Use of wi-spy

Submitted by Anonymous metageek on Sun, 10/29/2006 - 17:03.

Guy's,

I am considering purchasing one of the wi-spy units for use when I race
direct my radio controlled car club meetings and as such would welcome
any comments on its suitability for my needs.

For those who are unaware over the last couple of years a new DSM
(2.4GHz) system has been bought to the market to slowly replace the
older 27MHz, 75MHz and 40 MHz methods of controlling our vehicles.

Due to the how the new systems work they can not work with our older
detection units which are used when we have frequency clashes\issues.
To this end I was looking at the Wi-SPy and its software as a tool for
running in such instances.

A typical DSM system is made by SPEKTRUM and its specification is:-

Freq band - 2.400 to 2.4835 GHz
Channels - 79
Channel spacing - 1MHZ
Chips/bits 64
DSSS coding gain 18dbm

With a typical
Transmitter:-
10mW output power
2dbi Antenna
Modulation of - digitial GFSK 160KHz df

Receiver:-
-98dbm sensitivity

Sorry for such a detailed posting but on first impression the wi-spy
unit would meet our requirments if the channels and spacing could be
detected.

I welcome your replies
Unlike the older systems their is not a single currently no signed

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Submitted by Anonymous metageek on Mon, 11/06/2006 - 13:53.

pe2er wrote:

8-O Typo

pe2er wrote:

The
top of the graph (RSSI = 28 - 31) corresponds to an received signal of
> -40dBm. An RSSI Value of 0 is displayed on the Wi-Spy software as
"-30dBm".

Should be
An RSSI Value of 31 is displayed on the Wi-Spy software as "-30dBm".

Thanks Mate,

Looks like I'm going to have to buy one of these babies and see how it works out. Thanks for the confirmation.

Submitted by pe2er on Tue, 10/31/2006 - 09:06.

8-O Typo

pe2er wrote:

The top of the graph (RSSI = 28 - 31) corresponds to an received signal of > -40dBm. An RSSI Value of 0 is displayed on the Wi-Spy software as "-30dBm".

Should be
An RSSI Value of 31 is displayed on the Wi-Spy software as "-30dBm".

Submitted by pe2er on Tue, 10/31/2006 - 08:08.

nvrdaz wrote:

Freq band - 2.400 to 2.4835 GHz
Channels - 79
Channel spacing - 1MHZ
Chips/bits 64
DSSS coding gain 18dbm

With a typical
Transmitter:-
10mW output power
2dbi Antenna
Modulation of - digitial GFSK 160KHz df

Receiver:-
-98dbm sensitivity

Sorry for such a detailed posting but on first impression the wi-spy unit would meet our requirments if the channels and spacing could be detected.

You are correct. The Wi-Spy matches the frequency range of the DSM system - 2400-2484MHz in 1 MHz steps.
Wi-Spy receiver sensitivity appears to be far less than -98dBm. The screen indicates lowest detection level is -60dBm, but actual sensitivity is better.

Looking at the spec of the CYWUSB6934 radio chip used in the Wi-Spy (now it's my turn to appologize for getting too technical ;-)), the Receive Signal Strength Indicator (RSSI)register has a value between 0 and 10 for signals below -95dBm. An RSSI Value of 0 is displayed on the
Wi-Spy software as "-61dBm".

The top of the graph (RSSI = 28 - 31) corresponds to an received signal of > -40dBm. An RSSI Value of 0 is displayed on the Wi-Spy software as "-30dBm".

I Estimate that you would be able to detect roque DSM transmitters at your location. The closer you get the Wi-Spy to the transmitter, the greater your changes of detecting is.

Erwin

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