[hpsdr] reducing computer radiated emissions

[Jeremy McDermond]

On Nov 30, 2010, at 12:03 AM, David McQuate wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> My Core 2 Duo on a Gigabyte main board in a CoolerMaster case radiates all sorts of junk, from somewhat noisy discrete signals to hash covering tens of kHz, that changes when I move the mouse, and when the DSL modem / router sends out ARP queries once a second.

ARP queries once per second?  What's wrong with your network?  ARP is only used when the host wants to contact another host on the local network.  The result is also cached, by default for around 5 minutes.  That means that you should only be seeing ARPs once for each IP on your network every 5 minutes.  If you're seeing something else, something's probably wrong.  This is a network capture from a minute of traffic on my network at the datacenter, which has 4 or 5 machines, and serves some websites and an APRS Tier2 server:

00:30:02.214755 arp who-has 198.178.136.84 tell 198.178.136.1
00:30:06.456115 arp who-has tsunami.xenotropic.com tell dstar.nh6z.net
00:30:06.456339 arp reply tsunami.xenotropic.com is-at 00:16:cb:xx:xx:xx (oui Unknown)
00:30:13.926378 arp who-has 198.178.136.1 (00:c0:b7:xx:xx:xx (oui Unknown)) tell power.xenotropic.com
00:30:14.040319 arp who-has 198.178.136.132 tell 198.178.136.1
00:30:33.853067 arp who-has 198.178.136.8 tell 198.178.136.1
00:30:37.374856 arp who-has 198.178.136.245 tell 198.178.136.1
00:30:38.853294 arp who-has tsunami.xenotropic.com tell dstar.nh6z.net
00:30:38.853702 arp reply tsunami.xenotropic.com is-at 00:16:cb:xx:xx:xx (oui Unknown)
00:31:02.572781 arp who-has 198.178.136.110 tell 198.178.136.1

That's 8 ARP queries in a minute.  On a busy network...

> Thanks!
> 73,
> Dave

--
Jeremy McDermond (NH6Z)
Xenotropic Systems
mcdermj at xenotropic.com




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