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TSP #214 - What is a good RF cable? Theory & Experiments with Junkosha Phase/Amplitude Stable Cables

18.1K views September 18, 2022 11:15 PM

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In this episode Shahriar discusses the engineering challenges associated with making good RF & mm-Wave cables. The significance of the connector, cable frequency range, loss, phase/amplitude stability & temperate are all examined from a theoretical & practical aspects.

The stability of Junkosha cables are demonstrated up to 50GHz through S11 & phase measurements. The Junkosha MWX7 series cables offer optimized PTFE dielectrics as well as some of the best phase/amplitude/temperature stable operation:​​​

TSP #213 - Teardown, Repair & Analysis of a Keysight 20GHz MXG Analog RF Signal Generator (Part 2)

10.8K views September 4, 2022 3:52 PM

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In this episode Shahriar returns to the MXG repair! The awesome engineers at Keysight have provided a replacement for the suspect part! The exchange is not easy due to the component's strict thermal requirements. A method to provide a good thermal & electrical contact is presented. The repaired instrument is verified for functionality.
A close look at the complex micro-module is also presented under the microscope with analysis of each sub-component ceramic part & III/V MMIC.​​​

TSP #212 - Siglent SNA5000A 8.5GHz 4-Port Vector Network Analyzer Review, Teardown & Experiments (I)

11.8K views August 28, 2022 10:31 PM

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In this episode (Part 1) Shahriar presents a detailed review of the Siglent SNA5000A series vector network analyzer. The Siglent SNA VNA has a frequency range of 9 kHz to 8.5 GHz, with 2- and 4-port models available. Designed to give you instant insight into scattering, differential, and time-domain measurements. Siglent VNAs enables measurements of the Q-factor, bandwidth, and insertion loss filters and feature impedance conversion, movement of measurement plane, limit testing, ripple test, fixture simulation, and adapter removal/insertion adjustments. There are five sweep types: Linear-Frequency, Log-Frequency, Power-Sweep, CW-Time, and Segment-Sweep mode. SNA5000A VNAs also support scattering-parameter correction of SOLT, SOLR, TRL, Response, and Enhanced Response for increased flexibility in R&D and manufacturing applications:

This (Part 1) of the review is organized as follows:

00:00 - Introductions.
01:02 - Instrument overview, design, user & RF interfaces.
04:27 - Detailed teardown, architecture, RF design & VNA board reverse engineering.
18-21 - Calibration, E-Cal compatibility, built-in procedures, initial GUI overview.
22:12 - High rejection filter characterization, pushing the dynamic range limit, port-to-port isolation, IF BW, filtering & averaging.
28:28 - Characterizing active devices, measurement topology, differential & common-mode responses, power control, waveform comparison, phase & magnitude response.
39:07 - Sweep types, power sweep, compression measurements, non-linear DUT characteristics, impedance & Smith charts.
44:12 - VNA as RF synthesizer, CW generation, tone purity & power accuracy.
45:26 - Concluding remarks.​​​

TSP #211 - Teardown, Repair & Analysis of a Keysight 20GHz MXG Analog RF Signal Generator (Part 1)

15K views August 20, 2022 3:59 PM

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In this episode Shahriar investigates a failed Keysight MXG RF generator. The instrument shows UNLEVEL for frequencies above 10GHz. The measurements confirm that the instrument fails to achieve the desired output power. The block diagram of the synthesizer is examined in details and potential failure points are identified.
The teardown of the instrument and various components are also presented. A detailed description of the multiplier unit is shown along with the PCB X-Ray. Measurements confirm the failure of an Agilent-branded component (doubler + amplifier module). The repair has to be paused for now until a replacement component is sourced.​​​

TNP #20 - Teardown, Repair & Experiments with Stanford Research Systems SR830 DSP Lock-in Amplifier

13.9K views August 4, 2022 10:09 PM

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In this episode Shahriar takes a look at a SRS SR830 DSP Lock-in amplifier. The repair of the instrument is fairly simple and provides a quick look at the internal construction of the unit.
The instrument is then used for characterizing nonlinearities of a pair of matched diodes in large-signal operation. A Tektronix 4-Series is also used alongside the SR830 in DDC mode to show the harmonic behavior of the DUT in frequency domain. The SR830 is able to discern extremely small variation in temperature between the diodes and the resultant 2nd order harmonic changes in both amplitude & phase.​​​

TSP #210 - Going off-grid! BigBattery RHINO 48V, 14kWh LiFePO4 Battery Review & Experiments

14.9K views July 31, 2022 12:49 PM

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In this episode Shahriar takes The Signal Path Lab off-grid! The BigBattery RHINO 48V LiFePO4, 276Ah, 14kWh is combined with a Growatt SPF 6000T inverter to provide 240V split-phase power to the house.

You can see the kit used in this video using this untracked, direct link to

The review of the battery is organized as follows:

00:00 – Introductions & considerations.
01:33 – BigBattery offerings, battery configurations, battery chemistry, specifications, warranty, etc.
05:51 – Battery construction quality, connector & fuse design, mobile cart, attachment options.
07:50 – Provided battery cable with Anderson connector, ratings, quality.
08:14 – Built-in LCD screen, GUI & BMS access from the battery, phone app & BMS configuration.
11:36 – Battery protection, BMS under small loads, BMS disconnect behavior, power reporting.
16:08 – Off-grid setup, Growatt inverter wiring & interfaces, transfer switch & AC access.
18:28 – Benefits of a boiler setup for battery backup operation.
18:59 – Ensuring correct earth-ground & neutral wiring of the backup system.
19:52 – Going off-grid! House power measurements, battery discharge behavior.
21:27 – Battery charging behavior, balancing, charging battery to maximum level, charge waveform.
22:44 – Concluding remarks.​​​

TSP #209 - Teardown, Repair & Analysis of an Agilent 83752A 10MHz - 20GHz RF Synthesized Sweeper

16.7K views July 22, 2022 1:07 PM

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In this episode Shahriar takes a close look at an HP 83752A which shows no signs of life. The power supply of the instrument does not produce standby or any other output voltages. The power supply is examined and the startup circuitry is at fault. The problem is traced to a bad startup capacitor for the primary PWM controller. A replacement resolves the issue and the instrument powers on.
The instrument however has other issues. An UNLOCK condition is displayed and further testing shows that the frequency output of the instrument below 2GHz is unstable. The overall block diagram of the unit is presented and the fault is logically traced to a potential problem with the reference 100MHz of the hetrodyne block. An X-Ray of the board allows us to reverse engineer the final output amplifier and a faulty NPN is located. A replacement resolves the UNLOCK condition and the instrument is fully functional.​​​

TNP #19 - Teardown & Repair of a Keysight U1253B 50,000 Count True RMS OLED Handheld Multimeter

14K views July 11, 2022 10:19 PM

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In this episode Shahriar takes a look a Keysight U1253B multimeter with a notorious problem of failed OLED screens. The OLED would degrade and stop working on some of these units. Since the original OLED model is almost impossible to find, replacement OLED would require a protocol translation layer. The replacement module uses an FPGA to achieve this.

The teardown of the unit as well as the repaired units are shown. The performance of the instrument is verified using a universal source and an 8.5-digit multimeter.​​​

TNP #18 - Repair & Analysis of a W-Band (75-110GHz) WR-10 12dBm Power Amplifier Module

14.2K views June 12, 2022 7:14 PM

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In this episode Shahriar takes a look at a non-functional W-Band (75-110GHz) power amplifier module with WR-10 waveguide ports. A quick inspection reveals a broken DC connector which can be easily repaired. Since a W-Band VNA or source is not available, the amplifier's excess noise is instead measured using an external mixer and a Keysight MXA-B. The noise power spectral density shows the the amplifier is likely functional with the expected noise and gain.​​​