Friday 21 October 2022

Autumn 2022 HF popagation charts updated


I have just updated my propagation charts for October, November and December 2022 with new sunspot numbers. 

I will update the Spring 2023 charts when we get a little closer as they are likely to change as we head towards the maximum of solar cycle 25. 

Anyway, it is nice to see some good predictions of DX on 10 metres and if the past two weeks are anything to go by they are pretty spot on with very loud signals from the USA. 

ARRL's W1AW's CW practice files were romping in the other day on 28.0675MHz Nice to see 10 metres doing what it does best! 

Click here for the charts or use the link on the right-hand side.

Friday 18 March 2022

Repairing a MFJ-1786 magnetic loop

I just wired up my MFJ-1786 magnetic loop, which hasn't been used for years. Unfortunately, it looked like the loop controller had gone U/S. 

The meter lit up, but pressing the loop buttons had virtually no effect. The amber lights flicked slightly, but they were not so bright as I remember them, and the motor didn't turn. I got hold of a schematic, but it is way more complex than I thought it would be. I first changed the only electrolytic capacitor in the unit as it was getting quite old, but it made no difference. 

I then stripped the antenna and made sure it was all OK. Connecting a 9V battery made the motor turn, so I sprayed the motor with grease and put it all back together. Turning to the controller again I first changed Q1, but that made no difference. Then I changed Q5, but nope! So I moved on to the U5 78L12 voltage regulator, which is fiddly job as it is an 8pin SMD. 

And low and behold it works! I just need to fix the power meter, which displays reflected power, but not forward, but that can wait until another day. Then finally I can mount it outside for final testing. I've attached the MFJ-1786 schematic as this was quite hard to track down - might come in handy for someone in the future.  Click on the image above to see a larger version.


Well, it wasn't a diode that was stopping the meter from working, just a poor connection. 

So I now have some spare diodes for the future! I've uploaded a higher resolution version of the schematic too.

Steve G0KYA