HIGH QUALITY RADIO MODULES


ALL BOARDS ARE FULLY ASSEMBLED AND TESTED. This is an excellent value! The boards are hand soldered, cleaned and inspected under a stereo microscope prior to testing. You simply can NOT get this level of quality elsewhere.

These boards are limited production, and are hand assembled one-at-a-time.

The only accepted means of payment will be PayPal. Please allow 30 days for delivery.

Questions about the boards or information on ordering should be directed to: aa8c@gridtoys.com


400 MHz DDS Frequency Synthesizer/RF Signal Generator with microcontroller and interface



The DDS board features an AD9951 DDS synthesizer chip with a 400MHz clock, up to 140MHz frequency coverage, tuning in 1Hz steps , High stability 0.28 ppm 25MHz TCXO, on-board RS-232 @ 115.2K, on-board CAN bus for connecting multiple DDS boards. The microcontroller is a Microchip dsPIC33FJ128MC804 clocked at 64 MHz. The circuit board is 4-layer. This is a very high quality and extremely reliable board, built to operate over a wide power supply range, withstand high temperatures, and is suitable for industrial use. Most of the components for the DDS board are military, industrial or automotive temperature range.

Control is via RS-232 at 115.2 K using a dedicated terminal, or terminal software on a PC. The user interface is simple, and easy to use.

When used with the provided firmware one of these synthesizer boards can be operated in stand-alone mode as an independent signal generator, as a low power CW transmitter with shaped envelope keying, or two of these boards can be connected together via an on-board controller area network to create a single conversion receiver that offers continuous coverage from 50 KHz to 54 MHz when used with the receiver board shown below. In addition, a third DDS board can be added to the CAN as a direct-synthesized CW transmitter/exciter with an output of approximately 5-7 dBm into a 50 ohm load. Spurious output: -50dB below 30 MHz (without filter) -40 dB from 50 MHz-140MHz (without filter), mirror frequency -20 dB without filtering (low pass filter recommended). Operates on 9VDC-15VDC @ 300mA. An on-board configuration switch, ICSP programming header and a 3.3V cmos logic compatible input for a telegraph key are provided on the board. If using the DDS board as a transmitter or as a stand-alone device, you will need to provide a low pass filter for the output. The RX board provides filtering for the DDS boards used for the receiver only.

Assembled, cleaned, inspected, and tested (no enclosure) $259

Optional BNC Coaxial Low-Pass Filter; Your choice of 30MHz, 50MHz, or 150MHz: $35 (not needed if the dds board is to be used with the rx board).

Postage will be paid inside continental U.S.

Please allow 30 days for delivery.



VLF/HF/VHF Receiver Board

Use this board with two of the the above DDS boards and one of the AF boards (below) to build a very nice, basic SSB/CW communications receiver with continuous coverage from HF through VHF. Alternatively you can use a local oscillator and BFO of your own design, but it needs to meet the requirements outlined in the specifications for this board if you expect it to work properly.

This radio is a little different. The overall design is conservative and simple. It relies on off-the-shelf wideband technology to provide simplicity, versatility and good performance at a reasonable price. The RX board features include: 50 KHz-52 MHz frequency coverage, single conversion design, 7 dBm diode ring mixer, 70 MHz IF, double sideband product detector, and good sensitivity across the specified tuning range. There is a 70 MHz axillary IF output on-board for use in SDR and experimental applications. The RF and IF amplifiers are high performance InGaP devices. Overall gain is approximately 50 dB @ 7 MHz. Typical RF amplifier noise figure: 2.7 dB or better. Sensitivity: 0.5 uV @ 10 dB (S+N)/N or better (0.2uV typical). Inputs: RF (antenna) 10 dBm, LO (0.5V p-p, 70.050MHz to 135MHz), BFO (63 MHz to 77MHz, 0.5V p-p). Click HERE to see a picture of a radio built as a “proof build”. Click HERE for an audio clip recorded from this radio in the evening on 40m. Click HERE to see a picture of a very nice radio built with a remote control head, custom microcontroller, with LCD and optical shaft encoder. The radio pictured features two canbus controller boards so that the radio can be controlled from the front panel, from the remote head, or using the RS-232. Operates on 11-15VDC @ < 140mA. The receiver board is intended to be used with the AF preamp/filter board shown below.

Assembled, cleaned, inspected and tested (no enclosure) $229

Postage will be paid inside continental U.S.



AF Preamplifier and Active Filter

This board is intended to connect directly to the product detector output of the receiver board kit or to the product detector output of a direct conversion/superhet receiver.

This board features a 50-ohm terminated, AF/RF diplexer to provide for adequate termination of ring mixers used as product detectors, and a gentle second order low-pass audio filter with a hand-tweaked response, suitable for listening to CW or SSB signals.

For more aggressive CW filtering there is also a switch-selected unity-gain fourth-order low-pass filter with a 6 dB cut-off frequency of 1 KHz. This filter is sharp while keeping ringing and noise to a minimum. An audio mute facility is also provided. Filter and mute inputs may be controlled with SPST toggle switches or driven directly with TTL compatible logic circuitry. The preamplifier board AF output is suitable for connection to line level inputs on a PC sound card, or to an audio amplifier, but can produce up to 4.9V P-P output without significant distortion into a 600 ohm load. Overall gain is approximately 30 dB @ 600Hz. Useful dynamic range (from noise floor to 4.9V P-P) is approximately 74 dB (narrow filter), and 68dB (wide filter). Noise floor at output (grounded input): 2 mV, typical (wide filter), less than 1 mV (narrow filter). Microphonics: less than 30 mV P-P, worst case. Operates on 11-18 VDC @ 35 mA.

Assembled, cleaned, inspected and tested (no enclosure, or toggle switches) $95

Postage paid inside continental U.S.


AA8C@GridToys.com