Re: [Discuss-gnuradio] software controlled antenna

[Eric Blossom]

On Tue, Dec 20, 2005 at 08:09:04AM -0500, 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 ;))

Cool.

You're definitely winning in the "look what I did with GNU Radio!"
category!

Looking forward to the next thing ;)

Eric