[Skimmertalk] Skimmer and aggregator question(s)

Fri May 11 06:24:08 PDT 2012

If you use the aggregator feature that lets you connect to it with telnet
and you have multiple instances on a machine don't you have to change the
port for the telnet connection on some of them?  I don't see how to do that
on the latest aggregator.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net

-----Original Message-----
From: Pete Smith N4ZR [mailto:n4zr at contesting.com] 
Sent: Friday, May 11, 2012 12:56
To: skimmertalk at contesting.com
Cc: skimmer at dxwatch.com
Subject: Re: [Skimmertalk] Skimmer and aggregator question(s)

Responses interleaved below, Kaz ...

73, Pete N4ZR
The World Contest Station Database, updated daily at www.conteststations.com
The Reverse Beacon Network at http://reversebeacon.net, blog at
reversebeacon.blogspot.com, spots at telnet.reversebeacon.net, port 7000 and
arcluster.reversebeacon.net, port 7000

On 5/10/2012 6:22 PM, kaz wrote:
> Hi folks.  First, apologies if this double posts to the list.
> Finally laid hands on a couple of softrock kits, and I am finally 
> getting a chance to play with skimmer and SDR.  Way fun.  I expected 
> the surface mount parts to be difficult when building the first Softrock.
> Never tried any surface mount project before.  Wrong.  Turns out 
> reading the numbers to sort out the capacitors was the hard part. 
> Bright lights and magnification, and even my 17yo son had trouble(and 
> he has 20/13 vision).
> But enough digression.
> Bought skimmer license, have skimmer running on 40m and 80m.  40m 
> calibrated(I think), 80m still pending.
> Question#1
> I'm not clear on the relationship between the skimmers and aggregator.
> If I run a skimmer session for each softrock, do I run aggregator for 
> each skimmer?
> My initial expectation was to run the skimmer sessions for each 
> Softrock, use wintelnetx to put the spots together, and use aggregator 
> to ship the spots to the RBN from the wintelnetx window/port used to 
> collect the spots.
> I found the documents N4ZR has written to be "spot on", but I have not 
> seen/found any that describe this relationship.  (I probably did not 
> look hard enough....???..hints appreciated)

Yes, this approach is fine, in principle.  The thing that is important, from
the RBN's perspective, is to keep the association between a given instance
of CW Skimmer and the Softrock for a given band.  That way, if we see a
calibration error coming up on the Skimmer Details page of the website
<http.reversebeacon.net> you'll be able to associate it with that instance
of Skimmer and make the necessary changes.

Rather than running WintelnetX, I suggest you do what Tim, KQ8M does.  
Here's a quote from an e-mail I just got from him.

"Every instance of skimmer has its own Aggregator. There is 3 instance of
skimmer and Aggregator running on 2 computers. The other 2 computers have 2
instances. What I had learned from Dick, W3UA, was to rename each instance
differently [he means to rename the exe file]and use separate directories,
of course. You have to do that with Skimmer anyhow. I keep Aggregator in
each skimmer's directories. Also, each skimmer uses the same callsign. If
you use separate callsigns it comes out separately on the RBN."
> Question #2
> Is it necessary/required to open the port to the skimmer/aggregator to 
> the world_wide_interwebz?  I would really rather not do that at this

Aggregator does not use a port, so you should be able just to start it and
> Other trivia:
> With two skimmers running on mostly dead bands, a dual core Pentium D 
> (Dell Optiplex 745) ticks off about 15-20% CPU when the skimmers are 
> minimized.  The 80m softrock skimmer is at 48khz on the on-boad 
> Soundmax.  The 40m softrock skimmer is at 96khz on an ASUS Xonar DG.
> The Xonar DG seems to be a fantastic value for a sound card. Also 
> available as PCI-E, Xonar DGX.  Its main limitation over the more 
> expensive siblings in the Xonar line seems to be its 96khz max sample 
> rate, vs 192khz for big brother.
96 KHz comes pretty cheap - the 192 KHz bandwidth is more of a specialty

When you first crank up your Softrocks it is likely that you will have
images on the opposite side of the center frequency from the real signals.
You need to run the I/Q Balance calibration to get rid of these.  That
routine requires strong signals across the entire range, so I've found the
easiest way is to turn my radio down very low (RF output) and provide the
signals it needs from one end of the range to the other.

The other thing that helps a lot is to use audio isolation transformers on
the two channels.  Without them you will probably see a fairly large noise
bump at the center frequency, resulting from hum.  The iso transformers will
"transform" this into a relatively narrow dead spot, caused by the lower
frequency roll-off of the iso transformer.  I used some relatively good
Triad isos in order no not have roll-off near the ends of the frequency
range, but if you already have some my suggestion would be to try them and

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