800 mhz mobile nmo antenna

[BlueMoon2]

Hello everyone,

I currently monitor the Charlottesville/Albemarle, VA 800 mhz radio system right now primarily on my BCD996XT using a antennex ABSCANC antenna with NMO mount. I sometimes go to local Richmond, VA that has a 800 mhz radio system as well. The antenna receives 150/450/800 mhz but doesn't seem to be doing a real good job on the 800 mhz portion. I am considering getting a just 800 mhz nmo mount antenna but I have some concerns.

One of the antennas I have looked at says receives from 806-866 mhz. Does that mean that it would also receive a frequency of say 866.5625? or does it cut off at 866? Another antenna I have looked at says receives from 806-896 mhz. I'm just wondering which type of antenna is going to be my better bet.

Keep in mind, the Richmond system that I mentioned above, is currently undergoing re-banding of their frequencies. Charlottesville/Albemarle has already rebanded.

 

[lep]

I have a 900 Mhz antenna that has a curly shaft and is about 18 inch long, it is a MOT antenna new in the package for NMO bought as NOS from a MOT dealer at a radio flea markedt. I have a Larsen/AS 3 band 150/450/800 in the trunk with a wrench for quick change but never use it and I find, as you did, the 800 performance is poor. (oh, and my local system is 700 MHZ, since the 996T is receive only, it doesn't seem to make the slightest difference about the exact frequency and I regular received sites 40 miles away.Don't worry about the 866 v 866.6, the radio won't know the difference.

 

[mmckenna]

The frequency range of an antenna is usually the slice of spectrum that would have a certain SWR if used for transmitting. Usually this is a value of 2:1, which is considered "ok" for a transmitter.
Different antenna designs will have wider or narrower bandwidth. A 1/4 wave antenna tends to have a wider frequency range at a 2:1 SWR (or less) than a higher gain antenna.

The antenna will work for receive outside this range, so the 806-866 antenna would work just fine at 866.5625. It'll probably work just fine up into the 900MHz range.

I'd suggest finding an antenna that covers the band and has some gain. It should work better than the try-band antennas.

 

[dixie729]

Hello everyone,

I currently monitor the Charlottesville/Albemarle, VA 800 mhz radio system right now primarily on my BCD996XT using a antennex ABSCANC antenna with NMO mount. I sometimes go to local Richmond, VA that has a 800 mhz radio system as well. The antenna receives 150/450/800 mhz but doesn't seem to be doing a real good job on the 800 mhz portion. I am considering getting a just 800 mhz nmo mount antenna but I have some concerns.

One of the antennas I have looked at says receives from 806-866 mhz. Does that mean that it would also receive a frequency of say 866.5625? or does it cut off at 866? Another antenna I have looked at says receives from 806-896 mhz. I'm just wondering which type of antenna is going to be my better bet.

Keep in mind, the Richmond system that I mentioned above, is currently undergoing re-banding of their frequencies. Charlottesville/Albemarle has already rebanded.

I have the same problem with my BCD996XT covering the 800mhz like crap. I've got a BMAX1000 NMO antenna on my truck roof

Kevin Absher - HTC Inspire 4G

 

[BlueMoon2]

BMax1000 NMO antenna?

Quick search of that came up with no results. Where did you find that antenna?

Thanks for all the quick replies. It's looking like I might be able to go ahead and get a Motorola antenna like is pictured here on Ebay:
Motorola MCS2000 Maxtrac Spectra XTL5000 800 900 MHz Mobile Radio Antenna X | eBay

OR THIS
Crown Victoria Vic 800MHz Roof Antenna Motorola Radio | eBay

Please let me know what you think.

 

[BlueMoon2]

Found the BMax 1000

Okay found the Bmax 1000 antenna after some searching. Very similar to my Antennex ABSCANC for sure. Still wanting to know about the antennas from my previous post.

 

[dixie729]

Okay found the Bmax 1000 antenna after some searching. Very similar to my Antennex ABSCANC for sure. Still wanting to know about the antennas from my previous post.

Well I have the BMAX1000 and it does very well on the vhf/uhf but 800 mhz EDACS doesn't come in too well sometimes.

Kevin Absher - HTC Inspire 4G

 

[LtDoc]

One suggestion would be to find a vertical-array type antenna for 800 Mhz. That 'array' means one antenna 'stacked' on top of another with a coil between them That coil is a 'phasing'/timing device to get all the energy accumulated by that antenna 'in-step', sort of. That sort of antenna does produce some gain over a single element antenna so should mean you could hear weaker signals. There are limits though, and a lot of other things that can attenuate a signal, so don't look for any guarantees. Such an antenna will be 'closer' to resonant so would be an improvement. Where would you find one? Beats me, I don't have a need for one so haven't looked.
Good luck.
- 'Doc

 

[nick1427d]

Try TESSCO - Wireless & Mobile Communications Products: Antennas, Cable, Towers, Test Equipment, Tools, Mobile Phone Accessories they have a good selection and give good specs as far as bandwidths. You don't have to buy there but can cross reference antennas you find on ebay and what not as far as the specs.

FYI I snagged a 800 maxrad nmo off ebay a few months back for $10 works excellent.

 

[lep]

The MOT Maxrad nmo pictured in the post from eBay is the one I bought new, in a sealed factory sleeve from a MOT dealer at a radio flea market for $15. Works fine on 700-900 MHz receive only no problem with it.

 

[mmckenna]

I would strongly suggest NOT using the Motorola 800MHz antennas like the ones you linked to on e-Bay. While they work well, the design does not stand up well to the weather. We had a bunch of those at work, and I've replaced them all. The base where the whip attaches lets water in. The spring loaded pin at the NMO base get fails and I've replaced a few where the entire base has split apart due to corrosion. Proper preventative maintenance will extend the life of that specific antenna, but you'd be better off spending your money on a better design.

It would work fine for a few years, likely, but it probably won't last long beyond that.

Just about anything will last longer than those.

I'd suggest one of the Larsen brand antennas designed for the 800MHz band. We used those on the police cars, while pretty much all the other mobiles used 1/4 wave antennas on 800.

 

[lep]

I have one of these on my personal auto, insalled by my MOT dealer, that has been in daily use for 11 years with none of the problems described. Maybe I have just been lucky, (yes, I supplied the antenna and he drilled the holes and ran the cable under the floor carpet)..

So, I can only relae my own expeience which has been positive. As I noted, I do have a Larsen in the trunk of the auto for "gain" but rarely find a need to swtich antennas.

 

[mmckenna]

Sounds like you got a good one, or that you are performing some level of preventative maintenance. In our fleet, it's hard to get people to look after things, or at least tell us when something isn't working right. I got a complaint that one of the police cars was having issues with it's 800MHz radio. When I took a look at it, this is what I found:

Obviously a neglected antenna, but that damage started on the inside and spread, something that most people wouldn't normally see. The corrosion on this one was bad enough that the spring loaded center pin was rusted up and the water leaked down on top of the NMO mount, creating a mess there also. Somehow the radio wasn't damaged by them transmitting into this catastrophe. We replaced these antennas with the Larsen NMO800B or the Larsen NMO 1/4 wave antennas and haven't had an issue since.
Now, to be fair, we are near the ocean and have a lot of fog, so you may not see this issue farther inland. But, just a heads up/word of caution, these types of antennas are prone to damage.

I hung onto this one to use as an example when we try to get users to talk to us about issues.

There is nothing magical about a Motorola branded antenna. They are made by a different vendor anyway, and don't hold any secret powers that make them work better than any other brand. If you are happy with the design, performance and look, then it's probably the right antenna for you, but for someone looking for a scanner antenna, it's certainly not the best antenna out there. If someone is looking for a new antenna and wants to spend their money wisely, finding something that has a better design and better track record would be a good idea.

 

[BlueMoon2]

So it sounds like the Larsen 800 antennas may well be the way to go. All be it, more expensive but I'm paying for quality. Thanks so much for the good advice guys!

 

[mmckenna]

Just keep in mind that any antenna needs some preventative maintenance. Make a point to remove the antenna now and then and inspect underneath it. Clean everything and make sure it's dry. I've also gone as far as to occasionally loosen the set screw, remove the whip, and clean all that out. Water can wick down inside there and cause some corrosion. Make sure the set screw stays tight. I'll occasionally remove the sealing gasket where the antenna base meets the rooftop and wipe it down with some Armor-All to keep it in good shape.
This applies to any mobile antenna, not just the Larsens. The Motorola antenna that I posted above would have lasted a lot longer with that sort of maintenance, but the guys who run the fleets don't understand and don't have time for that sort of stuff.

 

[Anderegg]

I use my mobile mounted scanners and Motorolas for work as a news photographer. I get paid per story, and reception is vital to me. After testing the standard Motorola pigtail against a 4.5db gain Larsen and a 1/4 wave 800, I found that the 1/4 wave gives the best reception. I used a 396XT RSSI signal through FreeSCAN to determine the best reception, comparing three different trunked systems, close and distant.

Consider that my income is determined by reception performance when evaluating my opinion. The black 1/4 wave 800's I got from theantennafarm.com only cost $14 too.

Paul

 

[W8RMH]

For the last few months I have been using a Laird Tech TRAB7603 Phantom antenna on a mag mount for 700/800 with great success. It has worked better than any antenna I have used for 800 MHz. I receive five bars on systems I couldn't get 1 bar on before.

 

[BlueMoon2]

Interesting. I was considering doing that phantom antenna but wasn't sure. I might have to go back to theantennafarm and change my order

 

[Anderegg]

That photon antenna is probably just a 1/4 wave with a coffee cup mounted over the top of it!

 

[LtDoc]

That 1/4 wave and a coffee cup is closer than you might think! They do work for the higher UHF bands, they are just a shortened antenna for those bands where a 1/4 wave is more than about 3 inches. The lower in frequency you go the worse they will perform.
Aside form the physically being easier to hide, or not being as noticeable as other kinds of antennas, they have no practical benefits, ain't no 'magic' in there.
They 'work' on lower bands because the transmitters on those lower bands are more prevalent, cover a wider area, lot's of repeaters, or things of that nature.
Just how 'short' of an antenna is acceptable for your use??
- 'Doc