Ensemble RXTX - External Connections
Band: 30, 20, 17m
Introduction
Band Specific Components
This stage involves band-specific components and is currently configured for the 30, 20, 17m band. If you need to configure this page for a different band, click on the "Band" tab in the menu above. This would take you to the home page, where you can select the new band and then return to this page.
General Info About the Stage
Congratulations! You have successfully built and (unit) tested your Ensemble SDR transceiver for the chosen "super-band". So did George, W5JDX, as depicted on this episode (#82)of HamNation, titled "The Softrock Payoff". His Softrock segment begins 27 minutes into the video.
This is the wrap-up stage, where we connect the rig to the outside world (PC (SDR program and soundcard), antenna, and paddles and actually put the transceiver through it paces.
The builder may, at this point, want to consider the hardware and software offerings (PSDR-IQ and USB2SDR card) from Christos SV1EIA (sv1eia@gmail.com). This combination represents the best quality software and hardware interface between the computer and the Ensemble RXTX.
Depending upon the option you have chosen to build and how you wish to operate within that built option, you may need to provide additional low-pass filtering between the transceiver and the antenna. The FCC requires that the mean power of any spurious emission from a station transmitter or external RF amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission. In the case of an 80m (3.5 MHz) transmitter, we must ensure that the mean power at the second harmonic (40m - 7.0 MHz) must be at least 43db below that of the fundamental 80m emission. This rule applies to the RXTX Ensemble. With the current design, the following options require low-pass filtering in order to reduce the second (and higher order) harmonics for the following options to at least 43 dB below that of the fundamental (first-mentioned) band (assuming you want to operate in that band):
| Band Option | Use LPF When Operating At | To Attenuate 2nd Harmonic At |
|---|---|---|
| 80/40m | (80m) 3.5 MHz | 7.0 MHz |
| 40/30/20m | (40m) 7.0 MHZ | 14 MHz |
| 30/20/17m | (30m)10.1 MHz | 20.2 MHz |
Alan, G4FZQ, has put together a clever, simple implementation and circuit board for the LPF for his 40/3/20m kit. The principles of his design apply to any of the above LPFs.
Tony, KB9YIG offers this suggestion for building the LPF: I would suggest that the external LP filter could be built along a 1.5 inch long piece of of #12 copper wire. The copper wire would be the common connection with the wound cores flat and slightly above the wire. The filter capacitors would connect between the core wires and the copper wire as shown in this schematic. Short lengths of coax would be connected to each end with the copper wire used to strain relief the coax. The filter could them be enclosed in an insulated sleeve and "potted" with RTV.
Theory of Operation
Summary Build Notes
Stage Schematic
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Click here for full schematic
(Red dots represent the "hairpin" (or left-hand or topmost) lead of the component)
Board Layouts
(there are no board layouts for this stage)
The following BOM contains components for the final connections plus the optional LPF)
External Connections Bill of Materials
(30, 20, 17m band option)
(details for installation of each component are provided in the step instructions, further down the page)
Be sure to use the correct wire gauge when winding inductor(s)
| Check | Type | Category | Component | Count | Marking | Image |
|---|---|---|---|---|---|---|
| ☐ | boardhdw | HDW | 4 X #4-40 hdw (nut, bolt, washer, spacer) | 1 |
|
|
| ☐ | Capacitor | Ceramic | 100 pF 5% | 2 | 101 |
|
| ☐ | Capacitor | Ceramic | 330 pF 5% | 1 | 331 |
|
| ☐ | inductor | Toroid | T37-2 toroid core | 2 | red |
|
| ☐ | inductor | Coil | 0.9uH: 15T #26(10 in) on T37-2 (red) | 2 | red | (magnetic wire) |
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Detailed Build Steps
Step_Connect I and Q leads
Recently, there have been extensive discussions on the reflector concerning the fact that some builders have a combination of soundcard, software, PC, and operating system in which the jumpers/leads for the TX I and Q signals must be the reverse of the jumpers/leads for the RX I and Q. This has been pretty much a case-by-case experience. We are building a spreadsheet depicting various combinations of the relevant variables (soundcard, program, kit, PS, OS, etc.) and the wiring that "works" for the RX and TX I and Q signals.
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Step_Connect USB
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Step_Connect Antenna
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Step_Connect Keyer
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Step_Connect Power
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Step_Install In Enclosure (Optional)
One possibility for a nice enclosure for this rig is the Specialty Bottle Rectangular, Windowed Tin.
Another - and a very nice one at that - is the enclosure offered by Tom KM5H on his website
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Step_Load and Run SDR Software
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Step_Build and Connect External LPF
Inductor Information
Common Techniques:
- Wire Gauge: remember the higher the number, the thinner the wire. E.g., #30 wire is thinner than #26 wire.
-
One turn:
- For toroids, one turn is a single pass through the center hole.
- For binocular cores, one turn is a pass in which the wire goes in the bottom, comes out the top, goes back in the other hole at the top, and comes out the other hole at the bottom.
- Bi (tri) filar means 2(3) equal lengths of wire. You get the bi(tri)filar strand by taking the length of wire specified for the primary winding, folding it into half(thirds), twisting it to 3~ twists per inch, and winding it over the primary winding. One end of such a strand will have two(three) leads; the other end will have a "hairpin" bend (and a single lead in the case of tri-filar).
- Multi-filar windings are usually done AFTER the uni-filar winding is done.
- Windings shoud be evenly spaced and ideally made such that the winding covers ~345 degrees of the toroid
- Inductance values given are for the single (uni-filar) winding. They are provided to help verify turn counts and core material selected. It's often reported inductances are higher using the theoretical number of turns as calculated by the manufacturer's windings calculator tool, e.g. http://toroids.info/. Normally though these are not too critical, especially with the LF bands antenna noise will still be seen.
-
Toroid nomenclature provides the outside diameter of the toroid (in hundredths
of an inch - the "30" in "T30-2"), and material code (the "2" in "T30-2").
Color codes used in these kits are:
- 2=Red
- 3=Gray
- 6=Yellow
- 7=White
- 10=Black
- 12=Green (with White on opposite side)
Inductors In This Step
L200COIL: 0.9uH: 15T #26(10 in) on T37-2 (red)
Using approximately 11 inches of #26 wire, wind 15 turns on a 0.37 inch od T37-2 (red) ferrite. Inductance = 0.90 uH.
COIL: 0.9uH: 15T #26(10 in) on T37-2 (red)
Using approximately 11 inches of #26 wire, wind 15 turns on a 0.37 inch od T37-2 (red) ferrite. Inductance = 0.90 uH.
Note: if you intend to operate on 80m, 40m, or 30m, you MUST build special low-pass filters for those bands and connect it/them between your kit's antenna jack and the antenna. The LPFs are designed for the lowest freq band in the group ( 80 for the 80/40, 40 for the 40/30/20, and 30 for the 30/20/17 ). Thus, the external LPFs are built for and used in the antenna feed as follows:
- 80m LPF with the 80m/40m option.
- 40m LPF with the 40m/30m/20m option.
- 30m LPF with the 30m/30m/17m option.
| Check | Designation | Component (top/bottom) | Orientation | Marking | Image | Band | Notes |
|---|---|---|---|---|---|---|---|
| ☐ | C200 | 100 pF 5% (top) | 101 |
|
30, 20, 17m | ||
| ☐ | C201 | 330 pF 5% (top) | 331 |
|
30, 20, 17m | ||
| ☐ | C202 | 100 pF 5% (top) | 101 |
|
30, 20, 17m | ||
| ☐ | L200 | 0.9uH: 15T #26(10 in) on T37-2 (red) (top) | red |
 |
30, 20, 17m | ||
| ☐ | L200-core | T37-2 toroid core (top) | red |
|
30, 20, 17m | ||
| ☐ | L201 | 0.9uH: 15T #26(10 in) on T37-2 (red) (top) | red |
|
30, 20, 17m | ||
| ☐ | L201-core | T37-2 toroid core (top) | red |
|
30, 20, 17m |
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Completed Photos
View of Completed Topside
View of Completed Underside
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Testing
Overview
There are no tests for this stage