Dave, John and group
As noted on my website and here the grabber I am running is very much
'experimental'.
in practical terms a useable service is provided with a 5 minute refresh
rate (even with the missing minute), and it certainly does not stress
bandwidth considerations. I personally am an impatient sort, and the ability
to offer a more frequent refresh and nice smooth scroll appealed to me.
I settled on the http server within spectrum lab for its simplicity, and for
the additional remote control it offers, and because I had in my estimation
sufficient bandwidth.
When I first experimented with it I had a small image and higher
compression, and made some measurements of the required bandwidth. I later
upped the image quality and size for a test, and did not re-measure.. though
I did not observe any issues.
The file size by the way, is related heavily to content with JPG files, I
have seen that the file size rises dramatically if the brightness is high,
as the 'noisy' image is harder to compress.
With the contrast and brightness at the correct level images off my system
are about 100K, and take about 1.6 to 2 seconds to upload to the client.
The experimental nature of the grabber is to gain experience of the system
requirements and limitations, with a view to offering this service long
term, when I am away from home (which with my present job is very frequent
at the moment)
If I cant operate, I can at least contribute a little to the experiment.
I am also working towards implementing grabbers for the SHF bands, where
QRSS is non-existent, some propagation modes are very short lived, and in
general, things are not quite the same as on 500KHz
Spectrum Labs looks like the best candidate for my goals, but there are
always more things I would like to do with the concept.
As always, the comments from this group on the functionality or otherwise of
these systems, is most welcome. After all they are intended for the benefit
of others as well as giving me a bit of fun.
Regards
Mark GM4ISM
----- Original Message -----
From: "Dave Sergeant" <[email protected]>
To: <[email protected]>
Sent: Saturday, January 05, 2008 10:32 AM
Subject: Re: LF: Re: GM4ISM 500KHz Grabber
Thanks for the explanation John. I am a little puzzled why Mark
wanted to update every few seconds for something used to display 3
sec dot QRSS or slower where it takes several minutes for the trace
to disappear off the screen.... Your 5 minute update seems far more
sensible. And you are right, doing it from a server at home on ADSL
brings the ADSL upload speed into the equation as well, something
many people forget. Remember that 512kbits/s (NOT Mbits...)
corresponds to only 40kBYTES/s and that is dead slow for large
files....
I see now that Mark has reduced his file size and display size which
has largely solved the issue. But I am puzzled when he said the old
file was 600kB, what I downloaded was most certainly 1.2Mb!!
Sorry to hear about your antennas John, hope you soon sort it out. I
worked MM0XAU on 40m on your island yesterday and he didn't mention
storms, only lousy HF conditions..
73 Dave G3YMC
On 5 Jan 2008 at 10:16, John Pumford-Green GM4SLV wrote:
On Fri, 04 Jan 2008 12:00:17 -0000
"Dave Sergeant" <[email protected]> wrote:
> Not sure how John GM4SLV does it, maybe you should find out.
Hi gang,
I use the old fashioned way....
Spec Lab (running on a Win98 box) saves a screenshot every 5 minutes
into a directory on my main Linux PC (via SaMBa filesharing).
The Linux box runs a simple script every 5 minutes to upload the new
screenshot to the web-hosting server - actually 2 different web-hosts
at the moment as I try a new hosting company - my normal ISP's
webspace www.sighthound.demon.co.uk/gm4slv/grabber.htm and a new
account at www.gm4slv.org.uk/grabber.htm
The script then renames the recent capturefile and moves it to a daily
archive directory on the Linux machine.
5 minutes later the whole thing repeats....
Mark is trying to use the built-in HTTP server of speclab and serve
the pages directly from his machine at home. I presume he has no
external web-hosting supplier to use and wants to do it all in-house.
>
> 73 Dave G3YMC (still off the air on 500k)
>
ditto....
Cheers,
John
http://www.davesergeant.com
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