[Skimmertalk] Difference of RP10 14 16

Tue Jul 16 19:06:57 EDT 2019

A good way to check whether your pre-amp was over driving your skimmer during the IARU contest is to do an RBN search on spots for N2TC.  Almost all spots for N2TC shown by the RBN are for N2IC, which gets busted to N2TC by over driven skimmers.

N2TC appears to not have been an active CQer, if he was even on in the contest.  There are no human generated spots for that call.

For any skimmer spotting N2TC, doing a comparison search for N2IC vs N2TC during IARU for that skimmer gives interesting results.  It shows at which level the skimmer is being over driven.  My own skimmer was busting this call when the signal was around 60 dB s/n.

I am sure there are other huge signals that get busted in similar ways.

Another problem caused by over driven skimmers is generation of spots on harmonic freqs, and no spot generated on the fundamental frequency.  My own skimmer reported a weak N6MJ on 10 meters when he was actually on 20.  10 meters was not open at the time.  I believe the KU7T skimmer was also doing this.  My DX Cluster rejects harmonics of good calls, but I do not believe AR Cluster software does this.

DX Clusters will be filtering out these busted N2TC spots, but using a RAW RBN feed will give you bad spots.

It's a trade off for me. Sensitivity on high bands with a 20 dB pre-amp or a few busted calls on lower bands.  

Lee VE7CC

----- Original Message -----
From: Björn Ekelund <bjorn at ekelund.nu>
To: Bob Wilson, N6TV <n6tv at arrl.net>
Cc: SkimmerTalk Reflector <skimmertalk at contesting.com>
Sent: Tue, 16 Jul 2019 00:27:26 -0600 (MDT)
Subject: Re: [Skimmertalk] Difference of RP10 14 16

The only difference between the RP-10 and RP-14 is the data converter, they
both use the Xilinx Zynq 7010 FPGA device.
So they should run the same OS and software and have the same capacity in
terms of bands.
The radio performance is however different.

I think whether or not the RP-16 needs a preamp depends on antenna
efficiency. With my simple multi-band
dipole, listening to the RP-16 via PowerSDR, I can not hear any increase in
band noise on 12m (and higher)
when I connect the antenna. This suggests it would benefit from some extra
front end gain. However, listening to
the spots I get on those higher bands with my main radio, performance seems
acceptable. The RP only fails to
decode the really weak stations.

73,

Björn SM7IUN

Den tis 16 juli 2019 kl 06:56 skrev Bob Wilson, N6TV <n6tv at arrl.net>:

> For RP-10 I think you use the "official" OS, Ubuntu, not Alpine Linux.
> The you open a web browser and enter the IP Address of the Red Pitaya, and
> it should open a page with a link to Application Marketplace that looks
> like this:   http://bazaar.redpitaya.com/ .  You can install / update the
> SDR Receiver HPSDR.
>
> More details here:
> http://hamsci.org/n6tv-red-pitaya-combine-cw-rtty-skimmer-hdsdr
>
> It looks like the RP-10 and RP-14 can run the same Ubuntu OS.
> Instructions to make a new image here:
>
> https://redpitaya.readthedocs.io/en/latest/quickStart/SDcard/SDcard.html
>
> 73,
> Bob, N6TV
>
>
> On Mon, Jul 15, 2019 at 9:21 PM Dai NAGAKURA <ndai at cameo.plala.or.jp>
> wrote:
>
>>
>> Thank you Bob
>>
>> Well RP-10 shall handle 8 bands,
>> but I could not find nor understand new OS and commands.
>> Would you tell where hidden gem and spell is ?
>>
>> >A preamp could make the problem worse.
>>
>> This is delicate issue.
>> At this point , We are expecting furtheｒ study.
>>
>> Thank you
>> Dai JF2IWL
>>
>>
>>
>>
>>
>> On Mon, 15 Jul 2019 20:46:33 -0700
>> "Bob Wilson, N6TV" <n6tv at arrl.net> wrote:
>>
>> > On Mon, Jul 15, 2019 at 8:09 PM Dai NAGAKURA <ndai at cameo.plala.or.jp>
>> wrote:
>> >
>> > > I have tested RP-10 and 14 , five weekdays and IARU HF 24 hours.
>> > >
>> >
>> > Thank you.
>> >
>> >
>> > > To write a brief paper, I would like to know two point below.
>> > >
>> > > (1) RP-10 could run only 6 bands at the same time
>> > > RP-14=8 bands , RP-16=8x2=16 bands . is it right ?
>> > >
>> >
>> > I'm not sure about the RP-10, I thought it was also 8 bands.  RP-14 is
>> > definitely 8 bands, and RP-16 = 8x2 = 16, correct.
>> >
>> >
>> > > (2) RP-10 and RP-14 need step down transformer and pre-amp Instead,
>> RP-16
>> > > need NOT Both.
>> > >
>> >
>> > Yes, RP-10 and RP-14 both need to have 14:1 impedance transformers (and
>> > shunt jumpers moved on both inputs), and they need about a 10 dB preamp.
>> >
>> > I am not sure if the RP-16 needs a preamp.  Maybe only on one antenna
>> > input, just for the high bands.  But it is easily overloaded (intermod)
>> by
>> > nearby FM broadcast stations between 88 and 108 Mhz, and needs a lowpass
>> > filter.  A preamp could make the problem worse.
>> >
>> > 73,
>> > Bob, N6TV
>>
>> --
>> Dai NAGAKURA <ndai at cameo.plala.or.jp>
>>
>> _______________________________________________
>> Skimmertalk mailing list
>> Skimmertalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/skimmertalk
>>
> _______________________________________________
> Skimmertalk mailing list
> Skimmertalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/skimmertalk
>