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Progrock2 for Atlas210x

 

Hello All,
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This is the first time joining a "group" so I am likely going to have difficulties navigating this place for while.
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I had xtal go bad on my Atlas 210x and its proving to be a challenge to find a replacement.? I am wondering if anyone has been successful using a Progrock2 for this?? The product is intriguing, but I am also certain I do not have the knowledge to figure it out on my own.? Anyone done this before with an Atlas 210x?
 

I have an Atlas 350XL I'm going to try these in, but first I plan to use them in a repeater project. They should work for either, and the prospect of having programmable band segments on the Atlas is intriguing to me.
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Bomar is the only US crystal company left that I know of. Try them if you don't choose a Progrock2.
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73 Chuck AI7SY
 

likely progrock will work.
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I use a variant of that to replace the VFO and both carrier crystals
same basic source (SI5351).? Works for me.
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--
Allison
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Post online only,?
direct email will go to a bit bucket.
 

A similar question came up just last week on the Antique Radio Forum.
I (and another ham) suggested looking at the ProgRock2 as a crystal
replacement.
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For the crystal replacement application, is a sine wave required?? My
understanding is that the Si5351 generates a square wave and that a
LPF is? then used to produce a sine wave.? Would this be needed for the crystal
replacement case?
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Thanks!
- Bruce K1FFX
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The waveform is not critical.? If sine is needed a low pass filter will achieve that.
Oddly the amplitude is critical too high or low impacts performance.
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Some applications the rich harmonics of the waveform is useful.
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FYI the Atlas 210X carrier osc is rather poor for waveform.? It looks like
an abused half sine.? ?Seems to work well.? I have two one stock and
works very well and one that was abused likely parts dog missing
VFO and carrier osc board and crystals.
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--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
 

I'd like to expand this to a more general discussion of using the ProgRock2 as crystal replacements in vintage crystal-controlled gear. I have a 1960s military CW-only manpack transceiver, the , which is crystal-controlled for both transmit and receive. For each of the six operating frequencies, it needs two crystals: the receive crystal is 455 Kc above the operating frequency, and the the transmit crystal is on the operating frequency. At today's prices, 12 crystals is a serious investment (if one could find crystals for the desired frequencies). Anyone have any experience with using the ProgRock2 as a crystal substitute in similar applications?
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Tks & 73,

Scott WB8ICQ
 

Scott, in general, applications will be slightly different, but will fall into a handful of approaches.
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For example, in my repeater application, I have oscillator modules using a FET. I will remove the crystal and the feedback in the oscillator circuit, replace the crystal with a progrock2, and use the former oscillator as a buffer. It's possible to replace both oscillators with a single progrock2, but in this case, I want to remain compatible with the original design, since the repeater can use eight selectable oscilator pairs. I have 10VDC available for power.
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For my Atlas, I plan to use a singe progrock2 directly for three of the ten user selectable band segments, directly replacing three crystals. I have 7.5VDC power there.
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Without seeing the inside of your radio and a schematic of the oscillator section, all I can say is your solution might resemble one of the above. Padding, filtering, and power are the things that can complicate basic replacement.
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The datasheet for the SI5351A will show other possibilities. It's a good starting point.
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73 Chuck AI7SY
 

I'm working on using the ProgRock2 for multiple oscillators in my IC-751A.? The ProgRock2 output turns off momentarily when changing to a different frequency bank.? In my initial attempt, I changed ProgRock2 banks when changing from receive to transmit mode.? One of the ProgRock2 outputs feeds a PLL circuit which goes wonky long enough for the initial transmitted signal to suffer.? I plan to insert solid state switches on the outputs so I won't have to change banks.
But when controlling a carrier or band-specific local oscillator where a PLL is not involved, it shouldn't matter.? Select your coupling capacitor to feed a signal strength similar to that given by the original crystal oscillator to the next stage.
As mentioned earlier in this thread, don't be concerned about the ProgRock2's squarish waveform; LP filters in the radio's original circuit will probably clean that up.
Halden VE7UTS
 

A little off-topic, but ..
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I've been using frequency generators as crystal replacements to get extended frequency
coverage on my Drake R-4B receiver for a while.? For several years, that was a major use
of my QRP-Labs VFO/SigGen (based on the Si5351a and a complete set of LPFs).
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More recently, I've been tinkering with Arduino-based signal generators.? Since I wasn't
sure about the need for a sine wave, and since I already had some experience with it, this
was based on the AD9850 module, which generates sine waves.
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My current iteration of this uses a Teensy 4.1, which has Ethernet on it, and a Python
program that runs on my desktop to select the appropriate "crystal" for 49 meters, 25
meters, etc., and talks over my LAN to the Teensy, which drives the AD9850.
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But, I will now get hold of another Si5351a module and TCXO from Hans for further
tinkering (previous tinkering a few years back found a library on GitHub for talking to
the Si5351a .. I will dust that off).
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Cheers -
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Bruce K1FFX
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I have used the ProgRock2 in numerous projects (mostly Heathkits), and detailed how to use the device in a recent article for ER Magazine.? Some pointers that may be helpful:
- The device isn't really a direct replacement for a crystal.? Generally speaking, it replaces the entire oscillator section.? For example, when using the ProgRock2 in a Heathkit HR-1680 receiver, the entire HFO board is stripped of components related to the old oscillators.? To use a ProgRock2, you have to decide how you will integrate it, as much depends on the existing engineering of the radio.
- The ProgRock2 is best powered from a well-regulated 5V source.? In my projects, I build in a simple LM-7805 regulator circuit if the existing power might be unsuitable.? 5V seems to be a sweet spot.
- To key the ProgRock2 to change to another frequency bank when a band switch is rotated, I use a diode matrix to create the logic pattern and three 2N3904 transistors to present the low signals to the bank selection pins.? It's bulletproof.
- Due to potential cross-talk in the Si5351a chip, test carefully in your project before using more than one frequency output at a time.??
- The square wave output has never created a problem in my applications (usually replacing old, defective, crystal-based heterodyne oscillator circuits in HF receivers and transmitters).
- Although the ProgRock2 technically holds up to 24 frequencies, I've found that in practical application the limit is really 8 (one for each bank).? Yes, you can use more than one bank, BUT I've not had good luck with more than one clock operating at a time (YMMV).? For more than 8 frequencies, I use an Arduino-based solution.
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Hope this was helpful.
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73 - Steve, KW4H
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Chuck,
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I've two Atlas 210Xs.
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The Atlas only uses two crystals (USB and LSB carrier osc)? other than
100khz calibrator.
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The band switch also selects the VFO frequency. Unlikek most radios?
the VFO operates at 5.220mhz higher (or lower for 15M and 10M)
than the band selected.? ?Unusual scheme and prone to drift.
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External OSC control input (plug on rear panel) allows for a
Crystal OSC or external source as substitute for the VFO for
nets and other "fixed" frequency work.
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That's the case for the 180, 210 and 210X, 215X.
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--
Allison
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Post online only,?
direct email will go to a bit bucket.

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