Instead of deviating the crystal, How about generating a super stable VCO using a PLL that has say a 5 second lock time instead of the typical 2mS lock time running all the time, this could even be frequency locked to a 10MHz source such as those found on GPS recievers.
Then to modulate it, we would use a double balenced mixer with filtered baseband audio on the second port and amplify what comes out and for keying just turn off the RF port from the VCO going into the mixer. This would create FM correct? But I would think you would need alot of AF and must be balanced audio with op-amps fed with + and - voltage or a good matching transformer. I have seen a ass load of mixers that say the "IF" port will accept DC to 200 MHz, Sounds perfect for 30Hz to 5000. On Tue, 21 Dec 2004 01:50:03 -0000, Coy Hilton <[EMAIL PROTECTED]> wrote: > > > Joe, youre right about the error in PPM. BUT taking a crystal and > deviding it also devides the error in PPM by the same amount and > multiply it you Multiply by the same factor so the reletive error is > the same in PPM. A 12 MHZ crystal with a 2PPM error will be off by > 24 Hz. Take that same crystal and multiply it by 12 ...(GE) and the > error is still 2ppm..but the error freq is now 12 * 24 or 288 HZ or > 144000288Hz > In the GE PLL exciter the VCO is devided and compaired to the ICOM > and the error voltage is fed back to the VCO so the Deviated Crystal > freq basically whips the VCO around to deviate it...THE VCO output > tracks the ICOM freq by way of the Error voltage generated in the > comparitor. Simple, AYE? > That is why I use A 10 MHZ output from a GPS as a time base for my > Direct Digital Synth. for my MASTRII. I take the 10 MHz Double it > and double it again to get 40 Mhz and use the DDS to set the freq. > The DDS has a 32 bit freq word and I can set the frequency by .2 Hz > increments that way,I can get dead on freq that way. > 73 > AC0Y > > --- In [email protected], Joe Montierth > <[EMAIL PROTECTED]> wrote: > > The frequency stability of any transmitter is only as > > good as it's reference oscillator (be that a PLL or a > > multiplied crystal)- dividing or multiplying the > > frequency will not change that constant (in PPM). It > > doesn't matter if you use a 100KHz, 1MHz, 10MHz or > > 100MHz reference frequency, if they are all the same > > in PPM. You don't somehow get better stability by > > dividing the frequency, and you don't get worse by > > multiplying the frequency. It is what it is. > > > > Joe > > > > > > --- Wade Lake <[EMAIL PROTECTED]> wrote: > > > > > Kevin, > > > > > > I now realize the mistake I was making in > > > looking at this. I am used to seeing newer PLL's > > > with a much higher reference oscillator frequency > > > and having a divider in the reference side before > > > the Phase Comparator. In that case the stability > > > does improve over that of the reference oscillator, > > > but that obviously does not apply here. > > > > > > Sorry, I will shut up now. > > > > > > Wade - KR7K > > > > > > ----- Original Message ----- > > > From: Kevin Custer > > > To: [email protected] > > > Sent: Sunday, December 19, 2004 4:16 PM > > > Subject: Re: [Repeater-Builder] GE Mastr II PLL vs. > > > Multiplier (crystal) exciter in duplex service. > > > > > > > > > Wade, > > > > > > If the PLL reference from the crystal is X3, and the > > > VCO sample has been divided by 4, what is the > > > product of 3 times 4? The answer is 12. If the > > > transmitter was any more stable in frequency than > > > the reference, shouldn't one think the stated > > > frequency stability would be better than 2 PPM or 5 > > > PPM, which is the stability of the ICOM itself? > > > Many times the manual states the VCO is locked to > > > the 12th multiple of the ICOM. This means the > > > output of the GE PLL exciter will have the stability > > > of the ICOM, times 12, period. > > > > > > Kevin Custer > > > > > > Wade Lake wrote: > > > > > > I stand corrected, in part anyway. In this > > > GE radio the deviation is indeed at a divide by 12 > > > from the output. This is why I said "usually", I am > > > not familiar with the intricate details of all > > > radios. Especially GE's, I was a Motorola tech for > > > quite a few years. I will leave the GE's to others > > > like you who are more familiar with their inner > > > workings. > > > > > > However, even in this particular radio, I > > > noticed the PLL circuit uses a X3 from the original > > > ICOM freq as the PLL reference. This is made > > > obvious by the divide by 4 fed back from the output > > > of the VCO. So even though the PLL circuit here is > > > not more stable by a factor of 12, as I initially > > > stated, it theoretically should be more stable by a > > > factor of 4. This does not appy to deviation in > > > this case but it will most definately apply to > > > frequency drift. > > > > > > My 2 and a half cents worth. > > > > > > Wade - KR7K > > > > > > > > > ----- Original Message ----- > > > From: Kevin Custer > > > To: [email protected] > > > Sent: Sunday, December 19, 2004 11:04 AM > > > Subject: Re: [Repeater-Builder] GE Mastr II PLL > > > vs. Multiplier (crystal) exciter in duplex service. > > > > > > > > > Hi Wade, > > > > > > I'm sorry, but I have to disagree with your > > > stability theory on the GE Mastr II PLL high-band > > > exciter. If you refer to the PDF manual for the PLL > > > exciter: > > > > > > > > <http://www.repeater-builder.com/ge/lbi-library/lbi-30398n.pdf> > > > You will see under the "Description" the exciter > > > utilizes the 12th multiple of the FM ICOM to lock > > > the VCO on frequency. It goes into more detail > > > about this in the "Circuit Analysis" section of the > > > same manual. So, the FM ICOM's multiplication > > > certainly does factor into the stability of the PLL > > > exciter, and one can generalize it has the same > > > frequency stability as its multiplier counterpart. > > > In addition, the modulation of the PLL exciter is > > > produced in the crystal reference (FM ICOM) as well, > > > and is also multiplied up to the desired deviation. > > > Since the time constant of the Lead/Lag filter > > > allows for near instantaneous correction of the VCO, > > > changes in frequency at the audio rate are > > > superimposed onto the output frequency. > > > > > > Hope this helps... > > > Kevin Custer > > > > > > > > > Wade Lake wrote: > > > > > > Kevin Custer wrote: > > > > > > The advantage here is the same frequency stability > > > is achieved by the use of the quartz reference > > > > > > Actually, a PLL oscillator is much more stable > > > than a multiplied crystal oscillator. because with > > > a multiplied quartz oscillator, frequency drift and > > > frequency error (usually deviation as well) is > > > multiplied by 12, at least in the case of the High > > > band GE MASTR II. > > > > > > Not to dissagree with you Kevin, your answer is > > > good, I think you nailed it. I just wanted to point > > > out that stability is a very strong point of the > > > PLL. Since it operates on the desired frequency, no > > > frequency error/drift is multiplied. > > > > > > Wade - KR7K > > > > > > > > > > > > > > > > __________________________________ > > Do you Yahoo!? > > All your favorites on one personal page â Try My Yahoo! > > http://my.yahoo.com > > > Yahoo! Groups Links > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
