Monday, February 20, 2017

CQ skimmer server during ARRL CW 2017 at OL7M

   A week ago I ordered nice piece of HW not only as measurement tool: Red Pitaya
This is really nice piece of HW with nice web tools like: logic analyzer, oscilloscope, signal generator, spectrum analyser etc + SDR TRX or RX ! What more, SDR RX allows you to run up to 6  x 192kHz independant RX and it all as CW + RTTY skimmer!

   So I connected it to NA1 beverage at OL7M via the BIG RX box with BPF and preamp and there are the results :)

First hour of the ARRL CW 2017

80m and all bands in 05 UTC

 And compare the signals

RX vs TX antennas ISOLATION - OL7M 160m + 80m

   I was very interested in how big or low isolation is between beverages and TX antennas. This is quite important for RXing on the second TRX when the RUN one is TXing.

   There is a picture with all RX antennas at OL7M in 2016 - 2017:

   And the table of results:

   As you can see, beverage antenna is vertically polarized and isolation between dipole is higher. And you can imagine how strong signal is on RX input :-)

Tuesday, February 14, 2017


   After our last year participation in the  M/S category, where we set new EU record as OL7M, I have decided to run SOSB 80m. It was third time on 80m in single and my goal was new OK record. Existing great 4th place on world holds Dan OK1DIG as OL6X - 2,34 mil points. In my last two participations the gol was 1000 QSO. Unfortunately there were not good condx and lower participation too.

   A few weeks ago I had a call from Jan OK1NP and he told me about his plan to run 80m too. I agreed to be on online score ( I do have inconsistent view on it. We have got a few negative experiences with that as OL7M... Maybe there is a room for some unfair game by the over-motivated guys :) On the other hand this contest has got good SO category rules - only assisted one! I think that it should be in all the rest CQ WW contests. This could stop maybe 90 percent of all frauds.

   But back to the contest. I focused mainly on the highest score of WPX mults. It was also nice to see another guys on the online score as Filippo (IZ1LBG) IQ1RY and Milos S53X. The first hour went well and I did have 94 QSO in log although there were 4 minutes without QSO. Conditions to NA were realy great and first night brought also some NA DXs as : WK7S from AZ, Jack WA7LNW from UT. And nice DXs as Hal ZS6WB and Luis XE2B. The second night looked little bit worse but thanks to NA gray line I could work Victor V31VP, PJ6TBob C6AKQ, Preston N6SS from AZ and Robert N7WY from WY. Difficul situation is with JA. Thanks to JA band plan... I could copy 3 JAs in 3520 kHz segment but they did not run the split. I stayed above 3600 and worked 3 JAs, but there were one mistake thanks it. The most of RBN skimmers do not work above 3600!? And than my surprise, I could copy some JAs around 3570kHz, is there new RTTY segment in JA? 

   Last part brought some nice east DXs as well: BY3CN, Aravind VU2ABS,  YE1K, Francisco YV5LAY, Caros BH4TXN. From JA I worked: Taka JH4UTP, Kishi JA1OVD, Toshi JA0RUG and An JM1NKT, thanks!

   What was amazing? The score. I still can not understand in this big improvement. I used the same TX antennas as last years. The main new part of setup was second TRX with independant RX antennas. Thanks to new BIG RX ants switch box I could select inependant antennas for both TRX. What more, in some cases, I could lsn on S&P TRX during my own TX. This was perfect! I could called CQ and search for another station on the second TRX. Also when the S&P station answered to my call with last TU, I could call CQ and save some time :) Thanks this contest I do have a lot of new ideas to INBAND antennas.

   This second TRX made 226 QSOs in S&P mode. Thanks thet great conditions I worked more DXCC than in CQ WW RTTY - 71 vs 70! also number of NA stations on RTTY is nice -  226

   The result is incredible not only for me. It is 1 milion over EE8W from 2011. So what next? Maybe 40m with new yagies :)

   Finaly I would like to thanks all for QSO and to IQ1RY, S53X and OK1NP for nice fight on the online score.  


RUN TRX: IC-7800
S&P TRX: IC-7600
SO2R switching by

Antenna 1: 4SQ of sloping dipoles
Antenna 2: dipole

RX antennas:

1) 2 x 290m , QTF 320 deg to  USA
2) 205m, QTF 305 deg USA
3) 180m, QTF 90 deg  to UA9
4) 170m, QTF 45 deg to  JA
5) 235m, QTF 0 deg
6) 200m, QTF 180 deg to South
7) 220m, QTF  245 deg to SA
8) 280m, QTF 270 deg
9) K9AY single loop
10) inband beverage to 325 deg
11) beverage to 145 deg to A6

All switched to 2 independant RX with BPF and preamp, controlled over LAN.

Monday, January 30, 2017

CQ WW 160m CW 2017 - OL7M MS

   The seven - is a number of our participations in the nice CQ WW TOP CW contest as OL7M in the MS category. This contest is one of the most difficult and also most beautiful one in the year! There is nice winter WX again after almost 5 years, we have got more than 25cm of snow and temperatures under the zero for a long weeks. During that, we prepared beverages and antennas most time in TWO persons...

   At first we used and tested new BIG BOX - RX antenna switch for 2 independant RX per each band by It worked great and I was surprised about the parameters. 

   The conditions during the contest were average. Opening to the NA during the Saturday night was quite low and we made most of the mults and QSO during the second one. There were nice hour around 22 UTC when JA and also NA came at the same time. Unfortunately with very weak signals! The best NA QSO is with KY7M from AZ, thanks Lee! Conditions to JA was also low-average and it was really crazy to hunt weak signals in the crowded JA window. Anyway after it all we are really satisfied with the result despite we know that it could be better :)

   We are really happy to make some rare DXCC and thanks a lot to Jorge CW5W, Alex HC2AO, Erik JW2US, Mike 5H3EE, Takuto 9M2/JE1SCJ, Jeff TZ4AM, Kevin VK6LW, Julio 4M1K etc and YE1K and S01WS club stations.

IC-7800  +  IC-7600 with SO2R/MO2R controller
ANTs: Vertical 42m + 120 radials and dipole
RX: abt 2500m of beverages + K9AY loop
RX switching: RX antenna switch 

   Again, thanks a lot everyone for calling and hope to hear - see you again! The log is on the LoTW.

73 Pavel OK1MU - OL7M

 Pavel OK1MU

 David OK1DTP

 Franta OK1DF

 Really the best way for coax?

 Someone of as run different contest...after first and second night

Tuesday, January 17, 2017

RX ANT Switching boxpart 5 - Assembling and measuring

   I have already finished new RX antenna switch for OL7M. You can see parts and measurements in old articles - here. This box is modular one, so you can build configuration as you need. The main idea is to allow the users to use one or independant two RX per band. It means that you can share every antenna input up to two independant RX per band. With no destroying effect. (For 2 RX you lost abt 3,5dB)

   Each antenna input goes to splitter board. There are bypass relays - if you use just single RX on the band, you can go around the splitter. For two RX, signal goes to splitter. Splitter must be isolated by LC band pass filter. If you do not use it, than you destroy impedance for all rest bands.

   Than the signal goes to the high isolation antenna switch. If you use it together with the splitter, than there must be the load resistors : 50 or 75 ohms. These resistors load unused ports of the splitters. There are two relays in series because of higher isolation. Isolation here is more than 90dB on 40m ( I am not able to measure it ).

   And finally signal goes to the single band PCB with: BPF + notch filters + ATT + HIGH IP3 preamp + simple BPF and some protections... more

First ideas ...

Maybe it should be bigger :D

All parts inside!


And some results:

160m Single A output

160m Output A - 2 RX outputs

160m Output - 2 RX Preamp ON

80m Single A output:

80m Single A + ATT ( 6dB )

80m Single A + preamp

80m Output B - 2 RX

80m Output B - 2 RX + preamp

40m Single A output

40m Single A output + preamp

40m output B - 2 RX + preamp