even -- gasp! -- some cheap RG-6) before putting something up 150' with all of the co-ax expense and hassle involved in getting meaningful signal that far. It may very well serve the OP's needs quite well. If the system(s) they are looking at are anything like the statewide TSYS here, all putting something up that high is going to accomplish will be to render the scanner(s) deaf due to massive front-end overload. I hear 8 counties and 2 ISP districts with RS ducks on the back of my scanners in the house.

"Massive front-end overload" - even more likely when trying to monitor a multi-site system where a well-aimed Yagi would have been worth the effort to be able to reject duplicate signals from other sites.

 

[AK9R]

I added the word "Scanner" to the thread title. The previous title kinda made it sound like you were looking for a TV antenna.

I agree that putting an 800 MHz antenna at the top of a 150 foot tower is probably unnecessary and introduces other issues. If the OP is trying to receive local systems, an antenna on the roof is probably a much better solution.

To answer a previous question about station engineers...Many TV stations are running on real tight budgets and may not have a full-time engineer. Whatever engineer they have is probably focused on more important issues like keeping the transmitter on the air. A lot of TV stations get their programming from a remote distribution site. There's a TV station in Indianapolis that provides the programming for 6-8 other TV stations. This practice has an impact on the need for technical people at the receiving station.

 

[lmrtek]

Discones are a safe choice for a "cover all bands" solution but their performance on UHF bands is less than impressive and sadly all the good antenna designs are no longer available

The channel master 5094 and the later ST 2 were both excellent antennas that easily outperformed a discone but slick marketing and uneducated consumers lead to their demise

All that is really needed for a scanner antenna is 155 MHz, 460mhz, and 800mhz so a simple ground plane antenna with those 3 radiators would work the best

Radio shack used to sell such an antenna and it worked excellent but AGAIN slick marketing and gullible consumers caused the discone antennas to infest thee industry