Monday, June 27, 2016

EA RTTY 2016 contest results
   Thanks a lot to URE and Jesus EC1KR for the nice contest and plaque! See you next time on PSK and another EA contests!!!

Wednesday, June 15, 2016

Common-mode current choke for the RX cables

   I am rebuilding all the RX low band antennas switching and filtering at OL7M. As you can find in a lot of literature - LBDX etc - it is really a good idea to do maximum for suppression of common-mode signals induced on the outside of the feed line:
source: ON4UN's LBDX

   Than I tried to use our ferrite cores. You can find it there: FT-25M533-CTY. So I used a good quality coax cable RG316 and wind it to 4 pieces of that core. As you can see on the pictures:

 There are the cores in original plastic cover - see the measurements

 Example of use in Bi-directiona beverage feeder - see

Common-mode attenuation for 4 cores and 5 turns of RG316
 Common-mode attenuation for 4 cores and 8 turns of RG316
 Common-mode attenuation for 4 cores in the plastic cover and 7 turns of RG316

   And the results? These cores are really suitable for the common-mode chokes! And 4 cores and 5 to 8 turns can by use in really wide frequency range: 160 to 6m. The 8 turns is great on 160m to 20m and fine up to 6m. Less turns improve parameters on higher frequencies.

   If you are interested in that, you can order the cores on the web page.

Thursday, June 9, 2016

Transformer materials (43, 61, 73) for RX antennas

   I have decided to order and measure 9:1 transformets for beverage and K9AY antennas. There are still some questions about the ferrite materials - loss vs SWR. I already have got 43, 61 and 73 materials. Please have a look at the results. Material 61 is not working on low bands. (?) Than 43 and 73 are both fine for these RX applications. 

   Insertion loss is better than 0,3 dB for -43 material and better than 0,2dB for -73 material on low bands. These materials has opposit insertion loss curves. Material -43 has got lower loss on higher bands and -73 has got higher loss on the higher bands. See the pictures. Anyway I think, that these values of insertion loss are  not important anyway.

S11 and SWR 470 / 50 Ohms on BN43-202
 S11 and SWR 470 / 50 Ohms on BN61-202
 S11 and SWR 470 / 50 Ohms on BN73-202
Insertion loss for TWO transformers in serieson BN43-202 (devide by 2)
 Insertion loss for TWO transformers in serieson BN73-202 (devide by 2)

Monday, June 6, 2016

Policko life and work

   Another weekend is over and there are some photos from it. We had another visit by Mike DM5XX/OK8XX and he was really enjoying the tractor driving :) We also did some work before FH HAM fest and there must be some fun too - my burgers and some vodka :) It was fine to see some another friends and Alex OK1RS and Ondra OK1CDJMartin OK1UGA and Slavek OK1CU did great work around EME hamshack and QTH is nicer and nicer... But we have to go back to some TWR and ANT work soon!

Mike DM5XX as Spider man ?

Ondra OK1CDJ testing some new antenna / and snowing?


 Some show desk to FH. TNX to Dan OK1HRA!

Happy like the kid by Mike

Friday, June 3, 2016

Experimental 10GHz OpenWebRX by OK2DL

   Marek OK2DL set up experimental OpenWebRX on 10GHz band. Rig consists of the sat LNB with PLL and RTL dongle. QTH is close to our city Zdar nad Sazavou. And direction of antenna is to SW.

Please enjoy it on :

Marek OK2DL and LNB ant

 Unesco church Zelena Hora and QTH of RX and OK0BZR repeater.