de draaggolf ~~~~~

Samsung Chromebook 303C

2013-03-24T19:00:00.001+01:00

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

2013-01-30T22:02:00.000+01:00

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.

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

2013-01-20T20:09:00.000+01:00

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

2013-01-04T12:06:00.001+01:00

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

2013-01-02T23:34:00.000+01:00

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

2012-04-02T22:07:00.000+02:00

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:

red on all fixtures to 100%
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:

red on all fixtures to 100% with a fast strobe
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

2012-03-02T18:30:00.000+01:00

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

2012-02-29T11:34:00.000+01:00

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

2012-02-28T00:48:00.002+01:00

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

2012-02-22T18:00:00.000+01:00

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.

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...
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

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".
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.
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.
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.

600m Signal Source

2012-02-19T13:09:00.001+01:00

As we know by now, 472-479kHz it will be. In an earlier post I revealed some "cheap" frequencies which would mix into the new band.

Some further options using industrial crystals:

DigiKey sells a 4.754687MHz crystal... count to (divide by) 5 and further divide by two results in 475kHz. A super-VXO could be an option here.

The above mentioned count to 5 solution applies to the following crystals, found at the same source: 9.494531MHz, 9.509375MHz and 9.545MHz. Other crystals would allow for an out of band I/Q-SDR LO: 9.600MHz, 9.625MHz and 9.7941MHz. Here, the chain would be count to 5, divide by 4.

Further: 18.9375MHz, 19.0625MHz and 19.069928MHz and for I/Q-SDR: 18.869MHz, 18.8696MHz, 19.200MHz, 19.280MHz and 19.440MHz. Consequenctly, the chain would be count to 5, divide by 8.

Plus: 28.59375MHz, 28.5938MHz, 28.636MHz, 28.6363MHz and 28.63636MHz (count to 3, count to 5, divide by 4).

Taking it even higher: 38.000MHz and 38.00053MHz (count to 5, divide by 16). I/Q-SDR: 38.400MHz and 38.880MHz.

Also found at DigiKey: a 7.680MHz crystal. Divide by 16 results in 480kHz. Again, a super-VXO and some (severe) down pull should generate a signal in the band. This crystal provides easy access to I/Q-SDR: LO spot om 480kHz, even a mere 24kbps sample rate would cover the whole band. The same applies to the 15.360MHz found at the same store.

All the above mentioned crystals are of industrial kind. One option would be order one for the favorit solution, the other option would be to carefully watch out for those frequencies before dumping old computers & Co.

600m SDR RX (TX)

2012-01-17T23:26:00.003+01:00

As we know, presently there are a couple of frequencies of the 600m band open to amateur radio operators.
Most of authorities allow transmission somewhere above 500kHz. In The Netherlands the permitted range is 501-505kHz. In the future, depending on the decision of the WRC12, this will possibly change to 472 to 480kHz. The U.S.of A. proposed the following ranges 461-469 and 471-478 kHz.

Lets look at the (inexpensive) option the box73 SDR. The 80m version of this receiver uses a 14.000MHz oscillator. Operation on the 600m band can be achieved by changing the front-end filter and the SDR-LO.
Considering 48kbps sampling, the LO-frequencies would be the following

QRG: 470kHz - LO: 1.843MHz
QRG: 500kHz - LO: 2.000MHz

This will result is RX-ranges of:

460.8 -/+ 24 = 436.8 .. 484.8
500.0 -/+ 24 = 476.0 .. 524.0

Concluding, a decent 600m receiver can be built with LOs using regular canned oscillators.

600m with CB-XTALs follow up

2012-01-17T23:03:00.001+01:00

Hi there... I am back!
Presently, amateurs in The Netherlands are really happy, not only have we got the permission to transmit on 4m, we also may transmit on 600m again. For the time being between 501 and 505kHz.
For this range (well, to the upper QRG of 504kHz) this article could lead to a cheap signal source.

However, in about a month's time, we will know is we need to redesign our exciters, i.e. to the range 472 to 480kHz. So, lets have another look at the cheap crystal solution.
The new range is not that easy really. One solution would be the mixing of two standard xtal frequencies:

4915.2 - 4433.6 = 481.6 somewhat high, could be pulled into the range

A spot on solution would be a 10m QRP crystal (28.060MHz) on its fundamental mixed with a 9.8304MHz standard crystal:

9830.4 - 28060/3 = 9830.4 - 9353.3 = 477.1

Another spot on option: a 40m QRP crystal, mixed with a 6.5536MHz standard xtal.

7030 - 6553.6 = 476.4

Starting from lower frequencies, crystals from box73.de:

14745.6 - 14270 = 475.6
7025 - 6553.6 = 471.4 (pull!)
3550 - 3072 = 478
4000 - 3530 = 470 (pull!) (*)
3555 - 3072 = 483 (pull!)

Subractive mixing has the advantage that some thermal effects may cancel. Assume to us several standard crystals in a super-VXO.
Mind you, the higher the frequencies, the easier to pull, i.e. create a nice tuning range. However, lower frequencies will give better stability.

(*) Note, there is a 4.00MHz ceramic resonator, which will allows for a nice VFO. Use a Pierce oscillator to obtain a QRG above the ceramic resonator's series resonance.

SDR Meets DJ Gear

2011-11-27T22:43:00.001+01:00

Hi there! Some of you may know that I am quite busy with music, dance and the stuff concerned.
Some rare occasions have it, and hamradio mixes with music mixing, aka DJing. And here is one of those occasions:
The DJ Mouse
http://www.dj-mouse.com/
Basically, there is nothing special about this mouse, other than the regular scroll wheel is somewhat wider and parallel with a jog wheel. It is just this jog wheel that makes all the difference.
All SDR software solutions I am aware of, are using the scroll wheel for sweeping the frequency. I always felt that this was somewhat awkward. Now we got a mouse with a rotary encoder, just like a VFO knob.
Still I scratch my head what can be done with the "scratch" button...

Central Heating Aerial

2011-11-24T21:54:00.001+01:00

Dear readers, there was not much going on here lately, sorry about that!
Today, some weird incident triggered another thought in me.... and here it comes:

Returning home, I felt an unfamiliar chill in my house... That's no good, I thought, and checked the central heating system, which indeed was dead. Quick check and the culprit was found. The expansion vessel (expansievat, Ausdehnungsgefäss, vase d'expansion, whatever you wanna call it) leaked. The local hardware store was still open, hence I hurried up to get a replacement of similar size.
Just €22.- will get you one with a 17l capacity.
Speaking of capacity, that came to my mind on my way back home. What about using the defective one as top-capacity for a short vertical? The roundish things got a nice thread which would easily fit Cu pipes and respective fittings.
The vessel itself is made from steal (Fe) most likely. OK, that's somewhat on the heavy end, electrically however, not that inferior to Al, which is used most.
The plan is to build a short tapered vertical from Cu-pipes with an expansion vessel on top.
I figure, one may also consider a short loaded dipole.
Possibly, just 2 of such vessels could make a broadband dipole for VHF.... one could also think of a broadband vertical for VHF, using just one vessel on a ground-plane.

There may just be one down-side, your neighbors will think you're completely mental, putting the expansion vessel of your heating system 5m above your roof ;-)

Happy experimenting.

Most Interesting

2011-11-08T22:31:00.000+01:00

What is going on here? A local station, a dx station and the radar, which seems to dislike the condx...

Broad-Band Aerial Update

2011-11-08T21:02:00.001+01:00

Short update on the 11m half-wave aerial conversion.

The 4:1 UnUn is placed, that was one of the two options. Actually, this was the easy option, since the UnUn came wound up and ready to use from a surplus dealer.

11m half wafe aerial base portion

The arial, about 5.5m long, w/o any further modification could be matched easily with the IC-703 builtin tuner on the band from 80m to 10m, with the exeption of 30m. I figure, some additional Al-tube extension could solve that problem.

SDR for the 600m band

2011-10-29T19:37:00.000+02:00

Some short not on an idea for the 600m band.
The typical SDR, as we all know, uses 4x the center frequency so that the 90 phase-shifts can easily be created by flip-flops.

In 2012, the Netherlands will most likely open the range 501-505kHz for ham radio operators. I figure a simple RX (maybe also TX) solution could be a 2.000MHz canned oscillator. This will get us spot on 500kHz center frequency, just as you may want. Comfortable 1 to 5kHz audio, which any sound card can handle easily, with a sample rate of only 24kHz. A further experiment should show if side-band suppression is required at all. I figure, a decent pre-selector should be enough already.
Should however, following a decision at the WRC-12, the range open to hams change to the range proposed by CEPT (472 to 480kHz), a 2.000MHz SDR-LO would be somewhat too high. In this case, the oscillator could easily be swapped with a 1.8432MHz one. Resulting in a center frequency of 460.8kHz. Audio up to 20kHz would still be somewhat a challenge for cheap sound hardware, never the less, a sample rate of 48kHz would cover it all.

No to the TX-part of it. One could either use a sound card generated signal, as provided by some software solution. One could also thing of generating an I/Q modulation signal at 4x the audio signal, divide and phase shift similarly to the LO chain. Unfortunately, we would now have a rich audio square wave. I figure some severe filtering will be required here, in order to end up with a sine wave.
I would not consider an AF phase-shifting network. I believe the frequency range is to great as provide accurate phase-shifting.
However, as in the RX part, it may be conceivable to filter the side-band at the RF range. A series of tank and trap circuits could possibly be enough. Mind you, the aerial matching itself is very selective too.

New Item in the Marine Radio Collection

2011-09-23T03:02:00.001+02:00

Could not stop myself from buying an "Emergency Radio Type 610". I believe it is made by Clifford & Snell, but I am not sure about that.
The radio services the frequencies 500kHz (RX/TX), 2182kHz (RX/TX) and 8364kHz (TX). As in this sort of package, cranks are provided as a power source.

The transmitter seem to be built around two electron tubes (have not checked the types yet), while the receiver seem to employ OC transistors, Germanium that is.
Whilst test TXing into the built-in dummy load, on 2182kHz (A3E), the antenna current meter nicely peaks when the matching variometer (coil with dive-in ferrite rod) is agitated. The two other frequencies would require the operator to have a third arm!?? My radio was supplied with the emergency instructions, which showed one operator only, even the text referred to a single operator doing the cranks and the communications all at once. Who ever wrote this may have never operated a radio himself. While in A3E, a carrier in generated anyway. One hand operating the crank, the other to tune the variometer, no problems here.
It is a different story with 500kHz and 8364kHz. Those are A2A frequencies. No, there is not typoe, A2A it is, AF modulated code. And yes, that makes sense. The signal is received in both, an AM receiver as well as a receiver employing a BFO. However, when tuning the emergency transmitter, one would need one arm/hand operating the crank for energy, a second arm/hand for operating the manual key and a third arm/hand for operating the tuning knob.
The makers of the radio seemed to have spent some thought on this issue, although, maybe not enough. The radio is equipped with a mechanical auto-keyer. Keying the transmitter for tuning can therefore be done, sort of, without three arms. However, the designers seemed to never had the code operator in mind. The built-in manual key is so close to the position of the cranks, that operating both at the same time seems to be a challenge per se. However, if that was your option to survive at sea, that what you would be going for.

Enough about the transmitter, lets have a word on the aerial system provided. A system which managed to impress me. As in all of those sets, the aerial is contained in the box itself. Motto: if your vessel is sinking, throw the emergency radio overboard, get in the life raft and hope for the best. Hence, the floating waterproof box of the emergency radio has to contain everything required to perform emergency communication, including the aerial.
The 610 comes with an antenna base, about 1m long, having a rubber foot (for not damaging the life raft's soft bottom). On this foot, a stainless steel telescopic whip is to be mounted, the whip having an impressive length of estimated 4m (maybe more).

To the downside, and the reason why this radio is not widely available.
In order to keep it smaller, I presume, the designers choose to have a low profile for the cranks. Fair enough... however, they put the cranks so low that they can't be used when the radio laying perfectly flat on the ground. A problem that the very similar TRP1 does not have. Is the TRP1 really as similar? Maybe not... think of it, the TRP1 uses TTL circuits, whilst the 610 employs electron valves and Germanium transistors...

Do I regret having bought on of the 610s? No! Would I buy another one? No!
What is the best thing about the type 610? The aerial provided. I believe, there is no other (convenient) way to get your hands on stuff alike... Think of it!

73!

Cheap Android Tablet Going Strong

2011-09-16T23:02:00.001+02:00

Some time ago, I reported about a very cheap Android Tablet (from kijkshop), which I used regularly for this and that.
The table came with some port accessory, which holds two regular USB ports and an Ethernet connection. Writing this, I am presently using the tablet via Ethernet (thus no WLAN) with a wireless keyboard attached via USB for convenient typing. The port accessory actually seem not to have functioned when I got the device first. However, in the course of time, I really could not believe that a design fault was the cause. Well, the was a design fault, not in the electronics though. The plastics chassis appeared to be too large and had to be sanded down in order to allow all pins to make contact. Seen that the tablet costed € 100.-, I should have bought a second one, since said shop stopped selling those devices.
Still, I have not mentioned any details about the product...
it is an iLC 7" tablet PC using an ARM 800MHz processor with 256MB RAM
the OS being Android 2.2 (Android Market installed) on 4GB flash storage, allowing for a microSD card
the device is further equipped with WiFi, stereo speakers, a headphone connector and a built-in microphone
finally, there is the port accessory, providing 10baseT and 2x USB
All in all, the gadget look comparably cheap, matching up with the proce somehow. At times the device's response is somewhat sluggish. Would I buy the gadget once again? YES!

4:1, 6:1 or 9:1?

2011-09-12T23:16:00.000+02:00

Thinking back and forth a bit, again on aerials, I came to the conclusion that using 75Ohms feedline some 4:1 would be appropriate.
But why?!

The developers at Diamond thought that for the BB6W, or the BB7V for good measures, a 6:1 transformation would be the way to go. This aerial design assumes a 50Ohms feedline. The aerial's feedpoint is therefore considered having an impedance of 300Ohms. Remember, in this design, there is 600Ohms of termination resistor to ensure a maximum SWR of 2:1.

Assuming that the average auto-ATU will match a transmitter's 50Ohms antenna connector to a 75Ohms feedline easily, a 4:1 transformation will do in order to match a feedpoint impedance of 300Ohms when using 75Ohms feedline.
This actually brings together good news from two worlds:

75Ohms coax cable has got less losses than 50Ohms coax (it is cheaper too)
a 4:1 transformer is easier to make than a 6:1 transformer (QRP: old TV-xformers)

So, now what about the 9:1 UnUn that so many use with endfed aerials? Personally, I used a 9:1 transformer with 50Ohms feedline. The 450Ohms feedpoint impedance works with endfed wires, about as good as 450Ohms window line (using a suitable ATU).

As a side remark, the feedpoint impedance at the voltage maximum is considered to be 5kOhms. Neither window line nor a 9:1 transformer gets us there. This can only be matched using ladder line (or open wire line) with a symmetric coupler.

Kizomba, the Name of the Game

2011-09-09T23:28:00.000+02:00

Hi folks,
this is completely off topic.You may have wondered why I am sooooo slooooow writing technical articles, well, there are some reasons. One of them reasons being, I am much more into dancing once again... and kizomba is the name of that game. Some may already know that I am severely into mambo dancing, this remains. For those of you readers that are into dancing, check out kizomba, aka. African tango. The dance is from Angola, the music is a mix of French creole "zouk" and Angolan "semba".
Dear fellow ham radio operators, there is more to life than a microphone or a Morse key. Get out, get social enjoy life, also on the dance floor!
BTW, WCS (West Coast Swing) is cool too! Go for it, grab a girl and off you go!

Surplus RF-Transformers for Random Wire Antennas

2011-08-27T21:06:00.001+02:00

In some of my last posts I was sharing thoughts about broadband aerials using transformers to match the high impedance of the non-resonant "random" wire. Well, the leghth of those wires is not that random at the end. Some typical lengths that come to my mind 6m, 7m, 7.5m, 11.5m, etc. you may know some more...

Now, let's have a look at some options provided by surplus (the junk box respectively).

CFL bulb transformer vs. surplus iron powder toroid

On the left side we have a transformer that was in a (defective) CFL bulb, aka as energy-saving light. The thing on the right side is one of the is a surplus transformer based on a T68-2, which came in bags of 5pc for just 0.80 €-cents.

So, what do we have, the CFL transformer countd 3:3:12 windings. Using the black and the white in series, that would be 6:12. This would be, in other words, be a fine 9:1 UnUn.

The T68-2 is provided with 12 bifilar windings. This would therefore make you average 4:1 UnUn. Obviously, those can also be 1:1 isolation transformer.

Both junk-box items are proven in ham-radio designs. I figure, I will experiment with both out of the box options. Additionally, I may possibly try a 6:1 UnUn, as in the BB6W/BB7V design. Staying at QRPP levels would even offer the change of trying the termination resistor used in the BB6W/BB7Vs.
Oh, I forgot, to get closer to the BB7V, I will add some additional Al-pipe to top of the 5.5m long 27MHz vertical.

Half-wave 27MHz Antenna as Broadband Vertical

2011-08-25T23:58:00.005+02:00

Years and years ago, a friend of mine gave me a (brand new) half-wave CB antenna. Well, I have never used it, for the reason of not being QRV on 11m. For 10m I had my double bazooka, so there was no need for it. Now that it has been sitting in a corner for a while, I thought, maybe it could be useful for something else. Some else as in broadband vertical...

Now, let's have a look how those things are built:


aerial schematics

This drawing is not made by me, however, it nicely sketches what the following photographs of my very own version of that antenna show.

all still in one part


taken apart

What we have is the cavity and the transformer that was sitting in it. The air core transformer has got a winding ratio of 7.5:2. I figure, using a ferrite or iron powder toroid would improve performance on lower frequencies.
The cavity measures 35mm in diameter, having a depth of 24mm. This clearly offers enough space to house a smaller toroid transformer.

At this place, I would like to remind you of the BB7V (Diamond) having an UnUn transformer with (resistive) termination shunt. This vertical would be 6.7m tall. The regular 11m half-wave vertical could possibly be stretched to a tallness somewhat beyond 5.5m. Close enough to me.

Now let's think... for QRP work a T80-2 would make an ok UnUn. With some luck, transformers with a T130-2 core could possibly be squeezed in the cavity, if made carefully.
Reconsidering the BB7V's terminator, would I put one in there? Only if I would be using this aerial for QRPp only. The base of the CB-aerial is made from plastics material, which is not able to conduct any heat. Hence, heat created inside the cavity would never be dissipated. For QRSs/QRPp, the resistive terminator is a very appealing option, in particular since for such power levels, a T50-2 transformer would offer sufficient empty space for the terminator.
A T130-2 would possibly be good for a regular 100W rig. However, in a worst case, 50W of heat have to be dissipated, hence, some cooling of the termination would be required, therefore, this is a no-go. Some adjustments and selective use of bands would still be an option for such an arrangement.
Personally, I am very tempted to try a version of a T68-2 transformer (not sure about termination yet), in combination with my IC-703. This is somewhat of a compromise...
Should I ever again get into QRPp/QRSs/WSPR/WSJT/ROS actively, my preference would be the small transformer&terminator option.

Additionally, I figure, it could be of use to add an additional Al-pipe of about one meter to the top of the vertical. This will result in a total length of about 6.4m and a further distance to a quarter-wave on 20m, without getting too close to a quarter-wave on 30m.

There you have it, a new life for a cheap half-wave 11m vertical.

455kHz SDR - a second thought

2011-08-06T22:53:00.000+02:00

My previous blog was all about the idea of adding a softrock, or any other simple SDR-DC-RX, to a cheap (synthesized) AM radio. Well, honestly said, when thinking of it, this may be a totally unnecessary overkill.
Why? Well, very simple. The main purpose of all the quadrature stuff is to make the two sidebands that a DC-RX receives different. But, what if there is not other sideband? The following may not apply to the absolute cheapest of AM-receivers.
Concerning the ATS-404, I have ambiguous information. While some technical data mention the AM i.f. being 450kHz, the schematics diagram mentions a LT455H, which is a 455kHz ceramic filter having +/-3kHz 6dB bandwidth (+/-9kHz for attenuated bandwidth). If we tap before that filter, we definitely need quadrature, should we however tap the i.f. behind that filter, a non-quadrature SDR would be OK too.
Most of the better world-band receivers use a first i.f. somewhere high with a relatively wide crystal filter. Most of the narrow filtering is done at 455kHz. In this case, we probably wont need quadrature at all. All we have to do is to ensure that our SDR center frequency (or SDR-l.o.) falls close to but outside the range of the intermediate frequency range. In such a scenario, there would not be a second sideband to care about and also a simple mono-audio interface would already do the job.
The Target HF3 would be an example for such a receiver. The first i.f. is at 45MHz having a bandwidth of +/-3.75kHz. The second i.f. band would consequently be 455-3.75=451.25 to 455+3.75=458.75 kHz. In yesterday's example, using a 1.8432Mhz local oscillator, we ended up at an SDR center frequency of 460.8kHz, which is close but outside the HF3's second i.f. band. A regular direct conversion receiver with a local oscillator at 460.8kHz would therefore receive only a lower side-band, since there is no signal in its upper side-band.
My idea would be to try that out using a canned oscillator and two flip-flops for frequency division. With some isolation amplification a singled ended diode mixer and a cheap USB audio adapter should round up that experiment.