http://www.cliftonlaboratories.com/off-the-air_frequency_measurement.htm If you peruse http://www.b4h.net/fmt/fmtresults201204.php you will see that HP3336A's also feature regularly. On Jun 21, 2016, at 4:52 AM, Pete Lancashire wrote: > Never tried it but a Selective Level Meter aka HP 3586A/B/C ? >