RGO ONE large signal modification tutorial by Chris, G7DDN

Hi all,

there is short tutorial how to make Large signal modification on RGO ONE transceiver by Chris, G7DDN...

1. Remove top cover and disconnect speaker

2. Remove fan assembly - 2 screws on each side of heatsink

3. Remove two screws holding shield to rear panel - accessed through the heatsink

4. Remove 2 sunken screws in the side panels holding the shield in place to the chassis

5. Remove 2 screws through the PCB holding the shield to the PCB

After that follow the procedure which I posted over here:

OK1RP - Ham radio in Renaissance...: RGO ONE large signal modification is available

RGO ONE large signal modification is available

Hi all,

Some users complained of interferences caused by strong local broadcast station on LW/MW. 

Boris, LZ2JR designed 7th order Chebyshev high-pass filter which was connected in line with the RX path. Filter effect though was inadequate and I was forced to look closer at receiver front end especially input point at RX/TX switch. Then realized that LPF diodes are not effectively cut off on RX so large signals can make them act like AM detector causing IMD problems. Adding pulldown resistor 100kohm would be enough for diodes to be reverse biased. (On RX cathodes see +13V). This way diodes and band LPF’s will be fully isolated from receive path and will no longer interact with incoming signals.

Needed parts:
1. SMD resistor 5% case 0805 value 100kohm
2. Firmware update to version 2.20A for front panel and main board processors

Added pulldown resistor is 100kohm SMD case 0805 and is easily placed onto the two vias in LPF board. LPF board is located on back panel PA assembly and can be accessed after removing PA shield and then completely pulling off the PA module.

100kohm pulldown resistor

This modification needs new firmware 2.20A to be uploaded in RGO ONE FP and MB processors. FW 2.20A completely disengage band LPF’s from receive path. Current band LPF is switched on only on TX.

https://lz2jr.com/blog/

Latest fw revision 2.20A for RGO ONE is now available

Hello,

latest firmware revision is available to upload on your RGO ONE transceiver. 

https://lz2jr.com/blog/index.php/new-firmware-2-20a-available/

This version includes some improvements in MB and FP microprocessors clock rate, speed and correct timing.
Setting proper clock rate for MB processor. (Clock frequency away from HAM bands). Main board microprocessor clock can be heard near 20m band (actually image signal) like “crackling wideband noise”. With this version MB clock rate is adjusted little lower so not to disturb 20m reception.
Added MENU 81 – FCAL2 correction coefficient (coarse calibration) for SI570 VCO chip. If your RGO ONE is calibrated without FCAL2 then parameter value of MENU 81 would be zero.
Low pass filters (LPF) in PA module now are switched only on TX and disabled on RX. This is part of a LARGE SIGNAL HANDLING MOD.
Along with added pull down resistor in LPF board, this mod significantly improves RX dynamic range and LW/MW BCI immunity.

FW 2.20A highlights:

1. Improved communication between transceiver and PC at low CAT speeds.
2. Resolved CW sidetone issue (sidetone punctuation) when CAT system is activated.
3. “Crackling”noise issue resolved by slightly reducing of MB microprocessor clock frequency (set at 31.800 MHz)
4. Meter display now predicts/ shows measure mode – SWR, RF, ALC. Default mode is RF on TX.
5. LCD icons for otional modules do not show up if corresponding optional board is not installed.
6. Internal keyer CW speed/ratio corrected
7. UP/DWN/FST buttons on mic now are active.
8. Service menu entry added – menu 81 FCAL2 – SI570 calibration correction coefficient.
9. LPF and dedicated filter on TX is switched only on TX and disabled on RX. This helps to improve large signal handling at receiver front end. (This is part of LARGE SIG HANDLING mod).

FW 2.20A Files