[CQ-Contest] Busted Reversed Beacon Network spots

Mark n2qt at yahoo.com
Sun Jun 9 12:45:05 EDT 2013

It is of course a lot more than just sdr architecture.  There is a real challenge in
creating a multiband capable skimmer.  Many installations use active wide band 
antennas or have other active components in the signal path.  With the signal
 levels being discussed it's easy to see the resulting harmonic and mixing products 
that result.  

Also many installations are co-located with their owner's active ham station. While it 
is one thing to protect a receiver from physical damage it is much harder to keep it
from generating spurs while in overload.  The ubiquitous diode limiters are notorious 
for this. 

The guys who deploy these skimmers have made a large investment in time, effort
and money to deploy these systems.  It's just not easy.

I think everyone continues to work to improve their particular system, and applauds the
efforts of the RBN team for their central role in this.

Mark. N2QT

On Jun 9, 2013, at 10:04 AM, Pete Smith N4ZR <n4zr at contesting.com> wrote:

> Interesting - I "admitted" what?  That there are a lot of Softrock-type receivers on the RBN, some of which have inadequate I/Q image reduction?  Sure. That direct downconversion receivers like the QS1R occasionally throw what look like I/Q spots, even though there is no simple explanation.  Sure.  I saw mine throw one of those just yesterday. Wish I knew why.
> The RBN teamis actively working on a promising technological solution to get rid of all of thisclass of busted spots.
> Wrong-band spots are quite another creature.  I'm still waiting for data on these, but think that either inadequate harmonic suppression and/or intermod will be shown to be the source. If that's the case, then the receiver used probably makes little difference.
> Bret, before you attack SDR receiver performance indiscriminately, take a look at Rob Sherwood's review of the KX3.
> 73, Pete N4ZR
> Check out the Reverse Beacon Network at
> http://reversebeacon.net,
> blog at reversebeacon.blogspot.com.
> For spots, please go to your favorite
> ARC V6 or VE7CC DX cluster node.
> On 6/8/2013 11:37 PM, Brett Graham wrote:
>> Eventual admission from N4ZR that a subset of just wrong-freq-same-band spots were seen at a tad over one-per-minute (during a contest) got me looking at this again, using non-weekend RBN data for 2013-03-08 (also with all spots of DXpedition/special event calls omitted, so hopefully missing majority of stations deliberately QRV on >1 band or >1 frequency within same band simultaneously, or deliberately transmitting a fecal signal as no contest that day).
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