10-23-2008, 11:45 AM
At Brian's suggestion I decided to do a comparison between the Philco 90 and the 650B. Since the 90 has only the broadcast band, I used that for the comparison. Let me say that I suppose that this is more so of qualitative comparison than a quantitative type, since I don't really have the necessary equipment or the inclination to do a quantitative analysis. I spent a couple of hours this morning with the two chassis side by side on the bench. I first started using my long wire antenna, switching it back and forth between receivers. What I first noticed was that it appeared that the 90 had a definite advantage in selectivity. That is, it has a tighter bandpass and it tunes sharper. Now, I suppose that how the I.F.'s are aligned may have a bearing on this.Both radios are aligned per Philco's alignment procedures. It is also likely that that the four gang tuner with the double tuned antenna coil may have some bearing on this too.
I also noticed that the 90 appeared to have a slight edge in sensitivity across the band. It was hard to tell for sure with that large antenna. So, I decide to reconfigure the test. I installed a four foot long wire antenna on each radio draped in parallel fashion from the ceiling. You will see them in the picture below. I then tuned each receiver to the weakest stations I could find, comparing one against the other. In each case except for band center, the 90 had better quieting than the 650B. At one point, I believe it was WWJ 950 AM Detroit, the signals were about equal. I suspect this has one has more to do with the overall tracking of each receiver than anything else.
Here is a pic of the test setup.
[Image: http://i135.photobucket.com/albums/q136/...vs650B.jpg]
We all know that the 650B is a darned good receiver with 'hot' sensitivity. But I think little is known about the Philco 90's. I have two of the 90 chassis with the four gang tuner and the single 47 output tube and I noticed almost immediately after restoring them what impressive performance they had. They seemed to be extremely sensitive and quite selective, but I really had no basis for comparison other than the sense about these kind of things that you get after using lots of receivers over many years. So for me, this test was worthwhile in terms of defining (at least somewhat) what that difference really is.
It would be interesting to get some other opinions about this.
Regards,
Ed
I also noticed that the 90 appeared to have a slight edge in sensitivity across the band. It was hard to tell for sure with that large antenna. So, I decide to reconfigure the test. I installed a four foot long wire antenna on each radio draped in parallel fashion from the ceiling. You will see them in the picture below. I then tuned each receiver to the weakest stations I could find, comparing one against the other. In each case except for band center, the 90 had better quieting than the 650B. At one point, I believe it was WWJ 950 AM Detroit, the signals were about equal. I suspect this has one has more to do with the overall tracking of each receiver than anything else.
Here is a pic of the test setup.
[Image: http://i135.photobucket.com/albums/q136/...vs650B.jpg]
We all know that the 650B is a darned good receiver with 'hot' sensitivity. But I think little is known about the Philco 90's. I have two of the 90 chassis with the four gang tuner and the single 47 output tube and I noticed almost immediately after restoring them what impressive performance they had. They seemed to be extremely sensitive and quite selective, but I really had no basis for comparison other than the sense about these kind of things that you get after using lots of receivers over many years. So for me, this test was worthwhile in terms of defining (at least somewhat) what that difference really is.
It would be interesting to get some other opinions about this.
Regards,
Ed
