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