Friday, August 13, 2021

 Well,... frustration with Ebay has pretty much ended my kitting projects.  It was fairly time consuming and it is actually nice to get on to other endeavors. 

I still have about 50 of the SB-220 diode board kits, I don't know what I will do with those.  Another ham has taken on the kitting and selling of the QRM-180s.  Victor is his name, KO4HHY check Ebay for his listings.

A Panadapter...

The current project in the shack is the creation of a simple panadapter for ham radios.  I have had one running on an old computer and tied to my FT-1000 for several years.  LOVE IT.  Being able to see the whole band and just click on an interesting signal at any time is certainly the easy way to play radio.

A couple of years ago I attempted to get a panadapter to run on a tablet.  I failed.  Maybe the tablet wasn't smart enough but mostly I wasn't smart enough.  Recently a friend of mine offered to help and I am again optimistic that we might come up with something.

With a good deal of effort, anyone can get a panadapter working on an old computer.  Just buy a software designed radio (SDR) adapter and then load HDSDR on the computer.   Add an antenna and away you go.  An SDR is cool anyway.  You can see the whole band and with a decent sound card you can listen to all of the activity on pretty much any band.  

The next trick is to connect it to your transceiver.  If the software can control the frequency of your radio then all you have to do is click on the spot on the waterfall display where the signal looks interesting and your radio will go there.  Almost any recent radio will have an input to accept commands through a serial port.

The last part of the task is to make the SDR disconnect during transmissions.  This will avoid some unnecessary smoke.  

One approach is to tie the SDR to the internal IF of the transceiver.  Then it simply doesn't see any RF during transmit.  That works great if you can do it.  Sometimes, however, the IF is not all that accessible.   And tearing the cover off of a new radio is not always a good idea.  The other answer is to simply switch out the SDR during transmit.  The QRM-180 did this with a small circuit and a relay to save itself during transmit.  There was also a nice bit of circuitry there to buffer the signal ahead of the transceiver.  Utilizing that, the transceiver can be used for receive (most sound better than an SDR anyway) while the SDR will only provide the display.

The current prototype is a Raspberry Pi running linux.  It would be nice to run HDSDR software, but that has problems on a small linux system.  Gqrx is open source software, and someone smarter than I (my friend Eric) may be able to create something dedicated to just being a ham radio panadapter.

Hard to know how this will evolve but the goal is to have a small box with the raspberry pi, some additional circuitry and a relay, and a couple of cables to connect the transceiver.  Plug in a standard computer monitor and you are off and running.  No extra software to load, with mysterious drivers and unused features.

We will see.  Stay tuned to this channel for further updates....