What Antenna to Buy?

[rgchristy]

I started posting my info in the ST2 thread, but since the ST2/Scantenna won't work horizontally I figured it was best to start a new thread.

Here's my situation:
My primary listening is as follows:
800 MHz - 40% 5-10 miles away
500 MHz - 50% Local to me
150 MHz - 10% Local to me
46 MHz - Very Little

I currently use a RS Discone with RG6 and F connectors with a BNC adapter at the scanner. My antenna is mounted above the insulation in a peak area below the roof. There are no ducts to worry about. I have about 5' in height and about 12' in length to work with.

Since becoming disabled, I don't have the ability to make the antenna suggested, so I'm limited to a purchase only and have my nephew install it. A kit would be ok for him to install. Unless someone has an antenna construction plan that I could walk him through.

Does anyone know if there is anything within those limitations that would be better than my current RS discone? Is there any type of gain antenna available?

Thanks in advance,
Rich

 

[CookeCityScanner]

Im not sure how much affect this would have but could that rg6 be hurting signal bad. Thats not a 50 ohm cable. Perhaps switch to a section of rg8 or even rg58 from radio shack. Itll come preassembled with connectors and you could get the bnc adapter too. Some will laugh at that and I too am now soldering my own connections after a short time in the hobby BUT the radio shack pre setup stuff works great on my rs discone like I said.

Reason I say is Im using the RS discone for almost similar purposes and achieving great results. Im using a 50 ohm cable on it though (cheap even rg58/u). I actually have better cable and a "higher quality" discone that i cant get to work at the moment.


Also is that mounting position clear of obstacles? When you say you have 5 feet in height to work with what do you mean exactly do you have 5 feet of an area you could strap a mast down with? If so go get some fence top rail or like I did 1/2" galvanized pipe in 20 foot section and stick that antenna higher on up. That would give you a 15 foot mast.

Others will have better ideas for you Im sure.

 

[Al42]

Im not sure how much affect this would have but could that rg6 be hurting signal bad. Thats not a 50 ohm cable. Perhaps switch to a section of rg8 or even rg58 from radio shack.

58 has much more loss than 6, and Radio Shack cable is pretty lossy. I doubt the cable is giving him much problem.

 

[Al42]

Is there any type of gain antenna available?

Yes, of course there is. For full coverage of 3 bands? No. Non-directional that you could mount in your attic? For 800, yes, for 450, maybe - not for 150.

Why are you looking for more gain? Is there a particular system you want to listen to? If so, what band, and how far away is it? (Also their antenna height and your roof height would help in figuring out whether it's even doable.)

 

[rgchristy]

I'm looking to improve my 800 MHz reception for 2 systems. One is approx. 5 miles away and the other is approx. 10 miles away. I'm trying not to ruin my 500 MHz reception because that is for the county that I live in.

 

[CookeCityScanner]

Im not sure how much affect this would have but could that rg6 be hurting signal bad. Thats not a 50 ohm cable. Perhaps switch to a section of rg8 or even rg58 from radio shack.

58 has much more loss than 6, and Radio Shack cable is pretty lossy. I doubt the cable is giving him much problem.

Shows what I know.... I thought the impedance difference of the rg6 made a big difference. So good rg6 should be as good as my "9913 type" cable or what? Man tell me it is so.... Ive got spools of that stuff laying around. Now your talking about somethign Ive actually got the tools to work with. I thought because it was a different ohm cable it would hurt bad.

 

[BJ_NORTON]

I thought the impedance difference of the rg6 made a big difference. So good rg6 should be as good as my "9913 type" cable or what? Man tell me it is so.... Ive got spools of that stuff laying around. Now your talking about somethign Ive actually got the tools to work with. Very Happy I thought because it was a different ohm cable it would hurt bad.

Impedance only matters for transmitting. For the highest efficiency the transmitter impeadance needs to match with the load (antenna). For scanning, the impedance really doesn't matter. The ranges we scan through (25-1300mhz) the impedance can vary wildly. Buy cable with the lowest loss per 100' you can. As a general rule of thumb, the thicker the cable the better the cable is.

If you want heavy duty stuff, you could try Andrew's Heliax, but that requires all sorts of new tools :wink: :!:

 

[CookeCityScanner]

Ok and I take it generally for most tx applications you go with the 50 ohm cables because thats what the antennas and equipment are at?

 

[BJ_NORTON]

for the most part yes, 50 ohm cable is used. Most transmitters want to see 50 ohms, but it is very common on HF to use 300 ohm "ladder" line. In the old days even regular lamp cord was used, but not so much any more. I think the most interesting transmission line I have ever read about is called G-line; it is just a single conductor, and a horn/funnel at either end. G-Line is supposedly very low loss.

But for scanner stuff, pretty much anything will work, but try to look for the lowest loss. That is the important thing. Once the signal leaks out the cable it is gone forever, and no radio can get it back.

 

[Al42]

I thought the impedance difference of the rg6 made a big difference. So good rg6 should be as good as my "9913 type" cable or what? Man tell me it is so.... Ive got spools of that stuff laying around. Now your talking about somethign Ive actually got the tools to work with. Very Happy I thought because it was a different ohm cable it would hurt bad.

Impedance only matters for transmitting.

That was nonsense the first time I heard it, snd it's been nonsense every time I've heard it in the 50 years since then. While the loss from 75 ohm cable in a 50 ohm system isn't severe, feeding a 50 ohm receiver from a 50 ohm antenna with 2 ohm or 2,000 ohm feedline is going to cause huge losses.

For the highest efficiency the transmitter impeadance needs to match with the load (antenna).

In receiving, the antenna is the signal source and the receiver is the load. Show me the difference in the equations due to whether the signal is going up the cable or down.

As a general rule of thumb, the thicker the cable the better the cable is.

For the same family of cable from the same manufacturer. Otherwise all bets are off. (One "RG-8 type" cable may have much more loss than another "RG-58 type".)

 

[Al42]

Shows what I know.... I thought the impedance difference of the rg6 made a big difference. So good rg6 should be as good as my "9913 type" cable or what?

Depends on the quality of the cable. Good RG6 is better, in this application, than lossy "9913-type". Poor quality cable is bad, regardless of the impedence.

Make up a length of RG6, long enough to go from the antenna to the scanner. Properly (drip loop, static arrestor, dressed properly). A lot of this hobby is like beer brewing - try it and see what happens. At least you can't poison yourself if the "batch" turns out "bad".

 

[Al42]

I'm looking to improve my 800 MHz reception for 2 systems. One is approx. 5 miles away and the other is approx. 10 miles away.

Any outdoor scanner antenna should be able to pull that in. The nearer one is probably line of sight to you from a clear spot, and 10 miles from a 20 foot high roof doesn't take much antenna unless it's a low power transmitter or their antenna is low to the ground.

Even cable with 6 inches of center conductor exposed, tied vertically a few feet above the peak of the roof, might be enough for all 3.