22-12-2015, 10:50 AM
In practice, I've never found the adjustment to be all that critical, surprising as that sounds.
From a look at the manuals for the RP38 Hunter, RP71 Harrier, and the RP76 Black Knight, that preset is described as "AM rejection", which makes a lot more sense than the details given in the RP25/37 manual. Some manuals are even more vague than the RP25 - some make no mention at all of it, while others begin FM alignment instructions by suggesting stating that it should be put in the centre position at the start, but no further mention is made - presumably on the assumption that everyone should know that it is for AM rejection?
Later models (e.g. Aviemore, Sovereign IV/RPC1, Consort) did away with it completely.
To adjust, inject 10.7MHz with AM modulation, then adjust for minimum output. No wobulator needed.
I've found that the FM IF alignment on these sets is usually quite good providing no-one has messed with them, and if I have a go at tweaking, the improvement is usually marginal. The same cannot be said for RF alignment, which will be miles out on both AM and FM. Start by aligning the pointer with the right hand edge of the openings on the scale. The scale markings are rather precise, but with patience, you should be able to get it millimetre-perfect, which is intellectually satisfying
Having said that, a full IF lineup is usually very worthwhile on the Mayflower sets. Just goes to show...
I don't have a wobulator - instead I sweep my Marconi TF2008 RF generator. I have an old Wavetek 162 function generator to do that, and also drive the X input of the 'scope. What's nice about the Wavetek is that it allows me to stop the sweep and with the rotation of a pot, I can swing the output over the whole 360 degrees of the waveform - this allows me to put the spot on the centre of the 'scope screen and set the RF generator to exactly 10.7Mz, and by swinging left or right, I can see how many kHz per horizontal division I have before setting the sweep stimulus going. This saves having to think about markers, etc.
I only use the Marconi because I have it. If not, there are plenty of other general-purpose generators that can be swept either side of 10.7MHz - you don't need a dedicated RF generator for this. Apologies if I'm stating the obvious, but with a bit of lateral thought, there's usually a way to work around a lack of specific gear.
Hope this helps,
Mark
From a look at the manuals for the RP38 Hunter, RP71 Harrier, and the RP76 Black Knight, that preset is described as "AM rejection", which makes a lot more sense than the details given in the RP25/37 manual. Some manuals are even more vague than the RP25 - some make no mention at all of it, while others begin FM alignment instructions by suggesting stating that it should be put in the centre position at the start, but no further mention is made - presumably on the assumption that everyone should know that it is for AM rejection?
Later models (e.g. Aviemore, Sovereign IV/RPC1, Consort) did away with it completely.
To adjust, inject 10.7MHz with AM modulation, then adjust for minimum output. No wobulator needed.
I've found that the FM IF alignment on these sets is usually quite good providing no-one has messed with them, and if I have a go at tweaking, the improvement is usually marginal. The same cannot be said for RF alignment, which will be miles out on both AM and FM. Start by aligning the pointer with the right hand edge of the openings on the scale. The scale markings are rather precise, but with patience, you should be able to get it millimetre-perfect, which is intellectually satisfying
Having said that, a full IF lineup is usually very worthwhile on the Mayflower sets. Just goes to show...
I don't have a wobulator - instead I sweep my Marconi TF2008 RF generator. I have an old Wavetek 162 function generator to do that, and also drive the X input of the 'scope. What's nice about the Wavetek is that it allows me to stop the sweep and with the rotation of a pot, I can swing the output over the whole 360 degrees of the waveform - this allows me to put the spot on the centre of the 'scope screen and set the RF generator to exactly 10.7Mz, and by swinging left or right, I can see how many kHz per horizontal division I have before setting the sweep stimulus going. This saves having to think about markers, etc.
I only use the Marconi because I have it. If not, there are plenty of other general-purpose generators that can be swept either side of 10.7MHz - you don't need a dedicated RF generator for this. Apologies if I'm stating the obvious, but with a bit of lateral thought, there's usually a way to work around a lack of specific gear.
Hope this helps,
Mark
