Re: [time-nuts] Small quantity custom crystals
I have had good results with the part if this circuit around T1. http://www.qsl.net/on7yd/minitx2.htm Varying L1 selects the right overtone for basic operation. The collector circuit here has a coupled resonator tuned for the 144, but it will probably work equally well for 216. A cheap (fundamental) 24Mhz computer crystal operating at 72 MHz will get you there. Just alter the filter for 3 x 72 instead of 2 x 72. Note as someone else posted that the frequency at 72 may be tens of KHz higher than that. Each brand or even each individual crystal will vary here. You could also stick to the collector circuit from your tracker transmitter circuit if you want to keep things as small as possible. It worked down to 1.1V in bench tests with a MPSH10 transistor. Tuning the bias with R2 helps to optimize the power for the desired output frequency. More bias then necessary will only consume more battery power and not contribute to the output. Actually power output may be less. For more insight look here: http://www.wenzel.com/pdffiles1/pdfs/choose.pdf Cheers, Joop - pe1cqp ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Small quantity custom crystals
On 9/30/2010 12:43 PM, Alan Melia wrote: Mark to my inexpert eye that doesnt look like a very good overtone oscillator but I appreciate that it is slimmed down to keep the weight and size down, I can see why it is touchy. There is nothing to make the oscillator degenerate at the crystal fundamental. In fact it looks like a Pierce with a tuned circuit in the anode. If it goes off at the overtone my guess is that it by luck! But there are more clever people than me in this Group who may be more useful to you. I agree completely. What I have found to work is: Build a free running Colpitts oscillator and get it tuned to the frequency you want. Then, insert the crystal in series with the emitter. Insert the load in series with the collector. Obviously, this is easiest if a grounded collector topology is used. I used this for many high volume crystal oscillators and they just worked, period. No tweaking. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Small quantity custom crystals
Hi Mark looking at the M15m article where the design seems to stem from suggests that the oscillator is NOT opertaing on 150 or 200 MHz but in fact 40 to 50 Mhz with a cheap crystal and the LC collector circuit is selecting the the 3rd or 5th harmonic (not overtone a common mis-apprehension) The pulsing is just an RC in the base bias where the high value of R wont allow the circuit to oscillate hence it takes no current until the C is charged up. My thought is a 200MHz overtone crystal could cost you $60, whereas a 50MHz 3rd OT will probably cost $20 and a cheap computer grade $2. The big difficulty will be getting cheap crystals on the right or anyway different enough frequencies. Crystals removed in rechannelling older 2-way radios may be a better source. I have hunders of these.unfortunately I am in the UK. Alan G3NYK - Original Message - From: Mark Sims hol...@hotmail.com To: time-nuts@febo.com Sent: Friday, October 01, 2010 10:18 PM Subject: [time-nuts] Small quantity custom crystals This type of circuit is NOT a free running oscillator. It is a type of blocking oscillator that generates a short, high powered ping every second or two. It is designed to be able to extract every bit of power out of the battery. It can run for over a month off of a couple of button cells, yet generate a signal detectable over a mile away while it is laying flat on the ground. The allowable frequency bands are at 216, 217, and 219 Mhz. Each unit must be on its own freq, hence the need for one-off custom crystals. Yes, it is a weird circuit and depends upon all sorts of unspecified parameters. The components have to be hand selected and matched. This is the price one has to pay for this sort of operation. --- -Build a free running Colpitts oscillator and get it tuned to the frequency you want. Then, insert the crystal in series with theemitter. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Small quantity custom crystals
Mark Sims wrote: This type of circuit is NOT a free running oscillator. It is a type of blocking oscillator that generates a short, high powered ping every second or two. It is designed to be able to extract every bit of power out of the battery. It can run for over a month off of a couple of button cells, yet generate a signal detectable over a mile away while it is laying flat on the ground. The allowable frequency bands are at 216, 217, and 219 Mhz. Each unit must be on its own freq, hence the need for one-off custom crystals. Yes, it is a weird circuit and depends upon all sorts of unspecified parameters. The components have to be hand selected and matched. This is the price one has to pay for this sort of operation. This is comparable, then, to the wildlife transmitters for Argos (which are at 400MHz-ish).. Does this application need good medium term stability (i.e. are you making a series of Doppler measurements?) --- -Build a free running Colpitts oscillator and get it tuned to the frequency you want. Then, insert the crystal in series with theemitter. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Small quantity custom crystals
Mark to my inexpert eye that doesnt look like a very good overtone oscillator but I appreciate that it is slimmed down to keep the weight and size down, I can see why it is touchy. There is nothing to make the oscillator degenerate at the crystal fundamental. In fact it looks like a Pierce with a tuned circuit in the anode. If it goes off at the overtone my guess is that it by luck! But there are more clever people than me in this Group who may be more useful to you. Old fashioned crystals (lapped to frequency) used 5th OT up to just over 100MHz and the 7th and then 9th the blank was too fragile to go further. I believe modern micro machining techniqes where a thicker ring of quartz surrounds the resonator will allow a 5th overtone operation at 200MHz but you still have to make sure it doesnt go off at the fundamental or the 3rd .it may still transmit, but it will be off-channel and lower in power. Overtones are not harmonics.in radio anyway. Alan G3NYK - Original Message - From: Mark Sims hol...@hotmail.com To: time-nuts@febo.com Sent: Thursday, September 30, 2010 7:57 PM Subject: [time-nuts] Small quantity custom crystals I need to build some small tracking transmitters (using a circuit similar to http://www.jbgizmo.com/page4.html This circuit uses a fifth overtone crystal to get an output in the 216 to 220 MHz range. The circuit is rather finicky about the crystal and transistor... most don't work. Smaller and more rugged crystals are preferred. Does anybody know of a place that can make 1 off crystals in this range for a reasonable price. Many of usual suspects don't seem to be able to make crystals in that range. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Small quantity custom crystals
To ease the requirements on your crystal, you might consider using a diode frequency multiplier to bring your oscillator frequency into that range. Wenzel has a good app note on one variety: http://www.wenzel.com/documents/2diomult.html --n On Thu, 2010-09-30 at 18:57 +, Mark Sims wrote: I need to build some small tracking transmitters (using a circuit similar to http://www.jbgizmo.com/page4.html This circuit uses a fifth overtone crystal to get an output in the 216 to 220 MHz range. The circuit is rather finicky about the crystal and transistor... most don't work. Smaller and more rugged crystals are preferred. Does anybody know of a place that can make 1 off crystals in this range for a reasonable price. Many of usual suspects don't seem to be able to make crystals in that range. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Small quantity custom crystals
When I was in the television transmitter biz, we ran 5th, 7th and 9th up to 216MHz using JFET Pierce oscillators. We used the same oscillator for low VHF to high VHF and only changed an LC circuit to make sure the oscillator would take off on the correct overtone. Our supplier of choice was Piezo Crystals. Ovenized at 65C and IIRC we used SC cut crystals. Not cheap, but we never had crystal problems. Also, a design engineer at Piezo named Lynn Heischman was always available as a consultant for osc and crystal design, even though we were a small quantity purchaser. Dave W8NF --- On Thu, 9/30/10, Rick Karlquist rich...@karlquist.com wrote: From: Rick Karlquist rich...@karlquist.com Subject: Re: [time-nuts] Small quantity custom crystals To: Discussion of precise time and frequency measurement time-nuts@febo.com Date: Thursday, September 30, 2010, 12:12 PM Mark Sims wrote: I need to build some small tracking transmitters (using a circuit similar to http://www.jbgizmo.com/page4.html This circuit uses a fifth overtone crystal to get an output in the 216 to 220 MHz range. The circuit is rather finicky about the crystal and transistor... most don't work. AFAIK, that is way too high a frequency for 5th overtone. Has something changed? Are you sure there isn't a frequency doubler after the oscillator? Anyway, you can get a complete synthesizer on a chip from Analog Devices that uses very low power (see the ADF4360-8) so you might want to consider that as an alternative. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
