Month: March 2013

Developing a HF transceiver around an Arduino – abandoned project

As you probably know, the Arduino platform is a very useful toy for development of electronic gizmos, and after I saw the Myriad RF project I started thinking how a small portable HF transceiver could be developed around the versatility the Arduino provides. The idea is to keep in line with the Arduino philosophy and level of knowledge, so the end product should be fairly simple and affordable, but still offering alot of fun. These are my targets:– 8-band SSB transceiver (LSB: 80m/40m, USB: 20m/17m/15m/12m/11m/10m)– weight: 500 grams– output: 10W– sensitivity: 0.5uV– consumption: [email protected] standby / [email protected] TX– display: mode, frequency, step, supply voltage, S-meter, SWR– encoder VFO with 2 selectable steps– bandswitch button Right away, the BITX concept seemed like a good match as the RF part of the Arduino: it is a simple and very popular HF transceiver, the performance is decent, there is a ton of documentation and the schematic and inner workings are easy to understand even to the less experienced in RF constructions. Plus, less complexity means smaller necessary space, and it might be perfect for portable QRP operations, wich is another interest of mine. The “BITX” board is basically the main BITX multiband board that includes AGC / S-meter output; the front panel is made out of a 16×2 HD44780 LCD and 74HCT164 shift registers (to use less Arduino pins), a rotary encoder,...

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Raspberry Pi as a WSPR beacon

Probably alot of you know what the Raspberry Pi is – a US$35 micro computer the size of a credit card that can be used for alot of simple but cool projects. Well, some guys at the Imperial College Robotics Society in UK found out that you can actually output a modulated clock signal on one of the GPIO pins to act as a small RF transmitter, then Dan MD1CLV and Guido PE1NNZ took the idea further and implemented the necessary coding in order to make it a working WSPR beacon – project’s name is WsprryPi . Considering the limits for the GPIO output (TTL 3.3V @ max 50mA) we can’t expect too much output power, 10mW (+10dBm) into 50ohm is a reasonable figure while about 20mW is the technical limit. One issue would be the fact that the output signal is a square waveform therefore rich in harmonics and a low-pass filter for each transmit frequency is mandatory (especially if you want to boost the power a bit); considering it covers from 0 to about 250Mhz, if you plan to make a multiband beacon out of it you will need alot of filters. At the moment it needs a permanent internet connection for time synchronisation, but i’m sure some handy fellow will implement a GPS time reference to make it completely...

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X1M – portable chinese HF transceiver

The Xiegu X1M is a recent attempt at HF portable QRP transceivers straight out of China, and it looks like they are on the right way: small and lightweight – check, simple and robust design – check, low power consumption – check, CW and SSB modulation – check, full HF coverage – check. Yes, it is not the prettiest girl in school … but who cares when it is the cheapest ? No really, it costs about US$260 as a kit or US$300 assembled, half of what an Yaesu FT-817ND does. Here’s the list of characteristics: – continuous RX and TX: 0.1 ~ 30 MHz– SSB / CW Output Power: 4-5 W;– operating voltage: min. 9.6V (DC), max. 14.5V (DC);– operating current: 0.35A (min), 1.2 A (max);– switchable RX preamplifier– 100 memory channels;– RIT– CW RX/TX delay adjustment– electronic bug key– switchable backlight– weight 500g (the FT-817ND is 1.2Kg)– size: 97x40x155mm (the FT-817ND is 135x38x165mm) The X1M is all made in SMD technology with 0603 parts; the RX preamplifier uses a very low-noise (NF:1.2dB) CATV 2SC3357 transistor, the IF is at 9MHz with a 6-pole crystal filter 2.2KHz wide, the mixer uses high-speed HSB88W Schottky diodes, the IF amplifier has a MC1350 stage with controllable gain (for AGC purposes), the audio amplifier is an LM386 (just 4mA of standby current) and the local oscillator is made around an Analog...

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Myriad RF – an Arduino transciever shield

Lime Microsystems is a rather new and fabless company specialised in multi-band multi-standard transciever IC’s; their only creation so far seems to be the LMS6002D, wich is a chip no bigger than the nail on your index finger but includes all the logic necessary for a configurable broadband transciever IC supporting all the modern 2G, 3G, 4G, CDMA, HSPA, WiMax or LTE standards: two ADC’s, two DAC’s, three low noise amplifiers, filters, mixers, gain control, the lot. Unless you are a seriously antisocial tech-freak that won’t sound extremely fascinating, luckily the best part is still to come: they have worked together with their distributor Azio and have implemented the tiny creation in a board called the Myriad RF, wich is basically an Arduino shield that houses an equally versatile transciever, allowing a … myriad of RF-based projects to be prototyped around these two tiny boards; the Myriad RF does everything radio-related and the Arduino controls it and interfaces with the user and other pheripherals. Everything (software, PCB design etc) is open-source and it becomes a great learning tool, plus it brings advanced radio technology closer to hobbyists. Of course, it is not just an Arduino shield, the manufacturer also offers a pre-designed solution to interface with an Altera FPGA in order to do some serious Software Defined Radio (SDR) work. The idea already generated a more advanced  concept in...

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The 630m band is official

The European Communications Comitee (ECC) of the European Conference of Postal and Telecommunications Administrations (CEPT) have recently approved the new European Table of Frequency Allocations and Applications in the frequency range of 8.3KHz to 3000GHz. It is basically the mother of all frequency table allocations, but it is only a recommandation and each country has a specific law that dictates exactly how the radiowave bands are to be used. For example, the new ETFAA still doesn’t mention the 60 meter or 4 meter band even though these bands are legal in some of the European countries, but it introduces the new 630m band wich is expected to be adopted by the state laws of each European country in the next period. The 630m band lies from 472 to 479 KHz and the official transmit power limit is 1W EIRP, with the possiblity to increase this limit to 5W EIRP if you are at least 800Km away from the borders of any of these countries : Algeria, Saudi Arabia, Azerbaijan, Bahrain, Belarus, China, Comoros, Djibouti, Egypt, United Arab Emirates, Russian Federation, Iran, Iraq, Jordan, Kazakhstan, Kuwait, Lebanon, Libya, Morocco, Mauritania, Oman, Uzbekistan, Qatar, Syrian Arab Republic, Kyrgyzstan, Somalia, Sudan, Tunisia, Ukraine or Yemen. Adding this to the fact that the band is only 7KHz wide, it would seem the appropriate use for it is weak-signal narrowband modes, such as JT65...

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DXpedition videos – T33R, T88CJ, VP88SSI, 7J1RL

After the previous post about DXpedition videos, I decided to add some more. Here they are: T33R T33T Banaba Island (1990) T88CJ Palau (2008)  VP88SSI South Sandwich Island (1992) – some of the worst conditions to operate in 7J1RL Okino Torishima (1976) – Huge effort by the Japan Amateur Radio League, taking alot of manpower to the shallow atoll in order to install suspended shacks and towers, in an era before GPS or DX...

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Kenwood TS-990s – inside pictures

Some pictures of the Kenwood TS-990s popped up recently, it’s a real beauty. The pictures are on the QRZ – Ham Radio Facebook page, not sure what is the original source. Also posted on my friend YO3IBW’s...

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A bit of solar activity

Hopefully these days we will finally get a bit of solar activity and of course, a bit of 10m openings. The number of sunspots continuously grew in the last five days (60 > 63 > 88 > 90 to 115 today), the SFI is a mediocre 115 and in the next few days quiet to unsettled  geomegnetic levels are expected. I had the chance to work a bit in 10m SSB and I got 2 new entities (GU3UOQ – Guernsey and XT2TT – Burkina Faso), it still appears to be open right now (about 19:00) as I am recieveing strong stations from South America on JT65-HF (LU5FD, PY2VM etc), as well as ZS1AW from South Africa. Unfortunately 10W doesn’t really cut it for me, I guess JT65 is indeed a low signal mode and not a low power...

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