[amsat-bb] Cross Country Sentry 10 Info
les at highnoonfilm.com
Fri Aug 8 01:57:31 UTC 2014
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
Here are the comments I've received from Chris, G4HYG.
I'm also a VHF/UHF weak signal enthusiast so I appreciate your kind
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
Les Rayburn, N1LF
121 Mayfair Park
Maylene, AL 35114
6M VUCC #1712
Grid Bandits #222
Southeastern VHF Society
Central States VHF Society Life Member
Six Club #2484
Active on 6 Meters thru 1296, 10GHz & Light
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