OK...Multiple Antenna Final Decission

[mikebires]

I have posted previous posts about using a splitter and different antennas. I received some phenominal advice and thank all that replied. Unfortunately, for one piece of good advice, I found another persons opinion voting against it. It's pretty much 50-50.

First, I will try just using an 800 6db gain antenna, and see how it does picking up other bands. In San Bernardino County, it's all 800. In LA County they primarily use 482 mhz. If this fails....

Using my Uniden 796, I am going to run LMR 400 up about 40 feet to an RF Systems splitter. The left will be about a 4' run of LMR 400 to a Comet gp15 6m(for low band)/2m(for VHF-hi/air)/440(for UHF), and the right side to an Antennex ATXFG8006, 6db gain 800 mhz antenna.

So...if my ballpark calculations are right, after facting in signal loss for cable and loss, I will still have better gain over my Diamond D130 Discone.

Here's what I came up with:
6m/2m/440 gp15 antenna gain is 3.0/6.2/8.6db
Antennex 800mhz antenna gain is 6.0db
Loss in about 50 of LMR400 is 6m(.4db),2m(.75db),440(1.3db) and 800 is (1.9db)
Loss on each port of splitter is 3db

sooooooo......
Final gain numbers are 6m is -.4db, 2m is 2.45db, 440 is 4.3db and 800 is 1.1 db

Did I do it right? Even though my problem area is the 800 mhz area, at least I'm getting 1.1 db (even though it is said not to be noticeable), it's still 1.1db over the 0db on the Discone.

If this doesn't work, I'm gonna tick off the wife and purchase a 796 for each band, with a dedicated antenna for each. So what if I lose the house, at least im monitoring!!!!!!!

IF you want to see the splitter and the 800 antenna, here are the links:

www.universal-radio.com/catalog/preamps/0973.html
www.shop.waltel.com/catalog/product_info.php/cPath/45_47_74/products_id/475

Thanks for all the help guys!

 

[N_Jay]

. . . .Here's what I came up with:
6m/2m/440 gp15 antenna gain is 3.0/6.2/8.6db
Antennex 800mhz antenna gain is 6.0db
Loss in about 50 of LMR400 is 6m(.4db),2m(.75db),440(1.3db) and 800 is (1.9db)
Loss on each port of splitter is 3db

. . . . . .

You don't say what the antennas are ratted in?
dBd, dBi, or dB-BS (Most other ratings)

Without that information you are working in the dark
(the way most scanner antenna companies like you to!)

 

[N_Jay]

. . . . .Loss on each port of splitter is 3db
. . . .

Check the specs.

Loss is 3.5 dB up to 400 MHz, and can be up to 4 dB up to 950 MHz

 

[DaveH]

. . . . .Loss on each port of splitter is 3db
. . . .

Check the specs.

Loss is 3.5 dB up to 400 MHz, and can be up to 4 dB up to 950 MHz

If you use a splitter from a single source (into say 2 scanners) the loss will be
3dB because power is split 2 ways (slightly higher due to internal losses). If you
use the "splitter" as a combiner from multiple sources, this 3dB loss does not
apply because there are multiple (different) sources combined into one. There
will be a slight loss per port, but not due to dividing power multiple ways,
because that's not happening!

Think of it another way. If I fed two ports of this combiner with the same signal,
in-phase, the output would be 3dB higher (gadzooks! it has gain!).

Dave

 

[N_Jay]

. . . . .Loss on each port of splitter is 3db
. . . .

Check the specs.

Loss is 3.5 dB up to 400 MHz, and can be up to 4 dB up to 950 MHz

If you use a splitter from a single source (into say 2 scanners) the loss will be
3dB because power is split 2 ways (slightly higher due to internal losses). If you
use the "splitter" as a combiner from multiple sources, this 3dB loss does not
apply because there are multiple (different) sources combined into one. There
will be a slight loss per port, but not due to dividing power multiple ways,
because that's not happening!

Think of it another way. If I fed two ports of this combiner with the same signal,
in-phase, the output would be 3dB higher (gadzooks! it has gain!).

Dave

Holy Smith Chart, Batman!
You might be right. (School was so long ago!) :wink:
Hmm, if you are right then I would count on at least 0.5 dB at 400 MHz and up to 1 dB at 950 MHz.

 

[Kirk]

Don't multiband antennas (like a 6m/2m/70cm omni) tend to have pretty narrow bandwidths? I know they tend to have pretty bad SWRs even when slightly out of band, but it's been years since I've messed with any of this.

Might be worth checking into, though.