I used these in my first HBR (photos are on the HBR Web Site). In mine, the transformers had 220 pF fixed capacitors across the coils. By changing them to 110 pF, I brought them up to 100 kc. They work very well. One small pitfall is that the tuning range of the trimmer capacitors used in them is very limit. 73, Darrell, WA5VGO