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!



DONE :)

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










Wednesday, January 11, 2017

ARRL Round UP 2017 as OL7M multi



   This year, the ARRL RU, was really extreme in the central EU. There was the record lowest temperature in last 10 years at our OL7M QTH. In the Saturday morning there were minus 25 deg Celsius. We needed to drive our cars, but it was really hard – impossible in the some cases  :) We did have a lot of fun with it. Also about 30cm of new snow made us happy... Thanks to ice and snow we did have a lot of work on wire antennas: 2 broken elements on our 10el wire yagi for 40m, torn wires on a few beverages etc. Finally everything was ready before the contest and we should enjoy it. I am affraid, condx was really poor. We started at 20m band but it was closed in 18:00 GMT. Than we moved to 40m and jumped to 80m and back. 10m band was closed all the contest and on 15m brought only a few QSOs and a few NA stations: KB8OW4GKM, N3KN, N9CK, K7BV and AC0C,. The result was the lowest count of NA stations in last 5 years:

2013 - 693 QSO with NA
2014 - 682 QSO with NA
2015 - 443 QSO with NA
2016 - 515 QSO with NA
2017 - 425 QSO with NA

   Anyway after all it was nice contest with a few visits of Murphy, nice BBQ in minus 25°C and some vodka drinks :) We would like to thanks to all for QSO and rare mults like: Luis CE4SFG, Peo D44TBT, Felimon DU1JM, John 9M6XRO, Ajaya VU2DED, Michael VP8NO, Alain TR8CA, Solo VR2CO, Eddy YB6DE and others! Beautiful end of the contest was the last QSO. It was on 40m with Eric W3DQ from DC – Thanks for mult Eric!

Some photos, thanks to Olda OK1YM :)


 Pavel OK1MU, Ondra OK1CDJ and Franta OK1DF












Our new (wild) member of OL7M - Marie :)
 



 Fun with cars in -25°C

Temperature: blue almost outside temp

And final score