Friday, 14 June 2019

Just a quick update to say I'm still kicking.

Been a quiet month or so and so I thought I better write something for this blog.  ;-)

First off I got fed up trying to get a clean signal from the Gemini 2-500 PA using the Anglian transverter and Icom 7300.   No matter what I seemed to do I could not stop it from occasionally causing splatter, along with the RF surges in power when first keying the transmitter.    Now this isn't to say the IC7300 is a bad radio it isn't but it certainly doesn't like playing the transverter and Gemini.    So to resolve the issue I went and bought an Elecraft K3S which has resolved all the issues and ok it's an expensive fix but the transmitter of the K3S is certainly worlds ahead of the IC7300, though I do still prefer the audio from the 7300 which is much easier on the ears.  

One of the nice things about using the K3S is the fact it displays the right frequency when using the transverters and in fact with in a few days of having it I also discovered it out from TTL logic from the ACC port so you can interface some kind of transverter switching.    

With the above in mind I wondered if a simple transverter switch and device sequencer could be bought and though I did find a couple they were quiet expensive so I decided to roll my own using an Arduino so a couple of prototypes later I've come up with a design with will switch between my 2m and 70cm transverters and handle the device sequencing for both units below is a couple of screenshots from KiCad of the front panel indicator and main board.  I'll do a full write up once I've confirmed all works as expected.  

A quick feature list is as follows.

  1. Handles two transverter. 
  2. Provides TX inhibit. 
  3. First sequence event can provide 12 - 28V up to a couple of amps to drive change over relays.
  4. Sequence events two and three can sink up to 40mA, though you could chuck in a darlington pair if you want to sequence more relays.
  5. The unit interfaces with my Wavenode so that if a high VSWR is seen the unit automatically ceases transmitting and puts the unit into the default RX mode.
  6. All sequence event are optocoupled to the Arduino just in case a FET or BJT decides to go legs up in a funny way.
Front panel layout from KiCad
Main board layout from KiCad.

I've also got another project on the go in the form of a 70cm 250W amplifier which I bought from eBay from a German amateur which was quite cheap at 55 Euros.  

70cm 250W PA module from eBay.
I rather helpfully came across the website of PA0EHG who had bought the same unit and documented what he had done to get the unit going on the 70cm band so once I've got a replacement RF terminator as the one that came with the unit the solder tab fell off as soon as I touched it I'll power it and see what's what.

So that's the end of this update I'll do a proper update once everything has progressed a bit further.