Signal strength/RSSI readings

wvbills · Posted: Thu Nov 20, 2008 6:24 am Post subject: Signal strength/RSSI readings

My setup:
Verizon USB727 modem - locked in HDR mode
10 ft USB cable between modem and laptop/router
3GStore Booster antenna
3GStore Yagi (I'll explain later)
Cradlepoint CTR350

After reading these forums for several weeks, I've determined that there are (at least) three ways to display signal strength/RSSI:

With the USB727 connected directly to the laptop:
1) In VZAM, hover mouse pointer over bars at bottom of window
2) In VZAM Field Test, there are readings for RSSI as well as Tx Power and Rx Power

With the USB727 connected to the CTR350 and the laptop connected by WiFi to the CTR:
3) In the CTR "Modem Info" Page

Using these three methods, here are the readings I got yesterday:
In the Car 1/4 mile from the tower with the booster antenna
Field Test: RSSI = 65, Tx = -23, Rx = -59
(Did not look at RSSI from the bars in VZAM)

At home 5 miles from the tower with booster antenna
Field Test: RSSI = 0, Tx = 12, Rx = -63
VZAM: RSSI = -93
CTR: RSSI = -83 (note, antenna and modem remained in exactly the same positions when USB cable moved from laptop to CTR)

At home, the Booster antenna was placed indoors in a basement window essentially at ground level but facing in the direction of the tower. To get a better signal, I am switching to a Yagi antenna. Currently mounted on the deck outside, 8 feet above the ground pointed toward the tower.

At home 5 miles from the tower with Yagi Antenna
Field Test: RSSI = 0, Tx = 6, Rx = -79
VZAM: RSSI = -83
CTR: RSSI = -77

Here's my speed test with the Yagi:

For some reason, if I try to include the speedtest link I get hit with the spam filter: I got 586 kb/s down, 114 kb/s up and a 373ms ping <50 miles

I have several questions:
1) Why can't I get an RSSI reading in Field Test at home?
2) Does the "RX Power" in Field Test relate to RSSI?
3) My major question is why is the RSSI reading by hovering over the bars in VZAM differrent from the RSSI reading from the CTR?
4) Based on these readings, it would appear from the VZAM numbers that I got a 10db signal strength increase with the Yagi over the Booster, while the CTR numbers indicate a 6db increase. Is this amount of increase Yagi over Booster what I should expect or do I need to work on the Yagi's height/pointing some more?

Thanks
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WVBill

Alex

wvbills · Posted: Thu Nov 20, 2008 11:01 am Post subject:

Thanks, Alex - I'll try some tweaking on the antenna pointing/height.

I was assuming that the USB727 itself "measures" the RSSI and writes that value to an internal memory location - which Cradlepoint and WZAM then simply read and report. Hadn't thought that they might be doing some manipulating of a USB727 value before reporting it.
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WVBill

Alex · Posted: Thu Nov 20, 2008 11:29 am Post subject:

oh, if only it where that easy.

the api/sdk for any cellular modem is so full of convoluted crap, you just KNOW the engineers who wrote it were paid by line of code.
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wvbills · Posted: Thu Nov 20, 2008 12:10 pm Post subject:

Speaking of convoluted.....

My CTR350 works perfectly right out of the box and set up with your easy-to-follow instructions.
But you should never have given me the password. Wink

Now that I'm "in", I see all kinds of settings I can presumably set. Twisted Evil

I'm smart enough that I haven't fooled around with anything - yet - but where's the documentation? I've gone out to Cradlepoint's web site and the only documentation I can find is the two-page Quick Set-up Guide.
Maybe it's like "If you have to ask you shouldn't fool around with this anyway." Cool

Anyway, I was frankly surprised that such a small router has what appears to be such a complete feature set!

I'd have PM'd this but I guess I need to make a few more posts before I'm "allowed".

Thanks
_________________
WVBill

Jim_in_VA · Posted: Thu Nov 20, 2008 12:47 pm Post subject:

When you open the router configuration in a browser - click the "Help" tab on the far right. It explains each and every setting in the router.
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wvbills · Posted: Thu Nov 20, 2008 1:16 pm Post subject:

...I should have thought of that....
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WVBill