27-03-2011, 01:39 AM
I see: thank you for the explanation.
Yes, things are a lot quieter on the short-waves these days compared to 30 - or so years ago. The current dip in propagation conditions doesn't help either.
As for IF realignment, that's not such a big job you know. The most critical feature is discovering the frequency of the crystal filter - and then aligning all the IF cans to that freq. as centre. I've done exactly that on many sets: CR100, various Eddystones, and even a few AR88's. You don't actually need the "scope/wobbulator" approach to obtain an IF response that is satisfactory: it just takes longer this way than by using the "scope/wobbulator" method. Obviously an accurate sig. gen is required - accurate not only in freq. setting and stability, but also accurate in its O/P attenuator. And an O/P indicator that is sensitive to small changes in signal level: I use a Marconi A.F. power meter and a Tek. 'scope. This set-up always work fine for me.
On this same subject of selectivity, apparent lack of, it might just be that you've got used to other receivers which don't have such a cramped dial, in terms of MHz per inch on the tuning scales.
Al. / Skywave.
Yes, things are a lot quieter on the short-waves these days compared to 30 - or so years ago. The current dip in propagation conditions doesn't help either.
As for IF realignment, that's not such a big job you know. The most critical feature is discovering the frequency of the crystal filter - and then aligning all the IF cans to that freq. as centre. I've done exactly that on many sets: CR100, various Eddystones, and even a few AR88's. You don't actually need the "scope/wobbulator" approach to obtain an IF response that is satisfactory: it just takes longer this way than by using the "scope/wobbulator" method. Obviously an accurate sig. gen is required - accurate not only in freq. setting and stability, but also accurate in its O/P attenuator. And an O/P indicator that is sensitive to small changes in signal level: I use a Marconi A.F. power meter and a Tek. 'scope. This set-up always work fine for me.
On this same subject of selectivity, apparent lack of, it might just be that you've got used to other receivers which don't have such a cramped dial, in terms of MHz per inch on the tuning scales.
Al. / Skywave.
