First of all, I should state that I have no financial interest in the Cross Country Sentry 10 SDR, nor any ax to grind against competitors. But I have gotten some additional information from it's developer that I think will be of interest to VHF operators. Overall, this product sounds like a real winner for both weak signal and satellite operators. The ability to have output on all VHF bands from 6 Meters thru 1.2 GHz would be perfect for rovers, and really simplify station design for the rest of us.
Here are the comments I've received from Chris, G4HYG. ===============================================================
I'm also a VHF/UHF weak signal enthusiast so I appreciate your kind comments.
We are in the final development phase of the transceiver and are planning to start a KickStarter project in about a month to put the transceiver into production.
To give you an idea of the technology used in the transceiver the RF front end device is a PGA-103+ low noise amplifier with a LTC5584 as a mixer. The PA stage uses the new BLP10H610 device from NXP. This NXP device is due to be released this month so it should be available when we are ready to start production.
The transceiver will work at 222 and 902/903 MHz for U.S. customers. Our intention is to supply different firmware and filter options depending on the customers location. For example the E.U., U.S, and Japan have different frequency specifications for imported amateur radio equipment. For in-house testing and any potential military customers we do have wideband firmware but I wouldn't like to release that firmware for general use for obvious reasons.
The approach we have taken with our existing SDR receivers is to try to design them so that they can use as many SDR programs as possible. The Sentry transceiver is somewhat different in that it doesn't divide the LO frequency by 4 to generate the 90 degree phase shift for the IQ LO injection. Programs will have to use the direct LO frequency without division. So far HDSDR and Quisk are the only programs I know of so far that will operate directly with the Sentry transceiver on both transmit and receive. SDR Radio and SDR Sharp work OK on receive. I'm in regular contact with most of the SDR software authors as I try to help them to add support for our products so I'll be in contact with them before launch to ask if they can add support for the Sentry transceiver.
Regarding the question about bandwidth the internal sound card has a 48 kHz sampling rate so the span bandwidth is limited to 48 kHz, The transceiver will have a IQ output to drive external sound cards up to 192 kHz. The transceiver is designed as a near zero IF (typically 100 Hz to avoid the AM and FM carrier appearing at DC). This helps prevent hams unintentionally transmitting out of band. The transmitter IQ chain is filtered with a 8.5 kHz filter to reduce the wideband noise that can be transmitted along with the wanted signal. We realize that many users will want to drive external high power amplifiers and transverters.
Recently I've been testing one of the the prototype transceivers during the weekly Tuesday night 4, 6, 2 and 70cm contests run by the RSGB. My local club (Bolton Wireless Club) have around 25 members who take part in the contest and as they are line of sight with my station it's a tough test of any receiver or transmitter during the contest. The latest tests have even included using unmatched antennas such as a HF dipole as a VHF antenna to see how the RF filtering worked in extreme mismatch conditions. A lot of the development time over the last two years has been dedicated to ensuring that the receiver is as good as we can make it and that the transmitter is clean with regard to wideband noise. All these on-air tests confirmed what had already been proved in the lab tests and proved that the design is good and now ready for production.
The original YouTube video and the photographs on the web page show an early prototype. The production version will have a different case more suited to fitting underneath a laptop PC. We are planning to add a new video showing a working prototype in action in a week or two.
Thanks for your kind comments about the plan for a KickStarter project. I'll update the web page and the CCW Yahoo group forum with regular progress reports.
Regards,
Chris, G4HYG
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