[amsat-bb] Fwd: Polluted time server causing issues with digital modes

Sun Apr 1 18:52:47 UTC 2018

Frank,

Since getting involved with FT8, I've been using 
the Meinberg Software on my computers to stay in
sync with other stations worldwide. It has served
me very well.

Bob  K8BL

https://www.meinbergglobal.com/english/productinfo/time-server.htm
________________________________
From: Frank <k6fw1 at verizon.net>
To: amsat-bb at amsat.org 
Sent: Sunday, April 1, 2018 1:41 PM
Subject: Re: [amsat-bb] Fwd: Polluted time server causing issues with digital modes

I looked at my log since 2009, my copy of Dimension 4 has never used 
this time sever.  The notes on this time server states closed and only 
for use by networks of 10 or more computers.  Matter of fact my 
Dimension 4 has only connected to the same time server since 2009.  I 
don't know what controls Dimension 4 and which time server it uses, but 
it does not seem to be random.  I agree that if a station is using a 
time server that is not accurate then the modes that rely on precise 
time syncing will not work.

Frank
K6FW

On 3/31/18 10:37 PM, Brad WF7T wrote:
> I am forwarding this for anyone interested. I think my discovery is correct
> and invite additional review/scrutiny.
>
> 73 Brad WF7T
>
> On Sunday, April 1, 2018 at 12:21:36 AM UTC-5, Brad WF7T wrote:
>> *I have discovered a polluted time server that is wreaking havoc with
>> time-synced digital modes, and worse. For everyone using round-robin style
>> time synchronization like Dimension 4, please remove the following time
>> server: rackety.udel.edu <http://rackety.udel.edu>.* It is consistently
>> sending time sync corrections that are between 10 and 41 seconds different
>> than every other SNTP server in the world. This will cause your PC clocks
>> to skip this amount and stay that way until another time sync occurs, e.g.
>> 5 to 15 minutes later, causing another massive time correction by another
>> accurate time NTP server. Please pass this information along to all
>> digital-active hams.
>>
>> While this amount of time is not of any consequence for RTTY, PSK and the
>> like, this behavior is detrimental to WSJT and QRSS modes. Terrestrial WSJT
>> modes like FT8, WSPR, Meteor scatter MSK144, and EME modes fail to decode
>> and will cause out of sequence transmissions.
>>
>> I also noticed a number of out-of-sequence FT8 tranmissions on 40M this
>> afternoon (BTW, open early to EU), which clued me into the situation. This
>> messed up time server could have been a contributor.
>>
>> *Remove or disable the following server: rackety.udel.edu
>> <http://rackety.udel.edu>.* Apparently it has been getting increasingly
>> worse since 3/8/2018 or so. I only discovered this tonight while I was
>> decoding WSPR on 474.2KHz (630M) and saw a huge time jump and lack of
>> decodes of some fairly strong signals.
>>
>> And yes, this is also an InfoSec problem. Time bases are important for
>> MANY Information Security purposes, but beyond the scope of this discussion.
>>
>> Excerpts of my Dimension4 time-base logs below. Please contact me with
>> questions/comments.
>>
>> 73 Brad WF7T
>> Nashville, TN
>>
>> ---
>>
>> ... First noted occurrence in my time-base logs
>>
>> 2018-03-07 10:36:44.461 -7.962988e+000 rackety.udel.edu SNTP <-- 7 second
>> correction
>> 2018-03-07 10:39:52.480 7.980464e+000 clock-1.cs.cmu.edu SNTP <-- fixed
>> on next round-robin sync
>>
>> ... Persists for a second day, appearing to get worse
>>
>> 2018-03-08 09:17:25.217 -1.015543e+001 rackety.udel.edu SNTP <-- 10
>> second correction
>> 2018-03-08 09:20:35.240 9.963055e+000 clock-1.cs.cmu.edu SNTP <-- Fixed
>> on next round-robin sync
>>
>> ... Jump ahead a week; yup, getting worse
>>
>> 2018-03-15 05:34:10.880 -1.761963e+001 rackety.udel.edu SNTP <--  17
>> second correction
>> 2018-03-15 05:37:29.176 1.812267e+001 ntp.cais.rnp.br         SNTP <--
>> Fixed on next round-robin sync
>>
>> ... Skipping ahead to tonight; SNAFU
>>
>> 2018-03-31 23:29:34.849 -4.165045e+001 rackety.udel.edu SNTP <-- 41.6
>> second correction!
>> 2018-03-31 23:33:35.421 4.192192e+001 ntp2.kansas.net SNTP <-- fixed on
>> next round-robin sync
>>
>>
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