Also if you tuned the exciter down from the commercial band to the ham band, did you change the VCO loop filter values per the manual?
Joe At 03:21 PM 12/19/2004 -0600, you wrote: >I had a similar problem with the PLL exciter. Did some research and the GE >manual has info on aluminum vs ferrite coils for the VCO voltage set. The >high split VHF exciter uses an aluminum core and the lower split VHF uses a >ferrite core. Get a ferrite core or replace the coil with ferrite core coil >and problem solved. > >Jeff KB3HF > >-----Original Message----- >From: Neil McKie [mailto:[EMAIL PROTECTED] >Sent: Sunday, December 19, 2004 2:20 PM >To: [email protected] >Subject: Re: [Repeater-Builder] GE Mastr II PLL vs. Multiplier (crystal) >exciterin duplex service. > > > > > The following is not meant to upset anyones view on the Mastr II > PLL exciter ... but ... > > A friend brought his hi-band Mastr II Station to me for tune up > some months ago. It had a PLL exciter on board. We tuned, reset > the VCO voltage according to the manual and finished the > transmitter which is what he wanted. > > We tuned up the receiver, got the repeater operating, set > frequencies, levels and he departed. > > Came back a coupe of weeks later complaining the PLL exciter was > unstable - sometimes didn't have any output. So, we finally yanked > the PLL exciter out, removed the ICOM and tossed the exciter board > into a corner. > > Then I went into the back room and grabbed a brown handle Mastr II > mobile, pulled the exciter board out, swapped the crystal from the > PLL ICOM, stuck it into a 5C ICOM and installed the exciter into the > equipment. Tuned it up and he left. That took care of that. > > Never did figure out what the problem was with the PLL exciter > board. > > 73 and happy Motorola !!! > > Neil McKie - WA6KLA > > >Kevin Custer wrote: > > > > Hi Matt, > > > > Matt wrote: > > > > >Hi Kevin, > > > > > >Just a quick question regarding your earlier email - I thought > > >crystal oscillators were cleaner (as far as noise sidebands are > > >concerned ) than PLL types. > > > > > > > Actually it depends on the circuitry associated with crystal. While > > some better crystal controlled exciters can exhibit lower side-band > > noise levels than poorly designed PLL units, better PLL designs can > > offer a considerable improvement in signal spectral purity. > > > > >Is this not the case in the GE Mastr II you mention below, as you > > >indicate the PLL type of exciter is better? Is this particular to > > >this design? > > > > > > > Correct, please refer to this information presented by GE and Dave > > Karr on the subject: <http://www.ka9fur.net/geduplex/duplex.html> > > > > If you look at the curves for the highband multiplier exciter, then > > compare them to the PLL model, you'll see the difference. These are > > the second and third links under the "Mastr II" section of Dave's > > page. The multiplier exciter shows needing about 78 dB of noise > > reduction at 600 kHz, where the PLL model needs about 56 dB at that > > same spacing, or a difference of 22 dB less transmitter side-band > > noise reduction for the same performance. > > > > >Don't get me wrong here Kevin- I'm not trying to poke holes in what > > >you are suggesting, I just thought xtals would be cleaner? > > > > > > > Actually, in the case of the GE Mastr II PLL exciter, the frequency > > determining element is still a quartz crystal located in a channel > > ICOM. The crystal frequency determines the operating frequency just > > like the multiplier exciter, however, there are elementary differences > > one needs to understand to see why the PLL exciter is spectrally > > cleaner. > > > > In a typical "Multiplier" exciter, a quartz crystal is used as a > > reference to determine the operating frequency. In addition to being > > the frequency reference, the quartz crystal is also the signal > > generator in which the operating frequency is the direct result of > > "multiplying" the crystals fundamental frequency a particular number > > of times. In the GE Mastr II highband exciter, this number is 12. As > > a result of having but one oscillator, and the math, the frequency is > > not the only thing multiplied; but also all of the noise on either > > side of it. Sure, the "Q" or bandwidth of the tuned circuitry helps > > with the spectral purity, but since they aren't critically sharp (like > > in a tuned tube PA circuit) noise on either side of the carrier is > > amplified and multiplied as well as the operating carrier. Since most > > exciters of this era would operate over several hundred kHz without > > retuning, one can easily see that circuit Q isn't going to help much > > with making the signal cleaner. > > > > In the GE PLL exciter, a quartz crystal is also used as a reference > > for determining the operating frequency, but that's where the > > similarities end. In a Mastr II PLL exciter you have two oscillators, > > one is the crystal oscillator described earlier, and, in addition, a > > free running L-C tuned oscillator capable of producing frequencies > > directly on the desired operating frequency. You see, we now have an > > oscillator that operates directly on the high-band, at its fundamental > > frequency; NOT one that has been 'multiplied' up to it. The quartz > > derived oscillator is used to set the desired operating frequency by > > holding it still. This is done by 'locking' the frequency of the free > > running oscillator to the quartz derived oscillator. The advantage > > here is the same frequency stability is achieved by the use of the > > quartz reference, but, the output signal is much cleaner because it > > was not 'multiplied' up. > > > > Although there is more to it than this generalization, you now see why > > the PLL exciter is spectrally cleaner than its multiplier counterpart. > > > > Hope this helps... > > Kevin Custer > > > > >Kevin Custer wrote: > > > > > >If you have a GE Mastr II two meter or highband repeater that has > > >inadequate duplexer isolation, change out the exciter to a PLL type > > >and take advantage of the 20+ dB less transmitter side-band noise. > > >Another thing is to consider using a tube type PA deck, like the GE > > >4EF5A1, with a typical 'multiplier' exciter. This could allow power > > >levels in excess of 200 watts or more without suffering from > > >inadequate transmitter side-band noise suppression. > > > > > >Kevin Custer > > > > > > > > > Yahoo! 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