Height gauges are really useful tools for accurate marking out but the surface plate usually used as the base reference surface takes up a lot of space if permanently installed and is far to heavy to casually move about.
Not too sure if they're available in the USA but in UK granite place "mats" and chopping boards are readily available. These are very handy because they're small enough and light enough to be stored in a drawer when not in use and adequately flat for marking out and routine measurement purposes.
Unlike granite surface plates the top surface of these items is polished flat so it's eay to check them against an optical flat by the capillary/surface tension method. Tests on two 15mm thick placemats with an optical flat showed better than 0.0005" deviation from flatness.
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Shows the test results one placemat. The 6" optical flat was supported at the top end with an 0.005" shim to give an airgap slope of about 5/6000. The equal thickness capillary edge displays a 6000/5 amplification of the flatness error - approx
Don't blame me. It was a crappy RCA NATO radio design that required every member nation to sign off on design changes. Even as a tech, I could have made a lot of improvements starting with a better transistor in the front end. Motorola was the only source, and it had been obsolete for several years when Cincinnati Electronics took over the contract from another company. Motorola agreed to make a batch, but wouldn't guarantee that they met Mil Spec. They shipped over 11,000 transistors to be tested in house in an attempt to get 10,000 that qualified.
There were about a dozen manufacturers, including someone in Pakistan. It was early '60s germanium technology, at best. Crystal mixers to synthesize the Local Oscillators, and designed to replace the PRC-25, which replaced the PRC-10. It used the same battery, ignoring the 90 V B+ and operating the radio off what had been the filament supply. It used the same crappy Korean War carbon microphone handset and antennas. In other words, it was a low budget radio designed to replace crap that replaced crap. The only thing that it had going for it was module interchangability, implying that it could be serviced in the field by swapping modules. It was to be replaced by the PRC-70, that used modern ICs and digital synthesis to generate the Local Oscillators. They were intended for short range communications only. There were a few linear amplifiers built for them to put out something like 20 watts instead of a half watt. I saw a few at Cincinnati Electronics, along with the motorized antennas designed for tactically equipped Jeeps.
BTW, that was the same place where a security guard accused me of stealing a 'GRC-106, Complete' and carrying it out of the plant in my shirt pocket. That was about 600 pounds of electronics, cables and spare parts. The head of security got mad when I laughed in his face. then I asked who made the complaint. He refused to tell me, so I asked how many were missing, and what were the serial numbers. Finally I explained that two, 'GRC-106, Complete' filled one pallet, and required a forklift to move. He wasn't amused, but called that department for conformation. He finally apologized.
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