PennyWhistle and Ensemble RXTX
- View SourceI recently finished building and packaging a transceiver using the Pennywhistle amplifier (http://www.tapr.org/kits_pw.html) and thought that sharing my experience might be helpful to others.
The Pennywhistle is a small (10 x 8 cm = 3.9 x 3.15 in) linear amplifier that uses two real RF MOSFETs (RD16HHF1's) in push pull and puts out 16 watts with 250 mw drive. I have seen recommendations on this list to keep the Ensemble at under .5 watts, so power in is just right. Build was simple, straight forward, and took less than a few hours. Lots of SMD's with big pads. The holes and pads for conventional components are a shade bigger than those for the Softrock. Only two simple coils to wind.
The Pennywhistle interfaces beautifully with the Ensemble RXTX. There is a 3 prong connector on the Pennywhistle to supply 12 volts and to turn the amplifier bias on and off. I connected the Pennywhistle bias control to the Ensemble /PTT line by soldering directly to pin 4 on U4). For the antenna relay, I tapped the S12v line at R35 (with some heat shrink tubing). Thus, when the PTT line on the Ensemble is activated, the bias on the amplifier is turned on and the antenna relay switches. No need to build a worrisome RF sensing relay circuit.
The Pennywhistle comes with a massive, pre drilled heat sink. After replacing the heat sink with a lower profile heat sink from a Pentium II, I was able to get the Ensemble, Pennywhistle, SB W-Fi sound card, USB hub, antenna relay, connecting cables and two low pass filters (one for 30 m and the other for 17 m) from Kits and Parts into a 5 x 9 x 2.25 in compartment box from the Container Store. My 30/20/17 Ensemble RXTX now puts out 16 watts on 40 to 17 meters.
- View SourceHi, do you have a circuit you used to key your relay? I ended up drawing too much current through Q3 and had to replace Q3. Before I try something else, I thought I might inquire about your circuit.