[Skimmertalk] Red Pitaya 1:14 impedance transformator + SV1AFN pre-amplifier

DD5XX (Saki) dd5xx at web.de
Mon Oct 23 05:59:53 EDT 2017

Hi Lee,

the key point is "reliable" signal :) I have also some nearby local RBN
skimmer but after long-ranged research I found that their local QRM
level differs heavily. Some of them have really big gaps between
day/time (up to 10dB!), others up to 3-4dB. There is only one single RBN
I am aware of that replies with constant signal levels during a 24h
period. I can use such a node for "realiable" tests. The same applies to
some WSPR beacons out there, I did also detailled tests on that because
I was curious how high the local noise on some beacons is. On my own
testing station the local noise is noticeable, too. That's because I
live in the city with lots of man-made-noise. In the late hours where
man-made-noise are low, the SNR reports are much better of course. The
OM should always have in mind that the reports are "Signal-TO-NOISE"
ratio. That's exactly the reason why currently I am planning in
installing a CW-RBN/WSPR receiving node on a very good low-noise area
onto a tower, hopefully to get constantly SNR values.

Thanks for sharing your thoughts Lee. Have a nice week and best 73

Saki, DD5XX

Am 23.10.2017 um 10:02 schrieb Lee Sawkins:
> I have found an easy way to accurately measure exact s/n ratio changes in any skimmer system.  This only requirement is a having a beacon or other reliable signal within ground wave range.  I have a beacon on 10 meters that I use.  Simply see what the skimmer is giving for a s/n report for this signal.  Then make your changes such as adding a 14:1 transformer, a pre-amp, or an inline filter etc.  After each change, wait a while and see what the new s/n report is.  The difference between the new and old reports is the exact difference caused by whatever you did.  This method is accurate, repeatable, and requires no test equipment.
> Lee VE7CC  
> ----- Original Message -----
> From: DD5XX (Saki) <dd5xx at web.de>
> To: skimmertalk at contesting.com
> Sent: Mon, 23 Oct 2017 01:15:09 -0600 (MDT)
> Subject: Re: [Skimmertalk] Red Pitaya 1:14 impedance transformator + SV1AFN pre-amplifier
> Hi Martin,
> thanks for feedback. I think I will order one from SV1AFN. I already did
> send him an email with some questions yesterday. Hopefully will order
> one this week. Thanks again and have a nice week.
> Best 73
> Saki, DD5XX
> Am 23.10.2017 um 01:32 schrieb Martin Rath:
>> Hi Saki,
>> I use Maki's J310 LNA in front of the red pitaya for 2 2 reasons:
>> 1) additional gain. As per Maki himself the res pitaya requires an
>> additional 5-10 dB amplification.
>> 2) to protect the inputs: less than 2 were after i got the RP a close
>> by lightning took out the AD8066 op amp. I did manage to replace don't
>> want to so that all too often: Singapore gets hit by major t-storms
>> over 200 days per year. Running a skimmer here is not always easy as i
>> cannot always be home to unplug the antennas. I would much rather have
>> to replace a J310 than the AD8066 another time.
>> I'm happy with the performance. I'm still waiting for one 14:1
>> transformer but it's already on the way.
>> 73's Martin 9V1RM 
>> On Mon, 23 Oct 2017 at 00:13, DD5XX (Saki) <dd5xx at web.de
>> <mailto:dd5xx at web.de>> wrote:
>> Hello all,
>> thanks to Bob (N6TV) I got one of those Red Pitaya impedance
>> transformator 1:14. I wonder if anyone did try to add a
>> pre-amplifier on
>> the input and if so what is your experience ? I have heard and did
>> read
>> lots of positive feedback on the pre-amplifier offered by SV1AFN
>> on his
>> website. I would be interested in the kit "J310 push-pull HF pre-amp
>> 0.5-54MHz" (see "https://www.sv1afn.com/j310preamp.html"). Do you
>> think
>> to gain some more dB performance with this combination ?
>> Red Pitaya INPUT1 <---- 1:14 impedance transformator <---- SV1AFN
>> pre-amp
>> Looking forward into your comments.
>> 73
>> Saki, DD5XX
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Vy 73s de DD5XX

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