To improve rx overload/crossmod performance of the HW9, particularly at night on 40m in Europe: Put 100uH choke across R243. This greatly increases the current through the switching diodes D404, D403 etc. Keeping R243 in place reduces the Q in case of any possible resonances. These diodes originally only had about 2 mA to switch them on. Putting normal silicon diodes in the receive signal path is just asking for trouble, especially if they are not fully conducting. The apparent poor selectivity reported by many users of the HW-9 is probably nothing more than the 'phantom signals' generated in these insufficiently biased switching diodes. This mod also renders the addition of any input attenuator unnecessary - even in Europe. This mod was my design and published in Sprat, the G-QRP Club magazine, no 72, Autumn 1992. Just thought I'd pass it on as you have a few mods for the HW9 already. I have had four very appreciative letters over the years regarding the effectiveness of this mod. 72/73 === Ian Liston-Smith G4JQTMy thanks to Ian for his input.
Back to the first page