22-06-2012, 09:38 AM
Yes Al you read that correct...no 'scope...just intuition/hunches and a bit of experience. I might treat myself to a 'scope sooner than later.
Just a quick note to say that I had a concerted effort to get the "borrowed" Xtal marker (500Khz) to come through on the 37th Harmonic (17 Mhz) in order to tune the 20 meter band, I managed to resolve a couple of strong SSB transmissions this morning, I double checked with the sig gen and it was definately the 37th harmonic, my conclusion is that at that harmonic it's getting pretty weak at that 'n th. Seeing that the end game is to use a 1 Mhz Xtal then it offers some hope.
In order to improve things I am now thinking of say taking the output from a Xtal osc then symetrically clipping it with a couple of solid state switching diodes (these would be allowed as per my original brief) and feeding that to a to a higher gain valve and tuning the tank to select the harmonic as I have already been doing, so overall it's Xtal osc...clipped....amplified...tune output at the harmonic required, there might be problems however as the output from a clipper might not be high enough to drive a single amp enough, if not then another stage might be required, I think this could still be done with two valve envelopes (including Xtal osc) as was originally planned. If I can find a spare valve and a couple of signal diodes I might try that in a lash up form just to see.
Of course in doing all this the ideal tool would be a spectrum analyzer, I have never owned or used one but one day I might consider buying a good used one, an old HP or similar, do you or any members have any experience with these things?
Lawrence.
Just a quick note to say that I had a concerted effort to get the "borrowed" Xtal marker (500Khz) to come through on the 37th Harmonic (17 Mhz) in order to tune the 20 meter band, I managed to resolve a couple of strong SSB transmissions this morning, I double checked with the sig gen and it was definately the 37th harmonic, my conclusion is that at that harmonic it's getting pretty weak at that 'n th. Seeing that the end game is to use a 1 Mhz Xtal then it offers some hope.
In order to improve things I am now thinking of say taking the output from a Xtal osc then symetrically clipping it with a couple of solid state switching diodes (these would be allowed as per my original brief) and feeding that to a to a higher gain valve and tuning the tank to select the harmonic as I have already been doing, so overall it's Xtal osc...clipped....amplified...tune output at the harmonic required, there might be problems however as the output from a clipper might not be high enough to drive a single amp enough, if not then another stage might be required, I think this could still be done with two valve envelopes (including Xtal osc) as was originally planned. If I can find a spare valve and a couple of signal diodes I might try that in a lash up form just to see.
Of course in doing all this the ideal tool would be a spectrum analyzer, I have never owned or used one but one day I might consider buying a good used one, an old HP or similar, do you or any members have any experience with these things?
Lawrence.
