06-22-2016, 02:10 PM
Ok I'm back to working on the Philco 118.
I replaced two 16K resistors (in series to make 32K) which were marginally rated far as the wattage goes given the discoloration of those resistors.
I also replaced the 800pF cap with two caps that make 800pF when put in parallel this time reading the numbers right to be sure I had the proper value of caps.
So far here's what I get.
At 595KHz on the dial with a received frequency of 600KHz the best I can get is -5.1Vdc AGC voltage.
At 1500KHz on the dial for a received frequency of 1500KHz I get -8.2Vdc AGC voltage.
Is it normal for an early-mid 30's Philco to have lower sensitivity on the lower BC band?
Think I may use my scope and do a frequency sweep of the RF stage to see if the RF level changes any as I go from 600-1500KHz
Then again I don't know if my RF generator is putting out the same RF level at 600KHz and 1500KHz.
If it is putting out a lower RF level at 600KHz that could partly explain the lower sensitivity.
I really need to get me a good quality modern RF generator versus the old service grade RF generators I have.
I'm thinking that something like this http://www.pongrance.com/DDS2016.html would work good for the time being.
EDIT:
And it looks like I have found one issue.
This is the output of my EICO 315 RF generator.
600KHz
[Image: http://i863.photobucket.com/albums/ab196...161425.jpg]
1500KHz
[Image: http://i863.photobucket.com/albums/ab196...161426.jpg]
Maybe that is part of the issue I am having with the alignment. The signal could be causing the frequency display to show the wrong frequency which would mean I am using the wrong frequency for the alignment.
I replaced two 16K resistors (in series to make 32K) which were marginally rated far as the wattage goes given the discoloration of those resistors.
I also replaced the 800pF cap with two caps that make 800pF when put in parallel this time reading the numbers right to be sure I had the proper value of caps.
So far here's what I get.
At 595KHz on the dial with a received frequency of 600KHz the best I can get is -5.1Vdc AGC voltage.
At 1500KHz on the dial for a received frequency of 1500KHz I get -8.2Vdc AGC voltage.
Is it normal for an early-mid 30's Philco to have lower sensitivity on the lower BC band?
Think I may use my scope and do a frequency sweep of the RF stage to see if the RF level changes any as I go from 600-1500KHz
Then again I don't know if my RF generator is putting out the same RF level at 600KHz and 1500KHz.
If it is putting out a lower RF level at 600KHz that could partly explain the lower sensitivity.
I really need to get me a good quality modern RF generator versus the old service grade RF generators I have.
I'm thinking that something like this http://www.pongrance.com/DDS2016.html would work good for the time being.
EDIT:
And it looks like I have found one issue.
This is the output of my EICO 315 RF generator.
600KHz
[Image: http://i863.photobucket.com/albums/ab196...161425.jpg]
1500KHz
[Image: http://i863.photobucket.com/albums/ab196...161426.jpg]
Maybe that is part of the issue I am having with the alignment. The signal could be causing the frequency display to show the wrong frequency which would mean I am using the wrong frequency for the alignment.