NT7S profile
NT7S
NT7S
Open source amateur radio and electronics
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Recent posts

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NT7S
Public post

I've got a modest new hardware product in production, with a related update for subscribers in the post below this one. In addition to working on that, I also recently pushed v1.3.1 of the JTEncode library, which adds a convenience function to convert decimal degrees to a Maidenhead locator. Handy for those of you paring your WSPR transmitter with a GPS.

Next up is to tackle an issue that's been plaguing the Si5351Arduino library. The PLL algorithms in the library aren't accurate enough to generate MSFK signals properly on VHF. I know that a lot of people have emailed me about this over the last few years and I haven't responded to many of the mails. I get a ton of unsolicited emails, and as much as I'd like to be able to help everyone, most of the requests I get would require a non-trivial amount of time for me to properly answer. However, this is one of the things that I hear about a lot, and it needs to be fixed.

My plan is to do a careful analysis of the current tuning characteristics of the library at VHF. In order to do that, I needed a new frequency counter with better precision than the ones I currently have (and also very importantly, the ability to lock to my 10 MHz GPSDO). I managed to find an affordable instrument through tequipment.net and was able to pay for a large chunk of the cost with the money I've received through SubscribeStar. Thank you very much subscribers for your support, which helps me to fund important new lab equipment!

So I'll be drafting up a test protocol so that I can quantify the current tuning inaccuracies and have a way to ensure that I improve them with new code. Stay tuned here for further updates on this project. I hope to have some good improvement to push in the near future!

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B0fe8ec0 8aa3 4d61 a1cd a367f7d24065 120x120 1x1 2374x2374
NT7S
Public post

I'm pleased to report some good news about the Si5351A Breakout Board reference oscillator situation. While the original Abracon TCXO is still basically unavailable as of the date of this post, I have found a suitable replacement TCXO for now. I spent a few days in the lab running a batch of test boards through the normal test and calibration routine (which they passed with flying colors), but also doing extended testing on frequency stability, temperature sensitivity, and very narrowband TCXO tuning compensation behavior. The new TCXO looks at least as good as the Abracon osc, and could possibly be even a bit better (although that's based on an estimation, since I didn't directly put the two different oscillators through the same tests at the same time). They are certainly suitable for the Si5351A Breakout Board according to my standards, so I will be using these going forward.

I've secured a decent amount of these, which should keep me supplied for at least a few months. Once the Abracon oscillators are available again, I may continue to use them if supplies of this new oscillator become scarce, but I don't expect that users will notice any significant difference between the two.

Also, I wanted to note a small change in the Si5351A Breakout Board calibration report due to some confusion. In previous reports, the calibration factor was written in the sign needed to add or subtract from the nominal 25 MHz ref osc frequency (in other words, if the ref osc was 1000 ppb high, the report would print the correction as "-1000 ppb"). However, in the Etherkit Si5351 Arduino library, the factor you need to use to set the correction has the opposite sign, so in the previous example, you'd need to put in a positive correction, not negative. From this date forward, our calibration reports will use the latter standard, so that you put the number printed on the calibration report as is into the Arduino library correction method.

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B0fe8ec0 8aa3 4d61 a1cd a367f7d24065 120x120 1x1 2374x2374
NT7S
Public post

In a bit of Etherkit news, we've encountered a supply chain issue that could put a squeeze on Si5351A Breakout Board with TCXO reference oscillator manufacturing. Late last year, there was a fire at the factory that manufactures many different oscillators, including the Abracon product that is used in the Etherkit Si5351A Breakout Board.

On Oct. 20, Abracon became aware of a fire at the Asahi Kasei Microsystem (AKM) semiconductor factory in Nobeoka, Miyazaki prefecture, Japan. Products produced at this factory are used in many Abracon TCXO oscillator products. At this time, there is limited information on the actual effect the fire will have on production and supply.

I have been able to acquire small quantities of the TCXO used in the breakout board until my most recent attempt. That particular part now is out of stock at all of my usual distributors, and is only available at one distributor but at a substantial markup from the usual price.

As of now, I'm considering the qualification of an alternate TCXO, but that will take some time to do. It may be necessary if Abracon cannot bring production back online in the near future, but I'm hoping they can source alternate manufacturers as is stated in the press release above. In the mean time, there may be a period where the Si5351A Breakout Board with TCXO is out of stock. The breakout board with crystal oscillator is not affected by this and will continue to be in stock.

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