From: "Dave Sergeant" <dave@davesergeant.com>
To: rsgb_lf_group@blacksheep.org
Date: Fri, 04 Jan 2008 12:00:17 -0000
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Subject: Re: LF: Re: GM4ISM 500KHz Grabber
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On 4 Jan 2008 at 12:25, Wolfgang B=FCscher wrote:

> If we have a Javascript expert here: Any idea how a Javascript
> (embedded in an HTML document) can detect if all embedded graphics
> have been updated ? In that case, the "refresh" interval could be
> restarted after the previous refresh is finished.
>=20

Well just got round to looking at this grabber after reading all the=20
mails. Exactly the same here....

Firstly, note we are indeed talking about Javascript here, earlier=20
emails talked about Java. How many times do we have to tell people=20
that Javascript (common browser scripting language, sometimes called=20
EcmaScript) and Java (compiled programming language from Sun) are=20
completely different things and must never be confused. Mark's site=20
certainly contains no Java applets.....

The basic problem is that each grabber image is 1.2Mb in size (not=20
sure if that is typical of grabbers?). If Mark is using a normal ADSL=20
connection the upload speed of that seriously affects the issue.=20
Plain ADSL upload will be around 20kbytes/sec, ADSLMax around=20
40kbytes/second. For that reason it takes ages to upload a single=20
image - it takes around 30 seconds here on my 2Mb ADSL which is=20
correct for a 40kbyte/sec upload - or much longer if there are=20
several people connected. Bear in mind if you are on a monthly=20
restricted usage limit all of us trying your grabber will soon use up=20
your allowance, especially if people leave it on all the time!!

So I am not sure if changing the javascript refresh will help, you=20
really need to either reduce the size of the images by a big margin=20
or similarly increase the refresh time. Or maybe do not set a refresh=20
time but get users to do a refresh. Not sure how John GM4SLV does it,=20
maybe you should find out.

73 Dave G3YMC (still off the air on 500k)

http://www.davesergeant.com