Re: [Discuss-gnuradio] software controlled antenna

[Robert McGwier]

Chuck that is sweet.  Nice work.

Bob
N4HY



Chuck Swiger wrote:

> This weekend's project was pretty easy and useful. My indoor antenna 
> is a loop
> with pretty sharp Q which requires touching up, manually, even if 
> receiver frequency
> is changed only 50kHz. I have to get up, walk over to the loop and 
> turn a 365pf variable
> cap to 'peak' the signal.
>
> I just found out about MVAM109 varactors, which go from about 40 - 400 
> pf with
> 0-9vdc bias, so it was fairly easy to use the gnuradio/usrp aux DAC 
> 'D', the sigma
> delta, which is brought out on J17 on the basic RX board, and makes 
> 0-3.3 vdc
> with 12-bit precision, a 2N2222 transistor dc amp with a 12v supply to 
> boost it
> up to 0-9vdc. Put two MVAM109's back to back on the loop fed thru 100k 
> resistors
> (they're very high Z) and now I can adjust and peak the antenna with a 
> slider on the gui ;))
>
> --Chuck
>
> http://partsandkits.com/MVAM109.pdf
> src.write_aux_dac(0,3,value)      0<value<4095
>
>
>
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AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats
Laziness is the number one inspiration for ingenuity.  Guilty as charged!