hi David , on Sydney today. I'll get back to u shortly on the HF paths,
I'll collect all the vertical incidence channel stuff I have into one place
and get it to you. The VI oaths are much harder than most, and SNR is
always in the toilet
more later, cheers
On 20 May 2018 11:28:55 am David Rowe <da...@rowetel.com> wrote:
Hi Glen,
I've been perusing the DRM spec, and noted the channel model you mentioned:
From the DRM spec, Annex B Definition of channel profiles
Channel 6, path 4
delta delay : 6mS, path gain RMS = 0.0625, dopplershift : 3.6Hz, dopper
spread 7.2Hz
There are four paths in this model, but only the first two at 0 and 2ms
delay have any significant energy. Would path 4, at -24dB down on the
main path, have any impact on the demod? I just can't see it being a
problem .... like a very low level interferer. Path 3 (4ms) is also 6dB
down.
The non-zero mean in the Doppler spread (i.e the Doppler Shift) is a new
parameter for me however. Need to think about the impact of that.
I've been developing against Channel 4 (CCIR poor), two paths, 2ms
delay, 1Hz Doppler spread. Suspect I'm on the right track with a HF
modem design designed against that.
Some day I might simulate Path 6.
Starting to get some samples from beta testers of 700D from Europe. The
modem is holding up fine so far on HF fading paths. Some issues with
Windows sound drivers, but we are working through them. Many of the
paths are quite high SNR.
- David
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