Archive for September, 2011

Softrock Ensemble VHF tuning

September 16th, 2011 No comments

This post has a specific audience in mind, so unless you have, or are interested in a Softrock Ensemble VHF receiver, you’ll be bored. You’ve been warned :) There are a few radio bands that are interesting near the ham 2 meter band.  NOAA weather satellites send images using APT at and around 137 Mhz and there are weather broadcasts at 162.5.  There was a question on the mailing list for the Softrock about whether it could be tuned to receive signals in all of these bands without re-tuning.  This post is simply documenting my experimentation with the front end.  I’m sampling the signal using an oscilloscope probe with the 10x setting and inserting the signal from the tracking generator connected to the antenna port.  It’s not really possible to measure the precise insertion loss absolutely, so I’ll measure it relative to the baseline of front end tuned for 2 meters.

Tuned for 2 meters

Read more…


SKY65116 Amplifier

September 15th, 2011 1 comment

Amplifier breakout board

I’ve finally gotten around to assembling a breakout board for the Skyworks SKY65116 UHF amplifier.  It’s really amazing how the state of the art in RF ICs has advanced.  They can still be on the expensive side ($6 at digikey), but still relatively cheap when you consider the cost of all the support parts that it takes to build an amplifier from a RF transistor.  This particular amplifier has a 50 ohm input and output, and 35dB of gain.  It works from 390Mhz to 500Mhz, which means its perfect for the 70cm ham band.  The breakout board is stupid simple, copied directly from the evaluation board schematic in the datasheet,  but I’ll include schematic and design files anyway. Read more…