Category Archives: Kūryba

Dead HDD’s – design issue, or… ?

Few years ago we tried to use cheap SATA disks in HP disk enclosures as “cheap storage” (where information isn’t so important). Idea failed – none of disks tested supported TLER (~500x Samsung 1TB, ~200x Western Digital 1TB); and SmartArray controllers can’t handle such issues (disks tried to fix their issues for long time, controller decided that disk is dead, rebuild started, next disk dies, etc).

OK, TLER issue can’t be fixed (at least, without disk firmware disassembly), but what is causing disks to generate such amount of internal errors (1-2 disks in one 25-disk enclosure/week)?

Those disks are out-of service, so i disassembled few of them to check. So….

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Parkelis… Ir kt.

Dar kelios naktinės foto. Parkelis – iš pasakos ;-)


Pasirodo antys naktį nemiega – atėjus prie upės staigiai prisistatė ir paprašė ko nors skanaus ;-)

Skanaus negavo, tai bent jau papozavo šiek tiek…

Ta proga dar ir seniau susuktas video (tik šitas jau dieną, ne naktį):

Simple portable RF power meter

I had several RF heads – based on AD8317 (and working from PC), also based on AD8313 (you can get entire RF head assembled for ~20$ or so at and decided that i need portable box for measuring signal levels and VTX power.

Did that, working well:

it’s actually very simple and entire box costs ~35$ or so (if you have basic parts and attenuators already). Accuracy is acceptable (+/- 1.5dBm in -10 … -40dBm range).

And no, it won’t work better than other tools (even RF explorer is much better with it’s -105dB+ range); it won’t do correct math for frequency (MCU is too weak to do proper calculations). So, if you need serious tool – go look for other solutions. If you need something cheap and working well enough to test antennas/TX/RX – it works good enough.

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Circular vs Linear polarisation – long range comparison

I’m working on long-range (60km+ one direction, 200km+ total range) FPV plane. Almost entire plane is built from scratch (batteries, airframe, autopilot, antennas) and i’m trying to choose right components.

For 60km+ range i probably can’t go with single antenna – i need array of antennas (other options – LNA (good LNA are very expensive!), more power to VTX (and i need electric power for motor, also – interference), trackers on both sides (too complex and error prone)). Now just need to choose correct polarisation option…

So, my options at this moment – circular polarized array (CP BiCircles – i like circles :P ) or linear polarized array (again, bicircles). Both have high gain (~16dBi for CP array, ~17dBi for LP array), both can be built to be flat (another reason why yagi antenna is out of scope – too big to transport).

Lots of resources on internet about CP/LP choice, in general all agree about:

  • LP is worse in banked turs, CP works well in any direction (agree 100%, that’s why satellites use CP – but question “how much banking is too much for LP?”)
  • For the same volume/weight LP offers higher gain (serious reason why i’m reverting to LP – huge CP antennas, easy damaged in transportation, higher gain antennas (such as QFH) are draggy a lot)
  • CP is a “must have” for higher frequencies (again, agree – LP on 5.8GHz sucks ballz due to multipathing issues, but for long range i’m going on 1.3GHz setup)
  • LP antennas are easy to make (and this is great – i killed three cloverleafs while flying in forest in one day, repairing them takes lots of time. Long range plane keeps antennas safe, but sometimes they break anyway and…)

So, question remains – how much banking is too much for LP, and how much image quality i will loose for using LP? Knowing this, i can choose right antenna array. To answer this question, i did simple test. Conditions:

  • 18dB attenuator on plane (cut range by 4 – i.e. 10km with attenuator = 40km without. Well, at least in theory)
  • my old CP antennas – verified, 15km without attenuator is “easy mode”, VSWR < 1.5 when new vs brand new, just “cooked” Vee’s + BiCircle (BiCircle gain = BiQuad gain and almost the same radiation pattern)
  • The same frequency (1280MHz), the same plane with the same setup (and the same battery), identical weather conditions (well, if possible – liftoff during sunset without wind, after second test landed in almost dark environment, with strong wind)
  • If possible, very bad conditions (RF noise – cell towers nearby, willage, mobile phones; clouds, moisture)

What i got (distance is top-middle):

OK, my old CP antennas lived trough hell (lots of crashes, repairs, re-soldering, tunning) and probably do not have < 1.5 SWR anymore. But i didn’t expected them to perform so bad, compared to LP…

< 5km range with CP (OK, bit better signal quality compared to LP – less noise, no sudden signal loss), that’s approx 20km total range. 10km range with LP (still good signal when banking – check video) – that’s approx 40km total range without attenuator and in better weather/RF conditions (and really simple antenna construction, Vee’s won’t be destroyed by trees anymore) – i think, we got clear winner here.

Next in work queue – BiCircle antenna array for 60km+ range (and i guess 80km range should be easy too).


  • results are valid for low freq (0.9-1.3GHz) video transmission. On higher frequencies (2.4GHz and esp. 5.8GHz) it’s a different story
  • Yes, i will perform “max range” tests without attenuator, when i finish my long-range plane. Currently i can’t go past 30km to one direction (temperature issues, also some issues with current plane setup) so i can’t test single antenna to it’s limits, not talking about array…
  • BiCircle and BiQuad have identical gain and (probably) just minor differences to gain pattern. I choose BiCircle for it’s look and simplicity. Also, tested on different frequencies – works great, so why bother bending corners?
  • In good weather (no forests around, no rain/moisture, no clouds layer, no RF noise) range should be better. Take off attenuator, mount antennas and… =)

2012 rudenėlis

Atėjo žiema (kas iš to, kad ruduo kalendorinis) – tai prisiminimui video su rudens vaizdais:

Viskas iš vieno copterio, be gimbalų ar stabilizacijos, taigi geresni video (lėktuvėlių, hex’o ir t.t.) dar bus kažkada ateityje. Gaila tik, kad vimeo persistengė su kompresija – ir taip pas pirmą GoPro ne pyragai su 1080p vaizdo kokybe, o dar šitaip perspaudus…


Dažnas klausimas forume – va, noriu skraidyt, noriu kelt DSLR’ą į orą, noriu skraidyt FPV, nuo ko pradėt…

Pamėginsiu aprašyt savo siūlomą startą. Priimam prielaidą, kad bazinės žinios jau yra, nereikia aiškinti, kas yra rudderis, kaip jungiasi imtuvas, kas yra ESC, bei kaip skristi “į save” – laikom, kad tas bandytojas jau skraidė su lėktuvėliu ir turi bazines žinias.

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