The LD-1C improves on the LD-1B and LD-1B2 with the addition of two RF gain stages (one ahead of the preselector filters, and one following them) for a sensitivity improvement of approximately 12 dB. It also features input-protection diodes for use with a separate transmitter. Like the earlier models, it can be upgraded by adding an LD-1TX transmitter module, making it the equivalent of an LD-1TR transceiver. However, the LD-1C includes an RF sampler which can feed the transmitter output (greately attenuated, of course!) back into the receiver for monitoring the transmitted signal and for adjustment of the transmitter.
"Wav" format demonstration files, recorded using Winrad, are also available on the Downloads page. These may be played back using Winrad, HDSDR or SDR Sharp, and will let you experience the LD-1 before you buy.
The LD-1C has a very nice extruded aluminum enclosure with an attractive black anodized finish. Licensed Radio Amateurs may upgrade any LD-1Creceiver by adding an LD-1TX transmitter module, or may order the LD-1TR 5-Watt transceiver which is an LD-1C with an LD-1TX installed.
| LD-1C Hardware: The LD-1C amplifies the RF input, bandpass filters it, and then amplifies it again before downconverting it using a quadrature sampling detector (QSD). The output of the QSDis a pair of intermediate-frequency (IF) signals, one of which is called the in-phase (I) signal and the other is called the quadrature (Q) signal. The I and Q signals, are conditioned by a simple lowpass filter, then send to the left (L) and right (R) channels of the soundcard's line-in connector.
Addition of the 5 Watt LD-1TX transmitter module is provided for with PCB headers, Line-In and Accessory connectors, and an antenna relay. Installation of the LD-1TX requires no cutting, drilling, soldering, etc.
An external "mute" or "transmit" switch may be connected via the Accessory connector. (Back to Top)
|Host Software: The host's SDR software, which is available from several third-parties at no cost, performs IF signal processing and demodulation. Compatible modes include AM, FM, SSB, CW, and in some cases DRM. "Soundcard" modes such as PSK31 are available using appropriate software and a second soundcard or Virtual Audio Cable. Winrad is preferred, because the LD-1C software installation package includes a DLL which connects it with Winrad's controls so the operator can change the LO frequency either from Winrad or from the LD-1 control panel. A standalone LD-1C control application is also included in the installation package to let you use your LD-1C with other SDR software, such as Rocky. (Back to Top)|
|USB-Controlled Frequency-Agility: The SDR software has a tuning range of 48 kHz, 96 kHz or 192 kHz, depending on the soundcard's sample rate. The tuning range is centered at the LO frequency, so the crystal-controlled LO found in many low-cost SDR's restricts the frequency coverage to a single 96-kHz range. The LD-1C uses a synchronized pair of direct digital synthesizer (DDS) chips as its quadrature LO, resulting in extreme frequency agility. The LO frequency is selected via a USB connection, either from the LD-1C's control panel (shown above) or directly from Winrad. When the LO frequency is changed, one of the five preselector filters is automatically selected. These control functions are performed by a microcontroller. The microcontroller's firmware may be updated by the user via the USB cable. (Back to Top)|
|Soundcard Considerations: Like any SDR which relys on a host computer and soundcard, the LD-1C's performance is dependent on the performance of the soundcard. An expensive professional-grade soundcard like the Delta-44 is NOT required. The LD-1C performs very well with a Creative SB1095 USB sound adapter, which is available for $50 - $75 dollars and is ideal for portable use with a notebook PC.
IMPORTANT: Most notebook PC's have a two-channel (stereo) audio output, but only a single-channel (monaural) mic input. This is not adequate for use with an SDR like the LD-1A, so if you plan to use a notebook as a host you MUST use a good-quality USB sound adapter like the Creative SB1090. When selecting a USB sound adapter, make sure it has a stereo line-in jack. Cheap ones and "dongle"-style adapters general have only a mono input. (Back to Top)
|Performance: The LD-1C's performance has not been fully characterized, but after using the prototype for several months with an MFJ Super High-Q loop antenna, an SB1090 sound adapter, and Winrad, it can be described as comparable to the performance of Yaesu FT-817 in terms of sensitivity and out-of-band signal rejection. In terms of usability, it is far superior. The SDR software provides a spectrum-analyzer-like graphical display of all signals within the tuning range, and the operator can instanly tune to any signal with a single mouse click. The IF bandwidth is highly adjustable, as are the AGC characteristics. After operating the LD-1C with Winrad, HDSDR or SDR Sharp, going back to a non-SDR receiver feels like flying blind. (Back to Top)|
|Professionally Designed For Amateurs: The LD-1C was designed by a lifelong ham with degrees in Electrical Engineering from Rose-Hulman Institute of Technology and Purdue University, and 30+ years of industrial and academic experience, so you can rely on its technical soundness. It is built on a high-quality PC board using dedicated power and ground planes as well as extensive decoupling to minimize EMI and EMC problems. (Back to Top)|
|Frequency Coverage:||100 kHz - 30 MHz|
|Sensitivity:||Better than 0.18 µV for 10 dB signal-to-noise ratio at 10 MHz|
|Image rejection:||Comparable to Amateur-grade receivers|
|Overload Characteristics:||Comparable to Amateur-grade receivers|
|Power Supply:||6 - 14 VDC "wall-wart" with 2.1 mm x 5.5 mm male connector, available seperately|
|Rear Panel:||3.5 mm stereo output jack, 3.5 mm stereo input jack (for planned transmitter module when available), 3.5 mm "stereo" accessory jack, USB mini-B for connection to host, SMA female antenna connector, and 2.1 mm x 5.5 mm coaxial female power connector (center positive).|
|Front Panel:||Power switch (push-on, push off), green LED power indicator, red LED mute / transmit indicator|
|Dimensions:||1.1875 x 3.125 x 7.0 HWD (overall)|