" Whistle-Through" was used on the VHF and UHF systems. The K-13 oscillator-relay box did that function. Whistle was activated by pressing down on the receiver tuning crank. Jeep K3HVG On 5/25/2013 12:27 AM, Tim wrote: > Wasn't "whistle through" only part of the ARC Type 12 UHF transverter > system? ARC-60 I think? > Tim > N6CC >