[Skimmertalk] A balanced Red-Pitaya-RBN-Station

[dd5xx at web.de]

Hi all,
 
I have a Red Pitaya with 14:1 impedance transformator from Bob, a pre-amp from SV1AFN and the well-known original active antenna "mini-whip" from PA0RDT. I wonder how you guys install such setups next to your transmitting station and how to realize the protection of that receiver.
 
My TX antenna (=5-band beam) is installed at 15 meters above ground level and for DX purposes I am using a 1.2kW amp. Let's say I would install the mini-whip at a height of 5m above ground and a horizontal distance of 20m to my TX ant. Won't the mini-whip get damaged in case I am transmitting with my radio at high power? I guess so because the mini-whip should be really sensitive and keep in mind that I am also using the pre-amp at Red Pitaya input.
 
So how do you guys handle that? Do you operate your skimmers on completely different locations where no transmitting occurs?
 
The Mini-Whip uses a kind of diplexer where it is fed with 12V DC, the power is supplied through the coaxial cable to the active antenna element. Would it be enough to implement a TX/RX relay that will power off (drop the 12V power supply for the mini whip) at the moment I am transmitting with my amateur radio station? Should I additionally protect the Red Pitaya input during a TX session just like HB9JCB described in his last post?
 
However ... in case I will be active on my radio station especially on contests, my skimmer mainly will not function because the TX/RX relay protection setup will disconnect the RX capability of the Red Pitaya all the time, right?
 
any suggestion appreciated. Looking forward to read your comments.
 
73
Saki, DD5XX
 

Gesendet: Donnerstag, 23. November 2017 um 21:19 Uhr
Von: "hb9jcb at bluewin.ch" <hb9jcb at bluewin.ch>
An: skimmertalk at contesting.com
Betreff: [Skimmertalk] A balanced Red-Pitaya-RBN-Station
Hi all

Yes the RP is build as a Measurement-Tool but adding
a Bandpass a Preamp and 1:14 Impedancetrafo makes it to a famus SDR!
and even a powerfull RBN-Station as you can see in the spots analysis tool

My RBN-Setup:
80m horizontal Loop - TPF(50MHz) - Preamp(9dB) - 1:16 - RP(125-14) - HP-Pavillon(2x2,4GHz) - SkimSrv

Some figures:
80m horizontal Loop plane but 8-13m above ground - wireman - 4:1 balun - koax
TPF 50MHz as designed from Phil Covington for his QS1R
Preamp symmetrical Norton 9dB Gain
1:16 Trafo wound quadrofilar on binocular
RP jumpering 2-5 and connected by GHz-Ethernet (80MHz traffic from 8 band listening)
HP-Pavillion 2-Core-2,4GHz 4GB Win7-HP-32bit
SkimSRV 96kHz scanning reduced only to the cwsegmentsize of the appropriate band
Powerconsumtion ca 80W

In test is a scalable Preamplifier-Kit with BPF 2-50MHz from Funkamateuer Kit BZ-100

Future plans:
Using the two Inputs from RP for Low/Highband-Antenna
Rx- and PTT-Tx-Protection switching the rp-input during transmission to a noise-source
Using two RP's and two SkimServers in separate directories on the same computer for morethaneigth bands

lets do it - have fun
73 de hb9jcb
Johann
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