Baycom USCC noise

Baycom USCC noise

[Øyvind Hanssen]

We are using a Baycom USCC card with DF9IC modem with
a T7F radio. It works ok, but since the radio is not squelched
there is a high number of rx interrupts and error rx packets. 

Also, some bad packets seems to slip through. Much garbage is 
seen in the mheard list. 

Is this normal? Is there a way to workaround this? 

73 de LA7ECA

The sccstat returns (for instance): 
speed       : 9600 baud
txdelay     : 5
persist     : 64
slottime    : 8
txtail      : 8
fulldup     : 0
waittime    : 2
mintime     : 3 sec
maxkeyup    : 7 sec
idletime    : 3 sec
maxdefer    : 120 sec
group       : 0x00
txoff       : off
softdcd     : off

Status:

HDLC                  Z8530           Interrupts         Buffers
-----------------------------------------------------------------------
Sent       :  147746  RxOver :     0  RxInts : 30689899  Size    :  384
Received   :  212184  TxUnder:     0  TxInts :  4982360  NoSpace :    0
RxErrors   : 1804229                  ExInts :  7823901
TxErrors   :       0                  SpInts :  1006105
Tx State   :    busy

Re : Baycom USCC noise

[Jean-Luc Coulon (f5ibh)]

Hi,

This is what I get with a DRSI card (1200bps) :
[jean-luc@tangerine] ~ $ sccstat scc0

Parameters:

speed       : 1200 baud
txdelay     : 18
persist     : 64
slottime    : 8
txtail      : 8
fulldup     : 0
waittime    : 12
mintime     : 3 sec
maxkeyup    : 7 sec
idletime    : 3 sec
maxdefer    : 120 sec
group       : 0x00
txoff       : off
softdcd     : off

Status:

HDLC                  Z8530           Interrupts         Buffers
-----------------------------------------------------------------------
Sent       :     674  RxOver :     0  RxInts :   271307  Size    :  384
Received   :    2312  TxUnder:     0  TxInts :    16175  NoSpace :    0
RxErrors   :   28054                  ExInts :   168026
TxErrors   :       0                  SpInts :    12003
Tx State   :    idle

I think _this_ is harmless... Everything is decoded fine with my drsi  
card.

--
Regards and 73
			- f5ibh - Jean-Luc 

Re: Baycom USCC noise

[pa3gcu]

On Wednesday 29 October 2003 11:50, Øyvind Hanssen wrote:
> We are using a Baycom USCC card with DF9IC modem with
> a T7F radio. It works ok, but since the radio is not squelched
> there is a high number of rx interrupts and error rx packets.
>
> Also, some bad packets seems to slip through. Much garbage is
> seen in the mheard list.
>
> Is this normal? Is there a way to workaround this?
>
> 73 de LA7ECA
>
> The sccstat returns (for instance):
> speed       : 9600 baud
> txdelay     : 5

txd of 5 is rather on the short side, you could well do better with it set to 
8 which should suit fine.

> persist     : 64
> slottime    : 8
> txtail      : 8
> fulldup     : 0
> waittime    : 2
> mintime     : 3 sec
> maxkeyup    : 7 sec
> idletime    : 3 sec
> maxdefer    : 120 sec
> group       : 0x00
> txoff       : off
> softdcd     : off
If you dont have a squelched radio why do you have softdcd off.?
Should it not be on otherwise the card will always be in a busy state as per 
below, IF i remember correctly that is.

> Status:
>
> HDLC                  Z8530           Interrupts         Buffers
> -----------------------------------------------------------------------
> Sent       :  147746  RxOver :     0  RxInts : 30689899  Size    :  384
                                                                                                   ^^^^^^^^^^^^
I played with buffersize a lot when i used a scc card (PA0HZP) i found that 
defining the following was best. ( i am presuming one still needs to define 
buffers in /etc/z8530drv.conf .
If it is not a option in that file then recompile scc.c with more buffers 
defined.
/usr/src/linux/drivers/net/hamradio/scc.c
#define SCC_BUFSIZE     1024  

> Received   :  212184  TxUnder:     0  TxInts :  4982360  NoSpace :    0
> RxErrors   : 1804229                  ExInts :  7823901
> TxErrors   :       0                  SpInts :  1006105
> Tx State   :    busy

You will always get a lot of ints without a hardware squelch, every spec of 
noise is an interrupt.
I had much the same problem with decoding at 4800 baud and a software dcd, too 
many interrupts make bad performance.
However having said that i have not followed or used my scc card for a few 
years now things may well have changed.

>
> -
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-- 
If the Linux community is a bunch of theives because they
try to imitate windows programs, then the Windows community
is built on organized crime.

Regards Richard
pa3gcu@zeelandnet.nl
http://people.zeelandnet.nl/pa3gcu/



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