How to test antenna signal strength

[bleague]

I've poked around and did several searches but I couldn't find an article about testing antennae.

I bought a couple of different antennae for my handheld scanner today and haven't really noticed a lot of difference between them and the stock antenna. The signal strength on the display appears to be the same no matter which one I use.

Is there any software out there that I can use to test signal strength on the different antennae?

[popnokick]

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Someone reading will reply with an answer explaining the instruments you'll need to test antenna gain and other performance metrics used to measure antennas. And there is software, but you also must have the test instrument the software uses.
Assuming you are not looking at spending that kind of money, you may want to try an approach that will work with the scanner you already have.
Find the weakest signal that you can barely hear with the squelch set all the way open/off. We're talking something with a lot of hissing and flutter, but is a known signal with regard to location of the transmitter, distance, and direction from you (approximate). NOAA weather radio broadcasts are good for this in the VHF HI band. Pick a NOAA transmitter that is not local to you... or the weakest one you can find. For other bands you want to optimize your antenna for you will need to find a known weak signal in that band.
Switch to the antenna you want to know works better or not. If the weak signal disappears.... Or gets stronger... you'll know the best antenna of the ones you test. Important thing here is to test only with weak signals.

What antennas are you comparing to each other, and what are you trying to hear (frequency and how far away from you)? Answering those two questions will help us suggest better antennas. And here's a "worst to best" list of generic antenna types for handheld scanners:

WORST - The rubberized stubby ("duck") that came with the scanner
So-So- A telescoping antenna that attaches to the handheld scanner
BETTER - An external indoor antenna in your attic/crawlspace or hanging in a window and connected via coaxial cable to your scanner
BEST- An external antenna connected via coaxial cable and mounted on your roof

... and there are multiple types within each of the general categories listed above.

[bleague]

Originally Posted by popnokick

What antennas are you comparing to each other, and what are you trying to hear (frequency and how far away from you)? Answering those two questions will help us suggest better antennas.
.

Thanks for the helpful info you have posted so far. The NOAA idea sounds good for testing.

In answer to your other questions:

My scanner is a BC346XT
The antennae I am testing are:
Radio Shack 20-283 - 7" rubber duck antenna tuned to the 800MHz range
Radio Shack 20-006 - center loaded telescoping scanner/ham antenna (can adjust the height for different frequency ranges - from 25MHz up to 1300MHz

I'm scanning for police and fire traffic in the 150MHz range and the 800MHz range - all analog at this point, but looking to upgrade to a digital scanner soon and will be looking for digital traffic in the 800MHz range.

[W8RMH]

Originally Posted by bleague

Is there any software out there that I can use to test signal strength on the different antennae?

You can try FreeScan. I believe the virtual control logs the RSS hits.

If your scanner is not supported look here.

[n5ims]

One issue with using NOAA for your testing is that will give you a good base for testing in the VHF-Hi range, but this may not be accurate for your 800 MHz signals. A great 800 MHz antenna may perform very poorly trying to pick up the NOAA 16x MHz signal. Try to find a stable and continuous signal on each band you're testing (say a not-too-close/not-too-far-away control channel on 800 MHz) and test with that. You can then have a standard "base reference" to use for comparison.

Nothing should prevent you from testing an antenna for one band using another band's reference signal, but what you'll be testing is how that antenna works on the other band, not how good that antenna is on the band it was designed to work on. Those kinds of tests will be helpful in cases where the marketing department, not the engineering department is who writes the final "specs" for that antenna. Like those dual-band ham antennas where the package indicates "Works on your scanner for all bands!" - "Works" and "Works Well" are two different things quite often in these situations.

[bleague]

Originally Posted by W8RMH

You can try FreeScan. I believe the virtual control logs the RSS hits.

I've been using FreeScan but didn't know about the RSSI info. You are correct, it logs this info. I used this to test the antennae and I ended up returning the 800MHz "rubber duck" from Radio Shack. I kept the telescoping antenna - it performed slightly better than the stock rubber duck antenna.

Thanks for pointing me toward this logging info - it was very helpful.