Regular readers of my blog will know that I am quite interested in using WSPR for checking antenna performance, evaluating different environments, and finding curious propagation effects.
In one way or another, at some time or another, WSPR is of use to just about all of us. Whilst drifts of +/- 4Hz can still produce reliable decodes, drift of that degree is very unusual, generally indicates non-TCXOs, and in the WSPR community, is not really tolerated as acceptable. Practically everyone produces zero drift, day in, day out.
Hence, as I look towards the next year, I am trying to find out as much as I can about, in particular, the Lab599 TX-500, which is not yet available in the UK.
This looks like a fine QRP transceiver. But how good is its frequency stability? I may have missed it, but I couldn't see any reference to the crystal stability anywhere for the TX-500; the manual's specifications pages (pp 28-29), accessed 10/09/20, has no reference to it.
Frequency stability is, these days, quite an unusual thing not to shout about. The forthcoming IC-705 from ICOM, in contrast, proudly announces its 0.5ppm stability.
Even the cheap (but excellent) WSPRlite units have a TCXO, and the WSPR database is full of their zero drift transmissons.
An exchange broke out on Julian, OH8STN's Facebook page over the past day. I was complaining that, despite several searches and requests, I still had no data on frequency stability for the TX-500.
Julian started off by somewhat seeming to take my disappointment about the lack of data as a personal attack. I replied that providing the stability data was as easy as someone - anyone - running a few minutes of WSPR transmissions. But nobody has done it. And nobody seems willing to try.
By now, Julian sounded less like an objective reviewer and more like someone trying to sell the TX-500. He asserted that the TX-500 was stable enough to run various digital modes, which wasn't addressing my question.
Eventually, I had this, rather suprising response:
Again, this isn't providing any data. It's merely someone's assertion. And one where providing the data to back up that assertion, if it's true, is easy. When I looked at Julian's call, with and without a /P extension over the past two weeks on the WSPR database, there were no entries.
A crystal stability of 2.5ppm is certainly not what we expect of a modern transceiver costing 890 Euro. My FT-450, now an old rig, but still significantly cheaper new than the TX-500, produces zero drift in WSPR, regardless of any environmental changes.
With the addition of a £15 generic, Chinese TCXO, my even older TS-480SAT also produces zero drift, regardless of working conditions. And, if we believe the maker, even the Xiegu X5105 has +/- 1ppm stability - for 200 Euro less than the TX-500.
Oddly, I started out as a strong supporter of the TX-500, provided it comes to be sold in the UK directly. But nobody seems willing to send some WSPR transmissions from it for five minutes, to which we can only submit the question: why?
Until I see someone demonstrate the actual frequency stability of a production TX-500, it will remain in the 'important questions not answered' category.
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