This blog will show some experiments around the two SoftRock RXTX ( Ref. , ) built so far. A SI570 oscillator (Ref. ) and an Elecraft T1 ATU (automatc antenna match box) (Ref. ) were also built and wait for their application to the SoftRock RXTXs. So this blog will show some modifications of SoftRock RXTXs and the addition of some accessories. If everything goes well I would like to end up with a multi-band transceiver
Practical tests will be done at our local clubstation DK0SU and sure — I would like to meet other "SoftRockers" on the air.
-  DF7TV's notes on RXTXv6.2 – 40m/30m
-  DF7TV's notes on RXTXv6.2 – 20m/30m
-  DF7TV's notes on SI570/PICAXE experiments
-  Elecraft T1 ATU (automatc antenna match box)
Two SoftRockRXTX v.6.2 kits were built so far. The RXTX v6.2 – 40m/30m was intensively tested for both bands and the RXTX v6.2 20m/30m was tested for reception only so far. Please have a look to the above mentioned references (, ) for further information on the two units. The RXTX v6.2 20m/30m was modified to cover the 17m band as well and will be used for operation on the 20m and 17m band in the intended multi-band transceiver SR1004. To facilitate things the two units will be called RXTX-40/30 and RXTX-20/17 for the rest of this blog.
1. Assembly of the PennyWhistle RF power amplifier
The HPSDR PennyWhistle kit is available (as a low volume production) from TAPR. If the kit is built according to the PennyWhistle Assembly and Operation Instructions it should cover 160m to 6m band and with about 1/4W input drive it should deliver 16 to 20W of maximum output power.
"HPSDR" stands for the High Performance Software Defined Radio project. "TAPR" — the Tucson Amateur Packet Radio community — provides assistance and a "storefront" for the HPSDR "products".
The PennyWhistle project team is:
- Graham Haddock, KE9H, designer
- Steve Niles, N5EN, kitting
- Walter Holmes, K5WH, kitting
- Scott Cowling, WA2DFI, parts procurement
- Nona Jurgens, parts procurement
- John Koster, W9DDD, final kit integration
Thanks to TAPR for making available the PennyWhistle Kit.
- Subscription to the HPSDR mailing list, where technical support for the PennyWhistle PA is available.
- Download of the PennyWhistle Assembly and Operation Instructions; this kit (No. 464) will be built according to Version 1.2 of the instructions (Author: Graham Haddock, KE9H).
- Inventory of components of the kit: all parts present and in good shape
- This PA uses two Silicon MOSFET Power Transistors RD16HHF1 of Mitsubishi in push-pull configuration.
- A value of 330pF is selected for C11, the tuning capacitor of the output transformer; this should maximize power output and amplifier flatness up to 30 MHz. (Operation at 50 MHz is not needed here at this time.)
- All chip capacitors and resistors are installed in the recommended sequence given in Appendix "D" of the instructions.
- Installed Q3: ZVP2106G, a P-Channel Enhancement Mode DMOS FET used in the bias control circuit.
- Installed R11: 2 kOhm (Bourns, Trimming Potentiometer model 3362P-1, Single-Turn, Cermet, Top adjust), used for bias control of Q1.
- Installed R17: 2 kOhm (Bourns, Trimming Potentiometer model 3362P-1, Single-Turn, Cermet, Top adjust), used for bias control of Q2.
- Installed U3: 78L06AD, 6V / 0.1A Positive Voltage Regulator (package 8-SOP) used in the bias control circuit.
- Installed C25: 100 uF
- Installed C2: 1000 uF
- Removed any sharp edges present at the ferrite beads (from Fair-Rite/Amidon) in the kit.
- Installed L3: FB73-101, ferrite bead, single turn, wire diameter 0,6 mm.
- Installed L4: FB73-101, ferrite bead, single turn, wire diameter 0,6 mm.
- Installed L2: FB73-801, ferrite bead, single turn, wire diameter 0,8 mm.
- Installed L1: FB73-801, ferrite bead, single turn, wire diameter 0,8 mm.
- Removed any sharp edges present at the ferrite cores (from Fair-Rite/Amidon) in the kit which have to be assembled by the builder.
- Installed T1: BN-43-302, binocular core (input transformer).
- Installed T2: BN-43-202, binocular core.
- Installed T3: RF800-4, output transformer, 4:1 Impedance Ratio (from Communications Concept, Inc.).
- Hardware: Installed 8 #4 by 1/4" hex-standoffs to the heat sink.
- Hardware: Applied some thermal compound at areas forseen for Q1 and Q2 on the heat sink.
- Bent legs of Q1 and Q2 and supplied some thermal compound to their package.
- Loosely fixed Q1 and Q2 to the heat sink.
- Loosely fixed the PCB to the heat sink.
- Fastened the four screws fixing the PCB in the near of Q1 and Q2.
- Fastened the remaining (outer) four screws fixing the PCB to the heat sink.
- Fastened the screws for fixing Q1 and Q2 tightly to the heat sink.
- Q1, Q2: RD16HHF1, Silicon MOSFET Power Transistors soldered to the board.
- This completes the assembly of the PennyWhistle board.
- Bias current of Q1 and Q2 set to 450mA each (current to the PA is at about 910mA with no RF input).
- Made a quick RF test to ensure that 15Watts output power are available from 160m to 10m. (Input power was about 0.2 to 0.6W).
- So the PennyWhisthle PA is now ready for application.
A snap shot of the PennyWhistle power amplifier: