10-23-2008, 02:59 PM
Chuck,
Thanks for the suggestion. I did think about the possibility of cross-talk between the two radios in my original test set-up. So, I plugged the 650B into the isolated variac and operated the 90 directly from the AC line. That turned out to be a bad choice. I realize now that with such a short antenna, each receiver was using the AC line as the other half of the antenna.
So in my next test, I plugged both receivers into the AC line and I would tune in the same weak station on both. Then I unplugged one while the other was playing to eliminate the possibility of cross-talk or interference from the other, and vice-versa. So, operating both receivers one at a time both plugged directly into the AC line, the 650B was improved. With this set-up, I would say the 650B was at best on par with the 90, maybe just slightly less sensitive, but so close that one could easily say that could have been a difference in alignment or tracking across the band. Overall, you would have to say the sensitivity was about equal.
However, the 90 still had the 650B beat on selectivity. It is considerably sharper. You could easily tell when tuning in a weak station nearby a strong station. There was considerably less splatter on the 90 from the strong station.
Regards,
Ed
Thanks for the suggestion. I did think about the possibility of cross-talk between the two radios in my original test set-up. So, I plugged the 650B into the isolated variac and operated the 90 directly from the AC line. That turned out to be a bad choice. I realize now that with such a short antenna, each receiver was using the AC line as the other half of the antenna.
So in my next test, I plugged both receivers into the AC line and I would tune in the same weak station on both. Then I unplugged one while the other was playing to eliminate the possibility of cross-talk or interference from the other, and vice-versa. So, operating both receivers one at a time both plugged directly into the AC line, the 650B was improved. With this set-up, I would say the 650B was at best on par with the 90, maybe just slightly less sensitive, but so close that one could easily say that could have been a difference in alignment or tracking across the band. Overall, you would have to say the sensitivity was about equal.
However, the 90 still had the 650B beat on selectivity. It is considerably sharper. You could easily tell when tuning in a weak station nearby a strong station. There was considerably less splatter on the 90 from the strong station.
Regards,
Ed
