BATC Wiki - User contributions [en-gb]

G0MJW Bias-T and reference-injection boards

2023-01-31T10:00:18Z

M0JUR: Link bills of materials, add note about the geometry and allowed dimensions of the LNB connector, remove the "work in progress" warning

For those among us who would like to feed external frequency reference to their LNBs, Mike G0MJW has designed two boards which combine the usual Bias-T with the ability to send the reference signal on the same feeder. This of course means having to adapt the LNB accordingly - but given you will likely have to modify it to accept external frequency reference in the first place, it shouldn't be a problem.

Both boards feature pads for Pi attenuators on both IF and reference lines, with resistor values as shown in the schematics providing 10dB attenuation on the former and 3dB attenuation on the latter. These can be omitted if not necessary, modified should different attenuation be desired, or possibly replaced with Pi filters.

===Note on the LNB connectors===

The boards have been designed so that one can easily substitute SMA or even F-type for Mike's preferred BNC. As a result the LNB connector must have the "ground pins in a square plus signal pin in the centre" geometry which while typical of SMA panel connectors is somewhat unusual (and more pricey) for BNC ones.

Furthermore, keep in mind that the maximum ground-pin spacing which can be accommodated by the boards is about 9mm outer edge to outer edge. This is not a problem for most SMA and F-type connectors, however many BNC connectors of this sort feature ground-pin spacing of over 10mm and will therefore ''not fit''. Bear that in mind should you aim to replace the BNC connectors listed in the BoMs with something cheaper.

== External reference ==

Described in CQ-TV 263. Useful if you have a stable 25MHz reference source such as a GPSDO.

[[File:G0MJW_bias-ext_ref-schematics.png|800px]] [[File:G0MJW_bias-ext_ref-model.png|800px]]

Bill of materials: [[File:G0MJW_BiasT_ext_ref-BoM.ods]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-bias-t-and-reference-injection-blank-pcb/ the BATC Shop].

Inductor pads can accommodate a wide range of different packages, both SMD and through-hole ones.

To omit attenuator on ''IF out'': replace R3 with a 0 Ohm jumper or a solder bridge, omit R1+R5.

To omit attenuator on ''Ref in'': replace R4 with a 0 Ohm jumper or a solder bridge, omit R2+R6.

== Onboard reference ==

Described in CQ-TV 266.

[[File:G0MJW_bias-int_ref-schematics.jpg|800px]] [[File:G0MJW_bias-int_ref-model.jpg|800px]]

Bill of materials: [[File:G0MJW_BiasT_TCXO_ref-BoM.ods]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-reference-bias-t-and-diplexer-blank-pcb/ the BATC Shop].

The TCXO has all the pads underneath and is therefore suggested to be fitted first, tinning the pads and with hot air or a hotplate.

C3 can be fitted as needed to tune the crystal filter. For the crystals specified in the BoM it shouldn't be necessary.

To omit attenuator on ''IF out'': replace R13 with a 0 Ohm jumper or a solder bridge, omit R11+R15.

To omit attenuator on TCXO reference: replace R14 with a 0 Ohm jumper or a solder bridge, omit R12+R16.

File:G0MJW BiasT ext ref-BoM.ods

2023-01-31T09:59:25Z

M0JUR: s/in/from/

== Summary ==
Bill of materials for the G0MJW Bias-T with injection of external 25MHz reference. To keep things simpler for constructors the original list from CQ-TV has been updated to suggest the same components, where possible of course, as for the onboard-TCXO variant. Furthermore, inductor descriptions now use imperial package sizes - however much it might pain me to use non-metric values for anything, that's what the original list used for all other components.

File:G0MJW BiasT ext ref-BoM.ods

2023-01-31T09:58:51Z

M0JUR: Bill of materials for the G0MJW Bias-T with injection of external 25MHz reference. To keep things simpler for constructors the original list in CQ-TV has been updated to suggest the same components, where possible of course, as for the onboard-TCXO variant. Furthermore, inductor descriptions now use imperial package sizes - however much it might pain me to use non-metric values for anything, that's what the original list used for all other components.

== Summary ==
Bill of materials for the G0MJW Bias-T with injection of external 25MHz reference. To keep things simpler for constructors the original list in CQ-TV has been updated to suggest the same components, where possible of course, as for the onboard-TCXO variant. Furthermore, inductor descriptions now use imperial package sizes - however much it might pain me to use non-metric values for anything, that's what the original list used for all other components.

File:G0MJW BiasT TCXO ref-BoM.ods

2023-01-31T09:42:19Z

M0JUR: Bill of materials for the G0MJW Bias-T with onboard 25MHz reference. Mostly identical to the one in CQ-TV, the only major difference being that the original BNC connector has since gone out of production and has been replaced with its successor.

== Summary ==
Bill of materials for the G0MJW Bias-T with onboard 25MHz reference. Mostly identical to the one in CQ-TV, the only major difference being that the original BNC connector has since gone out of production and has been replaced with its successor.

G0MJW Bias-T and reference-injection boards

2023-01-30T23:21:34Z

M0JUR: Note on TCXO soldering as per CQ-TV 266

WORK IN PROGRESS! Still needs the BoMs, and possibly some reformatting.

For those among us who would like to feed external frequency reference to their LNBs, Mike G0MJW has designed two boards which combine the usual Bias-T with the ability to send the reference signal on the same feeder. This of course means having to adapt the LNB accordingly - but given you will likely have to modify it to accept external frequency reference in the first place, it shouldn't be a problem.

Both boards feature pads for Pi attenuators on both IF and reference lines, with resistor values as shown in the schematics providing 10dB attenuation on the former and 3dB attenuation on the latter. These can be omitted if not necessary, modified should different attenuation be desired, or possibly replaced with Pi filters.

== External reference ==

Described in CQ-TV 263. Useful if you have a stable 25MHz reference source such as a GPSDO.

[[File:G0MJW_bias-ext_ref-schematics.png|800px]] [[File:G0MJW_bias-ext_ref-model.png|800px]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-bias-t-and-reference-injection-blank-pcb/ the BATC Shop].

Inductor pads can accommodate a wide range of different packages, both SMD and through-hole ones.

To omit attenuator on ''IF out'': replace R3 with a 0 Ohm jumper or a solder bridge, omit R1+R5.

To omit attenuator on ''Ref in'': replace R4 with a 0 Ohm jumper or a solder bridge, omit R2+R6.

== Onboard reference ==

Described in CQ-TV 266.

[[File:G0MJW_bias-int_ref-schematics.jpg|800px]] [[File:G0MJW_bias-int_ref-model.jpg|800px]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-reference-bias-t-and-diplexer-blank-pcb/ the BATC Shop].

The TCXO has all the pads underneath and is therefore suggested to be fitted first, tinning the pads and with hot air or a hotplate.

C3 can be fitted as needed to tune the crystal filter. For the crystals specified in the BoM it shouldn't be necessary.

To omit attenuator on ''IF out'': replace R13 with a 0 Ohm jumper or a solder bridge, omit R11+R15.

To omit attenuator on TCXO reference: replace R14 with a 0 Ohm jumper or a solder bridge, omit R12+R16.

G0MJW Bias-T and reference-injection boards

2023-01-30T23:15:49Z

M0JUR: Specify attenuation of both IF and reference attenuators in the case of them having been built using resistors specified on the schematics

WORK IN PROGRESS! Still needs the BoMs, and possibly some reformatting.

For those among us who would like to feed external frequency reference to their LNBs, Mike G0MJW has designed two boards which combine the usual Bias-T with the ability to send the reference signal on the same feeder. This of course means having to adapt the LNB accordingly - but given you will likely have to modify it to accept external frequency reference in the first place, it shouldn't be a problem.

Both boards feature pads for Pi attenuators on both IF and reference lines, with resistor values as shown in the schematics providing 10dB attenuation on the former and 3dB attenuation on the latter. These can be omitted if not necessary, modified should different attenuation be desired, or possibly replaced with Pi filters.

== External reference ==

Described in CQ-TV 263. Useful if you have a stable 25MHz reference source such as a GPSDO.

[[File:G0MJW_bias-ext_ref-schematics.png|800px]] [[File:G0MJW_bias-ext_ref-model.png|800px]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-bias-t-and-reference-injection-blank-pcb/ the BATC Shop].

Inductor pads can accommodate a wide range of different packages, both SMD and through-hole ones.

To omit attenuator on ''IF out'': replace R3 with a 0 Ohm jumper or a solder bridge, omit R1+R5.

To omit attenuator on ''Ref in'': replace R4 with a 0 Ohm jumper or a solder bridge, omit R2+R6.

== Onboard reference ==

Described in CQ-TV 266.

[[File:G0MJW_bias-int_ref-schematics.jpg|800px]] [[File:G0MJW_bias-int_ref-model.jpg|800px]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-reference-bias-t-and-diplexer-blank-pcb/ the BATC Shop].

C3 can be fitted as needed to tune the crystal filter. For the crystals specified in the BoM it shouldn't be necessary.

To omit attenuator on ''IF out'': replace R13 with a 0 Ohm jumper or a solder bridge, omit R11+R15.

To omit attenuator on TCXO reference: replace R14 with a 0 Ohm jumper or a solder bridge, omit R12+R16.

G0MJW Bias-T and reference-injection boards

2023-01-30T11:52:01Z

M0JUR: Add some content

WORK IN PROGRESS! Still needs the BoMs, and possibly some reformatting.

For those among us who would like to feed external frequency reference to their LNBs, Mike G0MJW has designed two boards which combine the usual Bias-T with the ability to send the reference signal on the same feeder. This of course means having to modify the LNB accordingly - but given you will likely have to modify it to accept external frequency reference in the first place, it shouldn't be a problem.

Both boards feature Pi attenuators on both RX and reference lines. These can be omitted if not necessary, or possibly replaced with Pi filters.

== External reference ==

Described in CQ-TV 263. Useful if you have a stable 25MHz reference source such as a GPSDO.

[[File:G0MJW_bias-ext_ref-schematics.png|800px]] [[File:G0MJW_bias-ext_ref-model.png|800px]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-bias-t-and-reference-injection-blank-pcb/ the BATC Shop].

Inductor pads can accommodate a wide range of different packages, both SMD and through-hole ones.

To omit attenuator on ''IF out'': replace R3 with a 0 Ohm jumper or a solder bridge, omit R1+R5.

To omit attenuator on ''Ref in'': replace R4 with a 0 Ohm jumper or a solder bridge, omit R2+R6.

== Onboard reference ==

Described in CQ-TV 266.

[[File:G0MJW_bias-int_ref-schematics.jpg|800px]] [[File:G0MJW_bias-int_ref-model.jpg|800px]]

A blank PCB for this project is available from [https://batc.org.uk/shop/lnb-reference-bias-t-and-diplexer-blank-pcb/ the BATC Shop].

C3 can be fitted as needed to tune the crystal filter. For the crystals specified in the BoM it shouldn't be necessary.

To omit attenuator on ''IF out'': replace R13 with a 0 Ohm jumper or a solder bridge, omit R11+R15.

To omit attenuator on TCXO reference: replace R14 with a 0 Ohm jumper or a solder bridge, omit R12+R16.

File:Int ref-model.jpg

2023-01-30T11:21:47Z

M0JUR: M0JUR moved page File:Int ref-model.jpg to File:G0MJW bias-int ref-model.jpg: Wrong name at upload time

#REDIRECT [[File:G0MJW bias-int ref-model.jpg]]

File:G0MJW bias-int ref-model.jpg

2023-01-30T11:21:47Z

M0JUR: M0JUR moved page File:Int ref-model.jpg to File:G0MJW bias-int ref-model.jpg: Wrong name at upload time

== Summary ==
3D model of the variant with an on-board 25MHz TCXO reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=20897#p20897

File:G0MJW bias-int ref-model.jpg

2023-01-30T11:21:07Z

M0JUR: 3D model of the variant with an on-board 25MHz TCXO reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=20897#p20897

== Summary ==
3D model of the variant with an on-board 25MHz TCXO reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=20897#p20897

File:G0MJW bias-int ref-schematics.jpg

2023-01-30T11:19:31Z

M0JUR: Schematics of the variant with an on-board 25MHz TCXO reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=20897#p20897

== Summary ==
Schematics of the variant with an on-board 25MHz TCXO reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=20897#p20897

File:Ext ref-model.png

2023-01-30T11:15:35Z

M0JUR: M0JUR moved page File:Ext ref-model.png to File:G0MJW bias-ext ref-model.png: Set wrong name at upload time

#REDIRECT [[File:G0MJW bias-ext ref-model.png]]

File:G0MJW bias-ext ref-model.png

2023-01-30T11:15:35Z

M0JUR: M0JUR moved page File:Ext ref-model.png to File:G0MJW bias-ext ref-model.png: Set wrong name at upload time

== Summary ==
3D model of the variant relying on an external 25MHz reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=17343#p17343 .

File:G0MJW bias-ext ref-model.png

2023-01-30T11:13:54Z

M0JUR: 3D model of the variant relying on an external 25MHz reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=17343#p17343 .

== Summary ==
3D model of the variant relying on an external 25MHz reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=17343#p17343 .

File:G0MJW bias-ext ref-schematics.png

2023-01-30T11:12:29Z

M0JUR: Schematics of the variant relying on an external 25MHz reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=17343#p17343 .

== Summary ==
Schematics of the variant relying on an external 25MHz reference, as posted by G0MJW on BATC Forums: https://forum.batc.org.uk/viewtopic.php?p=17343#p17343 .

G0MJW Bias-T and reference-injection boards

2023-01-29T11:52:34Z

M0JUR: Stub

WORK IN PROGRESS! I am about to put on this page the schematics of, bills of materials for etc. for the two boards for which the BATC Shop has PCBs.

G4WIM PA controller

2022-11-18T11:01:12Z

M0JUR: More details on firmware building and flashing based in private correspondence with G4WIM

An advanced PA controller design by Tim G4WIM and described in CQ-TV 265 - PCB's will be available from the BATC shop.

==Introduction==

This project came about as a result of needing to remote control and monitor a 2.4GHz power amplifier for the QO-100 satellite up link.
In the case of G4WIM the amplifier is at the end of 75 metres of cable directly beneath the feed point of a 1.2 metre dish. So running from the shack to the PA was not an option!

It has evolved from a simple controller which relied on either 5 or 12 Volts being sent up the coax to set off, standby or transmit modes into a multi-purpose design.

===Configurations===

The resulting system can be configured in three ways:

* Full remote control of the PA and shack monitoring of vital signs – using radio link.
* When PA is in the shack, local control and monitoring - no radio link.
* Remote control of PA by means of DC down the coax – no radio link or remote monitoring

The most likely use cases are 1 and 2.
In this article I refer to the PA with associated control and telemetry hardware as the MASTER and the remote display / control in the shack as the SLAVE.
When used as #2 above there is no SLAVE and the MASTER serves as control and display.

===Monitoring===

In all cases it allows monitoring of the following analogue signals:

* Vdd, 100mV resolution
* Idd, 100mA resolution
* PA temperature, 0.3C resolution
* Bias voltage, 10mV resolution for LDMOS
* RF power (forward or reverse but not both – depends on HW implementation)
* Fan status on or off
* Standby status on or off

===Amplifier choices===

The design was initially conceived for a Pyro Jo PA which needs 24V DC bias to activate it, subsequently it was modified to provide a temperature compensated bias for LDMOS FET’s. Basically for the LDMOS FET use the temp compensated bias circuit and for the Pyro JO PA use the 24V DC device – one or the other NOT both.

See CQ-TV article and schematics for more detail.

===Hardware===
The design uses the same PCB in all cases but populated slightly differently for each of the three use cases above. The BoM and schematics indicate what needs to be fitted for each use case.

[[File:G4WIM PA CONTROLLER SS V2-0.png|400px]]

For each use case firmware works differently and is jumper selected as mentioned above.

Note, if RF power is not being monitored then the RF power sensor input on pin 1 of J3 must be connected to ground to disable the function. Normally RF power will only be shown when on transmit and above a certain threshold.

==Documentation==

Bill of material

[[:File:G4WIM PA CONTROLLER V2-0 BOM.xlsx]]

Schematics

*[[:File:G4WIM PA CONTROLLER V2-0 SHT 1 (1).pdf]]

*[[:File:G4WIM PA CONTROLLER V2-0 SHT 2 (1).pdf]]

*[[:File:G4WIM PA CONTROLLER V2-0 SHT 3 (1).pdf]]

*[[:File:PA CONTROL WIRING SHACK DISPLAY.pdf]]

*[[:File:PA CONTROL WIRING SHACK DISPLAY.pdf]]

*[[:File:PA CONTROL WIRING PJ SHACK.pdf]]

*[[:File:PA CONTROL WIRING LDMOS THERMISTOR.pdf]]

*[[:File:PA CONTROL WIRING PJ MAST.pdf]]

*[[:File:PA CONTROL WIRING LDMOS SHACK.pdf]]

*[[:File:PA CONTROL WIRING LDMOS MAST.pdf]]

==Microcontroller Firmware==

Source code + pre-built hex files (in respective subdirectories): [[:File:BATC_PA_Controller_Firmware_V2.zip]]

The controller logic is driven by a standalone ATmega328P, whereas the the radio link uses an nRF905 + Arduino Nano v3 (which has its own ATmega328P).
The Arduino Nano code is based on this solution http://blog.zakkemble.net/nrf905-avrarduino-librarydriver/comment-page-1/

IMPORTANT - after building several of these links it became apparent that the timings required for the nRF905 are not the same for all modules. To fix this issue I've created a new improved version of Zak's C code for the Nano. The code for the standalone ATmega328P has also been changed to match.

Any chips supplied by the BATC shop will have the correct code installed for both the ATmega and the Nano.

=== Flashing ===

Any ordinary AVR programmer + appropriate software should work here. If you do not use a GUI for this, look into ''avrdude'' - it is Free Software, supports quite a wide range of programmers, and there are many tutorials and examples available on the Web should the bundled documentation prove insufficient.

In case there is any confusion here: ''BATC_Unified_PA_Controller.hex'' goes onto the standalone ATmega328p and ''avrwirelessuart.hex'' goes onto the Nano.

==== Variants of code ====

Let us re-emphasise that the improved radio-link code for the Arduino Nano is '''not''' compatible with the Arduino environment and boot loader! Both the standalone and the Nano-based ATmega should be programmed as a standalone device. In other words, we treat the Nano simply as a collection of parts conveniently already wired to the microcontroller rather than as an Arduino board.

Using Zak Kemble's original code in the Arduino environment might work - but it is better to use his C code version with my modifications as documented and provided in the above source code link.

You cannot mix and match Arduino and plain-ATmega code.

==== Fuses ====

Before programming the hex files make sure the "divide clock frequency by 8" fuse (low bit 7) is unchecked and that the fuses specifying the clock source (low bits 0-3) select an external 8-16 MHz crystal. All these fuses should already be set correctly on the Nano because it comes with its own 16-MHz crystal but will likely have to be adjusted on the standalone ATmega328P (the factory settings are different). It is highly recommended that you read the fuses settings out having programmed them to make sure they have been set correctly.

Values of all the other fuses (low bits 4-6 as well as all high and extended bits) are less important. If confused by the plethora of available settings, values used by the Arduino environment (these can be found in the file ''boards.txt''; use 'Arduino Nano w/ ATmega328P' values for the Nano and 'Arduino Uno' ones for the standalone ATmega328P) are a safe choice.

Note that the extended fuses might in the end appear different from what they told them to be because different batches of ATmega328P react differently to the attempts of programming "reserved" fuses. As long as the difference does not cover the "brown-out detection" bits, this is completely harmless.

When in doubt regarding any of the values here, consult an AVR fuse calculator such as this one: https://www.engbedded.com/fusecalc/

=== Building ===

The code can be built using Atmel Studio, or if you have a standalone AVR toolchain installed you can simply use GNU make on the project. In either case, you will want to use the "Debug" target to build the hex files - the "Release" target has never been tested by G4WIM so it may or may not work (and in his own words, it shouldn't make any practical difference).

If building using Atmel Studio V7.0 set optimisation to -Os (optimise for size). This is a good idea in general unless you use a very old AVR compiler known to have problems with this optimisation mode.

File:8 BAND RF SWITCH V3.0 PARTS.xls

2022-06-10T23:19:41Z

M0JUR: Latest version of G8GKQ's 8_BAND_RF_SWITCH_V2.2a_PARTS.xls with another sheet added to cover Version 3.0 changes.

== Summary ==
Latest version of G8GKQ's 8_BAND_RF_SWITCH_V2.2a_PARTS.xls with another sheet added to cover Version 3.0 changes.

8-Band RF Output Switch

2022-06-10T23:15:58Z

M0JUR: If I manage to upload it, the latest parts list will now cover version 3.0

For those of you who want to drive Microwave transverters from your Portsdown or need a higher drive level, the team have developed an 8-Band RF output switch that includes an RF amplifier.

It is capable of amplifying the variable level from the Filter Modulator board / Lime SDR up to 10 dBm and switching it to separate external amplifiers for the 70, 144, 437, 1255 bands and up to 4 transverters for the higher bands. One of the 4 transverter output can also be used for 2300 / 2400 MHz - see mods below to maintain output level.

The module should be used with the 8 band decoder which will provide PTT steering for the 8 bands - [[8-Band Decoder|see this page for more details.]]

PCBs and the control PIC are available from the BATC Shop.

The latest parts list is here [[:File:8_BAND_RF_SWITCH_V3.0_PARTS.xls]].

===Version 3 PCB - October 2021===

We have seen a number of failures caused by the use of the 8 way switches with the LimeSDR (the PCB was originally designed for use with the Filter-Modulator Board). The problem with the LimeSDR is that it can easily deliver +17 dBm during its calibration pulse, thus feeding +22 dBm into the RF switch, which exceeds its absolute maximum rating at 146 and 437 MHz.

The version PCB provides a solution by increasing the attenuation on the input to the 8-way RF switch, or to use a lower gain RF amplifier. The revised layout is as show:

[[File:8 way switch v3.JPG|400px]]

[[File:8 way switch v3 circuit.JPG|400px]]

===Version 2.2 PCBs===

The circuit for Version 2.1 and 2.2 PCBs is here: [[Media:8 BAND RF SWITCH V2-1 SCH.pdf]].
Note that the value of C13 should be increased to 2.2 uF to prevent the 5V regulator from oscillating.

===Version 2.1 PCBs===

The previous version, V2.1 requires 2 minor corrections during construction.

The grounded ends of R1 and R2 on the input attenuator need properly connecting to ground. Thanks to Colin G4EML for spotting this and pointing out that this can be corrected by scraping away some of the solder resist next to the pads and adding a blob of solder to connect the resistors to ground as shown in his picture here:

[[File:V2.1 Rework.JPG|240px]]

====Lime SDR====

When used with the Lime SDR, Dave G8GKQ recommended changes to the input attenutor in his article in CQ-TV 262 to improve performance at 2.4GHz. C16 changes to 1pF and R5 becomes a Zero Ohms link. The modification is shown here on a prototype PCB with the 1pf capacitor on the white square.

[[File:6 8RF Mod.JPG|400px]]

All the parts in the attenuator are 0603 sized; the V2.3 arrangement is in the revised parts list.

Here is a V2.3 PCB for LimeSDR Mini use, and the underside showing the wire link. Assembled by David M0YDH

[[File:20190201 182759-1008x756.jpg|400px]] [[File:20190201 182818-1008x756.jpg|480px]]

===Version 1 PCBs===

[[File:8-Band RF Switch Built V1 small.jpg|576px]]

The initial design was as shown above - the first batch of boards will be supplied in this form. The initial (V1.0) circuit is here: [[Media:8 BAND RF SWITCH V1-0 SCH.pdf]].

HOWEVER, the circuit needed some simple rework to provide a more stable power supply for the SKY MMIC and to equalise the levels across the bands. The modifications are to:

# Cut the track on the underside between the output of the voltage regulator and the link point marked 5VA.
# Replace the 7805 with a 7808 regulator (for 8 volts) and wire a 30 ohm resistor between the regulator output and the the point marked 5VB. Note that the resistor will need to dissipate 300mW (it passes 100mA), so 3 1/8 watt 10 ohm resistors in series might be easiest.
# Wire a new 78L05 regulator on the underside of the board with its input from the 12V supply and its output to the point marked 5VA.
# The input attenuator should be set up with R1=R2=68 ohms, and R3=220 ohms. To get the full 10 dBm output on 1255 MHz, add a series combination of 68 ohms and 2.7 pf across R3. The first batch of PCBs do not have pads for the extra capacitor and resistor.

The modified board is shown below.

[[File:8-Way RF Prototype Small.jpg|556px]]

G4WIM PA controller

2022-04-27T22:19:48Z

M0JUR: Elaborate on fuse settings, including a link to an AVR fuse calculator. And since fuse settings can vary between microcontroller models, make it clear the Nano v3 has an ATmega328P on board

G4WIM PA controller

2022-04-27T22:01:20Z

M0JUR: It's ARDUINO Nano, not Atmel Nano. Moreover, since the compiler flags indicate the Nano firmware is built for ATmega328P as well make it clear that version 3 of the Nano is required - older versions used an ATmega168

G4WIM PA controller

2022-04-27T21:54:03Z

M0JUR: Clarify that the standalone controller is a 328P (that's what the compiler flags in the source archive say) rather than a plain 328

G4WIM PA controller

2022-04-27T21:46:55Z

M0JUR: The firmware section probably shouldn't have been part of "Documentation", fixed. Also, make it clear the archive contains pre-built firmware blobs