According to Wouter, PA3WEG, who designed the AO-73 transponder, PLL frequency generation is possible now within the power budget of a 1U CubeSat, but was not when the FUNcube's transponder was designed.
See his post from last month:
http://amsat.org/pipermail/amsat-bb/2013-December/047815.html
73,
Paul, N8HM
On Sat, Jan 11, 2014 at 9:22 AM, Rich/wa4bue richard.siff@verizon.net wrote:
AO7 and FO29 seem to be very stable. VO52 was my first experience with a drifty transponder oscillators. I read some explanations on the BB.
What design element needs to be changed to stabilize the linear transponders oscillators on the new CUBESATS.
Are the beacons crystal controlled?
Rich W4BUE _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb