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anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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Robin Midgett
Hi Jim, Not a MASTR Exec, but a low band MASTR II mobile for use as a 6m beacon. I'm working on using the ProgRock in place of the crystal in the channel element. Once I get the low band beacon going in good order, I plan to expand to 2m, 1.25cm & 70 cm. I started this project over a year ago, set it aside for several months, and just today returned to it.
I plan to inject the RF from the ProgRock directly into the channel element connections on the exciter board, and key it on/off with a small memory keyer. It works just fine using a simple relay to key, but I want a solid state switch instead of a mechanical relay, so I've been working toward that.
I tried inserting the on/off keying in the bias & tripler circuits downstream of the channel element, but that didn't work well at all; the resulting RF was dirty & splattered across the narrow beacon sub-band. The original mic PTT simply turned the power to the oscillator in the channel element on/off, so that seems to be a good starting point.
Presently I have good stability using the ProgRock stand-alone (no GPS PPS discipline); it's running less than 10 Hertz off my desired frequency. I expected much better performance with GPS 1PPS discipline, but after trying 3 different GPS modules, I've not had better success than without. I'm beginning to question the 1PPS I've been giving the ProgRock relative to the ProgRock 1PPS requirement; perhaps the ProgRock needs a wider pulse width than 1mS, so I'm considering trying a pulse stretcher stage; perhaps 10mS will do the trick.
I did find a significant increase in stability by thermally bonding the 27MHz. crystal on the Si5351A Synth module to the heat sink of the 5V regulator AND the aluminum Bud box enclosure, so if you don't want to deal with the GPS discipline, by all means make the effort to thermally stabilize the 27MHz. crystal & then thermally isolate the ProgRock enclosure from the environment. By the way, it's an inverse relationship...warmer crystal shifts the frequency down. Simply holding my finger on the crystal is enough to move the oscillator.
QRPLabs offers a OCXO module to replace the crystal on the Si5351A Synth module; you might consider using it. There's info in the archives of this email list on the various issues that may entail. I haven't tried that module so I can say anything about it's performance. I'm happy to share anything I learn along the way; feel free to contact me. Thanks,
Robin Midgett K4IDC
anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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Hi Robin
Several comments:
1. ProgRock was developed in conjunction with the QRP Labs QLG1 GPS http://qrp-labs.com/qlg1 which has 100ms (0.1ms) positive-going pulse. Though if your pulse-length is 1ms I would not expect there to be problems... but couldn't know for sure without testing it. I know something very short like a microsecond would be an issue. But a millisecond is relatively ages...
2. Watch out for voltage level problems. Most GPS chips operate at 2.8V supply, the ProgRock operates with 5V supply. The logic level threshold for a "1" is 3V if I recall correctly. Therefore with many GPS module models you need a level converter. A pull-up resistor to +5V can do the job often but you need the right resistor value. And even then, the noise immunity suffers compared to a "real" level converter. The QLG1 kit has a proper logic level converter so with its 5V logic outputs you never have an issue.
3. A heatsink on the crystal helps with thermal stability. So does putting the project in an enclosure to avoid drafts etc.
4. ON/OFF keying... are you aware of the frequency bank feature of ProgRock? There are three logic inputs, the permutations of high/low control signals in these allow you to choose one of three banks of output frequencies. If any frequencies are zero the output is just disabled. So it is often quite convenient to uses these logic level inputs to on/off key the output frequency you want.
5. Read the manual section about the GPS correction threshold register. For finest precision you want this to be 0Hz. The default is 5Hz which means the correction is only applied when the error if the 27MHz value exceeds 5Hz.
When all is well you should be well within 0.05ppm.
73 Hans G0UPL
On Fri, Jul 5, 2019, 03:49 Robin Midgett < K4IDC@...> wrote: Hi Jim, Not a MASTR Exec, but a low band MASTR II mobile for use as a 6m beacon. I'm working on using the ProgRock in place of the crystal in the channel element. Once I get the low band beacon going in good order, I plan to expand to 2m, 1.25cm & 70 cm. I started this project over a year ago, set it aside for several months, and just today returned to it.
I plan to inject the RF from the ProgRock directly into the channel element connections on the exciter board, and key it on/off with a small memory keyer. It works just fine using a simple relay to key, but I want a solid state switch instead of a mechanical relay, so I've been working toward that.
I tried inserting the on/off keying in the bias & tripler circuits downstream of the channel element, but that didn't work well at all; the resulting RF was dirty & splattered across the narrow beacon sub-band. The original mic PTT simply turned the power to the oscillator in the channel element on/off, so that seems to be a good starting point.
Presently I have good stability using the ProgRock stand-alone (no GPS PPS discipline); it's running less than 10 Hertz off my desired frequency. I expected much better performance with GPS 1PPS discipline, but after trying 3 different GPS modules, I've not had better success than without. I'm beginning to question the 1PPS I've been giving the ProgRock relative to the ProgRock 1PPS requirement; perhaps the ProgRock needs a wider pulse width than 1mS, so I'm considering trying a pulse stretcher stage; perhaps 10mS will do the trick.
I did find a significant increase in stability by thermally bonding the 27MHz. crystal on the Si5351A Synth module to the heat sink of the 5V regulator AND the aluminum Bud box enclosure, so if you don't want to deal with the GPS discipline, by all means make the effort to thermally stabilize the 27MHz. crystal & then thermally isolate the ProgRock enclosure from the environment. By the way, it's an inverse relationship...warmer crystal shifts the frequency down. Simply holding my finger on the crystal is enough to move the oscillator.
QRPLabs offers a OCXO module to replace the crystal on the Si5351A Synth module; you might consider using it. There's info in the archives of this email list on the various issues that may entail. I haven't tried that module so I can say anything about it's performance. I'm happy to share anything I learn along the way; feel free to contact me. Thanks,
Robin Midgett K4IDC
anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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I had been working on something similar with a Mastr II repeater on UHF and could make the proper frequency oscillator on the frequency I needed. The problem is the GE uses PM or Phase Modulation. I have not yet been able to get real clean audio because I believe there is too much phase noise from the prog rock. If you are doing a CW beacon this may not matter, but on a repeater with PL tones I did not see it working for my needs without more filtering.
73
Thomas KC5KCT
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On a workbench, I wired a GE Master II to a ProgRock simply by capacitively-coupling into the "hot" side of the crystal of an ICOM - an "EC" type is fine - 1000pF is suitable, but it could probably be a magnitude different in either direction. For a Mastr Exec II, the same would apply as their crystal modules are electrically similar in the ways that matter. When stability is desired, I've been using TCXOs with my ProgRocks rather than the OCXO: A 2.5 or 1 ppm TCXO is less than $3.00 US from Mouser or DigiKey and I described the use of a 1ppm TCXO here: https://ka7oei.blogspot.com/2018/02/better-frequency-stability-for-qrp-labs.html The present run of the ProgRock boards permit the installation of the 2.5ppm version, but the smaller, different-style 1ppm requires a bit more care: 2.5ppm should be suitable even for UHF operation. In testing the suitability of the spectral purity, it would *NOT* recommend using more than one output of the ProgRock at the same time as there is some cross-talk. If only one output is active, we found that for VHF and UHF the spurious signals were well under -60dBc, worst-case - usually much better than that: We didn't evaluate whether or not they were "clean" enough to allow for full-duplex repeater use, but it looked like they might be. Were I to try it for repeater use I would, at the very least, include narrow L/C bandpass filtering between the ProgRock and ICOM input - but then again, for a repeater, spending $50 or so for a pair of crystals isn't too onerous a burden. 73, Clint KA7OEI
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As far as using a ProgRock goes, see the other posting that I just made - but I thought that I'd comment on using a Ge Mastr II (or Exec II) for a propagation beacon. Years ago (2001, actually) I worked with WA7X in assembling a 6 meter, 2 meter and 70cm beacon using cast-off Ge Mastr Exec IIs - and here's what I found: - You can't key the beacon with the PTT line: It's WAY too "clicky" - but this isn't too surprising. With a crystal, you end up with chirp (no surprise) but the fact is that keying the signal feeding a string of non-linear stages (multipliers, Class-C amplifier stages) means that on the attack and decay, you will not only get a sharp edge, but you will also get a very brief burst of noise as these multiple stages are momentarily in an indeterminate state, which means that the key clicks are as much as a few 10s of kHz wide. Because of this, the PTT line is used only for a "beacon disable" function (via remote control) and, instead, a closed-loop servo power control was used, replacing the original RF output power control circuitry of the PA. If you want to see the gory details, go here: http://www.wa7x.com/beacon_tech.html#transmittersNot only does this provide an acceptable keying waveform, it also provides the ability for three power steps (e.g. 1 watt, 10 watts, 100 watts) which are useful for both propagation analysis (the beacon message includes a 5 second key-down at each power level) but it also saves on the power bill: For a long time, the WA7X beacons operate at 100 watts only during the initial "VVV", the 5 second test carrier and its announcement and the final ID, the rest of the time operate at 10 watts. As mentioned, these beacons have been operating since about 2001 with very little required maintenance (the 2 meter beacon lost a pre-driver early on - easily replaced). If we were to build these beacons again, I'd certainly consider using a ProgRock (one per beacon) with a TCXO, but I would do the keying the same way. 73, Clint KA7OEI
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Bob M.
I'm working on a similar project, but in my case it's an old Motorola Compa-Station (Motrac-based) on 10m and it uses phase modulation after the crystal, so a ProgRock should be a good substitute for a signal in the 7-10 MHz range. This station uses channel elements. I plan on removing the crystals and feeding the ProgRock into the channel element, using it as a buffer stage. I may need more gain and possibly some filtering to turn the square waves into something more sinusoidal (crystal-like).
I plan on using bank switching by connecting the active-low PTT signal in the station (through a diode) to the Bank Select 0 input. That way I can have just one output active at a time, or at least disable the TX output from the ProgRock.
I initially installed the supplied crystal just to make sure the ProgRock worked. I then installed the Fox 27 MHz TCXO and after adjusting the reference register, I got its 10 MHz output to within 1 Hz. I plan on installing the ProgRock into a small aluminum box and stuffing it with pink fiberglass insulation. In my case, a drift of a few Hz at 10 MHz will only result in a drift of maybe 10 Hz at 30 MHz, and that's definitely close enough for me.
Bob M.
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One of the reasons that the Mastr II (Exec) was chosen for the ProgRock tests was precisely because it is phase-modulated: This makes it agnostic to the signal source since it is not required that the source (the ProgRock, in this case) be modulated.
In our assessment, in an "A/B" test, we found that the ProgRock versus Quartz different was minimal on VHF, very difficult to tell between the two in terms of phase noise (e.g. background hiss) on an unmodulated carrier. At UHF (70cm) the background hiss was more noticeable, but we quickly realized that it depended on the radio used: Some HTs were phase-noisier than the ProgRock-originated signal. One can check this onesself by simply programming the ProgRock to the intended crystal frequency and tuning into the would-be harmonic had it actually been used in a radio: If, after passing through multiplier stages, it is noisier than the "raw" ProgRock's harmonics, something in the multiplier chain is unhappy.
Our assessment was that base on phase noise alone, it was just fine on VHF - and it was probably fine on UHF, too - as long as one didn't have a string of series-linked repeaters, each with a ProgRock as its main reference.
As far as overall cleanliness, the ProgRock produces more low-level spurs than a crystal alone as one might expect: A tight L/C band-pass filter may help, but since there are already such things within the radio's exciter, anyway, it may not be worth the difference. When we looked at it on an analyzer at the 600 kHz and 5 MHz points (for 2m and 70cm splits, respectively) it looked "clean enough", but more scrutiny would be required if it was used on a shared site. To be sure, we would be certain to use a true band-pass cavity since almost none of the so-called "Bp-Br" duplexers actually have true-bandpass response - but for lightning protection and good-neighborliness, we have always done that on our club's mountaintop sites, anyway!
73,
Clint
KA7OEI
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Robin Midgett
Thanks Clint! Very helpful!
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Robin Midgett
Bob, The low pass filter kits from QRPLabs are very effective for making sine waves from the square wave outputs of the ProgRock. Thanks,
Robin Midgett K4IDC
On Fri, Jul 5, 2019 at 1:18 PM Bob / WA1MIK < wa1mik@...> wrote: I'm working on a similar project, but in my case it's an old Motorola Compa-Station (Motrac-based) on 10m and it uses phase modulation after the crystal, so a ProgRock should be a good substitute for a signal in the 7-10 MHz range. This station uses channel elements. I plan on removing the crystals and feeding the ProgRock into the channel element, using it as a buffer stage. I may need more gain and possibly some filtering to turn the square waves into something more sinusoidal (crystal-like).
I plan on using bank switching by connecting the active-low PTT signal in the station (through a diode) to the Bank Select 0 input. That way I can have just one output active at a time, or at least disable the TX output from the ProgRock.
I initially installed the supplied crystal just to make sure the ProgRock worked. I then installed the Fox 27 MHz TCXO and after adjusting the reference register, I got its 10 MHz output to within 1 Hz. I plan on installing the ProgRock into a small aluminum box and stuffing it with pink fiberglass insulation. In my case, a drift of a few Hz at 10 MHz will only result in a drift of maybe 10 Hz at 30 MHz, and that's definitely close enough for me.
Bob M.
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Robin Midgett
Hi Clint, Thanks for speaking up. I recall looking at the description of the WA7X beacon power control & keying circuits a year or more ago when I first started working on this project. Coming back to it now, it seems that my decision back then to do the task a different way was premature. Looking at your work now, I can see that although it's more complicated that I'd hoped, it certainly opens the door for clean keying with the benefit of varying power levels. I like it! Thank you very much for the detailed explanation of it's workings and the follow on of the later modifications. Thanks,
Robin Midgett K4IDC
As far as using a ProgRock goes, see the other posting that I just made - but I thought that I'd comment on using a Ge Mastr II (or Exec II) for a propagation beacon.
Years ago (2001, actually) I worked with WA7X in assembling a 6 meter, 2 meter and 70cm beacon using cast-off Ge Mastr Exec IIs - and here's what I found:
- You can't key the beacon with the PTT line: It's WAY too "clicky" - but this isn't too surprising. With a crystal, you end up with chirp (no surprise) but the fact is that keying the signal feeding a string of non-linear stages (multipliers, Class-C amplifier stages) means that on the attack and decay, you will not only get a sharp edge, but you will also get a very brief burst of noise as these multiple stages are momentarily in an indeterminate state, which means that the key clicks are as much as a few 10s of kHz wide.
Because of this, the PTT line is used only for a "beacon disable" function (via remote control) and, instead, a closed-loop servo power control was used, replacing the original RF output power control circuitry of the PA. If you want to see the gory details, go here:
http://www.wa7x.com/beacon_tech.html#transmitters
Not only does this provide an acceptable keying waveform, it also provides the ability for three power steps (e.g. 1 watt, 10 watts, 100 watts) which are useful for both propagation analysis (the beacon message includes a 5 second key-down at each power level) but it also saves on the power bill: For a long time, the WA7X beacons operate at 100 watts only during the initial "VVV", the 5 second test carrier and its announcement and the final ID, the rest of the time operate at 10 watts.
As mentioned, these beacons have been operating since about 2001 with very little required maintenance (the 2 meter beacon lost a pre-driver early on - easily replaced).
If we were to build these beacons again, I'd certainly consider using a ProgRock (one per beacon) with a TCXO, but I would do the keying the same way.
73,
Clint
KA7OEI
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Robin Midgett
Hi Hans, Thank you very much for the tips. I was able today to get my old oscilloscope dialed in enough to measure the pulse width of the 1 PPS output of the Trimble Resolution T GPS board...it's a 1mS pulse width. Further, and perhaps the better news, you're correct...it's only making about 3 volts above ground, so that might be the sole issue with the GPS discipline problem. I'll try a level converter & see how it goes.
Yes, I'm aware of the frequency bank switching scheme, but I hadn't realized one could take advantage of that for on/off keying..I'll give that a try & follow up with my findings. That seems rather clever to me.
Question on your point 5: Is that 27MHz. correction threshold only valid for GPS discipline mode,or does it apply for both GPS/non GPS mode? The way your point is stated makes it seem to me that perhaps the threshold is only effective while under GPS discipline...but maybe I'm mistaken.
Thanks,
Robin Midgett K4IDC
Hi Robin
Several comments:
1. ProgRock was developed in conjunction with the QRP Labs QLG1 GPS http://qrp-labs.com/qlg1 which has 100ms (0.1ms) positive-going pulse. Though if your pulse-length is 1ms I would not expect there to be problems... but couldn't know for sure without testing it. I know something very short like a microsecond would be an issue. But a millisecond is relatively ages...
2. Watch out for voltage level problems. Most GPS chips operate at 2.8V supply, the ProgRock operates with 5V supply. The logic level threshold for a "1" is 3V if I recall correctly. Therefore with many GPS module models you need a level converter. A pull-up resistor to +5V can do the job often but you need the right resistor value. And even then, the noise immunity suffers compared to a "real" level converter. The QLG1 kit has a proper logic level converter so with its 5V logic outputs you never have an issue.
3. A heatsink on the crystal helps with thermal stability. So does putting the project in an enclosure to avoid drafts etc.
4. ON/OFF keying... are you aware of the frequency bank feature of ProgRock? There are three logic inputs, the permutations of high/low control signals in these allow you to choose one of three banks of output frequencies. If any frequencies are zero the output is just disabled. So it is often quite convenient to uses these logic level inputs to on/off key the output frequency you want.
5. Read the manual section about the GPS correction threshold register. For finest precision you want this to be 0Hz. The default is 5Hz which means the correction is only applied when the error if the 27MHz value exceeds 5Hz.
When all is well you should be well within 0.05ppm.
73 Hans G0UPL On Fri, Jul 5, 2019, 03:49 Robin Midgett < K4IDC@...> wrote: Hi Jim, Not a MASTR Exec, but a low band MASTR II mobile for use as a 6m beacon. I'm working on using the ProgRock in place of the crystal in the channel element. Once I get the low band beacon going in good order, I plan to expand to 2m, 1.25cm & 70 cm. I started this project over a year ago, set it aside for several months, and just today returned to it.
I plan to inject the RF from the ProgRock directly into the channel element connections on the exciter board, and key it on/off with a small memory keyer. It works just fine using a simple relay to key, but I want a solid state switch instead of a mechanical relay, so I've been working toward that.
I tried inserting the on/off keying in the bias & tripler circuits downstream of the channel element, but that didn't work well at all; the resulting RF was dirty & splattered across the narrow beacon sub-band. The original mic PTT simply turned the power to the oscillator in the channel element on/off, so that seems to be a good starting point.
Presently I have good stability using the ProgRock stand-alone (no GPS PPS discipline); it's running less than 10 Hertz off my desired frequency. I expected much better performance with GPS 1PPS discipline, but after trying 3 different GPS modules, I've not had better success than without. I'm beginning to question the 1PPS I've been giving the ProgRock relative to the ProgRock 1PPS requirement; perhaps the ProgRock needs a wider pulse width than 1mS, so I'm considering trying a pulse stretcher stage; perhaps 10mS will do the trick.
I did find a significant increase in stability by thermally bonding the 27MHz. crystal on the Si5351A Synth module to the heat sink of the 5V regulator AND the aluminum Bud box enclosure, so if you don't want to deal with the GPS discipline, by all means make the effort to thermally stabilize the 27MHz. crystal & then thermally isolate the ProgRock enclosure from the environment. By the way, it's an inverse relationship...warmer crystal shifts the frequency down. Simply holding my finger on the crystal is enough to move the oscillator.
QRPLabs offers a OCXO module to replace the crystal on the Si5351A Synth module; you might consider using it. There's info in the archives of this email list on the various issues that may entail. I haven't tried that module so I can say anything about it's performance. I'm happy to share anything I learn along the way; feel free to contact me. Thanks,
Robin Midgett K4IDC
anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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Hi Robin
The 27MHz correction threshold parameter only applies during GPS correction. Only when you have a GPS 1pps connected.
73 Hans G0UPL
On Mon, Jul 8, 2019, 03:06 Robin Midgett < K4IDC@...> wrote: Hi Hans, Thank you very much for the tips. I was able today to get my old oscilloscope dialed in enough to measure the pulse width of the 1 PPS output of the Trimble Resolution T GPS board...it's a 1mS pulse width. Further, and perhaps the better news, you're correct...it's only making about 3 volts above ground, so that might be the sole issue with the GPS discipline problem. I'll try a level converter & see how it goes.
Yes, I'm aware of the frequency bank switching scheme, but I hadn't realized one could take advantage of that for on/off keying..I'll give that a try & follow up with my findings. That seems rather clever to me.
Question on your point 5: Is that 27MHz. correction threshold only valid for GPS discipline mode,or does it apply for both GPS/non GPS mode? The way your point is stated makes it seem to me that perhaps the threshold is only effective while under GPS discipline...but maybe I'm mistaken.
Thanks,
Robin Midgett K4IDC
Hi Robin
Several comments:
1. ProgRock was developed in conjunction with the QRP Labs QLG1 GPS http://qrp-labs.com/qlg1 which has 100ms (0.1ms) positive-going pulse. Though if your pulse-length is 1ms I would not expect there to be problems... but couldn't know for sure without testing it. I know something very short like a microsecond would be an issue. But a millisecond is relatively ages...
2. Watch out for voltage level problems. Most GPS chips operate at 2.8V supply, the ProgRock operates with 5V supply. The logic level threshold for a "1" is 3V if I recall correctly. Therefore with many GPS module models you need a level converter. A pull-up resistor to +5V can do the job often but you need the right resistor value. And even then, the noise immunity suffers compared to a "real" level converter. The QLG1 kit has a proper logic level converter so with its 5V logic outputs you never have an issue.
3. A heatsink on the crystal helps with thermal stability. So does putting the project in an enclosure to avoid drafts etc.
4. ON/OFF keying... are you aware of the frequency bank feature of ProgRock? There are three logic inputs, the permutations of high/low control signals in these allow you to choose one of three banks of output frequencies. If any frequencies are zero the output is just disabled. So it is often quite convenient to uses these logic level inputs to on/off key the output frequency you want.
5. Read the manual section about the GPS correction threshold register. For finest precision you want this to be 0Hz. The default is 5Hz which means the correction is only applied when the error if the 27MHz value exceeds 5Hz.
When all is well you should be well within 0.05ppm.
73 Hans G0UPL On Fri, Jul 5, 2019, 03:49 Robin Midgett < K4IDC@...> wrote: Hi Jim, Not a MASTR Exec, but a low band MASTR II mobile for use as a 6m beacon. I'm working on using the ProgRock in place of the crystal in the channel element. Once I get the low band beacon going in good order, I plan to expand to 2m, 1.25cm & 70 cm. I started this project over a year ago, set it aside for several months, and just today returned to it.
I plan to inject the RF from the ProgRock directly into the channel element connections on the exciter board, and key it on/off with a small memory keyer. It works just fine using a simple relay to key, but I want a solid state switch instead of a mechanical relay, so I've been working toward that.
I tried inserting the on/off keying in the bias & tripler circuits downstream of the channel element, but that didn't work well at all; the resulting RF was dirty & splattered across the narrow beacon sub-band. The original mic PTT simply turned the power to the oscillator in the channel element on/off, so that seems to be a good starting point.
Presently I have good stability using the ProgRock stand-alone (no GPS PPS discipline); it's running less than 10 Hertz off my desired frequency. I expected much better performance with GPS 1PPS discipline, but after trying 3 different GPS modules, I've not had better success than without. I'm beginning to question the 1PPS I've been giving the ProgRock relative to the ProgRock 1PPS requirement; perhaps the ProgRock needs a wider pulse width than 1mS, so I'm considering trying a pulse stretcher stage; perhaps 10mS will do the trick.
I did find a significant increase in stability by thermally bonding the 27MHz. crystal on the Si5351A Synth module to the heat sink of the 5V regulator AND the aluminum Bud box enclosure, so if you don't want to deal with the GPS discipline, by all means make the effort to thermally stabilize the 27MHz. crystal & then thermally isolate the ProgRock enclosure from the environment. By the way, it's an inverse relationship...warmer crystal shifts the frequency down. Simply holding my finger on the crystal is enough to move the oscillator.
QRPLabs offers a OCXO module to replace the crystal on the Si5351A Synth module; you might consider using it. There's info in the archives of this email list on the various issues that may entail. I haven't tried that module so I can say anything about it's performance. I'm happy to share anything I learn along the way; feel free to contact me. Thanks,
Robin Midgett K4IDC
anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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Bob M.
Robin: Thanks for the filter recommendation. I would need two of them though, one for TX, one for RX, and the freqs are significantly far from the common ham bands that I'd need to fiddle with component values to make them do anything useful. One would need to cover 6.5-7.5 MHz, the other 9-11 MHz. Granted, once I retune the station from 26.31 MHz to 29.6 MHz, I would only need one set of filters, at the high end of those ranges.
Easily tunable filters would be more useful for this project, possibly with variable capacitors in each stage.
Bob M.
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Robin Midgett
Thank you. That certainly explains why my ProgRock is on an Australian walkabout without a 1PPS signal...even a sub 4 volt 1 PPS! Lovin' the learning! Thanks,
Robin Midgett K4IDC
Hi Robin
The 27MHz correction threshold parameter only applies during GPS correction. Only when you have a GPS 1pps connected.
73 Hans G0UPL
On Mon, Jul 8, 2019, 03:06 Robin Midgett < K4IDC@...> wrote: Hi Hans, Thank you very much for the tips. I was able today to get my old oscilloscope dialed in enough to measure the pulse width of the 1 PPS output of the Trimble Resolution T GPS board...it's a 1mS pulse width. Further, and perhaps the better news, you're correct...it's only making about 3 volts above ground, so that might be the sole issue with the GPS discipline problem. I'll try a level converter & see how it goes.
Yes, I'm aware of the frequency bank switching scheme, but I hadn't realized one could take advantage of that for on/off keying..I'll give that a try & follow up with my findings. That seems rather clever to me.
Question on your point 5: Is that 27MHz. correction threshold only valid for GPS discipline mode,or does it apply for both GPS/non GPS mode? The way your point is stated makes it seem to me that perhaps the threshold is only effective while under GPS discipline...but maybe I'm mistaken.
Thanks,
Robin Midgett K4IDC
Hi Robin
Several comments:
1. ProgRock was developed in conjunction with the QRP Labs QLG1 GPS http://qrp-labs.com/qlg1 which has 100ms (0.1ms) positive-going pulse. Though if your pulse-length is 1ms I would not expect there to be problems... but couldn't know for sure without testing it. I know something very short like a microsecond would be an issue. But a millisecond is relatively ages...
2. Watch out for voltage level problems. Most GPS chips operate at 2.8V supply, the ProgRock operates with 5V supply. The logic level threshold for a "1" is 3V if I recall correctly. Therefore with many GPS module models you need a level converter. A pull-up resistor to +5V can do the job often but you need the right resistor value. And even then, the noise immunity suffers compared to a "real" level converter. The QLG1 kit has a proper logic level converter so with its 5V logic outputs you never have an issue.
3. A heatsink on the crystal helps with thermal stability. So does putting the project in an enclosure to avoid drafts etc.
4. ON/OFF keying... are you aware of the frequency bank feature of ProgRock? There are three logic inputs, the permutations of high/low control signals in these allow you to choose one of three banks of output frequencies. If any frequencies are zero the output is just disabled. So it is often quite convenient to uses these logic level inputs to on/off key the output frequency you want.
5. Read the manual section about the GPS correction threshold register. For finest precision you want this to be 0Hz. The default is 5Hz which means the correction is only applied when the error if the 27MHz value exceeds 5Hz.
When all is well you should be well within 0.05ppm.
73 Hans G0UPL On Fri, Jul 5, 2019, 03:49 Robin Midgett < K4IDC@...> wrote: Hi Jim, Not a MASTR Exec, but a low band MASTR II mobile for use as a 6m beacon. I'm working on using the ProgRock in place of the crystal in the channel element. Once I get the low band beacon going in good order, I plan to expand to 2m, 1.25cm & 70 cm. I started this project over a year ago, set it aside for several months, and just today returned to it.
I plan to inject the RF from the ProgRock directly into the channel element connections on the exciter board, and key it on/off with a small memory keyer. It works just fine using a simple relay to key, but I want a solid state switch instead of a mechanical relay, so I've been working toward that.
I tried inserting the on/off keying in the bias & tripler circuits downstream of the channel element, but that didn't work well at all; the resulting RF was dirty & splattered across the narrow beacon sub-band. The original mic PTT simply turned the power to the oscillator in the channel element on/off, so that seems to be a good starting point.
Presently I have good stability using the ProgRock stand-alone (no GPS PPS discipline); it's running less than 10 Hertz off my desired frequency. I expected much better performance with GPS 1PPS discipline, but after trying 3 different GPS modules, I've not had better success than without. I'm beginning to question the 1PPS I've been giving the ProgRock relative to the ProgRock 1PPS requirement; perhaps the ProgRock needs a wider pulse width than 1mS, so I'm considering trying a pulse stretcher stage; perhaps 10mS will do the trick.
I did find a significant increase in stability by thermally bonding the 27MHz. crystal on the Si5351A Synth module to the heat sink of the 5V regulator AND the aluminum Bud box enclosure, so if you don't want to deal with the GPS discipline, by all means make the effort to thermally stabilize the 27MHz. crystal & then thermally isolate the ProgRock enclosure from the environment. By the way, it's an inverse relationship...warmer crystal shifts the frequency down. Simply holding my finger on the crystal is enough to move the oscillator.
QRPLabs offers a OCXO module to replace the crystal on the Si5351A Synth module; you might consider using it. There's info in the archives of this email list on the various issues that may entail. I haven't tried that module so I can say anything about it's performance. I'm happy to share anything I learn along the way; feel free to contact me. Thanks,
Robin Midgett K4IDC
anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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Robin Midgett
Yes indeed. Given that the LPF kits require the builder to wind the toroids and the ease of replacing or supplementing the fixed value caps with narrow value trimmers, it seems that a tuneable LPF could be had by using the kit as a springboard. Thanks,
Robin Midgett K4IDC
On Mon, Jul 8, 2019 at 7:41 AM Bob / WA1MIK < wa1mik@...> wrote: Robin: Thanks for the filter recommendation. I would need two of them though, one for TX, one for RX, and the freqs are significantly far from the common ham bands that I'd need to fiddle with component values to make them do anything useful. One would need to cover 6.5-7.5 MHz, the other 9-11 MHz. Granted, once I retune the station from 26.31 MHz to 29.6 MHz, I would only need one set of filters, at the high end of those ranges.
Easily tunable filters would be more useful for this project, possibly with variable capacitors in each stage.
Bob M.
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When it comes to filtering the output of the ProgRock prior to multiplication, it's worth noting that the original crystal oscillator did not produce a nice sine wave: Remember that the crystal output is immediately used to produce harmonics in the following multiplier stages. In other words, for the purpose of harmonics alone, there is no reason why one would go through the trouble of doing so: For the receive crystal on the Mastr II, I *think* that you can simply program the ProgRock for the output frequency of the first multiplier, anyway, rather than crystal frequency, eliminating one such step - something that cannot be done on transmit due to the frequency-selective nature of the phase modulator.
The sole reason for some sort of filtering would be to attenuate energy that was far removed from the intended output frequency or its harmonics. While a low-pass filter would probably take care of 2x energy and higher, it will do nothing for energy that was much below this, near the desired output frequency or below it. Again, there may not be a need for such a filter in one's specific application - and if there is undesirable energy that is too close to the intended frequency (e.g. within a 100 kHz or closer) it may be challenging to construct suitably-tight filtering, anyway: In either case, even QRP-Labs' own band-pass filters might be too narrow for this - unless there is a redesign.
* * *
Somewhat OT, this reminds me of past discussions that I've seen (not in this group) where it was asked if one needs to low-pass a local oscillator prior to applying it to a mixer. The answer to this - assuming that the local oscillator is outputting ONLY integer-related harmonic energy - is simply "no, you don't." The reasons for this are:
- Doing the math, if one has appropriately used input bandpass filtering (on the "RF" port) and output filtering (on the "IF" port) you will find that harmonics won't contribute to spurious signals, anyway. (If one doesn't do the bandpass filtering, the use of a filtered local oscillator won't help you escape spurious signals, anyway...)
- Any mixer will produce harmonics during its switching, anyway - that's what it does.
- If you have ever used a switching mixer (e.g. QSD or "Tayloe") - such as that found in the QCX, many Elecraft radios, etc. it uses square waves, by definition.
A really good reference to this is Mini-Circuits Labs book "The care and feeding of diode ring mixers" (or something close to that) - an article from at least the 1980s - where they actually recommend square wave drive of mixers to lower insertion loss and improve power handling, citing the reasons above.
Again, if the local oscillator contains something *other* than integer harmonics, filtering is probably a good idea.
73,
Clint
KA7OEI
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Bob M.
I know the crystal signal isn't a nice sine wave, but it certainly isn't a square wave with very steep rise and fall times. Both have plenty of harmonic energy, which is why the multiplier stage can tune to the 3rd harmonic so easily. One of these days I plan on using a function generator's square wave output to drive my station, because that's easily adjustable up to 15 MHz, which will at least give me the crystal fundamental frequency to play with as an input signal to the channel element, in lieu of the crystal.
Bob M.
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Robin Midgett
Hi Hans, I've taken your very good recommendations into account & still no joy. Please see my reply in message # 36114. Thanks,
Robin Midgett K4IDC
Hi Robin
Several comments:
1. ProgRock was developed in conjunction with the QRP Labs QLG1 GPS http://qrp-labs.com/qlg1 which has 100ms (0.1ms) positive-going pulse. Though if your pulse-length is 1ms I would not expect there to be problems... but couldn't know for sure without testing it. I know something very short like a microsecond would be an issue. But a millisecond is relatively ages...
2. Watch out for voltage level problems. Most GPS chips operate at 2.8V supply, the ProgRock operates with 5V supply. The logic level threshold for a "1" is 3V if I recall correctly. Therefore with many GPS module models you need a level converter. A pull-up resistor to +5V can do the job often but you need the right resistor value. And even then, the noise immunity suffers compared to a "real" level converter. The QLG1 kit has a proper logic level converter so with its 5V logic outputs you never have an issue.
3. A heatsink on the crystal helps with thermal stability. So does putting the project in an enclosure to avoid drafts etc.
4. ON/OFF keying... are you aware of the frequency bank feature of ProgRock? There are three logic inputs, the permutations of high/low control signals in these allow you to choose one of three banks of output frequencies. If any frequencies are zero the output is just disabled. So it is often quite convenient to uses these logic level inputs to on/off key the output frequency you want.
5. Read the manual section about the GPS correction threshold register. For finest precision you want this to be 0Hz. The default is 5Hz which means the correction is only applied when the error if the 27MHz value exceeds 5Hz.
When all is well you should be well within 0.05ppm.
73 Hans G0UPL On Fri, Jul 5, 2019, 03:49 Robin Midgett < K4IDC@...> wrote: Hi Jim, Not a MASTR Exec, but a low band MASTR II mobile for use as a 6m beacon. I'm working on using the ProgRock in place of the crystal in the channel element. Once I get the low band beacon going in good order, I plan to expand to 2m, 1.25cm & 70 cm. I started this project over a year ago, set it aside for several months, and just today returned to it.
I plan to inject the RF from the ProgRock directly into the channel element connections on the exciter board, and key it on/off with a small memory keyer. It works just fine using a simple relay to key, but I want a solid state switch instead of a mechanical relay, so I've been working toward that.
I tried inserting the on/off keying in the bias & tripler circuits downstream of the channel element, but that didn't work well at all; the resulting RF was dirty & splattered across the narrow beacon sub-band. The original mic PTT simply turned the power to the oscillator in the channel element on/off, so that seems to be a good starting point.
Presently I have good stability using the ProgRock stand-alone (no GPS PPS discipline); it's running less than 10 Hertz off my desired frequency. I expected much better performance with GPS 1PPS discipline, but after trying 3 different GPS modules, I've not had better success than without. I'm beginning to question the 1PPS I've been giving the ProgRock relative to the ProgRock 1PPS requirement; perhaps the ProgRock needs a wider pulse width than 1mS, so I'm considering trying a pulse stretcher stage; perhaps 10mS will do the trick.
I did find a significant increase in stability by thermally bonding the 27MHz. crystal on the Si5351A Synth module to the heat sink of the 5V regulator AND the aluminum Bud box enclosure, so if you don't want to deal with the GPS discipline, by all means make the effort to thermally stabilize the 27MHz. crystal & then thermally isolate the ProgRock enclosure from the environment. By the way, it's an inverse relationship...warmer crystal shifts the frequency down. Simply holding my finger on the crystal is enough to move the oscillator.
QRPLabs offers a OCXO module to replace the crystal on the Si5351A Synth module; you might consider using it. There's info in the archives of this email list on the various issues that may entail. I haven't tried that module so I can say anything about it's performance. I'm happy to share anything I learn along the way; feel free to contact me. Thanks,
Robin Midgett K4IDC
anyone ever tried a prog rock as a crystal replacement in a ge mastr exec and how was it wired?
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