mcHF SDR
Informations about mcHF Transceiver you can find on M0NKA pages (also you can ordered) ; DF8OE github ; Yahoo group ; DARC group
My mcHF Transceiver is PCB 0.4 (RS-918 SSB) version with many mods:
MCHF TX Carrier suppression improvements (4. 4. 2020) . Exchanged T4, U19, R101, R86, R87, C84-C87, R68, R67 to capacitor, remove R70.
On RF PCB added switchable 16dB attenuator before RX preamp Q1 and after BPF (on removed R4), 2 pole changeover switch for attenuator bypass, Pi configuration, Parallel In and Out resistor 68R, Series resistor 150R
On RF PCB added RX / TX relay on TX PA output / RX attenuator input (5V coil, two switch over contacts, anti-parallel diode), remove D3, D4 and RFC, R, C around (this is standard mod on RS-918) (must be for more than 5W out)
On UI PCB changed U7 from 24LC01 to 24LC512 (must be for DF8OE FW, otherwise you can after few months broken Flash in CPU)
On RF PCB changed U11 74LCX74M to Potato chip and remove U9, U12, U13, R19
On RF PCB added TX preamp U20 HMC482ST89E (as on v0.6) and L, C, R around, add C107a, C108a (as on v0.6), remove U20, U21, U22, U23 and some R and C around
On RF PCB changed RFC5 and RFC 6 from 47uH SMD to 150uH 9 windings on "transformer" core
On RF PCB as power finals paired RD15HVF1, one 0,25A and second 0,26A at the same gate voltage.
On RF PCB totally rebuild TX power amplifier, changed T7, T5, add another bias for Q3, Q4, remove T6, change to self-made RFC8, add C96, R83 (as on v0.6)
On UI PCB added TCXO 16MHz, add R44 0R, removed R43 for Y1 Quartz disconnect
On UI PCB changed power for microphone R8 from U1-17 to A_3V
On UI PCB changed power for U3 and U3a from UI_3V3 to A_3V
On UI PCB changed RFC1 from 4u7H to 33uH
On UI PCB changed RFC2 from 4u7H to 33uH
On UI PCB changed RFC3 from 4u7H to 33uH
On UI PCB added R1a 100R (as on v0.6) for protection for PTT from J3 Mic connector (together with 3V3 zener diode)
On UI PCB added C24b 100nF (as on v0.6) in parallel with R14
On UI PCB added C1a, C1b, C1c 3x 1nF close to CPU (as on v0.6)
On UI PCB added parallel to C47a 100uF two additional 47uF tantals
On RF PCB added R15c and R15d 2x 100R resistors for protection P_DAH (also for ACC jack J3), P_DIT from J2 CW Paddles jack
On RF PCB added D2a and D2b zener diodes 3V3 for protection PTT from MIC, P_DIT, P_DAH from J2 CW Paddles jack (also for ACC jack J3)
On RF PCB added 1nF on P1-9 (PWR_RET)
On RF PCB added 1nF on P1-10 (PWR_FWD)
On RF PCB added C67a 10uF
On RF PCB changed values of R35 from 100R to 22R
On RF PCB changed C71 and C73 100nF to 0R resistors
On RF PCB changed D5 and D6 from PMEG6010CEH to BAS85
On RF PCB changed C82 and C83 100nF to 2u2F
On RF PCB changed R59 and R60 1kR to 0R
On RF PCB changed R59 and R60 0R to 47uH choke
On RF PCB changed R55 and R56 0R to 47uH choke
On RF PCB removed C38, C39
On RF PCB added 100nF from the center pad of T1 to GND
On RF PCB added additional wire from U15 pin 8 GND to C65 GND pad
Schematics with the mods come in next weeks :)
Planned mods:
Change LCD from Parallel to SPI mode (LCD must be removed from PCB)
Add RTC mod with quartz and battery (must be done after LCD change to SPI mode), quartz ordered
Photos with TX Carrier suppression improvements mods (4. 4. 2020)
Measurements of LPF (measured between BNC and removed R26):
Measurements of BPF (measured between removed R4 and removed R1):
Measurements of LPF + BPF (measured between BNC and removed R1):
Measurements of power out and consumption current at defined supply voltage (modded PA with TX preamp, fw 25.06.2017):
PA Bias: 43 = 500mA
Photos of MCHF (RS-918 SSB) from Quanzhou Risen Electronics Co.,Ltd: Google Photos album
Please, don't order mcHF (RS-918 SSB) from this company, support author of mcHF M0NKA. (Second ordered mcHF for OM1VL was from M0NKA).
mcHF from China is cheaper, but you obtain old PCB v0.4 with some mods (sales as v0.5, but it is not v0.5), without TCXO, without bigger EEPROM for new firmwares on DF8OE Github, with not working speaker jack (don't disconnect internal speaker) and without support if something is broken, answer is "please update firmware in attachment" (renamed file from DF8OE Github). For upgrade to v0.6 you need hours and hours of time, skills with SMDs and also cash for parts like TCXO, EEPROM, MMIC headphone jack and many passive components, so in final is price higher than from M0NKA and yours mcHF is still worse because new routing of signals on v0.6 and higher interferences on v0.4! Also you get >10W only on 40m and 20m with >14V DC (for more power you need many mods).
Edited 4.4.2020