Another quick and dirty but very effective test method is to hold the antenna of a GSM mobile phone over each part of the circuit in turn. Only the first few seconds of each test call should be used because after that the dynamic power control may reduce the signal level.
For lower frequencies a dual-band VHF/UHF DMR digital walkie-talkie is useful. These are now available fairly cheaply from China. Make sure that you choose one that supports dual timeslot repeater operation as some of them cheat and radiate continuously rather than pulsing the carrier on and off at 16.666Hz. Some of these radios are now available with 10W output power at VHF and 8W at UHF. You can get a business radio license (in the UK at least) that makes it legal to radiate at selected VHF and UHF frequencies. The new Ailunce HD1 looks easier to configure from the handset for such tests than most of the others. I have not tried one of these (yet) and have no connection with Retevis who make it. However, I am planning to get one for this purpose.
Here is my VME EMI MasterBlaster board. We can use this to pump RF onto zones on either side of the VME board that I'm having EMI troubles with. We might drive it from a fast pulse generator, or from an RF signal generator. I'd expect to find fairly narrowband resonances on the victim board.
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No, it's not some precision matched-impedance antenna thing. If I get ambitious I guess I could replace the long runs with hardlines.
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John Larkin Highland Technology, Inc
picosecond timing precision measurement
To get those low offset voltages in OP-27s and such they used tricks that make a front end very non-linear. I had nothing but trouble using them in the RF rich environment of a fusion energy experiment. Filtering worked, but expensive.
It's got a bipolar input. FET input op amps do better when the problem comes from higher RF frequency interference - above the bandwidth of the op amp.
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