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Multiband Bandpass filters 1..30 MHz

August 13, 2019

Four bandpass filters are used in the RX and TX path to cover all HF bands. Filters are implemented using standard values capacitors and inductors.


This is one of the most simple, compact and easy to build filters, not inferior to the filters of other designs.

Recommends for novice or ham radio who do not want to make windings.


Filter switching is achieved via CMOS switches SN74CBT3253, two of them – one at the input and one at the output to prevent crosstalk. Two parallel data lines are used for control, plus the RX/TX lines that selects Receive or Transmit mode. Truth table is included in the schematics. Input DC of bandpass filter is 8-15Volts, but the Recommended input voltage for IC control is 3-5Volts.


It is very convenient to use DDS synthesizer for switching bands, however switching could be easily realized by standard rotate switcher.


Connectors on board

  • DC – power supply of filter is 8-15V

· RX ANT – RX input signal from antenna

· RX OUT – output from bandpass of rx path -> going to mainboard of receiver/transceiver

· TX IN – input from motherboard of transceiver or transmitter.

  • TX ANT – output from bandpass -> usually going to power amplifier or antenna


This design has standard values of inductors and capacitors and If elements soldered accurately and correctly it works from first power on and no need the adjustment. 


June 05, 2018

Video of assembled original board: https://www.youtube.com/watch?v=LtlJt0odZKI - click here to open link.



   Long-term, for several years, the operation of the transceiver "Desna" showed its high parameters, reliability and, most importantly, ease of installation. A minimum of scarce items that can be found on almost any radio market, provides an opportunity to repeat the design by many novice radio Amateurs. This design has not any unique solutions, rather it is a constructor of most popular well-known tranceivers. The main requirements when choosing units and blocks for the transceiver are repeatability, simplicity while maintaining the maximum achievable characteristics, the use of available today element bases. Many decisions of course can be subjected to criticism – the creative process is endless, but this design has a complete version of the transceiver, and to engage in alterations and improvements – it is a personal matter of every radio Amateur. By its parameters, the transceiver " Desna "is not inferior to such well - known to all radio transceivers. The apparatus may be a base when creating a VHF transceivers.

   Initially, the transceiver "Desna" was conceived as a simple design for SSB operation, as the main type of radiation and for repetition by novice radio Amateurs at the station of Young Technology (in the form of a radio constructor). But gradually the basic model (ROSA transceiver) was brought to the finished design of the transceiver designed for Amateur radio communications in the short-wave range of 1.8...29 MHz. Type of work - phone (SSB) and Telegraph (CW). HF transceiver "Desna" was produced in Bryansk from 1996 to August 1998 from November 1999. Then, with slight modifications have been produced transceiver “DRUZHBA” in Kharkiv.

   The sensitivity of the receiving path at a signal/noise ratio of 10 dB, not worse than 0.5 mV. The bandwidth is determined by the applied quartz filter.  

DDS Low Frequency Signal Generator

June 05, 2018

This DDS Low Frequency Signal Generator designed and developed for easy adjustment of Amateur radio equipment (Receivers/Transceivers).

The device’s core is a microcontroller ATTiny2313 which generating a signal by direct digital synthesis method. Also, there are encoder with “Step” button, one more button “Mode” and high-quality liquid crystal display. Based on the compact size of the product and low consumption– its applicability in everyday life Amateur radio knows no bounds!


Technical parameters

Frequency range: 10Hz – 20kHz.

• Rotary encoder tuning

• Selectable tuning steps: 10Hz or 100Hz


Output RF voltage: 0 – 2.5 V (regulates by variable resistor)


The calculated harmonic distortion:

  • up to 5 kHz – 0.5%,

  • above 5 kHz – no more than 5%


Working modes and output waveforms:

  • Sine wave,

  • Sawtooth wave,

  • Dual tone mode,

  • Square wave

Ham radio RV3YF Forums has a forum.

March 29, 2018

Our website has launched a forum. On the forum you can discuss topics about products: recommendations, assembly details, mods for kits, etc.

KLOPIK v.2.2 mainboard - mistake on PCB found!

December 09, 2017

Dear Customers,

We've found the mistake on PCB v.2.2. 

Capacitor C36, C37, C38 are grounded. They should not be ground. To fix it need to accuratelly cut the ground around the pin C36, C37, C38 and make it similar to C40, C41, C42. Looe the picture with details. 

Our appologies for factory's mistake. 

Best regards,


Simple Double Band Receiver "Lidia-2band" (40m and 80m)

November 01, 2017

Receiver "Lydia-band 2" is a simple direct conversion receiver designed for listening to SSB/CW Amateur radio stations, Amateur radio developed by the Polish Wlodzimierz Salwa (SP5DDJ) at the request of the novice radio Amateurs. 


First and foremost, this project is intended for beginning hams, not having much experience in the design of the equipment. And for radio Amateurs who want a weekend to relax and do radio.

 The receiver operates in two frequency bands 3495 kHz - 3805 kHz and 6995 kHz - 7105 kHz. The main element is a MC3361, which is used in FM receivers with double frequency conversion.

In the receiver used: internal oscillator circuits, mixer and active filter. Bandpass filters at the receiver input, in spite of using axial inductors, provides the appropriate bandwidth, sensitivity, and harmonizing with the mixer. Input sensitivity of the receiver is adjusted by a simple antenna attenuator "Level treble" on the variable resistor integrated with a manual gain control. The VFO (Variable Frequency Oscillator) is running in the circuit with the chokes on 80 m and 40 m, varactors and variable resistor configuration. The stability of the VFO enough to listen to the stations. 


In the receiver circuit "Lydia-2 band" is possible for conneting of external VFO or DDS synthesizer.
There is also the possibility to easily connect your digital frequency counter (on-Board there is built-in input unit).

NEW PCB: Simple VFO DDS synthesizer 1..160MHz

October 24, 2017


  • Single band VFO: Any band from 1 – 160MHz

  • Rotary encoder tuning

  • Selectable tuning steps: 1Hz, 50Hz, 1kHz and 10kHz

  • Simultaneous VFO and BFO/CIO oscillator outputs

  • 2x16 alphanumeric LCD

  • LCD display of VFO status: VFO frequencies (to 1Hz), tuning step size

  • S-meter/RF power display: 0-3.3V DC input is displayed as 50 pixel wide bargraph

  • Two outputs: VFO  and BFO (reference oscillator)

  • Atmel ATtiny85 processor using the internal 8MHz clock

  • Low current – Less than 30mA at 3.3V (with LCD backlighting)

  • Start-up frequency, IF offset, +IF, -IF, IF=0, BFO frequency, Calibration of crystal could be programmed via built-in Settings menu.

July 23, 2017

New Frequency Counter for sale. 

The frequency counter is a flexible device with programmable IF offset allow make measurement guaranteed up to 50MHz frequency. Frequency counter could display the actual frequency of with user defined IF offset.  

  • PIC16F628A processor

  • 16x2 character LCD

  • Pre-programmed IF offsets

  • Direct frequency measurement (no IF offsets)

  • Indirect frequency measurement (IF+VFO, VFO-IF, IF-VFO)

  • Accuracy ±10Hz

  • Frequency resolution 10Hz

  • PCB dimensions: 82 x 38 mm

  • Power supply +7..12V, 20mA

  • Input frequency: 100Hz..50MHz

QRP Transceiver "TAURUS"

July 23, 2017

Low cost QRP transceiver "Taurus" this is a amateur transceiver designed by Włodzimierz Salwa SP5DDJ.

Taurus-20 (14MHZ) and Taurus-40 (7MHZ) are available for sale. The transceiver consists of receiver, transmitter and power amplifier units. Each board could be used separetly in other designs. 

Main board of Amateur Trensceiver "ROSA"

July 23, 2017

New PCB of main board of the favorite and popular transceiver "ROSA"

“Rosa” is Amateur HF Transceiver of single frequency conversion. It is designed to work in SSB and CW modes. The transceiver is very popular for beginners in ham radio because of its simplicity of design and a minimum of scarce parts. Long-term usage of the device has shown its high parameters, reliability and ease of adjustment. The transceiver performs the functions of receiver and transmitter, providing performance at the following Amateur HF bands: 1,9; 3,5; 7; 10, 14; 18, 21; 24, 28 MHz. Depending on the permissions of the station can be connected the different types of power amplifiers. In receive mode the transceiver has a sensitivity when the ratio of signal to noise ratio 10dB – not more than 0.5 mV. Bandwidth is determined by the quartz filter. In TX mode the power output in 75 Ohms is 10 or 30 watts. The transceiver may be a base when creating a VHF transceiver. The transceiver is designed according to the block principle.

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