Scanner Antenna

[tree68]

Here's a really simple antenna - and it's even pretty close to tuned:

Get some coax - RG58 or RG8, your choice.  You can buy it preterminated (with plugs at both ends) but you're gonna cut one of the connectors off.  If you're going on the road, the RG58 is the better choice - not as bulky, and for the distance we're talking, insignificant loss.

After you cut the plug off one end (assuming that's how you're going to do it), measure either 34.925" or 17.4627" from the end and mark the spot. (Don't bother with the micrometer - 17.5" or 35" will be fine).  Those are the half and quarter wavelengths for 160.800 - Amtrak's frequency in many areas.

CAREFULLY score the insulation around the cable at your mark.  Not cutting the braid is the whole idea.  A hobby knife will do just fine.

CAREFULLY score the insulation lengthwise on the cable from the mark back to the end of the cable.  Once again, not cutting the braid is the whole idea, and is especially important for the next part to work.

Once the insulation is removed, pull the shield back over the remaining insulation.  It's kinda like peeling a sock off.  When you get done, you should have the 17.5" (or 35") center conductor sticking out of the end, and the braid will be more or less 17" (or 34") back along the cable.

You may want to put shrink tubing over the braid, if you will be handling this very often, or if you are going to put it outside.  Tape would probably work, too.

If you want to have a way to hang it up, put a crimp lug or something like that on the end of the center conductor.

Get it as high in the air as you can.  If you are out on the road, you might even think about taking along a fishing pole as a temporary mast.   They usually travel compactly.  That 14' bamboo probably won't work unless you're driving a motorhome...

I've seen ground plane versions done with a PL239 (female) connector.  PM me if you're interested.

[Willy2]

Well, I still want it to be handheld and I usually don't listen at home, mainly just on the road and at the train track, so I'm not looking for anything too extravagant. I'm still reviewing all of this info everyone has given me and trying to figure out what will work best. Thanks to Chad for all of that information, it'll influence what I end up getting.

Like someone said - get a cheap 2M ham antenna - if you don't have a store close.

Call one

AES or HRO  - various places, Universal Radio - Columbus.

Just ask them to make sure you get a cutting chart and snip to the correct length - not required - but will help a little.

I use a Larson 2M 0 cut to 155 for ALL my scanner work and it works good enough.

Just handheld you can get one of the 2 meter extendables  -  http://www.universal-radio.com/catalog/hamantht/0786.html
They do a GREAT job.


Been scanning for 40+ years.  Also a Ham N8PFF

Ok, that sounds good. I'll probably get it this weekend and then see how it works and let everyone know. 

 I honestly don't understand a particle of what Chad said, but I'm trying to learn. 

[MP173]

I went to a local electronics store this pm and they helped me out.  Showed me what they had, it was antenna and a mast with hardware, all for about $75.  Gotta figure out where to put it and then I will probably go with it.

Chad, I re-read what you wrote and after visualizing some of the stuff, it made a little sense to me, not much, but a little....I got a lot to learn.

Similarly, the post on dynamic brakes left me at the starting blocks...

ed

[Anonymous]

Well, I still want it to be handheld and I usually don't listen at home, mainly just on the road and at the train track, so I'm not looking for anything too extravagant. I'm still reviewing all of this info everyone has given me and trying to figure out what will work best. Thanks to Chad for all of that information, it'll influence what I end up getting.

Like someone said - get a cheap 2M ham antenna - if you don't have a store close.

Call one

AES or HRO  - various places, Universal Radio - Columbus.

Just ask them to make sure you get a cutting chart and snip to the correct length - not required - but will help a little.

I use a Larson 2M 0 cut to 155 for ALL my scanner work and it works good enough.

Just handheld you can get one of the 2 meter extendables  -  http://www.universal-radio.com/catalog/hamantht/0786.html
They do a GREAT job.


Been scanning for 40+ years.  Also a Ham N8PFF

[MP173]

Chad:

You are one of the most informative and valuable members of this forum...but in all honestly, I didnt understand a word you wrote!

I should have paid more attention in shop class when we studied electricity.

Looks like I am just going to keep what I got, perhaps go to a local radio store (other than radio shack, as they really didnt know what to do), or buy some more file cabinet!

thanks,

ed

[JSGreen]

Another antenna that works well at home is called a "J-Pole". It can be made from copper pipe...find out at the local radio shack if there is a Ham club near you.  Someone may even make one for you for the cost of parts...jsut make sure they know you want to use it at 160 MHZ, the ham band is a bit lower in frequency, so it will work better for you if it is the correct length.  It would still work, but it works better at the correct length.

[tree68]

As Chad said, elevation is everything for home scanning.  A caveat - and an important one - if you do put up some sort of antenna at home and it involves a metal mast, Watch out for WIRES.  Most of us don't have much of a yen for fried railfan...

I'll second the tuned antenna.  There are several outfits that will sell you one, and if you check around locally for a communications company (usually dealing with Motorola, EF Johnson or one of the other major radio companies), they'll sell you one, too, and cut it to length for you.

A tuned quarter wave spike is a good start, but a longer antenna and/or a base load will bring in even more.

[Willy2]

Well, I still want it to be handheld and I usually don't listen at home, mainly just on the road and at the train track, so I'm not looking for anything too extravagant. I'm still reviewing all of this info everyone has given me and trying to figure out what will work best. Thanks to Chad for all of that information, it'll influence what I end up getting.

[squeeze]

Chad Thomas has it pretty much on the button. One point to add on the co-ax cable: RG-8 and RG-58 are 50 ohms impedance, and RG-11 and RG-59 are 75 ohms. RG-8 and RG-11 are rated for 2000 watts, while RG-58 and RG-59 are rated for about 300 watts. Look on the spec. sheet to find out the impedance in ohms as to which applies to your unit. As long as the length doesn't go over 50 ft., there is very little in there performance. If you are running 100 ft. or longer, the difference would start to become noticable. Chad pretty much is on the right track. I agree that this could go on for a long time as everyone has their pet setup.

 

Thanks, Squeeze

[TimChgo9]

I have a 14 year old Radio Shack 50 channel scanner.  For those 14 years I have had a telescoping antenna for it, and I have gotten great reception from it.  Of course, being on the 3rd floor of most of the apartment building I have lived has helped.  Out where I live, 30 miles from my former residence, I still pick up the fire departments from that area, and I get signals from as far as 90 miles from me. Don't know why, but reception has always been good.

[Anonymous]

I USE A RAILCOM 7" ANTENNA. AND IT WORKS WOUNDERFULL. THE OTHER RAILCOM ANTENNA ON MY TRUCK IS THE GREATEST INVESTMENT I HAVE EVER GOTTEN. I CAN PICK UP RAILROAD SIGNALS AS FAR AWAY AS 30 MILES.

[chad thomas]

This is a topic that could go on and on and on...

Elevation is very important, especially if there are buildings or terestrial obstacles. If you live in a houseing tract then you want to get above the roof peeks of the surrounding buildings. For a few dollars ($20-30) you can get a 20' telescopeing mast from radio shack and for another $20+/- 3 eye hooks (or better yet, 4 eyehooks) and the guy wire to secure it to the peek of you roof. A one story house will typicaly get you 15', plus the 20' mast and that gets you 35' above terain. More importantly it gets you above surrounding obstacles that could do more damage reflecting signal away from your antennae.

As far as the antennae goes, if you can afford it get a tunned whip and the nessasary hardware to mount it on top of the mast. In this case be sure to have a solid ground connection as direct a path as possible to EARTH ground. A 2 1/2 - 3' copper ground rod should work if the soil has some moisture in it. If your soil is like sand or another dry material then use as big a ground rod as possible (within reason). That's not the setup I would go with but it is simpler. A better antennae would be a tunned 1/2 wave di-pole (mounted vertical of course) and offset at least a few feet from the mast with insulated material like PVC or dry & weathersealed wood. A di-pole might look like two whips with one element pointed straight up and one pointed straight down. For 160Mhz a 1/2 wave diepole should be 34" tip to tip, or each element 17" long. With a di-pole ground is not important as it is with a whip or a stock "rubber duckie" because a di-pole is balanced and does not need a ground referance. A di-pole is easy to make from scratch if you have a little hardware around the house. At 17" per element it need not be real strong, just strong enough the wind (or ice) will not bend them. A 300 to 75 ohm matching transformer (like the kind you had to have to hook coax to older TVs) works just fine to hook the elements up with and the F type connector is just right for hooking up to the coax lead.

*** note, if useing a di-pole mounted offset from the mast the mast will block a bit of the signal in that direction relative to the ant. so orient it so the mast is on the side of the antennae wherethere is least likly to be signal comming from.

 

Don't skimp on the cable. RG59 (the cheap stuff) will have 2-3 times the loss of RG8 or RG11 and that cuts right into the front end sensitivity of the scanner. And like I said if you are useing a whip run the lead directly to a ground block hooked up to a good EARTH ground (you cold use the power panels ground rod below you power meter but connect to the rod NOT one of the ground wires to the phone/cable/power box). Then another RGxx F type fitting and an adapter to your scanner connector (usually BNC type) and you are good to go.

Now this is a typical setup but if you can spend the $$$ to go higher (like say a 40' radio shack mast) then you will be much better off.

Also if you are in a rural area away from any VHF transmitters like FM stations or Police / fire radio base stations or TV transmitters (VHF ch2-13) then you could take it a step further and get a VHF PRE-AMP and mount it at least 2' below the lowest point on the bottom element. You can get thes at radio shack for $20+/-. You will want to use 300 ohm twin lead to connect the ant. to the pre-amp and the pre-amp's stock lead will not be long enough, so get 5-6' of twin lead and twist it like a helix and use insulated & offset mounts to secure it. The pre-amp will be two parts, the amp that mounts next to the antennae & the power supply that goes next to a 110vac wall outlet (and EARTH ground the lead between the two). It must be a PRE-AMP that covers the VHF midband. Any other type of amp will either do more harm then good or will not pass the 160Mhz band.

** you could also use a pre-amp near high power transmitters but you will need a band pass filter in front of the amp and those are not radio shack items. But there is rarely a need for an amp in that situation.

Another thing to consider is are you trying to get better reception from a single fixed direction? In that case if gain is more desireable in one direction and you are willing to sacrifice omnidirectional equality, then you can go with a verticle mounted Yagi or log-periodic aimed in the desired direction and get extraordinary gain over whips & di-poles. Antennae cut for TV channel 5 works great, though you may have to find a antennae dealer to get one.

If anyone wants a picture of the mounting arangement or has any specific questions feel free to e-mail me, [e-mail]

  

[videomaker]

Your cabinet acts as a ground plane(reception)...Danny

[MP173]

Scanner reception is an interesting topic for me.  I dont understand the physics of it and would appreciate any help.

I have 2 Radio Shack desktop models and a RS handheld.  The 2 desktops are located in separate locations of the house and interestingly one scanner will pickup certain transmissions which the other doesnt.  The scanners are no more than 30 feet apart.  I am not really happy with either scanner's reception.

I often use my handheld in the house (3 scanners!) and have it connected to a RS cartop antenna with a magnet.  I have it on a file cabinet upstairs and get great reception.

 

Now my question...is the great reception based on it being upstairs?  or it being hooked to an antenna which is on a file cabinet?  Does the steel of the cabinet act as a booster of some sort?

thanks,

ed

[JSGreen]

How do you want to use your scanner?  If you still want it to be handheld, you might try something like the Diamond RH707CA.. ($25 at Ham Radio Outlet).  It looks like this...
http://www.universal-radio.com/CATALOG/scanants/2368.html

If you want even better reception, consider a car mounted antenna.  You get a better ground plane, and can mount a larger antenna.  Anything in the 2M (two meter) ham band will work ok for receiving in the 160Mhz band.  Something like the Diamond MR77, which comes with a magmount base, would work well.  HRO sell it for aoubt $35, but you would need an adapter for UHF to BNC. (UHF connector is sometimes called PL239, or CB type antenna plug.  A BNC is a quarter twist quick connecting type, found on lots of hand held and scanner radios.

http://www.universal-radio.com/CATALOG/hamantm/3243.html

Basic rule of thumb, the higher you can get the antenna, the better it will work. 

[Willy2]

I was planning on going to Radio Shack either tomorrow or next weekend, but I thought that before I went I would check here just to see if anyone could give me an idea of what might be good.

[CANADIANPACIFIC2816]

Have you talked with your local Radio Shack dealer? It seems to me that they can get what you need if they don't currently have it in stock. But then I could be wrong. It wouldn't hurt to ask them.

CANADIANPACIFIC2816

[Willy2]

I have had a Radio Shack Pro-83 scanner for the past couple of years. It has served its purpose very well with only the antenna that it came with, but I would like to upgrade to a more powerful antenna with a wider range soon. Can anyone suggest a certain type or brand of antenna I should get and where I should get it?

Thanks.