[time-nuts] LPRO101 Lamp Exciter Frequency

Roberto Barrios rbarrioss at msn.com
Mon Oct 26 06:54:28 UTC 2009



<* previous mails in this thread have been cropped *>


> Date: Sun, 25 Oct 2009 22:33:59 +0100
> From: "iovane\@inwind\.it" <iovane at inwind.it>
> Subject: Re: [time-nuts] LPRO101 Lamp Exciter Frequency
> To: "time-nuts" <time-nuts at febo.com>
> Message-ID: <KS3AKN$221A366B9EA1A7373EFB295C9A27E92D at libero.it>
> Content-Type: text/plain; charset=iso-8859-1
> Roberto Barrios wrote:
> >>>>> - 10Mhz out swings between 10.000191 and 9.999875, 
> taking 40s to go up and 60s to go down in freq.
> Roberto, 
> please tell me, does the 10 MHz output swing continuously 
> between the lower and upper limits, or does it stop at the 
> lower or upper limit after one or two swings?
> >>>> Everything seems to be fine, it would be great to confirm
> if other LPROs work at 70Mhz or actually at 140, like mine.
> Sorry that I can't check at present, I'm away. Actually I've 
> read both (about) 70 and 140 MHz at least on two units using a
> one turn link and depending on its position, and this is not 
> enough to say that the oscillator works at 70 MHz. I could re-
> check maybe next week-end and will let you know if the matter 
> is not solved in the meantime.
> Antonio I8IOV


Hi Antonio,


The 10Mhz out does not stop, never. It swings around 10.000.000Mhz continuously, +-150Hz, which is expected. It takes 40s to go up and 60s to go down, which is quite close to what the repair guide says (but with switched times...). This brings a question, since the swing times on my units are exactly opposite as appear in the guide, could it be that the 20Mhz oscillator is responding to control voltage to the wrong way?. That would explain the switched ramp times and also why it does not lock... but I wonder how on earth such a failure could occur.


Yes, everything I've seen points me to think that the oscillator runs at 140Mhz and not 70. It would be quite easy to conclude that the oscillator runs at 70 if we pick up the 2nd harmonic and the look at the FRS manual, which says the exciter oscillator is adjustable from 70-100Mhz. I also wonder which is actually the optimum frequency for the exciter, since (in my LPRO) the lamp ignites at all frequencies along the whole range of the tuning capacitor values, but lamp voltage peaks at maximum capacitance. If maximum photocell output was the objetive of tuning the exciter frequency, it should peak somewhere between the tuning limits of the oscillator, not at an extreme. It would be nice to clarify this.


Please, come back to us when you measure the exciter frequency on your LPRO, thank you.



Roberto Eb4EQA

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