Re: [Discuss-gnuradio] Modify the Basic RX Daughterboard

[valentac]

My mistake, I am using the BasicRX with the transformer (I was looking at the
wrong datasheet). I could go ahead and get a new transformer, but I would
ideally like a higher impedance than is offered. I just tried to modify the
transformers in the schematic
(http://code.ettus.com/redmine/ettus/documents/2) by removing R3 and R9, and
then changing R6 and R7 to 1 MOhm, however, this didn't seem to give me a
large enough impedance.

Is there a better way to modify the transformer that is on the BasicRX to
give me a high impedance?



Marcus D. Leech wrote:
> 
> On 09/08/2011 01:08 PM, valentac wrote:
>> I have my own RF front end i'm using with the USRP, but it requires a
>> High
>> impedance load to operate correctly. Since the basic RX daughterboard has
>> a
>> 50 ohm impedance, I have to modify it or add a separate voltage buffer
>> before the input. However, since the basic RX daughter board in the USRP
>> has
>> an op-amp in its first stage, perhaps I could modify this.
>>
>> I've tried removing R3 and R9
>> (http://code.ettus.com/redmine/ettus/documents/4), but this did not seem
>> to
>> load the RF front end sufficiently. Would changing the 348 ohm resistors
>> to
>> a higher value help increase the input impedance into the basic RX
>> daughterboard? If so, how would this affect the output going into the A/D
>> (besides the obvious filtering effects).
> I'd say consult the data-sheet for the AD8132.  But just to clear things 
> up, you're discussing
>    the *LF_RX* daughtercard, *NOT* the BASIC_RX, which has no op-amp on 
> it at all, just a
>    transformer.
> 
> If your input impedance isn't insanely high, you could use a 
> transformer.  4:1 broadband impedance
>    transformers are available fairly cheaply from Mini-circuits, etc.
> 
> 
> 
> 
> -- 
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
> 
> 
> 
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
> 

-- 
View this message in context: 
http://old.nabble.com/Modify-the-Basic-RX-Daughterboard-tp32425579p32426977.html
Sent from the GnuRadio mailing list archive at Nabble.com.