Hi, Brooke, Very interesting stuff. Thanks for the link. Question - Is any of the older chirp sounder equipment now available on the surplus market?? Thanks. ... Martin VE3OAT On 02/07/2016 12:00, time-nuts-request@febo.com wrote: > > Hi Mike: > > For quite a while I was heavily into "chirp" transmissions. These are HF ionosphere radio transmissions that sweep from > 2 to 30 MHz at 100 kHz/sec. ... (snipped)