3 Band Transverter Box - K7MDL2/IC-705-BLE-Serial-Example GitHub Wiki

The same CI-V band decoder code is reconfigured with #define M5STAMPC3U set to compile on a M5STack miniature CPU module "M5StampC3U". The C3U is an ESP32-C3 module and does not have BT, it does have 2.4GHz WiFi, has no screen, limited IO ports, serial, LED with switch, I2C and USB-C. It is pretty small. It uses wired input for PTT and band selection, not CI-V.

The main use case for me is this box will be located at some distance and out of sight, like on the floor in the back seat of my rover truck, and I wanted simple RFI-resistant interconnect cabling to my CI-V decoder/display located on my IC-705 radio mounted at the front seat. Attached to the Xvtr box are high power amps for each band with dedicated PTT for each amp. If it was not remote located, then you could mount the display unit in or on top of the Xvtr box and have very short interconnect (just inches). There is a small OLED display on the XVTR box to show some basic status - band, RX/TX, voltage, current, and if the active band is a Xvtr band or not.

The radio side display and transverter controller

The transverter box withe radio side controller sitting on top for testing (normally next to the radio).

The box local display screen pages. The display will be surface mounted in a 3D printed bezel later

This box (XvtrBox for short) is targeted at the IC-705 to add 222, 902/903, and 1296 bands that the radio lacks. I am using the latest UR3LM transverter boards which feature optional 10Mhz external reference. The 903 and 222 use 28Mhz IF, and 1296 uses 144Mhz IF. All IF drive levels are around 0dBm. I use my IC-705 BT CI-V band decoder to convert CI-V frequency to BCD band decoder wire outputs that close to ground. This is the same way that many radios like some Yaesu, Kenwood, and Elecraft radios work.

There is no reason this box cannot be used to compliment popular multiband radios like the IC-9700, IC-9100, IC-7100, IC-706. The Icom radios lack BCD outputs so a CI-V decoder is required to break out the band indication and to break out PTT for amps dedicated to each band, or switch antennas. My CI-V decoder has transverter focused features (all ham bands up to 122Ghz are predefined) to restore the settings to each Xvtr IF band and the last used non-Xvtr band, and displays the correct band dial frequency for the Xvtr bands. A simple button push switches the Xvtr bands on and off. For example, 902 uses 28Mhz IF, 903 uses 29Mhz IF, 1296 is 144 IF, and 222 is 28Mhz IF.

Non-CI-V radios like the FT-817, the K3 or KX3 with their internal 144 Xvtrs installed, and other radio models with BCD band outputs (native or external decoder). You could also adapt this to plug in standalone high power Xvtrs including microwave bands with some software tweaks.

The chassis is a Cheval (Thailand) black DIY audio box. It features 2 internal rails and several slots with sliding nuts. I slip a bare PCB plate in between the rail slots to act as a base mounting plate. The left and right side panels are thicker aluminum with fins for heat sinking. To these plates I internally mounted the 8W 222 board, the 2W 1296 amp and the 50W 903 amp. In the center are 2 stacked Rx and Tx IF SP6T switches and on top of those is a 4-relay opto-isolated module for 12V power distribution.

The 903 and 1296 boards output up to 20dBm (100mW) so require amplifier and are split IF and split RF. I have SMA SPDT relays on the RF output for T/R. The amps will be inserted before the relays.

The 222 is configured by a jumper to split the IF and uses the default common RF directly out to the antenna. It is about 8-9W. I also have the 144 boards, it is identical but puts out around 15W.

For 1296 RF power I will use a 12V 2W amp module (eta early January) to drive and external SG-Labs 25W PA/LNA combo unit that runs on 12VDC. The 2W module mounts inside on the end plates next to the 222 transverter.

For 903 I use a 50W enclosed RF pallet (eta early January). It is 28V. I have a 120W 12-28VDC DC-DC converter on order for that, it will mount on the outside of the back panel.

I had a spare Downeast Microwave 2005 vintage TC Kit. It is a smallish PCB kit used in their microwave transverters. It features an IF T/R relay, RX and TX level adjust, up to 10W attenuation on TX, 28V charge boost for 28V T/R relays, and a DPDT aux relay that switches 13.8V and 9V. I left off the 28V boost relay since I have 12V relays. I also left off the 9V regulator and jumper which leaves the 2nd Form C contacts (was 9V) open for any use you may have on T/R. I am not using it.

A SP4T coax switch mounted on the back is used to route the radio RF to dedicated antennas for HF/6M, 144, and 432 bands. For Xvtr bands (222, 903, 1296) the switch routes the RF (now becomes the IF) internally to the TC board. The only time Radio RF goes inside the XvtrBox, and any internal relays operate, is when one of the 3 Xvtr bands are active.

The TC board splits the IF into Rx and Tx paths and attenuates/amplifiers as needed. Each RX and TX path has its own SP6T solid state RF switch to break out the IF between the 3 Xvtr boards. I added a MAR-3 MMIC to the RX out path to get S9 on the 705 when a -70dBm signal was fed to each band.

12V power to each Xvtr board and the 903 amp DC-DC converter is switched by a 4-relay module. Each relay is rated for 10A. The 50W 903 amp should draw 8-9A at 12V so I gave it a dedicated relay. The 2W 1296 PA will share the 1296 Xvtr 12V power. Neither amp has a bias supply so turning power off to them when not active is desired to keep hea and power draw to minimum.

PTT for the Xvtr boards, the IF switch position, the 903 and 1296 T/R relays, the TX board T/T relay and the SP4T switch all are controlled by the M5StampC3U. Since it has limited ports I use 2 MCP23017 i2c connected port expanders. I use 1 ULN2803A module on each of the MCp23017 modules for buffered outputs.

The PTT and 3 band decoder input wires go directly to the CPU IO pins for now. They need to be buffered, on my To:Do list.

I will probably expand the band decoder wires to or 5 total. I have 8 wires on the round connector. This would permit communicating every HF and VHF/UHF band. Right now I only care about 50, 144, 222, 432, 903 and 1296. Any HF band and 6M band defaults to "HF/6M" and routes out the SP4T switch port 1. You could use a SP5T or SP6T switch and break out 6M from the HF bands. PTT is broke out for each band as well. HF/50, 144, 222, 432, 903, and 1296 with standard phono jacks on the back panel.

On one side of the box I have the 3 transverters. The other side is a DEMI (or Q5 Signal) 4 port 10Mhz reference distribution board mounted in a small enclosure with a 10Mhz OCXO attached with VHB tape. Stacked on the OCXO are 2 pieces of proto board. 1 small piece is the switched 12V high current terminals and an INA226 voltage and current sensor. A larger proto board is the control board with 12V (SP4T, 903 and 1296 relay power), 3.3V, and 5V power (light loads) and the CPU, 2x MCP23017 port expanders with 2 ULN2803A buffer modules attached to them (1 each), a 5V regulator for CPU power and connectors for i2c display, the INA226

The 903 and 1296 RF T/R relays are fail-safe 12V SMA switches with single TTL logic control. The SP4T is also 12V and TTL controlled, though not fail-safe. When the Xvtr box is powered off, the 705 antenna will be disconnected. Nothing in the Xvtr box will be harmed, possibly the 705 may be damaged due to transmitting into an open circuit at max power for too long.

One idea I might do is use 12V voltage from the radio side controller to activate a relay in in series with the 12V front panel power switch. This way the box will power on and off automatically as long as the front panel switch is also on.