Samsung Chromebook 303C

This is very off-topic, compared to what I usually would publish.

Some week ago, I got myself a Samsung Chromebook 303C. The device is best described as a 10" ARM-powered netbook-like gadget.


Some details in short

The device has got

• a really nice full-sized keyboard,
• multi-touch touchpad,
• a built-in webcam,
• a built-in microphone,
• built-in stereo speakers,
• 2GB RAM,
• 16GB SSD storage,
• a integrated WiFi interface,
• 1 USB 3.0 port,
• 1 USB 2.0 port,
• an HDMI interface,
• an SDHC card reader,
• a single jack headset connector,
• and a power jack.

I may have forgotten one or the other thing, more specific information can be found on Samsung's webpage.

First of all, I bought the thing for having something lightweight, inexpensive to carry about daily. One of the most important points for my was a decent keyboard... and actually, I am very very happy with this one!

Some observations

Things I like:

• the keyboard is really smooth and precise
• the sound of the little speakers is impressive
• the touchpad is very responsive
• the display is crisp and has an excellent brightness range and is matte
• the lower power device does not generate a lot of heat and no noise at all
• very low battery drain during sleep
• the start-up time from cold boot is amazing!
• the device needs 12V, making it ideal for field-day operations

Things that could be better:

• the white power-LED on the right side of the keyboard is somewhat irritating
• a replaceable battery would be a benefit for longer journeys
• individual sound-in and sound-out connectors
• the headset connector is not really smooth
• WiFi occasionally stops transfers, although the connection did not drop

Things I don't like, but can understand / live with

• the display hinge projects quite a bit, I figure, this way it still is sturdy
• there is an access port in the back, which is for a SIM card of more pricey models, with a very flimsy lid
• one needs 2 hands to open the display lid
• the plastic feels cheap, but than again, it is a cheap device

Things I really don't like at all

• there are no left / right mouse buttons, a right-click is a strange two-finger gesture
• there is not obvious way to quickly disengage the touchpad, which would be practical for writing longer texts
• an SDHC-card projects a whopping 7mm out, rendering the card reader useless a storage extension, the card reader has no "spring action", a card to be easily accidentally pulled out... what were they thinking?!
• the power supply is really out of date and weight...

Conclusions and Thoughts

All in all, this is a cloud device. Being offline means that many things can't be done. There are some applications which can be used offline, hence basic functions as text-processing, using a calendar or a basic spread-sheet are still available.

ChomeOS, which runs on the device, is a very down scaled Linux, which in essence uses the Chrome browser for running HTML5 applications.

There are presently first attempts to create full Linux distributions, e.g. Ubuntu by Canonical. Over time there should be some stable distributions available for a full offline experience.

I am happy with the device, knowing its' limitations and the intended use.

Acer Aspire H340 & NAS4Free

Once again an off-topic post in the blog. Somehow the strange desire to share computing / IT topics occasionally took over.

Presently, I am rebuilding my IT, trying to catch up with recent technologies.

Years ago, I purchased an Acer Aspire easyStore H340. The neat little device came with 3 1TB HDDs and MS Windows Home Server. The latter, although doing its job, sucked. Finally, I decided to look for alternatives, in particular some with RAID redundancy and modern file-systems, such as ZFS.

The first alternative I found was "freeNAS". This product, along side some others, is supposed to run from flash drives or SSDs. This would helps to speed up boot and also preserves valuable HDD slots for volume data devices.
And here it comes, the H340 carries an onboard 256MB flash memory device, which is used for MS WHS recovery.
Early versions of FreeNAS were small enough to fit on this device. However, FreeNAS has evolved and grew somewhat larger.

The good new is, that there is some other product, which originates in FreeNAS and is still small enough... check out NAS4Free.

To install NAS4Free, I figure, there is only one option: equip the headless H340 with a head, i.e. a keyboard and a screen. I choose to obtain a PCIe-1x graphics card and use a USB keyboard for input.
Additionally, JP3 needs to be installed!!! Do not remove the jumper at any later stage... at least my H340 would not boot NAS4Free w/o it. Contrary to JP3, the graphics card can be removed, e.g. to reduce power consumption.

Here comes the tricky bit, the H340 needs some strange tweaks to get it to boot from USB sticks, USB CD drives etc. The CMOS setup is not that straight forward, but, it will get you there. The F12-key will help to select the boot device, if it has been recognized by the system.

To get up my system, I choose to boot the NAS4Free live CD with a USB CD-drive.
The option to install an embedded system w/o swap will install the OS on the H340's internal flash drive, just about... no room to spare, all done with a screen/kb attached.

Here comes the more fancy bit.
In such a setup, you would like to go for the most senior option of storage, which presently seems to be ZFS.
The configuration of ZFS is actually not very well documented, neither at SUN, nor at NAS4Free. So, here's what I did to get ZFS up and running on an H340.

1. install NAS4Free from a CD using a screen and keyboard attached
2. reboot after installation has finished, the console should offer a possibility to use DHCP now
3. note the IP-address given to the H340
4. using a remote computer, connect to the H340 using a webbrowser
5. go to the "disks" menu and "import" all disks
6. go to the "disks format" menu and format all HDDs with ZFS
7. go to the "disks zfs pools" menu and create a virtual device (I used single parity raid)
8. go to the "disks zfs pools management" menu and create a "pool"
9. go to the "disks zfs datasets" menu and create a dataset using your pool(s)
10. go to the "disks zfs volumes" menu and create a volume using your dataset(s)

The volume(s) should now be ready to use, i.e. assign to services. Under the "services" menu, one can activate various services such as NFS, CIFS/SMB, AFP etc. Assign those services to a mount point in your volume(s).

You'll by now be running a rather robust ZFS NAS made of relatively cheap WHS hardware.
I figure it is pretty cool that NAS4Free still fits on the onboard flash drive of the H340.

PSK Transceiver Kit

Very unfortunately, but understandably, Dave (Small Wonder Labs) has discontinued his marvelous PSK-series transceivers.

Lucky for us, there is another kit vendor, who's kits have the potential to replace the ones of Dave.
Have a look at the KN-Q7A kits.

The 20m KN-Q7A operates with an i.f. of 4.194MHz, using a ladder filter made of standard xtals. The transceiver makes us of a moderately pulled VXO of 18.432MHz. All parts a relatively standard and well known, apart from a couple of inductors. The design makes use of subtractive mixing, which increases stability.

Here's what we can learn from Dave's PSK-series, the combination of standard crystals to result in an operating frequency near enough to the PSK bands.

• 30m: 4.000MHz + 6.144MHz
• 20m: 5.0688MHz + 9.000MHz

The only difference to the KN-Q7A is that additive mixing is used. 

The 40m KN-Q7A involves two different i.f., dependent on the frequency range ordered, either 8.467MHz or 8.192MHz. The l.o. will make use of any of those frequencies: 15.360MHz, 15.418MHz, 15.500MHz, 15.536MHz or 15.570MHz. I have not yet figured out a combination to reach 7.040MHz, however, I am sure that one can be found.

Further, I am convinced that the design can easily be adapted to the 80m band. Think of 10.000-6.400 for starters.

As to QRSS/WSPR:

• 30m already cover the mod above
• 15m 4.000MHz i.f. and 25.000MHz l.o.
• 15m WSPR:  4.096MHz i.f. and 25.000MHz l.o.
• 20m could be reached by 4.000MHz i.f. and 18.000Mhz l.o.
• 20m WSPR: 4.096MHz i.f. and 10.000MHz l.o.
• 40m best option would be 4.000MHz i.f. and 11.000Mhz l.o. (alternatively 11.059Mhz)

Easy 472kHz Superhet

Just a thought, a 4.000 MHz (industrial xtal) signal mixed with a 3.530 MHz (80m xtal) signal would result in 470kHz, somewhat shy of our band.

The 4MHz would make a nice intermediate frequency, with a cheap ladder filter. Tweaking QRG is hence restricted to the 3.5x MHz frequency

A couple of options

• pull 80m xtal down
• pen the 80m xtal down (super VXO)

A thought outside the box could be to get dividers into the equation. Douple 3.530 and you will get 7.060. As stated above, the 3.53 are just a bit too high.
Expanded Spectrum Systems sells 40m crystals, which, divided by 2, would result in in-band frequencies.

• 7.042 MHz => 479kHz
• 7.050 MHz => 475kHz
• 7.055 MHz => 472.5kHz

Also here, a super VXO would be an option.

For a WSPR transceiver, the 7.050 MHz option seems ideal. A small downward pull of some hundred Hz should be easily doable without compromising stability. Mind you, WSPR need a "USB dial frequency" of 474.2kHz.

600m Octaplumb update II

A while ago, I built the Octaplumb octagonal RX loop, made from heavy gauge copper wire and PVC plumbing parts (see earlier posts). The loop was tuned to 504kHz, since that was what we had at the time.

Very recently, we know got a slightly different range. Hence, the center QRG of the Octaplumb had to be changed. Some experimentation showed that adding 82pF to the 680pF which are in parallel to the butterfly configed poly-vary-con.

Light Communications Idea

Once again, the entertainment industry inspired me to this one. In stage illumination, the most recent development is the use of multi-color LED spots and washers. Those devices contain either three or four differently colored groups of ultra-bright LEDs. Controlling of the spots or washlight is usually done a serial protocol called DMX, by so called DMX-controllers or DMX control software.

In stage lighting language one controls different settings of "fixtures" (the lighting devices) and stores this control settings in "scenes". The scenes than can be called either manually or automatically as a sequence called "chase". The frequency in which the scenes of a chase are being called usually can be set by a sliding fader.

So, what's the trick about all this and where is the link to amateur radio?
Very simple, in long range light communication or cloud scatter experiment, usually QRSS is used. Now the link should be obvious... the fixture(s) are, very obviously, the light source(s), while the DMX-controller serves a beacon keyer.

A simple series of unmodulated dots (A1A) can be programmed with the following 2 scenes:

1. red on all fixtures to 100%
2. red on all fixtures to 0%

The next step would be to program of a chase of scene 1 and scene 2.

Unmodulated signals may be hard to discriminate. However, with the strobe function, the entertainment industry offers a solution to this problem. The strobe will create sidebands in the known fashion.
So, for a modulated signal (A2A) the following scenes can be used:

1. red on all fixtures to 100% with a fast strobe
2. red on all fixtures to 0%

Again, the chase would simply repeat scenes 1 and 2.

In order to know what I am writing about, I actually bought some material at a local pro-audio store:

• the washlight I obtained is a relatively small one: http://www.chauvetlighting.com/slimpar-38.html
• and this is the controller of my choice: http://www.highlite.nl/silver.econtent/catalog/highlite/entertainment_products/showtec/lightcontrollers/dmx_lightcontrollers/sm_8_2_16_channel_lighting_desk

Reasons for the decision on just those devices:
The washlight can be controlled by either 3 or 7 DMX channels. 3 channel resemble the control of the red, green and blue LED groups. 7 channels include said RGB-controls and some more stuff, which can be found on the respective webpage (#4=hue, #5=strobe, #6=color cycles, #7=luminance).
The lighting controller employs 8 faders to control 16 channels before switching to another "fixture" (i.e. bank) is required. This 8 channels fader control comes handy to control 7 channels of the SlimPar 38 or (and that's another trick) 3 channels of 2 SlimPar washers. In the latter case, two devices are controlled by a single fixture channel.
Just for the interested: the trick is the address of the washer or spot. The address of the first device (officially called fixture, but this can be confusing here, hence, let's call the individual washers or spots "devices" for now) will be "1".  If the device is using 3 channels, the address of the second device could be "4". In this case, provided the above mentioned controller is used, the first 3 faders would control the first device's R, G and B groups and faders 4, 5 and 6 would control the second device's R, G and B groups. The advantage, the two devices are now dealt with as a single fixture.
Advice: With a 16 channel controller (as the one I am using) one could potentially control 5 3-channel devices, however, the assignment of the fader will be rather confusing. Therefore, I recommend controlling 4 3-channel devices only. For sake of convenience, I would assign the second device to address (channel) 5, the third to address 9 and the fourth to channel 13.

Back to QRSS. Even the cheapest of DMX-controllers with the cheapest of LED-spots would make a real nice light beacon setup. OK, I went for something more sophisticated... since I see a secondary use in my light beacon setup... just in case I want to through a party, I now have a club-worthy lighting setup.

Concluding, there may be "red only" devices. However, stage worthy multi-color devices would even allow for multiplexing, depending on the receiver filters. The ones I use through out 1500lx @ 1m each, all LEDs engaged (at a power consumption of about 20W). Since I bought 4 (for good measures) that would be 6000lx @ 1m in white or about 2000lx using just one color.
Now I need to work out some receiver concept.

30m OPERA TRX

There is a new mode on the market which was named OPERA. The interesting bit about it, it uses A1A modulation. This makes it suitable for LF and MF operations in The Netherlands, reason enough for me to have a further look.

It seems, the mode is used on HF and VHF too. There are frequencies mentioned for all the bands.
Since one has to start somewhere, 30m is the band of choice.

The OEPRA center frequency is mentioned to be 10.1365MHz. This frequency should immediatly ring a bell, at least if the dear reader is familiar with my blog and stuff I posted earlier about.

There is a standart crystal (and canned oscillator), which comes along quite handy for a subharmonic receiver: 5.0688MHz. This as an oscillator would result in a direct conversion LO of 10.1376MHz. Consequently, such a receiver would create an audio signal of 1.1kHz on the lower side band. Since the modulation is A1A, this does not matter at all. It is conceivable to add a crystal notch filter for the upper side band.

As to the transmitter, the solution is similarly simple. Just an oscillator using a 5.0688MHz crystal with a tiny downwards pull of 550Hz. That should be easily doable. Should I intend to build such a transmitter, I will use a VXO as to just cover the frequency range 10.1363-10.1369MHz, which, translated into oscillator range reads 5.068150-5.068450MHz, reflecting a VXO range of 300Hz.
Frequency doubling could be done either actively or passively by just two diodes.
The trusty old 74HC240 could serve as a driver or power amplifier.

Since the mode is keyed, both RX and TX can be easily tied together in a QSK fashion.
As a bonus, if the mode should become out of fashion once, the rig can easily converted into a QRSS receiver by changing the crystal notch filter to a normal crystal filter and pull the TX oscillator up.

In ITU region 2, this transceiver could be used for Feld Hell. Seen that the Hell frequency is rather close to the local oscillator frequency, it may be desireable to change the RX oscillator to 5.0680MHz. CMOS oscillators are available for this frequency.

472kHz I/Q-SDR kit

Nothing is for free, up to now, there is no kit available for 472kHz.
However, there is one for 136kHz, which can be easily modified to match the new band.
Check out box73's longwave I/Q-SDR kit.

You will see that a 15MHz signal is divided by 25. This results in a 600kHz signal which is further divded by 4 in order to create the phase shift. All in all, this ends up in a center frequency of 150kHz.

We can use the same oscillator and divide the signal by 8. This results in 1.875MHz, which will be further divided by 4 providing a center frequency of 468.75kHz.
With a sampling rate of mere 24kbps, or +/- 12kHz bandwidth, the entire band (472 to 479kHz) will be covered.

The digital part is rather simple to modify. A suitable ripple counter could be the 74HC93.
The frontend is even more simple... just pick a 455kHz i.f.-filter/transformer and replace C1, C2 and L1.

Should the old experimental range, somewhere above 500kHz, be a desired range, the additional modification would simply replacing the 15MHz canned oscillator with a 16MHz one.

I will see if I can persuade the OM at box73.de to provide such a kit.

MF/HF Aerial

And along came an idea....
You may have heard about the CobbWeb aerial. Essentially, this is a cluster of dipoles for the bands 20m, 17m 15m, 12m and 10m. The cluster is fed via a coax choke.
Maybe there is a way to squeeze more out of this aerial. The amount of wire in the dipole array creates a decent capacity, I figure.
It may be worth a try to build such an aerial, feed it with RG-6. And, for MF purposes, use the feedline's shield (and core) as vertical and the dipole array as capacitive load. The rf choke could further help to increase the load on the (very) short Marconi for 600m.

This would be somewhat like the antenna disclosed in the U.S. Patent 3,569,970, (see Figs.7a,7b) but using the CobWebb in place of the stretched dipoles.

472kHz Phasing Transmitter

We have seen that a 1.8432MHz oscillator will provide us with a 460.8kHz I/Q-SDR LO.
This is very much in a comfortable range for of the new amateur radio MF band, i.e. 11.2kHz to the lower band edge and 18.2kHz to the higher band edge.
Now, how to generate the modulator signal? Phasing style, the easiest would be to build an oscillator for the 44.8 to 72.8kHz and use two Flip-Flops to generated the 90 degrees phase shift.

1. Such an oscillator could be a rather simple function generator. Other solutions could be based on micro-controllers such as PICs, PICAXE, AT-Tiny, etc. With such a controller, it would also be possible to program features like memory channels, frequency display, beacon-keyer...
2. Another approach would be to build a crystal oscillator, using cheap industrial xtals, and divide it down. Some ideas could be crystals from the XMHz range divided by N (by means of a binary counter) before feeding the Flip-Flops:
• 3.000MHz / 64 = 46.88kHz resulting in 472.5kHz
• 3.072MHz / 64 = 48.0kHz resulting in 472.8kHz
• 3.2768MHz / 64 = 51.2kHz finally resulting in 473.6kHz
• 3.579545MHz / 64 = 55.93kHz resulting in 474.78kHz
• 3.6864MHz / 64 = 57.6kHz resulting in 475.2kHz
• 3.93216MHz / 64 = 61.44kHz resulting in 476.16kHz
• 4.000MHz / 64 = 62.5kHz resulting in 476.4kHz
• 4.096MHz / 64 = 64.0kHz resulting in 4768kHz
• 4.194394MhZ / 64 = 65.54kHz resulting in 477.2kHz
• 4.433619MHz / 64 = 69.28kHz resulting in 478.1kHz
3. In the light of the above, ham-radio crystal such as (in MHz) 3.530, 3.535, 5.540, 3.550, 3.555, 3.560, 3.575611, 3.880, 3.885 can fill in gaps. Those crystals are found at box73.de "expanded spectrum systems".
4. With some luck, one finds tons and tons of surplus crystals in the range of 2.8672MHz to 4.6592MHz. As I recall, there where channelised commercial transceivers (e.g. military, maritime etc.) making use of crystals in that range.
5. Similar to the crystal approach, one could consider to use 3.58MHz, 4.0MHz, 4.19Mhz, 4.50MHz and 4.91MHz ceramic resonators for a VFO. The 6.00MHz, 6.50MHz and 8.00MHz resonators would require one additional division.
6. The deluxe version of it all would be a DDS for the range 2.8672MHz to 4.6592MHz. I wonder is there is any kit in which the LO offset can be easily programmed to (f/256)+460800Hz. Maybe a project with the DDS60 board.

When modulating the phase shifted AF signals, one has to consider that those are essentially square waves. In order to reduce harmonics, it would be required to do some severe low pass filtering at about 19kHz before injecting the signals into the I/Q mixers.

As to receiving, the 11.2kHz to 18.2kHz is in the comfort zone of any 48kbps sampling sound card.

There you have it, my presently preferred solution for the new 600m amateur radio band.