[R-390] No Peak on T701

[Flowertime01 at wmconnect.com]

Barry,

Open up the sweep. Rather than try and see the wave pattern just go for a big 
blur.
All you really care is the amplitude is equal across the range. Pick the 
largest peak to peak point on the scope face. Run the VFO to the other end and 
look at the peak to peak there. Expect the garbage on the trace to be of equal 
amplitude from one end of the VFO to the other end of the VFO and to trash the 
wave form equally every where. 

Let the wobble be. Grab a grease marker and mark the high point, mark the low 
point. Dial the VFO to the other end. Is the VFO output now the same as 
larger than or smaller than the grease marking? Turn the scope to a low voltage 
setting and shift the trace off the screen. Mark your maximum point as the trash 
on the wave form runs across the screen. Dial the VFO to the other end and 
compare the output peak to your first reference. 

Just watch the maximum excursion on the scope as you dial the VFO through all 
10 turns. The signal is in there and all you need is for it to have the same 
amplitude across the band.

Stop trying for exact science and start trying for get er done.

How is the output looking in terms of amplitude?

As an oscillator goes up in frequency, they mostly loose amplitude.
The output tuning circuit resonates higher than the oscillator and has low Q.
At the low end the oscillator has high voltage and the tuned circuit has 
little effect.
At the high end the oscillator has low voltage and the tuned circuit tries to 
peak the voltage.

By playing with the tuned output parts (the cap and transformer) you are just 
trying to get the slope of the low Q output to be the exact opposite as the 
slope of the oscillator output. The differences cancel and the output is flat 
across.

Your just looking for a setting of C and L that makes a good fit.

If you work with more stages of the receiver, then you start to introduce 
more variables into the mix and you wonder if you have a better VFO output or are 
you tuning the VFO output to compensate for some other circuit non linear 
problem.

Worry not about your test equipment and your un shielded un filtered 
environment. Just let that stray stuff ride alone and be part of the picture. 

Looking at 2 volt RF signals is a pain in the best of shop conditions.

The question is the mess on the scope more or less than the last mess on the 
scope?

Hope this helps.

Roger.