Thank you to Analog Devices!

Thank you to Jacob Gordon from Analog Devices for the enormous donation of RF test equipment to the MIT Radio Society and UHF Repeater Association!

Analog Devices is a cutting-edge designer of analog and RF chips with a long history with the Radio Society–their founder, Ray Stata, was in the club when he was at MIT.

The metrology department at ADI, which oversees keeping all of their test equipment in calibrated and fully-working condition, had a large cache of older instruments in partially-working states or that were too old for the production work that ADI does. However, instead of just trashing the equipment, Jacob reached out to us at the MIT Radio Society. A few of us visited ADI’s headquarters in Wilmington to get a tour and see the test equipment.

As soon as we looked at the stuff, we quickly realized it would completely revolutionize the capabilities of our workshop. Before this donation, the Radio Society had few modern RF analysis and development tools, so we relied on 1970s and 1980s vintage equipment (with the exception of the FieldFox, see previous press release). We used an HP 141T spectrum analyzer (a fully-analog harmonic spectrum analyzer from the ‘70s) for most of our microwave work above 1 GHz and did not have any VNAs other than one 1.3 GHz HP 8752.

The trove of instruments ADI gave us took the workshop’s capability from around 1 GHz to 50 GHz in a single day. Since we frequently work with older equipment, the club is pretty familiar with repairing RF test equipment, so we were able to service many of the instruments. ADI was kind enough to give us multiple of each type of instrument, so we were able to do module-level service and swap parts between them.

One of the major changes this makes to our workshop is the ability to train students on the actual kinds of equipment they might encounter in a job or internship. Having worked at RF test companies before, I was familiar with many of the instruments from ADI and recognized them as the high-end stuff that is typically seen in a commercial microwave development lab. Being able to train students on working with these systems will help them get valuable experience for getting into the RF industry.

Instruments

Vector Network Analyzers

The biggest improvement to our shop’s capabilities undoubtedly came from the commercial-grade benchtop VNAs. Before this donation, we mostly used portable hobbyist VNAs like the NanoVNA, which tend to be inaccurate. ADI donated us four E5071-series benchtop VNAs and 2 20 GHz PNA-L’s, which we quickly repaired and started using. A lot of the more precise measurements we have wanted to make were simply impossible on NanoVNAs. For example, Daniel Sheen (KC1EPN) recently designed ultra-low-loss interdigital microwave bandpass filters to improve the receive performance of our radio telescope on the building 54 roof (see older press releases for the story of the radome). Precisely measuring the <1 dB losses of this filter required a quality, calibrated VNA with coverage of 1420 MHz and above (see below).

We even the FieldFox (see previous press release) to analyze some of the internal components of the PNAs for repair:

Spectrum Analyzers

The ADI donation also massively improved our spectral analysis capabilities, with newer PXAs that go to 50 GHz and can measure phase noise. This capability is already spawning a new project from Daniel Desantis (KC3FKR) to design a modular microwave transverter that will do all of the amateur microwave bands using swappable modules and a shared local oscillator (look out for future news about this project and its use for the radome).

The ability to precisely measure close-in phase noise was completely missing from our shop before and will be extremely useful for developing the PLLs and other clock/time-distribution systems that are at the core of almost all modern radio systems.

RF Signal Generators

ADI also gave us many RF signal generators from the Keysight/Agilent MXG and PSG series, which are known for their level accuracy, good phase noise, and high output power. The donation included many Hewlett-Packard 40 and 50 GHz CW signal sweepers from the 1980s and 1990s in the 836- series, which we were able to get working. The ability to generate low phase-noise reference signals up to 50 GHz lets us work directly on upconverters and other microwave projects that were completely out of reach before.

Additionally, the MXG signal generators have better modulation capabilities and frequency range than what we had before. We have already started using one of the 4 GHz MXGs as our main benchtop RF signal generator. These newer signal generators are also better for educational use because they are designed to tolerate more DC bias and reverse power on their output ports, decreasing the chance that students break them while learning.