Amps/preamps for wardriving/stumbling

Entropy42 · 09-06-2002

Out of curiosity, anyone know when Netstumbler will be modified to become completely passive like Kismet for Linux (http://www.kismetwireless.net/)

I was thinking that there might be an interesting solution to amps for those who are running a "fully passive" setup.

For a transmit/receive setup, you need a bidirectional amp that either has an external T/R line (not possible without modding your card, and so far only ancient Proxim Symphonies have been modified in such a manner), or RF sensing. Both are complex and cost $$$.

But with Kismet (and NS if it's ever patched to be completely passive) you only need to receive. As such, you could use a cheap MMIC-based preamp for increased receive gain.

Has anyone tried this?

mr_wlan · 09-06-2002

hi, yes we run gasfet preamplified antenna's here for wlan surveying. have a look at the pictures : http://www.frars.org.uk/cgi-bin/render.pl?pageid=1103

i will post some pics of my wlan setup tommorow

regards,

mr_wlan

oh btw, most of the mar-x mmics are a little crappy at 2.5ghz in terms of nf.

Entropy42 · 09-06-2002

That is one SWEET antenna you found.

Did the preamp come with the ant or is that something you added?

I agree, the MARs aren't too hot NF-wise. Their gain also drops really low by the time you reach 2.4.

The ERAs are much better, still not a super NF, but lower than the ERAs and much higher gain.

Some really nice results could be obtained with some of Down East Microwave's preamps - They have a .5 dB NF/17 dB gain amp, and a 2 db NF/21 dB gain preamp.

Also n9zia's site has some info on a preamp based on a Maxim device - Cheap, although more difficult to create a PCB due to the packaging.

I'm thinking of trying a homebrew ERA-based preamp, maybe with a filter on the frontend, coupled with a simple quarter-wave groundplane or maybe a 5 dBi omni.

09-06-2002	#1 (permalink)
Entropy42 Registered Member Join Date: Sep 2002 Posts: 32	Amps/preamps for wardriving/stumbling Out of curiosity, anyone know when Netstumbler will be modified to become completely passive like Kismet for Linux (http://www.kismetwireless.net/) I was thinking that there might be an interesting solution to amps for those who are running a "fully passive" setup. For a transmit/receive setup, you need a bidirectional amp that either has an external T/R line (not possible without modding your card, and so far only ancient Proxim Symphonies have been modified in such a manner), or RF sensing. Both are complex and cost $$$. But with Kismet (and NS if it's ever patched to be completely passive) you only need to receive. As such, you could use a cheap MMIC-based preamp for increased receive gain. Has anyone tried this?

09-06-2002	#2 (permalink)
mr_wlan Registered Member Join Date: Apr 2002 Posts: 40	preamp hi, yes we run gasfet preamplified antenna's here for wlan surveying. have a look at the pictures : http://www.frars.org.uk/cgi-bin/render.pl?pageid=1103 i will post some pics of my wlan setup tommorow regards, mr_wlan oh btw, most of the mar-x mmics are a little crappy at 2.5ghz in terms of nf.

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09-06-2002	#3 (permalink)
Entropy42 Registered Member Join Date: Sep 2002 Posts: 32	That is one SWEET antenna you found. Did the preamp come with the ant or is that something you added? I agree, the MARs aren't too hot NF-wise. Their gain also drops really low by the time you reach 2.4. The ERAs are much better, still not a super NF, but lower than the ERAs and much higher gain. Some really nice results could be obtained with some of Down East Microwave's preamps - They have a .5 dB NF/17 dB gain amp, and a 2 db NF/21 dB gain preamp. Also n9zia's site has some info on a preamp based on a Maxim device - Cheap, although more difficult to create a PCB due to the packaging. I'm thinking of trying a homebrew ERA-based preamp, maybe with a filter on the frontend, coupled with a simple quarter-wave groundplane or maybe a 5 dBi omni.