The Radware receiver, introduced in 1994, was probably the first SDR (
software defined radio) sold in the amateur market. The receiver was not a
commercial success possibly for some of the reasons outlined below.
Free Radware
cards
- The receiver was a ISA bus card which was quickly outdated by the
PCI bus.
- The only sound cards that it worked with were based on
the analog devices DSP, and these cards were not that common.
- The card was introduced for windows 31 and the development costs for
upgrading to windows 95 became excessive for a limited market product.
- As the receiver was plugged into the card rack inside a computer case it
was necessary to build the power amplifier for transmit as and outboard unit.
The FCC did not approve this. Had the FCC given approval
for this, there would have been far more incentive for investors to continue
with the project.
Performance of the Radware card.
- In direct conversion radios, and those using a very low IF,
problems arise with the second order intermodulation products which are not
present on superhetrodyne radios. The second order products result
from the mixing of two signals to produce the sum an difference frequencies.
Normally in a superhetrodyne receiver these products are removed by the front
end filters. In a direct conversion the "difference signal" between two
close in signals will produce a signal within the base band or the low IF. A
test should be added on direct conversion receivers to measure this
intermodulation as it is often far worse than IIP3. An even worse issue
related to this product is that it does not involve the receiver LO and thus
any signals producing this product will cause interference across the whole
band.
- Direct conversion receivers rarely have image rejections grater than 50 dB
and the Radware card was about 45 dB.
- Software for AM and FM were never developed to a truly acceptable
level.
An other SDR radio using the same basic architecture as the Radware card is
now on the amateur market. This is the SDR1000 marketed by Flex Radio
www.flex_radio.com . This
product has none of the issues discussed above in he section relating to
commercial success. As it is a receiver with a very low IF it still has the
problems outlined in 1 and 2 of the Performance of the Radware card. The
problem listed in 2 above can be reduced to better than 70 dB by software tuning
but is only valid for the band it is tuned on.
Radware Block Diagram
Download Archived Radware files. These files are
unsorted and contain the source and install files for all software. The last
known working version is 1.24.
There is absolutely no warrantee or indication that they will work for
anyone. They do work on the machine that they were developed on, running windows
31 with an ECHO sound card.
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