Table of contents
RFzero™
The RFzero™ is fully assembled and ready to use. Four LEDs, headers, jumpers for LCD voltage selection and GPS back-up and the ground wire are also supplied for individual mounting and fitting. A pair of test wires are also included.
The items included with the RFzero™.
The price for an RFzero™ is
- 625 DKK incl. VAT
See approx value in EUR - 500 DKK excl. VAT for customers outside the EU. Local import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
To release the full potential of your RFzero you must connect it to a GPS antenna. If you don’t have a GPS antenna already you may find inspiration in the third party accessories section further down on this page.
RFzero accessories
The RFzero accessories are also designed by the RFzero team.
RFzero shield
Just like many other Arduino boards the RFzero also has a shield that you can use to build your own solution on top of the RFzero.
The RFzero do-it-yourself shield PCB.
The price for the RFzero shield is
- 25 DKK incl. VAT
See approx value in EUR - 20 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
ICOM IC-9700 coupler and cable
The ICOM IC-9700 coupler and cable are used to lock the ICOM IC-9700 transceiver to an external 49,152 MHz signal, e.g. the RFzero running the IC-9700 program.
The IC-9700 coupler board and SMA-U.FL cable (sorry for the poor image quality).
Please download the installation and setup guide here.
The price for the IC-9700 coupler and cable is
- 150 DKK incl. VAT
See approx value in EUR - 120 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Low, high, band pass and band stop filters
For the RFzero, but also for general use, two types of filter PCBs have been designed. The PCBs fit into a 37 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding. You can design your very own filter that matches the topology of the PCB e.g. using the free Elsie by Tonne Software Jim, W4ENE, or the online tool from RF Tools. The PCBs are designed for 0805 SMD components. High Q capacitors, NP0 or better, and inductors should be used for best performance especially as frequency increases and/or for best stop-band attenuation. The maximum power is 1 W.
An unpopulated filter PCB and a populated PCB with SMD connectors mounted too.
Below are series of possible low pass filter designs where the second harmonic is attenuated at least 10 dB and the third harmonic is attenuated at least 55 dB by the low pass filter itself. When used in combination with an RFzero the harmonics will then be attenuated at least 60 dBc if used between fmin and fmax.
| fmin | fmax | Z1 | Z2 | Z3 | Z4 | Z5 | Z6 | Z7 | Z8 | Z9 | Z10 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 400 kHz | 550 kHz | 3,3 nF | 300 pF | 8,2 nF | 1,2 nF | 8,2 nF | 1 nF | 2,7 nF | 18 µH | 18 µH | 15 µH |
| 1,6 MHz | 3 MHz | 1 nF | 120 pF | 1,5 nF | 560 pF | 1,5 nF | 470 pF | 820 pF | 3,9 µH | 2,7 µH | 2,7 µH |
| 2,9 MHz | 5,1 MHz | 680 pF | 68 pF | 1 nF | 360 pF | 820 pF | 220 pF | 470 pF | 1,8 µH | 1,5 µH | 1,5 µH |
| 5 MHz | 9,3 MHz | 390 pF | 56 pF | 560 pF | 220 pF | 470 pF | 150 pF | 330 pF | 1 µH | 820 nH | 820 nH |
| 9,1 MHz | 16,4 MHz | 220 pF | 39 pF | 270 pF | 120 pF | 220 pF | 82 pF | 120 pF | 560 nH | 470 nH | 470 nH |
| 16 MHz | 30 MHz | 100 pF | 12 pF | 180 pF | 56 pF | 150 pF | 39 pF | 56 pF | 330 nH | 270 nH | 270 nH |
| 30 MHz | 56 MHz | 47 pF | 2,2 pF | 100 pF | 12 pF | 100 pF | 8,2 pF | 47 pF | 180 nH | 180 nH | 180 nH |
| 54 MHz | 72 MHz | 33 pF | 2,2 pF | 68 pF | 15 pF | 82 pF | 10 pF | 47 pF | 150 nH | 120 nH | 120 nH |
| 100 MHz | 150 MHz | 15 pF | 1 pF | 33 pF | 3,9 pF | 33 pF | 3,3 pF | 12 pF | 68 nH | 68 nH | 68 nH |
Attenuation at fmax is typically 1 dB. The above values do not take into account the stray capacitance in the filter PCB which is about 2 pF.
Filter characteristics of a 52 MHz low pass filter from 1 MHz to 400 MHz. The insertion loss is 0,7 dB at 52 MHz. Red is the transfer function (10 dB/div), blue is input return loss (10 dB/div) and green is the input SWR (At 1 MHz it is 1:1).
Below is a possible high pass filter design that can be used to extract third and higher harmonic above 400 MHz, e.g. to get a 432 MHz signal.
| fmin | Z1 | Z2 | Z3 | Z4 | Z5 | Z6 | Z7 | Z8 | Z9 | Z10 |
|---|---|---|---|---|---|---|---|---|---|---|
| 400 MHz | 6,8 nH | 130 nH | 6,8 nH | 27 nH | 6,8 nH | 39 nH | 8,2 nH | 10 pF | 12 pF | 12 pF |
The Elsie filter design files can be downloaded here or use the online tool from RF Tools.
The price for a filter PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Download the filter design and general assembly guide.
Filter (LPF/HPF)
The Filter PCB has ten positions that can be used for either a low pass filter or a high pass filter. It has the same topology as the RFzero output filter itself.
The Filter PCB.
The generic Filter topology where each Z# is replaced with either a C or L or shorted/omitted.
The value and type of each Z# depends on the design criteria, e.g. for a low pass filter Z1, Z3, Z5 and Z7 are capacitors and Z8, Z9 and Z10 are inductors and if Z2, Z4 and Z6 are used they are capacitors. Not all Z# have to be used. If so they can be omitted or shorted whichever applies.
Multi Filter (LPF/HPF/BPF/BSF)
The Multi Filter PCB has 14 positions that can be used for either a low pass filter (LPF), high pass filter (HPF), band pass filter (BPF) or band stop filter (BSF).
The Multi Filter PCB.
The generic Multi Filter topology where each Z# is replaced with either a C or L or shorted/omitted.
The value and type of each Z# depends on the design criteria, e.g. for a low pass filter Z1, Z3, Z5 and Z7 are capacitors and Z8, Z9 and Z10 are inductors and if Z2, Z4 and Z6 are used they are capacitors and Z12 and Z13 are shorted. Not all Z# have to be used. If so they can be omitted or shorted whichever applies.
Voltage regulator
The voltage regulator PCB can replace situations, where a voltage regulator is bolted to the chassis or where the wires are unsupported, thus prone to failure or short circuits. The PCB can be used for voltage regulators in TO-220, e.g. LM78xx, two or three pin TO-252/DPAK or TO-263/D2PAK packages where the center pin is ground. For best thermal conductivity a TO-220 package should be used. Wires to and from the PCB may be soldered to the PCB or attached to terminal blocks.
Topside view of the voltage regulator PCB.
If leaded capacitors or terminal blocks are not used then the PCB may be lying flat on the surface. If leaded capacitors and/or terminal blocks are used, then the PCB has to be mounted on stand-offs and upside-down. If a TO-220 voltage regulator is used, then the input and output, as printed on the topside, change side. If using a TO-252/DPAK or TO-263/D2PAK then the input and output don’t change side. With a felt tip pen you may write “In” and “Out” in the relevant boxes.
Example of a PCB with a TO-263/D2PAK-3 package and SMD capacitors.
Example of a PCB with a TO-220 package and SMD capacitors.
Example of a PCB with leaded capacitors, terminal blocks and a TO-220 voltage regulator. Note the handwritten “In” and “Out”.
The voltage regulator topology. The values of the capacitors are subject to the voltage regulator datasheet and required voltages too
The price for a voltage regulator PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Transformer-combiner/splitter
For the RFzero but also for general use a transformer combiner/splitter (TCS) PCB has been designed. Especially when using the RFzero as a signal generator the TCS may be quite handy. The PCB fits into a 37 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding.
The transformer-combiner/splitter PCB.
T1 is either the standard RFzero transformer, Coilcraft PWB-2-BLB, or the recommended splitter, Mini-Circuits ADP-2-1W+.
The transformer topology for the Coilcraft PWB-2-BLB.
The combiner/splitter topology for the Mini-Circuits ADP-2-1W+.
When mounting a transformer pin 1 must be located to the lower right in the above picture of the PCB. If a combiner/splitter is mounted pin 1 must be located to the upper right in the above picture of the PCB.
The PCB pin numbering using roman numbers.
Table showing which PCB pints should be used for the different T1 solutions.
| PCB pin number | PCB functionality | Coilcraft PWB-2-BLB pin number | Mini-Circuits ADP-2-1W+ pin number |
|---|---|---|---|
| I | GND | 1 | 6 |
| II | GND | 2 | - |
| III | Common | 3 | 1 |
| IV | Port A | 4 | 3 |
| V | GND | 5 | - |
| Vi | Port B | 6 | 4 |
The price for a TCS PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Resistive power splitters
For the RFzero but also for general use two resistive power splitter PCBs have been designed. The PCBs fits into a 37 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding. The PCBs are designed for 0805 SMD components.
The resistive power splitter PCBs, 1:2 left and 1:3 right.
| Type | Outputs | Loss | Number of resistors | Resistor value* |
|---|---|---|---|---|
| 1:2 | 2 | 6,0 dB | 3 | 16,7 Ω |
| 1:3 | 3 | 9,5 dB | 4 | 25,0 Ω |
*: The resistor value is the same for all three/four resistors and should be 5% tolerance or lower.
The port-to-port isolation in a resistive splitter is equal to the loss. This is unlike a transformer combiner/splitter, where the isolation is typically better than 20 dB even, if the loss is less than 4 dB.
The price for a resistive power splitter PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Pi attenuator
For the RFzero but also for general use a Pi attenuator PCB has been designed. The PCB fits into a 37 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding. The PCB is designed for 0805 SMD components.
The Pi attenuator PCB.
The generic Pi attenuator topology.
SMD 0805 resistors are rated for 21 dBm/125 mW. If you need to attenuate more power you may add a resistor in parallel, but, remember to also double the resistor values.
Here is a link to an online Pi attenuator tool.
The price for a Pi attenuator PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Bias-T
For the RFzero but also for general use a Bias-T PCB has been designed. DC power can be applied through the J1 connector. The PCB fits into a 37 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding. High Q capacitors, NP0 or better, and inductors should be used for best performance especially as frequency increases. The PCB is designed for 0805 SMD components.
The Bias-T PCB.
The generic Bias-T topology where C1 and L1 are frequency specific.
Here is a link to the BTC (Bias-T Calculator) program by Alexander, K6VHF. E.g. for 25 MHz C1 =10 nF and L1 = 33 uH will do fine.
The price for a Bias-T PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Diplexer
For the RFzero but also for general use a diplexer PCB has been designed. DC power can be applied through the J1 connector. The PCB fits into a 37 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding. High Q capacitors, NP0 or better, and inductors should be used for best performance especially as frequency increases. The PCB is designed for 0805 SMD components.
The Diplexer PCB.
The generic diplexer topology where capacitors and inductors are frequency specific.
You can use the Diplexer program by Tonne Software Jim, W4ENE, to design a diplexer for another crossover frequency.
The price for a diplexer PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
MMIC gain blocks
For the RFzero but also for general use four MMIC gain block PCBs (MAR MSA, SOT89, SOT343 and SOT363) have been designed. DC power can be applied through the J1 connector. The PCB fits into a 37 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding. High Q capacitors, NP0 or better, and inductors should be used for best performance especially as frequency increases. The PCBs are designed for 0805 SMD components.
MMIC gain block PCBs for MAR MSA, SOT89, SOT343 and SOT363 (left to right).
Here is an online tool to calculate the MMIC bias capacitor and inductor values.
The price for one MMIC gain block PCB is
- 10 DKK incl. VAT
See approx value in EUR - 8 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
FET amplifier
For the RFzero but also for general use an FET amplifier PCB has been designed. The pads on the PCB are designed for a SOT89 device such as the AFT05MS004N and PD85004, but other devices with the same SOT89 footprint may also be used. The PCB fits into a 74 mm x 37 mm x 30 mm metal sheet box (Weissblechgehäuse) for best RF performance and shielding. High Q resistor, capacitors, NP0 or better, and inductors should be used for best performance especially as frequency increases. The PCBs are designed for 0603/0805 SMD components.
The FET amplifier PCB.
The generic FET amplifier schematic.
The amplifier bias may be disabled by pulling the J2-2 pin low. If the pin is floating the amplifier is biased and active.
The PCB has been designed with a generic schematic in mind. However, it is possible to omit some components, place them in a different location and cut the RF tracks if needed for your own specific design.
The R3 bias trimmer footprint is made for a 23AR10KLFTR type, but other types may be used.
If the PCB is mounted on a heat sink, J1 and J2 should not be mounted, if there is a risk, they will short circuit to the heat sink. In this case solder the supply and control leads to SJ1 and SJ2 instead.
Broadband amplifier, 1 MHz to 150 MHz
More details to come.
2 m amplifier
The 2 m amplifier uses an NXP AFT05MS004N capable of delivering more than 4 W.
Picture of the FET amplifier for 2 m.
Component values for the 2 m amplifier. All other components values as in the schematic.
| Component | Value | Notes |
|---|---|---|
| C1 | 1 nF | |
| C2 | 1 nF | |
| C7 | 33 pF | Mount as close to Z1 as possible |
| C8 | 33 pF | Mount as close to Z2 as possible |
| C9 | 1 nF | |
| C10 | 10 nF | |
| C11 | 1 nF | |
| L3 | 18 nH | |
| L4 | 33 Ω | Changed to a 0805 resistor |
| Z1 | 33 nH | |
| Z2 | 33 nH |
Performance of the 2 m amplifier.
| Voltage [V] | Bias current [mA] | Current [mA] | Input power [dBm/mW] | Output power [W] | n [%] | Notes |
|---|---|---|---|---|---|---|
| 5,0 | 100 | 300 | 13/20 | 1,3 | 90 | |
| 7,5 | 100 | 500 | 13/20 | 2,9 | 77 | |
| 12 | 100 | 750 | 13/20 | 4,9 | 55 | A heat sink is required |
Running the amplifier at 7,5 V is an ideal voltage for supplying the RFzero too.
23 cm amplifier
The 23 cm amplifier uses an STMicroelectronics PD85004 capable of delivering more than 2 W.
Picture of the FET amplifier for 23 cm. The buffer is used at OZ7IGY.
Component values for the 23 cm amplifier. All other components values as in the schematic.
| Component | Value | Notes |
|---|---|---|
| C1 | 33 pF | 0603 |
| C2 | 33 pF | 0603 |
| C7 | 4,7 pF | 0603, mounted 19 mm from the Q1 gate |
| C7A | 6,8 pF | 0603, mounted 6 mm from the Q1 gate |
| C8 | 4,7 pF | 0603, mounted 8 mm from the Q1 drain. As close to Z2 as possible |
| C9 | 120 pF | 0603 |
| C10 | 120 pF | 0603 |
| L3 | 12 nH | 0805 |
| L4 | 2,7 kΩ | Changed to a 0603 resistor |
| Z1 | 0 Ω | 0603 |
| Z2 | 0 Ω | 0603 |
Performance of the 23 cm amplifier.
| Voltage [V] | Bias current [mA] | Current [mA] | Input power [dBm/mW] | Output power [W] | n [%] | Notes |
|---|---|---|---|---|---|---|
| 7,5 | 200 | 250 | 16/40 | 0,68 | 36 | |
| 12 | 200 | 275 | 16/40 | 1,5 | 45 | A heat sink is required |
| 15 | 200 | 330 | 16/40 | 2,2 | 43 | A heat sink is required |
The price for one FET amplifier PCB is
- 20 DKK incl. VAT
See approx value in EUR - 16 DKK excl. VAT for customers outside the EU. Import taxes and fees may apply
See approx value in AUD, CAD, GBP, JPY, USD and ZAR
Please use the contact form to send your purchase inquiry.
Third party accessories
Below are a number of typical accessories that can be used together with your RFzero. You may find them on flea markets, in electronics shops and online too. Please look for the sellers with top customer ratings even if it means that you will have to pay a bit more. Especially when it comes to buying RF cables and connectors look for those who ONLY sell RF stuff. Avoid those who sell RF, beauty products and spark plugs from the same shop since they haven’t got a clue about RF and specifications.
GPS antennas
The GPS antenna must be made for the civilian frequency L1 at 1575,42 MHz. The cable should be fitted with a SMA male connector. Never use Reverse Polarity (RP) connectors! If there is a built-in pre-amplifier, i.e. active antenna, it must operate on 3,3 V and draw max 100 mA.
If your primary use of your RFzero is casual then a “hockey puck” antenna will do just fine. The price level is ~5 USD. Please keep in mind that this kind of antenna is neither water- nor UV-proof. So you may have to put it into a proper box.
Example of a GPS hockey puck antenna with SMA male connector.
If you plan to use your RFzero for regular or long term use a real outdoor antenna is recommended. Perhaps even a marine grade antenna if you live in a coastal environment. Outdoor antennas are not cheap but well worth the investment as they are UV proof too.
Boxes and enclosures
The physical size of the RFzero board is 79 mm x 99,5 mm, thus it fits perfectly with a half Eurocard PCB. Thus there are a myriad of boxes and enclosures available where the RFzero will slide in nicely.
Example of an enclosure (150 mm x 105 mm x 55 mm).
Fischer Elektronik has some really nice looking profiles, two is needed for box. You will also need a front and back plate. The profiles and plates comes in various sizes.
Fischer Elektronik KO H 6 profile.
Here are their worldwide distributors.
Metal sheet boxes (Weissblechgehäuse)
For the very best RF performance the RFzero should be mounted inside a metal sheet box (Weissblechgehäuse) 102 mm x 82 mm x 30 mm. They are available from many RF specialist shops.
Metal sheet box 102 mm x 82 mm x 30 mm (Weissblechgehäuse).
The Filter PCBs, Pi-attenuator, Bias-T, diplexer Transformer/Splitter and MMIC PCBs all fit into a metal sheet box (Weissblechgehäuse) 37 mm x 37 mm x 30 mm.
Amplifier
If the level from the RFzero is not enough for your application you may boost the signal with an amplifier. There are really many amplifiers, both ready made, kits and designs, that can increase the 8 dBm to 13 dBm from the RFzero to whatever level you are looking for.
Example of an up to 2 W amplifier. This amplifier has more gain than necessary. So remove the first stage device and its drain choke both marked with yellow dots. Then short the input and output pads left by the removed device.
Even though this is a neat solution you should not run the above type of amplifier on more than 10 V or more than max 1 W out, if your antenna has a dubious SWR.
But you can also find amplifiers that is not recommend.
A NOT recommended amplifier.
Please don’t buy amplifiers similar to the one above. After three days of continuous operation the output device died.
Cables
Coaxial cables for the RFzero GPS and RF output must be fitted with SMA male type connectors.
SMA male connector.
If you will use a Hitachi HD44780 compatible LCD connected to JP12 two six wire jumper cables Single In Line (SIL) 1 module (2,54 mm) are needed.
Two six-wire cables.
Headers
The RFzero is supplied with headers. But should you be in need for additional headers just remember to buy Single In Line (SIL) 1 module (2,54 mm) types. They are typically sold in a row with 40 male or female contacts.
A row of male SIL headers.
Level converter
3,3 V to/from 5 V level converters come in many shapes and forms. You can put it together yourself, buy a module or an IC.
Do-it-yourself level converter schematic. Most other N-channel FETs will work too. The number of level conversion channels can be expanded if required.
Example of a four bits level converter module where LV goes to 3,3V and HV to the 5 V and the LV1 to the 3,3 V I/O pin and the HV1 to the 5 V I/O pin and so on.
Typical level converter ICs, also called bus transceivers, include the popular 74LVC245.
Displays
The RFzero library supports both HD44780 compatible LCDs and two TFT displays ILI9341 and ILI9488. Please see the display page for more details. The actual physical size of a display is up to you.
Example of a 20×4 LCD.
Example of an ILI9341 and 2,4″ display with SPI connector.
The RFzero LCD connector JP12 is designed for Hitachi HD44780 compatible LCDs. They are typically available with 16 characters per line and two lines (16×2) and 20 characters per line and four lines (20×4) but other sizes also exist. The LCD can easily be connected using two six-wire jumper cables – please see above.
The RFzero is a 3,3 V board, however, it is possible to use a 5 V supplied LCD. BUT not all 5 V LCDs will work with 3,3 V digital logic signals. Therefore, it is highly recommended that you use a 3,3 V LCD and specifically ask the seller for such one. We have very positive experience with 3,3 V LCDs from BuyDisplay.com. To avoid having to twist the backlight wires you should only buy LCDs, that have the anode on pin 15 and the cathode on pin 16, however, most do.
We have had very bad experience with the below eBay vendors who all say they sell 3,3 V LCDs. But unfortunately the LCDs from them don’t work properly on 3,3 V. In reality they need 5 V.
- diybox
- sensesmart
- shieldfans
- worldchips
Liquid crystal displays using I2C (Wire)
If you are short free pins but still want to connect a LCD then you can use the I2C bus together with a driver board, which is also a port expander below, and use the default I2C bus on your board. The RFzero library supports the use of the PCF8574, ~A and ~T models. Other may work but have not been tested.
Example of a LCD I2C (Wire) driver board with a PCF8574 expander.
Please see the display page for more information.
Port expander
Even if the RFzero has a lot of digital I/Os available a situation might occur, where you will need more I/O power. The MCP23008, MCP23017, MCP23S08, MCP23S17 and SX1509 chips are brilliant and cost effective solutions that add either eight or 16 I/Os, and connect to either I2C/Wire or SPI at the other end, thus requiring only two or three pins that can be found on the RFzero I2C User Bus or SPI bus.
Example of port expander modules, SX1509 (L) and MCP23017 (R).
If you buy a module it might be an idea to find one with mounting holes in it.
Rotary encoders
There exists a huge variety of rotary encoders with and without a push button too, but also in a very different price ranges. You know your own requirements. However, the fairly cheap rotary encoders will do the trick for most users.
It is a good idea to use rotary encoders where none of the push button pins, X and Y, have connection to the rotary encoder ground pin.
T1 combiner
For T1 the RFzero is factory mounted with a Coilcraft PWB-2-BLB transformer. But if your main use is generating two-tone signals it is a good idea to change T1 to a combiner like the Mini-Circuits ADP-2-1W+ or equivalent.
The Mini-Circuits ADP-2-1W+ combiner.
U.FL connectors and cables
If you need to use your RFzero as an I/Q generator you will need two U.FL connectors for PCB mount.
U.FL connectors seen from the bottom and top.
Two U.FL connectors mounted on the RFzero PCB and T1 removed.
Don’t forget to get some cables if you don’t have those with the right connectors already, e.g. U.FL in one end and SMA female bulk head at the other end.
Example of a cable with SMA female bulk head and U.FL connectors.
