Category Archives: HF home made transceiver

LOW PASS FILTER BLOCK 3.5-30MHz

This board consist of the following modules:

5 sub PCB with low pass filters chebyshev type for all HF bands. There is place where to be nested one optional LPF subboard (for 160m)

High voltage (210V) scheme (voltage tripler)

Antenna RX/TX switching

SWR directional coupler and measurement of Vfwd/Vref

Optional LPF (160m) connector

This module ensures clear harmonic output of the linear amplifier, also fits the components for antenna RX/TX switching. Following the “click-less” concept, there are no mechanical relays in the circuit. After long searching for suitable power switching component I found VISHAY high voltage rectifier diode S07J (S07M) that met all the requirements for reverse voltage capacity, reverse recovery time, forward current and reverse voltage. So S07J were used in the project to ensure good switching of TX power to the antenna via proper LPF and also reliable isolation between each other low pass filters not selected for this band portion.

High voltage generated from input signal polarizes unused switching diodes in reverse direction ceasing the chance for signal leak. Same votage is used in RX/TX switch for completely disconnecting receiver front end on transmit.

PCB layout
Component side (bottom) values:

Component side (bottom) reference names

Top – connector side:

Picture of the ready board with filter subboards on it:

 

 

Block interconnection diagram

My homebrew HF transceiver RGO ONE consists of the following printed circuit boards:

  1. Front Panel assembly – plastic front panel, control knobs, FSTN display and keyboards, control board
  2. Mother board – fits all connectors on the rear panel, power supply, I/O controller (second CPU) intended to be a chassis for all RF boards and options, as long as “cable harness” and board interconnections.
  3. IF/AF Board – IF and audio circuitry, IF AGC 134kHz. Second narrow band crystal filter (option). AF filter (option)
  4. RF mixer board – RX/TX switching, receiver front end, first RX mixer, TX mixer, first roofing crystal filter, ALC circuit. Noise blanker (option). SSB monitor amplifier.
  5. Band pass filters – Front end filters 160-10m (160m option)
  6. SSB GEN board – forms both CW and SSB signals, microphone amplifier, compressor unit (option, Line in/Mic in circuit.
  7. LO board – local oscillators, side tone and beep tone oscillator. First oscillator and BFO oscillator. SSB monitor .
  8. Compressor unit (option)
  9. Automatic antenna tuner (option).
  10. Transverter/RX antenna board (option).
  11. Power amplifier assembly – consist of two boards PA55W and LPF nested directly onto the rear panel

    Block diagram and coax interconnections

Crystal filter 9MHz 2.7kHz

One of the most important modules in the home made HF transceiver project is the crystal filter. It is made of individual quartz crystals with matched parameters – Fser. (+/- 15Hz), Lm and Q factor > 100 000.  A large quantity of 9MHz oscillator crystals were purchased to extract only few to fit those requirements. Three type of quartz filters are used in this project – main (roofing) filter, narrow filter for SSB or CW modes and noise filter. All the filters are internally impedance matched to 50 ohm input/output circuitry and individually aligned.

img_3916  img_3917

Here is information about first – wide 2.7kHz SSB filter:

Filter type                          Chebyshev 8 pole

Center frequency             9MHz

Bandwith at -6db             2.7kHz

shape factor -6/-60db    1.75

IN/OUT impedance        50ohm

Band pass ripple              <1db

Stop band attenuation    >80db

VNA plot

9mhz-2-7khz

Circuit diagram. Chebyshev 8 pole ladder type crystal filter

xtalfil-9mhz-2-7khz

Custom multicolor backlit FSTN LCD for HF QRP transceiver project

In order to fulfill all the requirements to show different modes and parameters we decided to make our own liquid crystal display.

lcd-v006 lcd-v006-pins

It is designed and built on the well proved – FSTN technology with high visibility and contrast.

Technical data:
LCD type                   FSTN
Mode                          positive
Poarizer type            transflective
View direction         12h
Connect type            pin
Glass thickness        1.1mm
Working Voltage     3/5V
Multiplex level        32/5
Operating temp      0 – 50C
Storage temp
Content                   Digits/Symbols
Measures                114.3 x 27.94mm
num of symbols    149
backlight type       LED multicolor

It was firstly designed with 5 multiplex lines but soon after receiving first samples it turned out that this is not suitable as there is no driver chips on the market with 5 multiplex lines so we redesign the LCD with 40/4 so the most common Phillips chip can drive it.

lcd-gd04611face-plate-new-cpu-front-pcb

My new HF home made QRP transceiver – first sight

Here it is – our home brew transceiver is alive.

img_3547  argo-image

Die plastic mold is not ready yet so we ordered CNC machined aluminum panel.

All the plastic knobs are 3D printed (waiting for the plastic mold)

FSTN display is super nice -bright and sharp in all viewing angles. We approved the 5 samples sent by the manufacturer and now wating for the first production batch.

Stay connected for future news!

73, LZ2JR/AC9IJ

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