Hi,
I have 20 900MHZ ISM band modules and I would like to measure RF
power. I have a a Tektronix 2712 Spectrum Analyzer and some
attenuators(BNC) and RG 58 coax. Unfortunately I do not have an SMA
connection on the antenna port. there are pads for the antenna that I
could fit an SMA to but I none of the ones I can find fit quite right
because of physical interference with the RF shield.

I tried soldering the RG 58 coax to the signal and ground pads but the
signal was not visible at the spectrum analyzer. I know RG 58 is lossy
but the Belden Coax calculator said I should lose about 20% of the
power at 1 mwatt.

Any thoughts or suggestions regarding coupling this signal (100 to
500mW) to a power measurement would be greatly appreciated.

Thanks,
Ed V.

Interesting...

What exactly do you want to measure? Power output from the Module? Or power
received by the module?

In an case, here are some check-ups you may find useful.

1. Check if your SpectrumAnalyzer "sees" 900 MHz signals. Take 75mm of bare
wire, attach it to the input of Spectrum Analizer - to central connector.
Orient the wire vertically. This will be your quarter-wave length antenna.
You should see activity in the band - signals, on different channels, of
different modulations.

I do not know where you are located, but if it is urban environment there
should be some activity on 900MHz ISM Band, and below the band you will see
cellular activity etc.

You will see signals with amplitude -40 to -80 dBm.

2. If you want to check if your modules transmit, bring it close to
antenna - you will not need even antenna on your modules to see the signal
from them. Again, I do not know what is your output power, but if it +10 -
+20 dBm, you will see plenty of signal when the module is close to your
antenna.

3. Have in mind, simply powering up the module typically does not make it
transmit. There is usually separate line that turns Tx 'on' and more.

I hope this helps,

Andrey


"Ed Vogel" wrote in message
om...
Hi,
I have 20 900MHZ ISM band modules and I would like to measure RF
power. I have a a Tektronix 2712 Spectrum Analyzer and some
attenuators(BNC) and RG 58 coax. Unfortunately I do not have an SMA
connection on the antenna port. there are pads for the antenna that I
could fit an SMA to but I none of the ones I can find fit quite right
because of physical interference with the RF shield.

I tried soldering the RG 58 coax to the signal and ground pads but the
signal was not visible at the spectrum analyzer. I know RG 58 is lossy
but the Belden Coax calculator said I should lose about 20% of the
power at 1 mwatt.

Any thoughts or suggestions regarding coupling this signal (100 to
500mW) to a power measurement would be greatly appreciated.

Thanks,
Ed V.

Hi Andrey,
thanks for the info. It turned out that the module that was
not showing any signal on the spectrum analyzer was dead. I got
another one and soldered in a RG 58 cable and hooked it to my spectrum
analyzer through a 20dbm attenuator. Its working fine.

Ed V.

"Andrey" wrote in message ...
Interesting...

What exactly do you want to measure? Power output from the Module? Or power
received by the module?

In an case, here are some check-ups you may find useful.

1. Check if your SpectrumAnalyzer "sees" 900 MHz signals. Take 75mm of bare
wire, attach it to the input of Spectrum Analizer - to central connector.
Orient the wire vertically. This will be your quarter-wave length antenna.
You should see activity in the band - signals, on different channels, of
different modulations.

I do not know where you are located, but if it is urban environment there
should be some activity on 900MHz ISM Band, and below the band you will see
cellular activity etc.

You will see signals with amplitude -40 to -80 dBm.

2. If you want to check if your modules transmit, bring it close to
antenna - you will not need even antenna on your modules to see the signal
from them. Again, I do not know what is your output power, but if it +10 -
+20 dBm, you will see plenty of signal when the module is close to your
antenna.

3. Have in mind, simply powering up the module typically does not make it
transmit. There is usually separate line that turns Tx 'on' and more.

I hope this helps,

Andrey


"Ed Vogel" wrote in message
om...
Hi,
I have 20 900MHZ ISM band modules and I would like to measure RF
power. I have a a Tektronix 2712 Spectrum Analyzer and some
attenuators(BNC) and RG 58 coax. Unfortunately I do not have an SMA
connection on the antenna port. there are pads for the antenna that I
could fit an SMA to but I none of the ones I can find fit quite right
because of physical interference with the RF shield.

I tried soldering the RG 58 coax to the signal and ground pads but the
signal was not visible at the spectrum analyzer. I know RG 58 is lossy
but the Belden Coax calculator said I should lose about 20% of the
power at 1 mwatt.

Any thoughts or suggestions regarding coupling this signal (100 to
500mW) to a power measurement would be greatly appreciated.

Thanks,
Ed V.