Not sure which G3PLX product you're referring to...
There is/was article in rad come
covering I think a dds tx/rx , may of been
only tx , but the project seemed to
stall at the end , it was a HF all mode tx
using software defined techniques .. as i say g3plx
was air testing on 80 quite a while ago ,
but nothing came of it ..pity
G..
Sent: Sunday, November 21, 2010 4:06 PM
Subject: Re: LF: ROS Latest with I/Q output
Not sure which G3PLX product you're referring to...
It is simple to do a DDS exciter, but you can only 'modulate' a DDS by
reprogramming it in freq/phase /amplitude tio teh extent the chip allows.
So FSK modes like WSPR and JTxx are a doddle.
Narrow band modes that need amplitude variation are possible if the
sampling rate (DDS reprogramming) is a lot higher than the signal
bandwidth - this is necessary to keep the alias products to a minimum as
subsequent anti-alias filtering is impossible if you are generating the waveform
this way. PSK31 formed by reprogramming an AD9852 DDS at
7812.5Hz (250 samples per symbol) gives < -60dB spurious.
The next 5MHz GB3RAL when it comes on line will use this technique.
A DDS followed by an I/Q upconverter is also straightforward.
I've built an AD9851, IQ upconverter and allpass network into a small diecast
box, frequency controlled via RS232 interface.
And for narrow modes, you don't even need I/Q outputs from the
software. A pair of opamp all-pass filters will generate quadrature
drive for a single tone input, and can be adjusted to give a couple of
100Hz bandwidth with 40 - 50dB sideband rejection. All
the design data / circuits can be found on my website
On 21 November 2010 15:47, Graham <[email protected]>
wrote:
>>> There are plenty of receiver packages for Softrock. clones
and similar - now how about more SDR transmitter
software.<<<<
What happened to the G3PLX project , I had
a ssb qso with him using it , but
never seen anything since ?
Surely it must be 'simple' to drive a
DDS to make a low power exciter ....
hopefully it will replace the 3 ft ( 1 mtr)
cube of racal equipment I need to use on
mf in the near future
Its just occurred to me , if I/Q is
now coded, then the ROS - VLF , based on 25
Hz max shift @ 8 KHz may be opened up to other
bands ?
G..
Sent: Sunday, November 21, 2010 1:41 PM
Subject: LF: ROS Latest with I/Q output
At last !!!!!!!!
The first software author to provide datamode stereo I/Q outputs to
drive a direct image cancelling upconverter
.
The latest version of the ROS software, Ver 5.9.8 beta, drives all my
direct upconverters (LF - HF and SHF)
perfectly, without any need for narrowband analogue phase
shift networks
Congratulations to Jose for listening and responding to this
request.
The only other software I know of to provide the I/Q output option is
G3PLX's SDR transmitter for SSB/FM/AM voice http://www.g4jnt.com/SDRTxSW.htm and one or two other
'specials'
There are plenty of receiver packages for Softrock. clones and
similar - now how about more SDR transmitter software.
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