RF

Boxfish

Introduction If you need help with: Repair of electronics Design of electronic systems Software Please send me …

Tuesday, February 6, 2024 | 1 minute Read

HP 8640B Part 2: Mains input and rectifier board replacement

Introduction 6 years ago I acquired an HP 8640B that needed work (see HP 8640B Part 1: initial state). Over the last few years, I managed to clean up the unit cosmetically, but not dive in to it any deeper. Until now. I recently found some time to work on it again and started looking at the power rails. I knew that (at least) the -5.2V rail had intermittent issues, and had noticed the caps on the AC input needed to be replaced as well.

Tuesday, February 6, 2024 | 8 minutes Read

DIY active / high impedance probe design

The “problem” I’ve been wanting to have an high-impedance (Hi-Z) probe for some time now. Up until now I’ve been searching for something like an HP 85024a which comes up on the second hand market from time to time. It would be overkill for my needs, but still nice… :) Recently I came across an old Elektor/Elektuur article from April 2004 titled “Poor man’s 1GHz active probe” by David Jewsbury. Some more research turned up the bachelor thesis of Thomas Hirschbuechler titled “Design of a low-cost 1GHz active probe”.

Wednesday, January 26, 2022 | 4 minutes Read

Hytera PD365 programming

Introduction I recently acquired a second-hand Hytera PD365 DMR radio. Hours of trying to program the radio learned me that this is a bit of an odd one out in the Hytera range of radios. I spent *a lot* of time trying to connect it to my computer to read out the memory and program it. I found a lot of information spread out on the internet, but lots of it is not applicable to the PD365. You’ll find remarks such as “There’s a different driver for the PD365.” but which one to use isn’t marked. There might be a page dedicated to the PD365, but I haven’t found it.

Monday, September 10, 2018 | 4 minutes Read

HP 8640B Part 1: initial state

Introduction I recently acquired a HP 8640B signal generator. A quick summary of the specs shows why this is an interesting piece of equipment: 500kHz to 512 MHz (option 2 adds a doubler, extending the range to 1.024 GHz) Available power range is -145dBm to +19 dBm, within +0.5dB across the full frequency range Extremely low phase noise (less then -130 dBc at 450 MHz, 20kHz from the carrier) Fine tuning (when in locked mode): >+/-20ppm Integrated counter, switchable between the internal generator and an external input FM and AM modulation Beautifully engineered (but that’s just an opinion) The retail price in the mid seventies was around 12.000 USD (which in 2017 would be about 90.000 USD).

Saturday, June 10, 2017 | 3 minutes Read

HP 8711(A): modifications, tweaks, refurbishing

Introduction I recently acquired a fairly well preserved HP 8711A network analyser. As sold, this is an economy model, offering only scalar measurements, although vector information can be acquired through the HP-IB bus. What makes this unit interesting, is that the hardware is the same as the never released 8712A, which has vector capabilities. Some changes in the bootrom allow the user to “convert” the unit, making it behave like a full fledged VNA.

Monday, November 14, 2016 | 4 minutes Read