Office Antenna

[kibbins]

Hi...I'm fairly new to scanning. I have a scanner in my office and I'd like to tune into our company's security and maintenance. The use frequencies in the 150-160Mhz range and becaus ethey sometimes operate in remote buildings or basements I'm not always hearing them. I realize I may not be able to hear everything since my office is on the far edge of our site )although I am up high--3rd floor).

I currently have a simple wire antenna that came with my scanner for use in a car that does not seem to work very wel. I have a metal cabinet I can use so I was considering a magnetic car antenna. I have tested a hanheld scanner someone else owns and it seems to pickup more than my base scanner in my office....so I think my antenna may be the weak link.

I will test the cheap telescopic antenna I have for my scanner but...

What antenna can I find that will be small and fit in my office that is optimized for 150-160? It has to fit in my office confines but I do have a metal cabinet to put it on. Any suggestions???

 

[ReceiverBeaver]

Hi there,

A mobile scanner that came with a piece of wire for an antenna? That doesn't sound right. Nevermind.

Next you want SMALL that works GREAT. That doesn't compute in Antennaland. Big performance is pretty much always going to come in a big box.

If you have a metal filing cabinet to put a mag mount ant. on, then a 5/8 ant is readily available and will be awesome.....but the whip-stinger in going to be around 46-50" long (high). If that is too long for you to be comfortable with, next up will be 1/4 wave which shrinks the stinger down to around 20".....but a 1/4 wave isn't nearly a good a performer as the 5/8. Both will be available at any place that sells scanner or ham gear. Either should be under $40

Good luck

Don't ask a beaver very many radio questions, they tend to be dumb animals.

 

[kibbins]

My scanner came with both a telescopic antenna and a wire/car antenna since it is a base/mobile unit. Here's one just like what I'm using now:

http://cgi.ebay.com/SCANNER-Suction...ryZ14956QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I'll try the telescopic antenna tomorrow. I have roughly 50-inches from the top of my metal cabinet to the ceiling to work with or more height if I don't have to mount it on the metal cabinet.

Will the 5/8 antenna work better than the wire (probably a stupid question)? Is there a specific 5/8 antenna you would recommend or any you would avoid? I don't want to spend a lot unless I'm sure it will work much better and I'm guessing there is no way to predict that without trying it.

Also any grounding issues here...i.e. does a mag mount antenna need to be on a metal surface?

Thanks

 

[ReceiverBeaver]

Hey Guy,

Any common brand should be OK.

Yes the tuned 5/8 will work far better than a random piece of wire.

Yes a mag mount MUST have a metal surface area that equates to at least 1/4 wavelength of the operating frequency you're using. In your case, only needs to be a minimum of 20" square. The filing cabinet will do fine. Folks have stuck mag mount ant's on stoves and refrigerators and get out well. About the same as sitting outside on the car.

Mag mount verticle antennas are all Ground Plane type antennas. The mag mount with whip is only HALF of the antenna. The metal surface the mount sits on is the ground plane.....the other half of the antenna.

Beavers make poor ground planes for any type antenna

 

[kibbins]

So if it is a non-magnetic mount just sitting it on a metal cabinet will be ok?

Any recommendations that anyone is using now would be great...OR any to avoid???

 

[consys]

Are you next to a window? I used a clip lead to a metal window frame (and it worked great!) for a looong time before my boss discovered what I was up to. And in the summer, I just hung it out the window. For that matter, hook your wire TO the file cabinet. Everything is an antenna, just some are better than others. I've had a lot of fun and some great outcomes trying the unconventional.

 

[kibbins]

I have the telescopic antenna on today. So far it is hard to tell any difference but I have not heard our staff on it yet. I have a window and I did try the suction cup on the window but that did not seem to help. Are you saying I should expose the wire and tape that to the metal frame of the window or file cabinet?

 

[kibbins]

I'm not having much luck finding many 5/8 antenna. Most are drill mount or no cable. Any sugggestions where to find a good mag mount one??

 

[ReceiverBeaver]

A very common choice will be a 2 Meter (VHF) ham 5/8 mag mount. A popular store is Ham Radio Outlet. I believe their site is simply www.hamradiooutlet.com If that isn't it. Then Google ham radio outlet.

Their catalog is pdf and difficult to sort through. Just lift their nearest store's 800 number off their website and call them. Ask for their least expensive complete 5/8 2 Meter Mag Mount with cable.

You are also probably going to have to adapter the coax connector down to whatever your scanner has on the back. If it's a BNC connector, they probably have a model that's already terminated in BNC. If it's a RCA plug, you'll probably need an adapter. A typical 2 Meter Mag M is going to be supplied with a PL 259 plug.

 

[fuzzymoto]

Hey Kibbins...what about the Valor PMM3B

I don't know if it is a 5/8 antenna but I hear a lot of good things about it on here and it's fairly cheap.

http://www.universal-radio.com/catalog/scanants/1190.html

I'll let the experts chime in on whether this is a 5/8 antenna or this will work out for your 150-160 monitoring.

Experts?

 

[Al42]

1) If you can find a 5/8 wave, VHF-hi antenna with an NMO mount, you can always get an NMO mount magnetic mount and put the antenna on it.

2) Try setting the telescopic antenna to around 19" from the top of the connector to the tip of the antenna.

 

[consys]

Yes- I had a (10 foot?) piece of RG-58 or similar with a BNC on only one end. At first I stripped the jacket & shield back to leave an "antenna" sticking out I could elevate. I played with diiferent lengths before I got silly and started connecting the end to anything metal it would reach. The window frame at work was outstanding. You just never know, I find it fun. That kid actor in the "sixth sence" movie saw dead people- I see antennas! The curse of the radio bug...

 

[kibbins]

So the Valor is NOT a 5/8 antenna?

What is NMO?

I'm testing the telescopic antenna now at 19-inches

 

[blinddog50]

What kind of building are you in?
Metal frame, metal siding, insulation with an aluminum sheathing.
All these can affect reception.

 

[Al42]

Yes- I had a (10 foot?) piece of RG-58 or similar with a BNC on only one end. At first I stripped the jacket & shield back to leave an "antenna" sticking out I could elevate. I played with diiferent lengths before I got silly and started connecting the end to anything metal it would reach. The window frame at work was outstanding. You just never know, I find it fun. That kid actor in the "sixth sence" movie saw dead people- I see antennas! The curse of the radio bug...

Here's another one to try. Strip off a little more than 1/4 wave of the jacket (which is 3.2" for 800, 6.5" for 450 and 19" for 150). Peel the shield back over the cable so you have 1/4 wave of shield running down the jacket. (Clip off the excess.) Cut the "antenna" to 1/4 wave. It's called a "coax" or "bazooka" antenna. Basically it's a dipole with a 1/4 wave 1:1 balun all in one. Back when mobile telephone was on 150 MHz, that's the antenna almost everyone used.

 

[kibbins]

My building is masonary, relatively new with brick exterior and a lot of glass.

If I can find some coax with a connector I'll try that 19-inch coax antenna. So I'll end up with a coax running out of my scanner with 19-inches of the core wire exposed and 19-inches of the sheild folded back over the cable. Does it matter how much coax I use before that, in other words should I have enough coax so that the 19-inch exposed end can be high in my office? Can the coax or sheild touch anything metal?

 

[bluesman905]

Antenex Phantom

I'm selling an Antenex antenna that may suit your needs. Just thought i'd mention it. You would need an NMO mount for it (this could be mounted on your metal cabinet). Check it out in the For Sale Forum. http://www.radioreference.com/forums/showthread.php?t=28527

 

[kibbins]

I just made a coax antenna. I'll try it at work on Monday to see if it helps.

 

[Al42]

Does it matter how much coax I use before that

Only in that the more cable you use, the more signal you lose. But 15 feet of cable would give you minimal loss at 150 MHz.

Can the coax or sheild touch anything metal?

The jacket can - the center conductor and shield shouldn't. But you can hang the antenna with string, as long as the string doesn't get wet or, if it does, it's not touching the center wire..

 

[kb2vxa]

Hi Kibbins and all,

Did someone say "Experts?" As Buckwheat said, "Hee ah eez!"

Antenna Specialists makes a whole line of commercial band antennas and I have just the one you want, sort of. Start with thier mag mount, add the VHF Hi Band resonator, top with the whip supplied cut to the frequency by using the chart that comes with it. Voile! You have assembled a 5/8 wave antenna specifically for the frequency you want.

Meanwhile do as Al said, adjust the telescoping antenna for 19" from connector to tip and set the scanner on the metal cabinet where you'll stick the 5/8 wave antenna eventually. Oh, unless they're using a repeater and you're listening to the input by mistake they can't hear each other any better than you hear them. That coaxial Bazooka is OK and works as well (or as poorly) as a groundplane which is what that telescopic whip atop the steel cabinet amounts to.

Sorry Simon, that antenna you're selling has unity gain which has nothing over the whip antenna on the back of his scanner. A 5/8 wave has a much lower vertical radiation angle he'll need to hear DOWN from the third floor to the basement where he's having trouble hearing now. It's a good antenna but unsuitable for the purpose.

BRAINSTORM! Since a groundplane has a fairly high vertical angle mounting one upside-down will invert the pattern! This technique is used at repeater sites when the antenna is at extreme altitude. It fills the shadow under the tower allowing close in mobiles to communicate as well as thier farther out counterparts. Oh, because there is always a hole in the doughnut don't expect any antenna to receive well straight down unless it's horizontal but that's another can of worms.

Oh Kibbles, if you're not the boss you're a real stinker spying on the employees and if you're the boss you're a BIGGER stinker. How do I know? Only the boss or a stinker kissing up to the boss could get away with a scanner in the office AND an ugly antenna to go with it. (;->) I'M KIDDING, JUST KIDDING! (;->)

(This is a thinly disguised hate mail from the janitor in the basement talking on the radio behind your back. Now I'm going encrypted, you stinker.)