Sunday, September 16, 2012

My Amateur Radio Hardware

So I finally decided to write about my ham radio setup. This is a blog post I promised in a tweet a long time ago:

 Wow, almost a year. Wait, what? Tomorrow (Sept 16th -- or possibly today by the time I actually publish this post) will be exactly one year since I got my license. Let's see my equipment so far.

Wouxun KG-UVD1P
A really neat hand-held FM dual-bander. Costs around $100 and works quite well. No fancy features (unless you count the flashlight as fancy), but does everything I'd expect it to do. It has nameable channels, keypad for entering the frequency, scan mode and it can even listen to two frequencies at once (or rather scan between them). TX power: 5W. Channels are computer programmable via a USB cable.

Baofeng UV-3R
Another hand-held FM dual-bander, but this one's smaller and cheaper. I think it can be found for around $50 on eBay, and it has 2W of TX power. A few downsides compared to the Wouxun: channels can not be named, nor does it have a keypad for entering the frequency. This makes it inconvenient to operate on too many repeaters or to program manually, but if you only have a few favorites, it'll do just fine. Programming cable is a must. Did I mention it's tiny?

SlimJim Antenna (from N9TAX)
This is a nice antenna (I have the dual-band 2m/70cm version) made from a section of ladder-line. It's durable and also flexible. So far I reached repeaters up to 25 miles away, but I'm planning to put the antenna up in the attic and try again for some further away ones. The fact that I'm surrounded by hills surely doesn't help.

SignaLink USB
This is basically a USB sound-card, but dedicated to interfacing between the radio and the computer. It can be used for digital modes with a SSB radio, or even to get on the air via Skype (I tried that with my handheld!).

In addition to these, I've also built a number of kits recently.

SoftRock Ensemble RXTX
This is a software defined radio (SDR) that can be built for a choice of frequency ranges. What I like about SDR's is that you can see a good chunk of the spectrum at once, in a waterfall view. Allows you to see all transmissions in that frequency range, and tune in by clicking one with the mouse. The transmit power of the RXTX is 1W, and I built mine for the 20m/30m/40m range. For the RXTX to work, two stereo audio cables need to be connected to a sound-card on your computer. This means that if you also want to hear anything, you'll need two sound-cards (you might get around with just one for the digital modes).

Peaberry SDR
This is clone of the SoftRock RXTX, that solves the cable clutter inherent to the RXTX by including a sound-card on the SDR device itself. Thus, only an USB cable needs to connect to your computer. Moreover, the Peaberry includes a second sound-card (with jack connectors so you can plug in your headphones and microphone), such that you can have a fully operational radio even if your computer doesn't have any sound hardware at all (embedded, anyone?) or you don't want to use it for any reason (e.g. me playing with the radio while YL watching a movie next to me on the same computer). Compared to the SoftRock, the Peaberry uses mostly surface mount components, which I actually find easier to assemble.

Other kits include K5BCQ's 20W amplifier and KitsAndParts' low-pass filters and SWR bridge, but these are more straightforward and don't really need explanation. Unfortunately, I haven't yet been able to transmit at the full 20W. I still need some more reliable means of connecting all my boards together and let's not even mention that everybody seeing my boards tells me I need boxes!

Antenna System
I'm not proud at all about my antenna. It's a 20m dipole, set up in the attic of my house. The problem is, I had to zig-zag it around a little, trying to keep it away from the various metallic things in the attic (some smaller, but others quite large).. And the other problem is, it's probably not tall enough, as my house is half-way inside a ditch. It's connected directly to a twin-lead cable which again connects directly to my Peaberry (I know this is probably extremely bad, and I promise I'll fix it using RG-58 coax and a homebrew balun as soon as the coax arrives). I also have a  2m dipole which connects to the same cable, but I polarized it wrong (it's horizontal while I only work FM on that band). When I'll install the coax I'll also replace the 2m dipole with my SlimJim, and I'm curious what my range will be after that.

I'm still looking for a solution to get active on other bands. I could either set up a 40m loaded dipole, or do my best to tune the 20m dipole (I don't have a tuner and I'm not planning to get one). Alternatively, I could build a magnetic loop antenna for the 20-40m bands: I already have the copper pipes assembled, all I need is to weld/solder them and  get/make a large enough variable capacitor to withstand the approx 1500 volts that are likely to build up from my 20W amplifier.

With that I think I exhausted all the ham radio stuff that I own. On VHF it works just fine, but on HF I'm still to make my first QSO (I have plenty of contacts on WSPR though - more on that in a later post).

73... KK4EDI

Friday, January 6, 2012

Android apps I use

I am not going to start telling people to use Android instead of iPhone/iPad (although they should!), but I've been using an Android tabled for the past couple of months, and there are some apps that I have found useful. This list will serve as a backup for me (sort of), but it may also help others.

So here it is:

  • Dolphin Mini Browser (tabbed web browser)
  • Skype (video chat)
  • MoboPlayer (excellent video player)
  • APV PDF Viewer (light pdf viewer, supports invert colors)
  • imo (multiple instant messenger client)
  • CSipSimple (soft-phone, SIP client)
  • DropBox, Ubuntu One (file hosting)
  • TeamSpeak (voice conferencing software)
  • KeePass (password manager)
  • screenshot (com.geeksoft.screenshot - take pics of your screen)
  • ClockSync (because the clock resets when it runs out of battery)

Thursday, August 11, 2011

Bucuresti in pragul declinului petrolului

This post is in Romanian. For an automated English translation, read this.

Am descoperit nu de mult timp fenomenul de Peak Oil, si posibilele implicatii ale acestuia. Recomand doua resurse pentru a va informa despre problema:

SUA ar fi cea mai afectata tara. Dar intrebarea mea a fost cum ar fi afectata Romania si in particular Bucurestiul? Am gasit urmatoarele informatii:

  • Prima productie comerciala de petrol a avut loc in Romania, in 1857. (sursa)
  • Populatia Romaniei in 1844: cca 3.6 milioane + evolutie (sursa - da, stiu, Wikipedia ca sursa nu-i o idee prea buna, dar nu are cum sa fie prea departe). Ce imi pare rau e ca nu am gasit cifre care sa mearga 1-2 secole mai devreme.
  • Populatia Bucurestiului in 1831: cca 61 de mii + grafic evolutie (sursa - tot Wikipedia)
Cresterea populatiei a fost facuta posibila de doua evenimente: revolutia industriala si descoperirea petrolului. Atat productia cat si consumul mondial de petrol au crescut constant in ultimii 150 de ani. Dar de cativa ani incoace, productia a stagnat (iar efectele s-au vazut imediat: asa zisa criza. Nu poti consuma mai mult decat produci). De acum incolo e foarte probabil ca productia sa o ia in jos. Asa ca acum ma intreb daca evolutia tehologica din ultimul secol este suficienta pentru a mentine populatia si nivelul de bunastare curent? Sper ca da, pentru ca altfel, in urmatorii ani vom fi fortati sa ne trezim brusc la o noua realitate, posibil chiar mai crunta decat regimul comunist.

Primul va pica sistemul financiar curent, care se bazeaza pe paradigma cresterii infinite (ca semnale vezi, de exemplu, instabilitatea bursei de valori, problemele imprumuturilor din tarile europene, si chiar intr-o oarecare masura revoltele din Anglia). Odata cu el, sper ca lumea se va trezi la realitate, si prin ponderare sau rationare vom reusi sa folosim ce rezerve mai avem intr-un mod mai inteligent decat pana acum. Astfel, schimbarile care urmeaza nu vor fi atat de dramatice, si ne vor da mai mult timp sa ne adaptam.

Sunt insa uimit cum publicul larg nu are nicio idee despre tema Peak Oil si posibilele implicatii ale acesteia. Traim ca si cum mai avem cel putin doua generatii pana la consecinte. Fals! Stagnarea deja a inceput, iar consecintele majore urmeaza in maximum 10-20 de ani, in contextul in care eu as numi criza curenta o consecinta minora. Si nici nu am zis nimic de posibilitatea unui al treilea razboi mondial (despre care unele persoane zic ca a inceput deja - 1, 2, 3 - sau e foarte aproape).

Sunday, April 3, 2011

Tilapia with eggplant and jalapeño vinaigrette

Do you know what time it is? Yes, I know it's late, but that's not what I meant. It's time for another food/recipe post!

This time, the credit for the vinaigrette goes to chef John from, while for everything else I have to thank Hoai <3

Jalapeño vinaigrette (original here)

  • 2 jalapeños (take most of the seeds and membranes out, but leave some in for the spice)
  • 1/4 cup rice vinegar
  • 1/4 cup olive oil
  • 1/2 teaspoon Dijon mustard
  • 1/4 teaspoon Asian (Vietnamese) hot chili sauce 
  • salt and pepper
This one is very easy, just combine everything in your blender or food processor. You should chop the jalapeños in smaller pieces so the blender can handle it. Make sure you don't use a large smoothie blender, as there isn't much liquid to begin with. The quantities should be enough for 4 portions.

Grilled tilapia fillets and eggplant
  • 2-3 tilapia fillets, fresh or from frozen, defrosted (I suppose you can count one fillet per serving, depending on how large it is)
  • one eggplant (I used a Japanese eggplant from the Asian market, but I suppose the regular one will do too), sliced to 2-3cm thick (1 inch) pieces
  • seasoning
Well, what do you know, this one is easy too. Just season the fish in your favorite flavors. Be creative! I think we used salt, ground pepper, cayenne pepper, crushed pepper flakes, Old Bay seasoning, lemon juice, and maybe others, I already forgot. The eggplant only needs salt and pepper. Grill the eggplant and the fish for 5 minutes each, or until cooked. 

We used our electric indoor grill, which we've become increasingly dependent on. It's quick, healthy and easy. If you don't have one, I would recommend considering to get one. Anyway, back to our dish. At this stage, it's ready to eat (don't forget the vinaigrette). We however like to chop the eggplant and the fish into small pieces (thin stripes, 2-3cm/1inch in length), put the sauce on top, and mix everything together. Pure deliciousness!

Oh, and I have another goodie for you. No recipe, just two pictures. 

Saturday, January 22, 2011

Faster mplayer & sshfs

Two tricks that I shouldn't forget (and maybe you should learn too :).

Multi-threaded mplayer for better HD decoding performance on multi-core processors:

sshfs using busybox, for attaching an USB harddrive to an OpenWRT router, without worrying about samba:
On OpenWRT device: opkg install openssh-sftp-server
On Ubuntu machine: sshfs -o sftp_server=/usr/lib/sftp-server user@192.168.x.y:/mnt/drive /path/to/dest

Thursday, May 27, 2010


Turns out that creating quite impressive panoramas (or rather, impressive for a newbie like me) isn't hard at all! A camera that has panorama-assist feature or a tripod are useful, but they're not required. Once you have the pictures (better to take too many than too few), try Hugin (open-source panorama photo stitcher). Most of the times it does everything automatically, but sometimes you'll have to match points across pictures by hand. 

The problem with the resulting image will be the (sometimes large, depends on the photographer's skill :) areas with no data. Fortunately, there's a solution to that. It's a Gimp plugin that can recreate an area of the picture based on the surrounding pixels only. It it works great in this case. Sure, it's not always perfect and you can get the occasional floating mountain in the middle of the sky, but you can usually fix it quickly by doing same operation on a smaller selection. This amazing plugin is called resynthesizer, and the easiest way to install it is from Ubuntu's repository.

Some samples now.

Sinaia, 2000m altitude

Bucharest, Titan

PDF forms on Linux

I will explain a method of filling in forms inside PDF documents for printing or saving (to send, for instance, a signed copy of a contract via e-mail). I've seen other methods described (see here), but I didn't like any of them: most turn the PDF file into an image, which reduces quality and/or increases filesize, and pdfedit seems overly complicated.

Software required: gimp, pdftk.

First split the original pdf into separate pages (this is one disadvantage, pages need to be edited separately):
pdftk file.pdf burst

Next, for each page that needs changing (let's call it page1.pdf), do the following:
  • Import that page in gimp, using whatever dpi you want for any images you are adding (the higher the dpi, the better the quality. Try 300).
  • The page will show up on a new (and only) layer. Do any modifications on separate layers (if you add text, gimp will automatically insert layers, but if you want to use brushes, make sure you create a new layer that you'll edit).
  • When you're done, hide the background layer (the one with the PDF image), and print to a pdf file (say stamp1.pdf).
  • Now, put the newly created pdf on top of the original page:
    pdftk page1.pdf stamp stamp1.pdf
If your PDF was only one page, you're done. Otherwise, you should join all pages together:
pdftk page1.pdf page2.pdf [...] cat output output.pdf

Now all you need is a high-quality copy of your signature :)