As you may already know I've been getting a 23cm station together over the last few years. Using a FT817 as the IF does seem to be the weapon of choice however they aren't the most stable frequency wise. The first mod is removing the crystal oscillator and replacing it with a TCXO.
The standard oscillator.
The after market (Chinese) TCXO. The advertised stability is 0.1 PPM after a six hour warm up. Not to bad however I don't think I have ever had a radio on for six hours straight. With this installed our best guess is I'm 400Hz off frequency at 1296.215Mhz. Workable but I can do better. Keeping in mind The SG-Labs transverter is using a TCXO and not locked to 10Mhz reference as yet.
Time to open up the FT817 and see what I can do with out letting out magic smoke.
Out with the Chinese TCXO-UNIT and in with a Leo Bodnar GPSDO.
Programmable from 400Hz to 810Mhz (22.62500Mhz required for the FT817). Also 4 power level settings. Wasn't able to find out the required drive levels. Time to fire up the DSO and measure the current TCXO. A reading of 5V peak to peak and 1.9V RMS. The GSPDO 3.3V peak to peak 1.8V RMS. These reading are from memory so might not be 100% accurate however the Leo Bodnar unit on low power is lower than the TCXO it has been running on for years so no smoke (fingers crossed). Quick test to see if it's enough for the FT817 to get PLL lock.
Success Radio gets lock and all is good. Now to mount the unit in the battery compartment with a 5V regulator. There is 5V at pins next to where I connected the external reference. Not sure if it could supply the required power for the GPSDO unit so I decided to run its own reg.
I don't have a bulkhead SMA connector to run the GPS aerial out the back of the radio, that's the black cable running out of the missing battery cover. The regulator is getting it's 13.8V from inside the radio case. Although I can't switch from internal to external reference it is reversible.
Next was an on air test. A quick call to Frank VK4FLR and seems I'm now around 100 Hz different to Franks setup. My transverter isn't gps locked YET. Frank has his SG-Labs transverter GPS locked and running a FT991A as an IF so I'm guessing a bit more accurate frequency wise than the old FT817 in standard form. The more accurate test will be my next Q65 session.
The components I used for the Data logger I have fitted in the WinLink shed.
The brain behind the logger. The ESP8266 is a small microcontroller with built WiFi. It can be programmed using Arduino IDE. It has 15 GPIO pins programmable HSPI UART and a 10Bit ADC.
Sparkfun Si7021 Temperature humidity. Uses a HSPI interface.
OLED Display 0.96" 128x64 I2C SSD1306. Not really needed but displays the current data. Connected via HSPI interface also.
The DC-DC converter supplies 5v to the micro USB connector on the ESP8266. It has a in built regulator and runs off 3.3v
The 10 bit ADC is only good for 1v input. The voltage divider Z1 8900 ohm Z2 480 ohm resisters were chosen to drop the 0v to 20v down to 0v to 1v. Different modes of the solar charger can reach 15 odd volts so I chose 20V to give some head room.
