The AMP400 is our high frequency Hysteresisgraph system which will be used to test the magnetic properties of soft magnetic materiel at frequencies in the approximate range of 100 Hz - 20M Hz.  The target upper end of 20MHz is ambitious and not currently available by any competing system on the market at this time.

Power Amplifier: Proprietary design based on multiple STV9556 parts(or similar video amp) in             parallel(see Doug Self 5532 parallel amp design)
Shunt:1 ohm 20 watts
Signal Generator:  AD9834 DC coupled with differential signaling for low noise operation
Acquisition: Multiple AD6649 parts with staggered clocks, interleaving controlled by FPGA
Frequency Range: 100 Hz - 20 M Hz

I worked at Walker Scientific from 1995 to 2000 and then again in 2005 + 2006.  They were in decline and discontinued their product line by 2008.  They were a part of Walker Magnetics group, here's a link:
https://www.walkermagnet.com/blog/125-years-of-heavy-lifting-walker-magnetics-reaches-historic-milestone/

Note that with China increasingly dominating the steel production as well as rare earth metal market, they also came to supply competing instrumentation. So all metal industries in the US were affected.

One of the signature products at Walker Scientific was their high Frequency Soft material tester.  This was leading in the world for testing magnetically soft up to 1MHz.
The system was completely redesigned after I was hired and I wrote all the software for this and their low frequency system.

When I first created this website, my intention was to design a higher frequency system that could do 20MHz, it would certainly be the highest frequency tester in the world.
One challenge for this is the amplifier, to deliver power at that frequency is not easy for a simple circuit.  Although could buy and amplifier.
My approach would be to se the STV9556 video amplifier IC which would allow for sufficiently high frequencies.

At 20 MHz, circuit design techniques need to account for potential radiation, impedance matching, and parasitic coupling, which are characteristic of RF engineering rather than low-frequency circuit design.