Monday, December 9, 2013

How to tune the suburban sub-harmonic receiver


Some help to adjust the balance and drive of the sub-harmonic receiver used in my grabber (dashed lines indicate 0.7V cut-in voltage for Si-diodes, V is mixer drive voltage).

1) Mixer correctly driven: Within one period a single diode opens for exactly 90 degrees (red). Within the same period, the other diode opens for 90 degrees (blue), while the rest of the time, the diodes are both closed (yellow). As you see, the first diode opens at 45 degrees, that is very important! You also see, the entire mixer is open twice within one period; that’s the trick of the frequency doubling. Any off-balance shift will produce harmonics, which you can’t get rid of.



2) Let’s have a look at the mixer being extremely out of balance. In this example, -0.7V, which would open the second diode, is never reached, hence, this diode will never open. Consequently, the mixer will open once in a period, thereby not doubling the frequency. Still, due to under-sampling, some signal will be received, however, this is essentially a DC-RX for the LO-frequency. Actually, one can make use of this, e.g. for a 14MHz sub-harmonic receiver, which, when adding the correct off-set, will turn into a 7MHz DC-RX (either with a second crystal filter, or non at all).

3) And now, the mixer in balance, but over-driven. This will let a lot of signal through and will actually also double the frequency. However, the phase of the mixer is now totally off, i.e. asymmetric. This will produce a lot harmonics, so the receiver will receiver on many multiples of the local oscillator.



Actually, it takes a bit of patience to find the sweet spot in such a receiver. For me, it works well, for many years by now.

Saturday, October 26, 2013

QSO?

What is a QSO nowadays? Not sure, in particular when talking QRSS.

The latest fashion seems to communicate via an online grabber. This this a QSO?
I don't think so, for the following reasons:
  1. both stations have contact to the grabber, which is rather an automated SWL connected to the internet
  2. there is no wireless link from the online grabber to neither of the two stations
  3. the online grabber does not repeat a signal per se
However, all in all, I believe using a grabber to communicate is somewhat fun, since the communication is somewhat full-duplex.

What amateur radio is concerned, there still is the issue of dependency of many non-amateur communication channels, namely the ISPs of the three involved parties.

Friday, October 18, 2013

Small Wonder Labs closed

Today I learned that Dave K1SWL closed his QRP business for good. Very understandably, after many years of excellent service.

I would like to thank Dave for all the inspiration he brought to the QRP community over the decades and wish him a good time in the house he built in NH!

72 es 73

Friday, August 23, 2013

the old phase shift question

Actually I am rather flattered by the fact that an experimental design, which I did a couple of years ago, still is under discussion.
The good ole question about how much phase shift you need to run Polyakov mixers for I/Q software defined radio (SDR).
Have a look: http://draaggolf.blogspot.com/2010/01/30m-subharmonic-iq-sdr-receiver.html
Yep, this is a very simple concept design, it worked, it suppressed the lower side-band. And yes, it uses 45 degrees of phase shift at the oscillator frequency, which is half the beat-frequency (for reasons of using frequency doubling Polyakov mixers).
Please see the comments on why other designs, resulting in 180 degrees of beat-frequency shift, still seem to work just fine.
My design is not perfect at all, using a potentiometer to adjust a radio-frequency phase-shift is neither elegant, nor stable. Keep in mind, that this quick and dirty design was more a proof of concept rather than a production ready machine.
73!

Wednesday, August 14, 2013

12m XTAL Controlled QRSS / WSPR / QRP / SDR

In a previous post, I described the use of CD-crystals for 17m weak signal operations. This post is attempting to do the same but for the 12m.
The crystals I am mentioning here are also used in CB-rigs, although harder to find. Here's would be a possible source.

QRSS: 37.340MHz => 12.446MHz x 2 = 24.892MHz
QRP/SDR: 37.350MHz => 12.450MHz x 2 = 24.900MHz
WSPR/QRSS: 37.395MHz =>  12.465MHz x 2 = 24.930MHz

SW+ 40 possible WSPR/QRSS mod

Regular readers of my blog will know that a PSK-Warbler could easily be modified into a 40m WSPR transceiver. I believe that Dave K1SWL even mentioned this mod during his talk at the FDIM-QRP-Convention.
Very unfortunately, the Warbler has been retired later that year. It seems the days for easy 40m transceivers are over.

However, there is hope, the 40m SW+.

The trx employs a 4MHz crystal filter for reception, since the SW+ is a superhet A1A transceiver, there is no if-filter in the tx-train.
The transmitter consists of the VFO, and up-converter (NE612), a link-filter, linear buffer and driver and a class-C power amplifier.

This is what I see, could be done to the rig... please grab a circuit diagram (can be found on K1SWL's homepage).




Concept


We want to have zero-beat at 7038.6kHz. So the sum of intermediate frequency and local oscillator should end up there. With the 4MHz intermediate frequency the kits comes with, we would need a frequency source of either 3038.6kHz or 11038.6kHz. Both are somewhat hard to reach on standard crystals.
Now, lets have a look what get's us close...
Lets check out the options:
  1. 5.000 + 2.048 = 7.048
  2. 5.200 + 1.843 = 7.043
Option one will require penning down the 2.048MHz crystal, however would open the option of using a 2.000MHz crystal for the lower band edge QRSS range. Additionally, a 2MHz ceramic resonator oscillator would enable operation in the regular CW portion of the 40m band.
Option two would probably work by just severely pulling of a 1.843MHz crystal.



VFO


This is were the mod begins. The VFO should be skipped; an external xo will be doing this job. Having the local oscillator external will provide some advantages for QRSS operations. First of all, temperature stabilization should be applied. Secondly, one may consider switching between several crystals.
Most importantly, an extra 7dBm output should be added for a transmit DSB modulator.


BFO

In a side-band transceiver, an offset between the BFO and the up-converter is not wanted. In a CW transceiver, one wishes to have an offset of about 800Hz between RX and TX. Since the SW+ is a CW transceiver, we would like to get rid of the off-set. The easiest way of doing this would be to buffer and feed the BFO into the up-converter.


Receiver

The receiver is pretty much were we would like to have it. All crystals should be changed according to the mod you would like to perform.


Transmitter

This is were the choice of option will become important. Buffer and driver look just fine, however, it is definitely required to convert the PA from class C into class AB for linearity. It might be easiest to just design a linear PA, potentially external, and feed the buffer into it. Another option would be to merge designs. Genesisradio.com.au once sold a qrp-transmitter kit, the Q5, which was equipped with a 500mW class A linear PA. The PA design itself genesisradio took from their SDR-TRX.

Wednesday, August 7, 2013

new blog created

Dear ham radio operator,
Lately I filled this blog, my radio blog, with some computer / IT related posts. This was due to a lack of a dedicated place to publish those posts.
It seems inappropriate to continue with this practice, hence, I decided to create another blog concerned with this sort of technology:
http://homebrew-it.blogspot.com/
Hopefully I will have to report something radio in the near future.
73

ccrrrcrcrc crcrrcccrccc ... SILENCIUM!

My workstation employs a mouse which performance-wise, I really like. It is a super cheap Logitech M100. The only thing that is really annoying is the sound and cheap feel of the scroll wheel.
I know, this is a matter of taste. However, here's one to try for yourself (and this may apply, mutatis mutandis, to other computer mice too!).

The feel and sound is created by a spring mounted against the inner corrugated surface of the wheel (of course, first you need to remove the single screw on the bottom of the device... you know all about this....
overview of the mouse
close-up of the click device
Key point of this very simple mod, compared to other attempts available in the mists of the internet, is to remove the bloody click thing all together.

In order to achieve the goal, the only thing to do is gently slide out the scroll wheel assembly. There is nothing holding down said assembly, just grab it and off it goes. The photograph below shows the assembly, the clicky spring device still in place, whilst the load spring held on the axle just fell off (this spring we actually want to place into its original place when assembling the mouse again!).
the wheel assembly taken removed from the mouse, note the load spring
Now, gently pull the actual wheel from the assembly. The clicky-clacky (ccrrrcrcrc crcrrcccrccc) spring will most likely fall off in the process. Do to the severe complexity of this stage, I forgot to take a picture... sorry for that ;-)

The following step will be to put the wheel back in its original position in the assembly, w/o the crcrcr-spring of course.

As a last step, we slide the wheel assembly back by using its guard rails. Mind the "scroll wheel click load spring"!
now w/o the noise device
Again, I leave it all to you to put the lid on it all and screw it all down by the single mounting means we had to dismantle in the first place.
As a result, I feel personally very positive about the modification. Not only is the bloody noise gone, the now freely spinning scroll wheel provides a real smooth experience.

Friday, July 26, 2013

Adding noise to the server room

The last few days have seen me changing my entire IT, not in terms of the system, rather the location. A land line connection needed to be pulled for the phone (skype - land line DECT combi phone), the RED ethernet had to be rewired and finally an ethernet switch was made redundant.

All in all, I am still running the following system:
  • smoothwall express with RED and GREEN connections, running a squid caching proxy
  • my old WiFi-router as an wireless access point (WPA2 of course)
  • the good ole ACER H340 running NAS4Free with a RAIDZ-1 ZFS pool using four 1TB disks, serving as a media server, a file server and a backup server
  • an AMD E-350 system running FreeNAS with a RAID-0 scrap data storage with two 2 TB disks
  • my good ole Buffalo NAS (1TB)
All storage devices are running NFS, SMB and AFP, expect for the Buffalo, which has nof NFS.
To me it is somewhat clear, the H340 is the main, safe, data storage. However, it happened today, one of the 4 HDDs stopped its service. We had a nice warm summer day, temps at about 27 centigrade. The HDDs in the H340 were running at about 50º centigrade, which is somewhat warm.
I shutdown the server, let it sit to cool for some while and fired it up again. The HHD was back, however, some data was potentially written when the HDD took a break. Luckily, I am running a ZFS pool, hence, the disk could be fixed, in ZFS this is called "clear". Everything is back to fine again.

The incident made me rethinking about the H340. There is a post on the internet somewhere, in which someone discloses a mod which changes the H340's case fan.
That seems to be exactly what I need to do, I figured. Indeed, the H340's regulated case fan sucks air out of the case. The fan is arrange such, that air is forced along the HDDs, before exiting the case. Well, that makes some sense :-s Drawing a regulated low amount of hot air along some disk drives...
In my scrap box, there still was this unregulated fan which came with the Antec water cooling used in my workstation. This thing is a real blower, however quite noisy, hence, I did not use it in my workstation PC. However, now that all my servers are in a dedicated noisy room, why not using it in the H340.
This noisy Antec fan is now doing service to blow cool air into the case, over the HHDs, with the following impact, on that same hot summer day (eve):

Temperatures before mod:
  • CPU: 45º C (essentially independent of the ambient temp)
  • HDDs: 47º - 50º C (during idle)
Temperature after mod:
  • CPU:  24º C (essentially the ambient temp)
  • HDDs: 29º - 36º C (during a ZFS pool scrub)
And here is the downside of it. A very quiet device device is now turned into a very noise but well cooled NAS.
Mind you, the H340 is a perfect machine for running NAS4Free! (see earlier post)

Thursday, July 18, 2013

Turn Your Old WiFi-Router Into a Wireless-AP

You may have noticed that I am busy renovating my IT. Some days ago, I posted a short text about the use of smoothwall as a caching web-proxy. Now it seems time to also hand over the routing to smoothwall. At the time of writing the last post, I simply hooked up my WiFi-router to the smoothwall box, telling it to get WAN from it (by DHCP). The rest of the routing was done by this trusty but old router. Downside of this router, it is equipped with 100Mbps only, while the rest of my wired network is 1Gbps.

Went shopping today, and grabbed a simple 5 port Gigabit switch, which is now connected to the smoothwall box.

How to get WiFi? I still could use the old router and tell it to get WAN from said switch. To tidy up address space, it would however be nice to have an Wireless access point in place of a WiFi-router.
A quick search in the internet revealed this page:
http://www.smallnetbuilder.com/wireless/wireless-basics/30338-how-to-convert-a-wireless-router-into-an-access-point
Very cool stuff! Works like a charm!

The next step would be to loose the cheap Gigabit switch again and integrate everything in the "production environment".

Saturday, July 13, 2013

WiFi for Hacks

The dear reader may have noticed that a concept called hackintosh caught my attention. Actually, some years ago, when Leopard (OS-X 10.5), the thirst OS-X running on x86 hardware, came out, I already built various systems (Intel Q6600, Intel E4600) capable of running OS-X.
That gets us what a hackintosh actually is. It is a PC, mainly based on Intel processors, which is able to run Apple's OS-X under certain circumstances. To learn more, please search the internet, also about the legal implications/requirements.

The whole trick about hackintoshs is to find the right hardware, being compatible with the original OS-X. Mind you, the name hackintosh refers to the hardware, not the operation system, meaning, that the OS remains absolutely original, i.e. unchanged and non-hacked.

There are to mini PCI-e cards which are fully compatible with OS-X 10.8 that I know of (and actually tested):
  1. Broadcom BCM94322HML 
  2. Atheros AR5BHB92
My hackintoshs are based on GA-Z77N-WiFi and GA-H77N-WiFi mobos. Both boards come equipped with an Intel mini PCI-e WiFi/BT-combo-card. Whilst BlueTooth is working fine under OS-X, the WiFi part of this card is just dead.
Some additional info here, the Intel cards are equipped with 2 coax connectors, which is reflected by the 2 aerials provided with the mobos. Both cards mentioned above have 2 coax connectors.

From here, there are two options:
  1. keep the Intel card for BT and use something else for WiFi
  2. exchange the Intel with any of the two mentioned above and use something else for BT 
I personally went for option 2. And here is why:
There is a TPlink WiFi PCI-E card which is 100% compatible and works really well. However, there is only one PCI-E slot with the mobos mentioned above. Using this slot forces the use of the low power on-board graphics. There are other options like compatible USB WiFi devices, however, I believe that the bandwidth would be compromised here.
The second option provides full bandwidth for WiFi, leaving the single PCI-E slot for a GPU. On the downside, one now has to look for an alternative BlueTooth device. It happens that I own a couple of old USB BT devices. All those devices seem to be compatible with OS-X. Due to the low bandwidth of BT, I can easily live with the USB solution.

Thursday, July 11, 2013

Modding Stuff for Astrophotography

Dear regular reader, by now you should be aware that I tend to think outside the box. My affiliation to astro-photography should be known, at least to readers of the knightsQRSS list of a couple of years ago, when I proposed stacking spectra to improve the SNR, as it is done in webcam-astro-photography.

So, here's another one for you, now we are crossing computing, the extreme corner of modding that is, with astronomy / astro-photography.

As we all know, human (biological) night vision (scotopic vision) is controlled by a molecule called "rhodopsin" which takes a couple of ten minutes to build up (cf. adaptation). It triggers the rods to go into night mode. In human vision, the rods create a gray-scale visual impression, like a good ole B&W-TV. The problem with scotopic vision is, that is disappears when a certain amount of light within the scopic wavelength range is seen (literally). Luckily, however, the scoptopic range ends at about 620nm. Meaning that red light will not affect scoptopic vision, i.e. red light will preserve the rhodopsin level in the rods. This is actually the reason why the night illumination on yachts, warships and vessels alike is red.
Now, check out the spectrum of red LEDs.

Now, lets turn to computer modding, something I never actually understood. To me, a computer has to perform and that's about it. Overclocking is somewhat understandable, so is watercolling, which are both concerned with performance.
Modding seems to be about visual appearance of a computer, which I personally never cared about. However, look at the recent IBM mainframes, i.e. zEnterprise architecture, these boxes are all odd, prismatic and what not. Did IBM copy the needs of modders to apply it to boxes worth millions of bucks? It seems so!
Modders are also interested in illumination effects of their boxes. Here it starts becoming interesting for the astronomer. Next to mean green and cool blue, there also is hot red illumination available for the modder.
Check this out!

Here comes the link between the two, modding and astronomy: in a modern observatory a computer is mandantory, to check sky-charts, control the dome, control the telescope mount or record data from a digital camera. A computer is found in every observatory I know, be it professional, be it hobbyist, be it amateur.
So, instead of illuminating the inside of your computer, you could equally use the device to illuminate the outside of your computer sitting in the observatory, hence the observatory, with a chain of red LEDs, preserving your scotopic vision during your astro session.


Tuesday, July 9, 2013

Delidding Photos (i5-3570k, i3-3225)

As promised, here are some photos taken during the process of delidding Ivy Bridge CPUs.

beginning to de-lidd the i5-3570k, knife stuck good, grease still present

different corner now, grease removed - mind you cutting the corners first does the trick

heat spreader and PCB apart - nasty black glue and grey thermal paste all over the place

glue removed (finger nails)

thermal paste removed by means of "akasa TIM clean" (citrus based)
same done to the i3-3225, although this was the second delidding, I cut myself, which did not happen during the first

Monday, July 8, 2013

More IT (scrap NAS)

More IT going on at my home. Some time ago I experimented with proxmox virtualization (déja vue!) and virtualization clusters. At the time, I built a second AMD E-350 rig, which at some stage was converted into a scrap-NAS for data migration purposes. To do this, I grabbed a 2TB-USB2 storage device which was on sale, salvaged the HDD and dumped the rest. The actual HDD would have been more expensive at the time. I figure the USB3 marketing helped to get a cheap HDD (WD green series).
At some stage, I decided to buy a second 2TB-USB2 storage device, in order to salvage the HDD.
Both disks are now living happily next to one another in the same mITX case, alongside with the E-350 board.
This setup is now my new 4TB scrap-NAS, running FreeNAS w/ZFS (stripe) for increased performance.
In the course of experimentation, I played with noise, energy and compression levels provided by FreeNAS. My preliminary decision was to run at maximum energy saving, minimum noise level and lzb-compression. Although very appealing, zfs-dedup remained dis-engaged, remember, it is a scrap-NAS.

Sunday, July 7, 2013

Overclocking the Hack

By now I am building Hackintosh setups for years. In the past, I was sticking to what the average user would be doing, happy to see my hackintosh doing what I want it to do.

With my present "production" hackintosh, yes, I do own the licenses, i.e. bought the DVD, thing are different. This particular build (i5-3570k) opens the possibility to overclock... and this is exactly what I am describing in this post.

The Hackintosh I am using is built in a BitFenix prodigy (white), I is equipped with an Antec Kühler 60 closed water cooling system and 1.6GHz DDR3 RAM. Speaking of the cooling system, the fan provided by Antec was too noisy for my taste, hence, I used the back fan provided by BitFenix for the radiator.

This blog is about overclocking... now that you know the baseline, let's talk about overclocking!

After some experimentation, I came up with the following parameters:

Base clock frequency: 109MHz
CPU clock ratio: 46 - resulting in a CPU clock of 5.01GHz
RAM clock at 1.744GHz (the RAM I am using being rated at 1.6GHZ)
Cinebench (on OS-X) reports a CPU score of 5.84 pts


CPU temperatures, running SETI@home at full cpu power, stayed below 50C.

Mind you, I am running a water cooled system! Overclocking from 3.80GHz to 5GHz is not nothing...




















Saturday, July 6, 2013

improve your web experience

Howdy!
Yet another off-topic post. Lately I am not doing a lot of radio. However, I think that the occasional experience with IT can be at least as much fun as good ole ham radio.
One of the last experiments was virtualization using proxmox on an AMD E-350 low power dual core processor. This particular system is now equipped with an additional ethernet card (100Mbps) and serves as a firewall w/ caching web-proxy using Smoothwall Express 3.1 RC1. The hardware I use is a total overkill: 8GB RAM and 250GB HDD space. As I said, it was used for experiments with virtualization.
The surfing experience has improved a lot since static features of webpages are now locally stored in the caching proxy.
Using smoothwall with squid is highly recommended!
Cheers!

Tuesday, July 2, 2013

Delidding the i5-3570K CPU

Yet another off-topic (non-radio that is) blog entry.
Having built the Core i5-3570K and the Core i3-3225 Hackintosh, the next field of experimentation was to understand the temperature differences of the core, as displayed by some software products.
To run the CPU cores at full load, I used SETI@home.
Doing that, I observed a 10 degrees centigrade difference between the hottest and the coldest core. I Believed that this would cause a lot of thermal strain on the CPU chip.
Hence, I decided to do what others did before, delidd the CPU and regrease the cooling.

I took some pictures during the process, there are not dissimilar to the ones which could be found on the www, i.e. a knife being stuck between the aluminum heat spreader and the CPU's PCB, etc. on demand, I will share my pictures...

My system is cooled by an ANTEC Kühler 60 and ran up to 52 degrees centigrade for the hottest core. Using MX2 between the heat spreader and the chip, as well as the heat spreader and the cooling pump, the hottest core shows 50 degrees centigrade. There is still a 10 degrees difference between the hottest and the coolest core.

Was it worth the trouble delidding a CPU, potentially damaging it? NO certainly not. However, it was fun to do it, and hence, I would do it again.

Should you intend to to this exercise yourself, here a tip: run your Ivy Bridge CPU hot before trying to cut the glue. The glue being soft helps a great deal reducing the risk of damaging the PCB due to larger forces being applied.

Mind you, delidding your (expensive) CPU is at your own risk!

Update: I noticed that the temperatures of the cores are much more linked as they were before. One core running at 100% load, whilst the others are at idle will increase the temperature of all core essentially equally. Before the delidding, this single core would got hot, while the others remained cool. Therefore, I would recommend the mod, which seems to remove thermal stress on the die of your cpu.

Update 2: Decided to nevertheless de-lid the Core i3-3225. In the process, I cut myself with the stupid hobby-knife. Probably, due to the lower price of the i3-3225, I was not taking as much care, and hence, the knife went straight into my thumb. Same procedure as before, cleaned the die, applied MX2 to the inside also to the outside, i.e. between the heat spreader and the cooling fan.

Saturday, June 29, 2013

inactive ...

Due to circumstances, I have been inactive for quite a while. In a way, I regret this, on the other hand, this provided me with some fresh ideas and also with the opportunity to cut off some old stuff.

Lately, I did some hackintoshing, which at some stage, I will document. Radio had a rest, however, I feel an urge to return to the wireless stuff.

Sooner or later, I will pick up things that are in the pipeline for long... and finally publish some here.

Cheers, 73, Joachim

Sunday, March 24, 2013

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.

Wednesday, January 30, 2013

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).

Update: It appears not to be necessary to use zfs volumes. It is advisable to mount the dataset. Additionally, it seems a good idea to use the "dedup" feature, although caution should be taken when removing a dataset, cf. advice given by nas4free.

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.

Sunday, January 20, 2013

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)

Friday, January 4, 2013

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.

Wednesday, January 2, 2013

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.