mcHF on-band LO supression mod

Photo of the mod in the R928+ transceiver (the first version of the board)

The mod is designed to treat the worst ailment of mcHF - to provide acceptable carrier suppression for transmission on any band. Requires the appropriate firmware (more on that later), works in all variations of mcHF, including replicas from SP3OSJ, a hybrid with a UI board from the OVI40 project of the UHSDR group, any Chinese clones and replicas, except BS188 (there are still problems with taming a non-standard display in the firmware, and The authors refuse to provide the necessary information, in violation of the requirements of open licenses).
The idea of ​​the mod has been in the air for a long time, but the specific implementation was taken from SP3OSJ in his Sparrow project. There, the TX mixer is balanced with trimming resistors to provide good carrier rejection on one selected band. The mod uses controlled DACs to achieve this, which allows for acceptable carrier rejection on every band, including a select frequency in the wild, for example in the CB 27 MHz band. I was not too lazy to conduct experiments to evaluate the dependence of the carrier suppression on the level of the useful signal - SSB can work safely, with careful adjustment at the "favorite" power level (5 W or FULL), the carrier level does not exceed -50 dB from the signal peak. The CW signal will also not "croak" on the edges envelopes of the bursts at the carrier frequency. Accordingly, you can safely connect a power amplifier up to 200-250 watts to the transceiver.
The mod's board is one-sided, without through holes. There are two options. The first one is intended for self-production using the LUT technology (for SMD resistors of standard size 1206), the second, more compact one - for ordering in a specialized company (standard size 0806), gerberas are in the project archive - Download here. The board is fixed with a neutral silicone sealant over the LFO driver, the wires leading to the TX mixer inputs must be kept to a minimum. So is the wire leading to the ground. Two contacts of the I2C bus must be connected through the free contacts of the board-to-board connector to the pins of the memory chip on the UI board according to the mod's schematic diagram.
With the kind permission of R5CT (ex UA3ATT), I also added to the archive his version of the mod's board. It is designed for manufacturing using the LUT technology, for 0603 resistors and tantalum capacitors of size A, dimensions 17x17 mm. Photo of the board in the transceiver:
About firmware - the TRX Amber project page has a link to its project archive. There is the latest mod-firmware for a wide range of mcHF-compatible transceivers, a user manual that is 90% relevant for your transceivers (for the Amber transceiver, just a little added, it's easy to figure it out). By the way, since version 2.12.0m4, an optional advanced adjustment mode for suppressing the mirror channel during transmission has been introduced. If you activate it, the suppression is adjusted on each range (in this case, the linear-polyline approximation of the adjustment parameters between the adjustment frequencies continues to work). As a result, it is possible to achieve suppression of the mirror channel as well, certainly not worse than 50 dB. The alignment procedure is detailed in the TRX Amber user manual.
This mod was included in the basic schematic diagram of the TRX Amber project, as one of my original modifications of the M0NKA mcHF project, and fit perfectly into the general concept of "let's do better for 3 cents". The DF8OE criticized the TX mixer on-range balancing idea very vigorously, seeing only a radical way to solve the problem of carrier suppression - direct digitization. Well, DDC / DUC will be a feature of the next project, TRX Axis.
If you have any questions, write, the address is listed below. 73!

I suggest a bare board and mod assembly. Prices are indicated in euros, when converted into other currencies, we round down. Prices do not include shipping costs. Orders are accepted by email.
Mod board
Price - 2.5

Assembled mod
Price - 23