Category: DDS VFO

“Gimme Five” reloaded – A compact 5 band QRP SSB transceiver in SMD technology: VFO, LO, MCU etc.

As mentioned in the introductory article to this radio the digital components in this transceiver are pre-manufactured modules that have only been put together in a more or less sensible way. ;-). These modules are: AD9850 as variable frequency oscillator (VFO), China made no-name board, Si5351 as local oscillator (LO) produced by “Adafruit”, Arduino Pro…

Read the full article

“Gimme Five” reloaded – A compact 5 band QRP SSB transceiver in SMD technology

Follow-up articles published so far: Digital and analog main units: VFO, Local oscillator, Display, TX-Gain control Receiver unit Transmitter unit Abstract A compact SSB transmitter/receiver will be presented. This unit covers 5 bands within the amateur radio spectrum (3.5, 7, 14, 21 and 28 MHz). Receiver is a single conversion unit with an interfrequency of…

Read the full article

Constructing a high performance transceiver for voice communication on 14MHz

  Abstract A general and good practice in engineering is a steady process of improvement. This  article describes the construction of a high performance transmitter/receiver for SSB (voice) communication covering the 14MHz (20 meters) high frequency amateur radio band. Various modules that have proven high performance, liability and ruggedness in recent constructions will be combined…

Read the full article

DDS and spurious signals – The role of the post-DDS-amplifier (Part I)

Abstract When building a direct-digital-synthesis (DDS)  frequency generator, the engineer has to take into account one inherit shortcoming of this state-of-the-art technology: Spurious signals that are an unwanted product of generating a radio frequency signal with a synthesizer. These signals occur in a wide range of frequencies and are a limiting factor for receiver performance…

Read the full article

SSB Transceiver, 7MHz, 50 Watts, with Dual-DDS-System

In this paper we will discuss a single sideband amateur radio transmitter/receiver for the 40 meter band that has been designed to ensure  good performance characteristics with reasonable number of parts (no “overkill” in component use), particularly concerning the receiver. Circuit simplicity and over-average performance were to be combined. The background: Some years ago I…

Read the full article