Impedance matching is an everyday problem for RF circuit designers. The L-Network is one of the easiest lossless ways of matching a low source impedance to a higher load impedance. This article shows how they work and how to design them. Matching a transistor amplifier’s low output impedance with the higher impedance of an antenna … [Read more…]
The ADF4360 series from Analog Devices is a a family of integer-N-synthesizer chips with on-board VCOs. Since the chips cover all amateur radio bands between 4m – 13 cm and are rather inexpensive, they are predestined to be used in homebrew amateur radio equipment. Not too long ago I reviewed ADI’s wideband PLL synthesizer ADF4351 … [Read more…]
The CC2531 is the second generation ZigBee/IEEE 802.15.4 compliant System-onChip with an optimized 8051 MCU core and radio for the 2.4 GHz unlicensed ISM/SRD band from Texas Instruments. But what good is it, really? To make the evaluation of the CC2531 a bit easier, TI put together the CC2531EMK. The CC2531EMK is a an evaluation … [Read more…]
Passive probes for the GHz range are costly and it’s usually not too economical to invest into one if you’re just a hobbyist. But regular, cheap probes will not work on signals in the GHz range. So is there a homebrew solution? Yes, there is, check it out! Every passive probe and every piece of … [Read more…]
Frequency generation is usually a very critical part in every RF design. The higher the target frequency, the higher complexity. Usually. With the ADF4351, Analog Devices offers an effort-saving component level solution for frequencies up to 4.4 GHz. The ADF4351 from Analog Devices (ADI) is a modern wideband PLL synthesizer with integrated low phase noise … [Read more…]
PSK31 is gaining more popularity among amateur radio enthusiasts. It’s extremely small bandwidth and excellent performance in weak signal conditions make this mode perfect for low power HF stations. PSK31 is a digital transmission mode with just about 31 Hz bandwidth. The signal conveys data at a data rate of 31.25 baud and is extremely … [Read more…]
The current issue of ARRL’s magazine QST features an article about PSK31 on 2m in FM. This article is going to show why this is an unnecessary waste of bandwidth and therefore nonsense. PSK31 is a digital transmission mode designed for minimum bandwidth and great performance even in weak signal conditions. Sending a PSK31 signal … [Read more…]
Clock recovery in Spread Spectrum applications and BPSK modulated signals can be somewhat tricky. There are no commercial solutions available solely for this task either. Or are there? This article shows a great off-label use of the Abracon ABFT. Clock recovery in a Direct Sequence Spread Spectrum (DSSS) receiver can be quite a challenge. Because … [Read more…]