I thought long and hard about which unit to choose; there are now quite a few on the market.
The three that made it to my shortlist were:
(1) The widely reported as very accurate, Array Solutions units, enjoying excellent Eham reports.
(2) The SARK-110, also reported as very accurate and with excellent Eham reports.
(3) One of the RigExpert units, which are in widespread use, also enjoying good Eham reviews.
The Array Solutions units are the reference standard by which the ARRL tests in QST are compared. So there is no doubt at all that these are top-of-the-range units, comparable to industrial analysers costing an awful lot more.
Two reasons went against the Array Solutions units: cost and the need to have a computer running alongside. This latter aspect can be overcome with a laptop, but it's not ideal for me.
The RigExpert units are very fine, very well thought-out analysers with a long and good reputation. A review in the latest QST magazine showed the 'Zoom' unit, the latest offering, to be accurate and reliable. However, it is quite expensive, and some have commented that the features offered, whilst more colourful on a new screen, are not that different from earlier, cheaper models like the AA-30 and AA-54.
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| The SARK-110 is very small - but extremely capable. |
Because one is often out in the cold and good-sized buttons built onto a battle-ready case such as enjoyed by the RigExperts are essential, I was very close indeed to selecting an AA-54.
In the end, I opted for the diminutive SARK-110. With its tiny dimensions and buttons, this has all the wrong features for me! Except that a QST review recently found it to return values almost identical to the Array Solutions reference unit. That, and the fact very many people - myself included - have found the maker to be very responsive to requests and questions. The firmware is regularly updated for free to accommodate not only bug fixes, but entirely new features as well.
Given that one can subtract the feedlines from the SARK-110 calculations and end-up with a virtual feed point measurement, the ability to use it inside, where it's warm and clean, means its unsuitability to extreme outdoor use isn't such a drawback.
UPDATE.
The SARK duly arrived at a local delivery point yesterday afternoon. The package is very small, so if you've spent money on this that your XYL preferred you hadn't, you can blandly pretend it's 'just a cheap SWR meter' inside the package!
I found myself thinking that the SARK is so small that I really ought to have stuck with the RigExpert models. But that feeling was washed clean away when I switched it on and saw firstly how intuitive it is to use - I've yet to resort to reading the manual - and secondly, how cleanly everything is displayed.
The frequency sweeps are very quick - maybe 2 seconds or so, so there's no hanging around, waiting for readings to be taken. Even the multiple HF sweeps are just as fast. The sweep can either be run continuously or as a 'single shot'. The continuous mode is very useful for watching in real-time as any changes are made.
The main question people will have before buying a SARK is: just what connector does it come with? I've read a lot about the SARK, including a very recent QST review where the supplied connector was an MCX (on the body of the SARK) to BNC female type. This meant that, for that review, adapters (BNC male to SMA female) were bought, albeit cheaply, to allow the SMA male calibration loads to be fitted.
The calibration loads you need are: an Amphenol SMA shorting cap, part number 523-132331 and an Amphenol SMA 50 Ohm termination cap, part number 523-132360. In the UK, from DigiKey, these tiny bits of metal and plastic will set you back an astonishing £25 or so.
You'll be glad to know that my production model came with an MCX to SMA female connector, with about 30cm of cable in between, which means the expensive calibration loads fit directly, making life much simpler.
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| The supplied SARK-to-outside world connector is currently an MCX to SMA female. You need an SMA male to SO239 or N-type connector for HF/VHF analysis. |
The calibration process is directed with simple 'connect this, connect that' on-screen instructions, which takes just two minutes or so. A comparison of factory calibration with my subsequent calibration shows this system works perfectly, with no evident anomalies. Do remember to keep your caps in the original, labelled bags, or lightly etch a label onto their tops, so that you don't confuse which is which - they both look identical!
Don't worry, as some have done, about the longevity of the MCX connector onto the SARK. True, the rated lifetime is about 500 connect/disconnect cycles. But you simply keep the MCX to SMA adapter permanently connected, and add a SMA male to SO239 or N or whatever. This really is no problem at all!
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| A photo of the SARK's screen (not a screen grab), showing the very clear layout. The results are for my 14MHz vertical delta loop, with a tiny tweak from my ATU. |
The SARK connects up to your PC easily; I found there were no driver headaches when installing onto a standard, elderly Windows 7 machine. The drivers were found from online sources, automatically.
After a few hours' use, I have to say I'm really, really glad I bought the SARK. I think the protective case might be a wise use of money, as it might be prone to knocks and bumps owing to its size. Data from measurements transfers across easily as CSV files, opened without fuss into any standard database program. Bitmap images can also easily be grabbed by the SARK.
One thing that strikes me about the whole concept of analysers is that, especially for beginners, they can provide far too much information. There is nothing wrong with - and was the only way possible for decades for the vast majority of hams - cutting a wire to the correct length and, through just a little pruning, getting a good match at the rig. This is how I made my delta loop, and it's worked without fuss, both with and without a matching unit, across the world.
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| There's little point being over-fussy about small antenna imperfections. This shows my 12m LFA Yagi's driven loop could do with a very minor lengthening. But with the SWR below 1.3:1 for the sections of the band I use, I won't be rushing to make changes - especially as I'm often the only one heard on 12m in the US. |
The danger is that a beginner might cut a wire, fire-up an analyser, and start obsessing over getting a perfect SWR and a perfect impedance. Just about all of us have antennas that are a little way off perfection, often due to environmental effects of surrounding cables, tin sheds and cars, and we live with it - with an ATU if it's that much out. There is leeway in antenna construction, and I hope some perfectionist types don't spend weeks banging their heads against brick walls because they just can't get that last bit of imperfection eliminated.
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| The dramatically-sharp tuning of my magnetic loop antenna (homebrew), at the 60m WSPR frequency. |
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| I love this plot. Just a simple elevated vertical, two elevated radials. Or, three wires up a fishing pole! That match is just beautiful for data modes, especially knowing the simplicity of the antenna - and also that it's pretty close to other antennas! |
If you think I'm being defeatist about small antenna imperfections, have a look at the specification of some really expensive commercial antennas. Quite a few can only claim an SWR "below 1.5". It's worth reflecting on that.
My score for the SARK? 10 out of 10. Absolutely brilliant piece of kit.
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