30/3/2006
updated 29/May/2009

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3 generations: Softrock, SDRZero and RFSPACE SDR-IQ

SDRZero G2

English manual (1).PDF 700 kB (2).html 93 kB just the text - 10 MB with images (with help from Eric, ZS6BUJ)

Some videos regarding hand soldering of SMD devices (wmv files)
Soldering a NE5532 SOIC 11MB
Soldering a BFR92 SMD 7.3MB
Soldering a conventional through-hole component: 78L05 7.2MB

Schematic (PDF)

Here is a brief summary. Inspired by the SDR1000 QEX article by Gerald Youngblood ("A Software-Defined Radio for the Masses" parts 1, 2, 3, and 4) software defined radio transceiver and EMRFD book, Edson, N1VTN /PU1JTE built a simple and effective SDR receiver in September/2004 and placed it on-line, sampling 48 kHz of the 40m band (the spectrometer, also see the new 20m spectrometer installed near the South Pole, with a page dedicated to the sampling of 100Hz above and below the 14.1 NCDXF beacons). About the same time I became interested in SDR, Edson sent me some FST3253 and INA163 samples and then I built a QSD much like the SDR1000 but with crystal control and some ideas found on the EMRFD book and also on the internet. Then came the Softrock40 simple SDR receiver and triggered a desire for something with good performance in first place, which could be transformed into a kit in order to spread the new technology, affordable to the average PY ham. Edson and I then developed a circuit and kit of a simple software defined receiver to offer to PY builders. We designed the circuit and the printed circuit board to make it easy to experiment while using not too difficult to find parts. We settled for a complete kit including wire, solder, connectors... etc..., and even a CD with software and building instructions; an aluminum box epoxy painted and SO239 female antenna jack are optional items. Most of the history of the development phase can be traced by looking at distinct pages corresponding to circuit sections: input antenna filter, RF MMIC sibling amplifier, low-noise crystal oscillator, quadrature generation, audio gain research. The design raised interest from hams abroad and now there are SDRZeros in 12 countries.

The receiver kit comes with crystal and input filter components for the 40m band. But the circuit has been used from 500 kHz to 30 MHz by only changing oscillator components or using an external oscillator and scaling input filter values (a table for component values for some bands can be found in "modifications" on the left pane).

On the printed circuit board there are six jumpers for the experimentally inclined: (1) on the oscillator to transform into a VXO or to place a second crystal and switch; (2) to switch oscillator off in order to use an external oscillator; (3) disconnect internal oscillator; (4 and 5) disconnect IQ osc. signals; (6) QSD wideband direct input.

Also, there are connecting points for (1) mute function; (2) IQ audio output; (3) differential audio output (0º, 90º, 180º and 270º); (4) external oscillator 4*F input/output; (5) external oscillator IQ input/output on the receiving frequency.

The circuit, beginning from antenna, employs a no-tune band filter using common commercial mid-sized RF chokes. Q factor, series equivalent resistance and component tolerance were included in the simulation, practical measuring confirmed simulated results. See http://py2wm.qsl.br/SDR/40m_filter.html

An RF amplifier follows, the main reason to use one here is to present resistive impedance to the QSD (quadrature sampling detector). The topology closely mimics a MMIC (pun intended!). Simulation indicates gain = 13 dB @100MHz and 11 dB @1GHz, input SWR 1.3:1 @100MHz, output SWR 1.05:1 @100MHz relative to 50 ohms, noise figure = 4.5 dB, OIP3 = 20dBm. See http://py2wm.qsl.br/MMIC/mmic3.html and parts 1 and 2 for development history. If 30~60 MHz use is envisioned it is a simple matter to increase gain by changing some resistors on the RF amplifier, this will lower MDS.

The QSD  comes next. Our contribution is the use of a wideband Guanella 1:4 RF transformer. As the FST3253 CMOS switch has different switch-on and switch-off duration times, using a transformer with grounded (for RF) center tap as in the SDR1000 allows for unbalancing and unnecessary switching spikes to appear at the output. The Guanella transformer is not ground referenced on the FST3253 side. Either there is current flowing when both sides’ switches are on or there's an open circuit when just one switch open. The Guanella 1 dB bandwidth points are on 500 kHz and 500 MHz. For lower frequencies just add some more turns. Later we discovered (indicated by PY2KO) that a current balun would be needed for a theoretically perfect balanced differential feed to the FST3253. It was not included in the kit nor in the schematic since there was no benefit in actual tests.

The four sampling 10nF metallized polyester film capacitors that come with the kit are hand selected and matched to be within 1% tolerance. Amplitude and phase balance are compromised when capacitor relative values differ 5% or more from each other, this is a measured discover. Although some software can automatically compensate for this unbalance, every effort was done to maximize IQ channels balance. This way the receiver can be used feeding quadrature audio channels, without a computer, for a conventional phasing direct conversion receiver with excellent image rejection. Several units were measured (using KGKSDR software); Unbalance has been found to be no more than 0.02 dB and 2º across a 96 kHz bandwidth. Phase error is a straight linear in frequency line; Across a 3 kHz bandwidth for a DC phasing receiver it is only 0.06º.

The audio outputs use NE5532 ICs in a "synthesized" instrumentation opamp, look at the INA163 datasheet. The circuit works well and noise seems to be adequate when the radio is hooked to a Delta 44 sound card. MDS = -135 dBm @ 7MHz, lowering to -130 dBm @ 30MHz. 1% tolerance resistors are used throughout in this stage. The NE5532 is the IC used on the first stage of the Delta 44 sound card inputs. This part of the SDRZero circuit is designed with common sound cards in mind. For higher performance in dynamic range, just feeding the three NE5532 opamps with +/- 15V boosts SFDR (spurious free dynamic range) more than 20 dB and the sound card will be the limiting factor when using a Delta 44 or similar card.

A crystal oscillator was chosen for simplicity, with low phase noise as an objective. With a common sound card it allows a 48 kHz band coverage span. The circuit is derived from one of a well known designer and builder, Leif Asbrink SM5BSZ (http://www.nitehawk.com/sm5bsz/linuxdsp/rxiq/osc.htm) and from the referenced bibliography, (http://py2wm.qsl.br/SDR/xtal_osc.html).

Central receiving frequency is 7048 or 7089 kHz (one must choose either one when ordering the kit).

The circuit is very docile and forgiving. Short circuiting the crystal starts the oscillator in a free running LC mode. This mode is useful for OM band and 455 kHz last IF use, as frequency drifting is less of a problem. The circuit also works well on the 3rd overtone with crystals not cut for this purpose. An 11MHz crystal was put to oscillate on 33 MHz, to give an 8.25 MHz central frequency that was used for a Yaesu FT840 HF radio, adding IF DSP to it and all the fabulous resources available in software.

On the PCB there are pads for an additional inductor and/or capacitor to transform the oscillator into a VXO or to switch the extra inductor in and out to extend frequency coverage cheaply.

A two transistor sine-square converter conditions the LO signal to the divider that follows. A Johnson counter divide-by-4 circuit offers good LO quadrature signals to the QSD and is wideband. The 74AC74 is good to 180 MHz. Hybrids were studied (http://py2wm.qsl.br/SDR/hybrid/hybrid.html) and deemed not suitable, although capable of very good narrow band performance.

In the printed circuit board there are many jumpers and headers to allow external oscillators (VFO, DDS...) and circuit experimentation and specific circuit stage access, also connecting points for a future transmitter companion QSE.

The power supply is very standard, delivering 10, 5 and 2.5Volts and requiring 12~15V unregulated.

The kit comes with all the components, many SMT, including connectors and even solder. Only the antenna connector is not furnished. The PCB is a high quality double-sided silk screened, solder masked and plated through fiberglass 1.6mm thick 1.6 ounce copper measuring 75x100 mm (3x4 inches). A CD with a manual containing video clips showing how (easy it is) to solder SMT parts is included.

There are the basic kit and the complete kit. The complete version includes an aluminum box, epoxy painted on semi gloss texturized gray color and SO239 UHF female connector with gold plated inner jack and Teflon dielectric.

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SORRY, SOLD OUT

IN THE NEAR FUTURE WE INTEND TO PRESENT A TX COMPANION EXCITER

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What comes in the kit:

All the material: all components (several are SMT parts size 0805) - resistors, capacitors (10 nF QSD capacitors are individually selected and matched under 1%), transistors, integrated circuits, crystal (choose the frequency!) etc..., PCB (high quality double-sided silk screened, with solder mask and plated through holes, fiberglass 1.6mm thick 1.6 ounce copper), connectors (only antenna connector is not furnished), 0.5 mm thick special solder, 10cm mini coaxial cable RG174, enameled wire, CD with SDR software, building manual with photos and instruction video clips.

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International orders
basic kit with all the parts but no box and no SO239 antenna jack US$35
kit + box and SO239 antenna jack US$53
2 crystal frequencies available 7053 or 7089, choose one (7048 no longer available)
shipping worldwide US$14
available payment methods: Western Union or Xoom (accepts Paypal)

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NÃO ESTÁ VENDO O MENU À ESQUERDA? CLIQUE AQUI.

ACABARAM-SE OS KITS

PARA BREVE PRETENDEMOS APRESENTAR UM TRANSMISSOR COMPANHEIRO

Custo do kit R$65,00 (sem caixa)
R$100 o kit completo.
Montado R$130.
correio para Brasil R$10

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Já disponível para kit completo: caixa de alumínio medindo 120x85x55 mm, acabamento em tinta epoxi cinza escuro texturizado, com toda furação, com rebite em aço rosqueado e parafuso para fixação da PCI.
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Também estamos encomendando em fábrica: Conector SO-239 adequado à furação da caixa, em latão niquelado com contato em bronze revestido com ouro e isolante de Teflon, o melhor que encontrei, no kit com caixa
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MANUAL DE MONTAGEM: versão PDF de baixa resolução, sem vídeos. (700 kB)

VIDEOS: SOLDAGEM DE COMPONENTES SMD (arquivos wmv)
COLOCANDO E SOLDANDO UM CI 11MB
COLOCANDO E SOLDANDO UM TRANSISTOR SMD 7.3MB
COLOCANDO E SOLDANDO UM COMPONENTE CONVENCIONAL 7.2MB

O que é um SDR?
Original: EB3EMD, Fernando Fenández de Villegas
Tradução: PY2GN, William Schauff
Formatação, adaptação, e ilustrações: N1VTN, Edson Pereira

Descrição do SDRZero, explicação do circuito e funcionamento (ainda não terminado)

31/5/2006 - As placas impressas finalmente chegaram. Agora serão tomadas fotos e vídeos de montagem na placa definitiva, para confecção de manual e gravação em CD-ROM. Estimativa é que tome 2 semanas, para então começar os envios.

21/6/2006 - Eu e Celso, PY2XT, estamos empenhando nosso tempo disponível para embalar os componentes dos kits. Já temos separado 100 kits, porém estamos em cidades diferentes, no final de semana estarei com o material que Celso preparou. Então começarão os envios dos kits sem caixa/conector.

7/7/2006 - Dois itens atrasaram os preparativos: parafusos para a caixa, adquiridos hoje pelo Celso, PY2XT. Aquele que eu encontrei não era adequado. Por último, terminal para soldar a malha do coaxial que vai ao conector; é um pequeno detalhe mas está tudo indo tão bem, não há porque atropelar na linha de chegada (de entrega...). Semana que vem tem FENARCOM. Levarei todos os kits que puder para quem estiver por lá e deixarei as remessas para a semana seguinte, ainda estou juntando material, escrevendo manual, gravando CD-ROM, preparando...etc...

21/7/2006 - Depois de muito trabalho despachamos os kits.

Também existe a opção do DttSP-Shell, software poderoso que funciona em Linux. Dentre as vantagens dele, uma é a de não precisar de computador rápido; Edson consegue bom funcionamento com um processador de 500 MHz enquanto os programas para Windows em geral recomendam 800 ou 1000 MHz como mínimo. Em breve (é intenção de inclui-lo no kit) haverá um CD "bootável", bastará colocar ele no drive e reinicializar, não precisando instalar/ocupar espaço no HD. Link para o DttSP-Shell. Para outras versões em Linux consulte a mensagem postada pelo Edson.

http://br.groups.yahoo.com/group/QRP-BR/message/18212

Depois é só curtir! Dá para sintonizar com o mouse (melhor se tiver aquela "rodinha"- wheel). Em ambos dá para ajustar o filtro à vontade até 50 Hz de largura em CW. E olhando no espectrograma dá para ver todo o trecho de 48 kHz, visualmente dá para corujar toda a sub-banda de CW!

Com o SDRadio dá para ouvir CW, AM, SSB, FM, e com uma segunda placa de som ou placa de 4 canais também PSK, packet, SSTV, etc...

E o melhor de tudo, não é um simples rádio, ele é mais capaz do que a vasta maioria de rádios!

O SDRZero depende do processamento realizado pelo computador, rodando o programa adequado. O computador mínimo recomendado para Windows (WinME ou XP, alguns rodam no Win98 última versão atualizado) é em torno de 800 MHz (depende do programa) e a versão Linux DttSP-Shell roda bem a 500 MHz.

1 - O primeiro passo é descarregar (download) do programa. Sugiro o ROCKY (CW e SSB) e/ou KGKSDR (CW/SSB/AM/FM), cada um tem prós e contras, o segundo é mais dotado de recursos atualmente. Existem outras opções; além do DttSP-Shell, que evoluiu para o SDR-Shell, e Linrad (p/ Linux) há o SDRadio (CW, SSB, AM, FM), o Winrad (CW/SSB) e o PowerSDR.

2 - Instale o programa escolhido.

3 - Depois, para simular a existência do SDRZero, descarregue (download) arquivos IQ 1 ou 2 (clique com o botão direito e salve no HD). Esses arquivos foram gravados da saída de um SDRZero. Para explicações sobre esses arquivos gravados veja aqui:
http://py2wm.qsl.br/SDR/SDRZero.html

Os arquivos contém um trecho inteiro de 48 kHz de uma banda, a sintonia é feita pelo mouse.

Como diz o Edson, benvindo ao mundo digital!

Para saber mais sobre como funciona um SDR visite a página do Roland, PY4ZBZ e do Edson, PU1JTE

para a página de PY2WM