omni-directional antenna?

[renze8173]

Hi, I'm putting up a 40' Rohn 25 tower. Is there any respectable omni-directional antennas out there that are priced right and perform well? This antenna will be for receiving only, which brings me to my next question- is Db loss important when it comes to receiving only? I will need 140' of coax cable. Can I get by with RG-8, or should I go with a better quality cable like LMR-400?


Any replies would be greatfull.

 

[Dubbin]

A scantenna and LMR400 would kick a$$ on top of that tower. Oh and yes, loss is very important.

 

[k8tmk]

Loss is dependent upon both length and frequency. As the frequency increases, so does the loss.

So, the type of cable you use depends upon what frequency range(s) you plan to listen to. Go out to Belden's website to see the loss specifications of their cables. I personally wouldn't use RG-8 for anything above VHF.

Randy

 

[renze8173]

Is there a difference in dB loss between connectors?

 

[n5ims]

Is there a difference in dB loss between connectors?

Use the connector that matches what you're connecting to whenever possible. Any adapters will most often more than wipe out any gains by using a "low loss" connector on the cable that doesn't match what it's being plugged into. If your antenna uses an "F" connector, this should be used there and if your scanner uses a BNC, then that's the best choice on that side of the cable. There's nothing that prevents you from using different connectors on the same cable (assuming that you get ones designed for that type of cable).

Since it sounds like you're doing a totally new installation, you're probably in good shape to do it right with minimal compromizes.

Without knowing specifics (like radio, antenna, frequencies, etc.), a good rule of thumb would be to use LMR400 for the coax and "N" connectors when possible (like on your lightning supressors). Be sure to seal all connections that are exposed to prevent water from getting into the cable. Since LMR400 is quite stiff, be sure to only have gentle bends in the cable. I often recommend that you make a patch cable (keep it short, 6 foot or less!) using flexible cable like RG-58, RG-6, etc. between the end of the LMR400 and your radio. This will reduce strain on the connector on your radio.

Good luck with your project!

 

[dan1son]

Is there a difference in dB loss between connectors?

Yes, but fairly minimal for the most part. http://www.qsl.net/vk3jeg/pl259tst.html

You'll see far more loss in the cable. 140' off even LMR-400 has about 4.5 DB of loss at 450mhz, rg-8x will be about 12db of loss. Get the best coax you can afford.

 

[renze8173]

Thanks for the information. It really helped. I'm a little shy of hights, so doing it correctly the first time will save a few extra trips up the tower.

 

[hoser147]

Thanks for the information. It really helped. I'm a little shy of hights, so doing it correctly the first time will save a few extra trips up the tower.

You might as well get used to going up and down, your going to have to do some preventive maintenance here and there. What antenna's do you have in mind? Good Scannin Hoser

 

[renze8173]

I think that I will use a Diamond D130NJ Discone antenna. Mostly Scanning 150-160 and UHF. Any thoughts?

 

[zz0468]

I think that I will use a Diamond D130NJ Discone antenna. Mostly Scanning 150-160 and UHF. Any thoughts?

Since you're afraid of heights, I'd choose a commercial grade antenna that just won't break. Look at the Kreco discones. They're expensive, but you're not gonna have to climb the tower because the elements are falling off.

 

[tonsoffun]

Thanks for the information. It really helped. I'm a little shy of hights, so doing it correctly the first time will save a few extra trips up the tower.

Hi,
If you don't want to climb that much and do it right the first time, I would invest(If you can afford it) Andrew Heliax cable especially going at that lenght. If you install this cable and seal it properly, don't worry for many, many years to come as it is a very tough cable, but is a little hard to work with. I use the superflexble and it was really nice.
140' long at 450MHz was about 3.2db of loss I believe with the Andrew Heliax FSJ4-50B Superflex.


Also the diamond D130J is a very good all around discone antenna.
I had mine up at least ten years now and never had a broken or elements coming off. Make sure to use loctite on the set screws to hold the longer elements.

Have you looked at the http://www.dpdproductions.com/ antennas. I just bought the Omni-X and have yet to install it but, it is a really strong and well built antenna.
Hope this helps and good luck on the install
Ron

 

[N9WP]

As far as the coax goes, I just replaced my RG-8 with LMR-400 and it improved things a lot and I'm only running about 40 feet of the coax into that Radio Shack 20-176 antenna and Uniden 996. For my 2 meter ham radio, I replaced 50 feet of the RG-8 Coax to LMR-400 and I get about 3-4 more s-units on receive and can hit repeaters further away more clearly. Just my 2 cents on the coax...For the amount of coax your going to be using, I would buy the best you can afford, it will make that big of a difference.