[USRP-users] USRP Input Protection

Marcus D. Leech mleech at ripnet.com
Wed Mar 2 11:12:01 EST 2016

On 03/02/2016 05:19 AM, Jan Safar via USRP-users wrote:
> Hello,
> We are looking to use the E310 for some over-the-air tests in the VHF 
> band. In our application we need to install our antennas within a few 
> meters (say 3 to 5 m) of another VHF system antenna. The transmitter 
> power of the co-located unit can be up to 25 W, antennas for both 
> systems are typically 0 dBd omnidirectional. The interfering 
> transmissions are intermittent and can be as close as on the adjacent 
> channel. The stated maximum input power for all USRPs is -15 dBm; for 
> the E310 and at VHF, the limit is probably somewhat higher but Ettus 
> haven’t been able to provide an exact figure.
> I’m wondering if anyone can advise on how to protect the USRP input in 
> this scenario?
> I looked into the availability of suitable limiters. Mini Circuits 
> don’t seem to have any with output power below 0 dBm. I found the 
> following two models from Herotek and RF-LAMBDA which limit at -10 
> dBm, but they are quite costly (~£600 excl. VAT) and the lead time is 
> 6 to 10 weeks. Does anyone know of a better solution?
> http://www.herotek.com/datasheets/pdf/Pin_Diode_Very_Low_Leakage_Limiters_10MHz-18GHz_LL_Series.pdf
> http://www.rflambda.com/pdf/limiter/RFAPLT01M05M.pdf
> Thanks & regards,
> Jan
You could install a notch filter for the other VHF frequency that is 
most likely to cause you issues.

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