FT-817 SDR adapter (panadapter)

Yaesu FT817 is an epic piece of ham radio world. It's been on the market for more than a decade (much more) with no changes. No portable transceiver can beat it's price and versatility. Yaesu doesn't put energy into improving this line, however it's not a big problem, for hiking it is still one of the best option.
There was a time when after moving to Hungary I had only a tiny 817 and no money to buy a bigger box. I was happy with it, with its CW filter it has a decent receiver, but I always wanted a bit more.
I have an sdr dongle with a cheap RTL chip inside. I decided to use it as IF receiver with my laptop.

There are many pages describing the background of the saga listed below:

https://iw0ffk.wordpress.com/2012/07/26/ft817-sdr-dongle-panadapter/

http://www.w1ghz.org/small_proj/FT817_Panadapter-N1JEZ.zip

http://www.radioamatoripeligni.it/i6ibe/panadapter/panadapter.htm

This is the best clip telling you everything you need.

I didn't want to leave the dongle connected during TX, so I inserted a tiny reed relay right after the cap coming from the filter. This way I can switch it off, and it also disconnects the IF connector on the back to avoid noise issues in the IF stage.

It is not a sort of rocket science. The relay is powered via the 2N2222 which is opened via 3k3. TX GND from the socket pulls the transistor to GND to stop powering the relay. 

There is switch as well on the back of the transceiver to switch the whole stuff off while it is not needed.

The relay is not critical, but its conductors can behave as capacitor when opened, so those reed type models are suitable. 

I use SMA connector, tiny switch, and short high quality microwave coax in the radio. Keep the dongle's coax as short as possible to avoid losses. Mine is only 3 inches long. There is an RF choke on the USB cable to filter RF noise from the PC. 

This way there is no noise coming from the laptop, no feedback problem during TX, no overload problem at all.

Even with the cheap RTL dongle the receiver is superb. The only issue with this dongle is some drifting due to the lack of heat sink inside the plastic house. After few minutes it stops drifting. 

I am tapping the signal after the filter. The bandwidth is more than enough this way. If you want a bit wider spectrum on your screen, you can choose to tap it on the other side, but I would not do it. 

You can link the 817 with FT817 commander via CAT interface cable as well. This way you can control the whole system from the pc. I did not want to waste my time with it, I feel OK with the small VFO dial.

Have fun!

HI Mate,

My name is Frank. At the moment my call sign HA7REM. It means I am living in Hungary at the moment. It is a tiny blog about ham radio (amateur radio) hobby. Nothing more but a good chance to share my crazy ideas with my friends all around the world.
Ham radio is not about making money, so feel free to use the content. You can link it, or copy-paste, it's up to you. If you show the source on your page it will make me feel good, but if not, I'm not going to commit suicide, or hurry to find a lawyer. I do not take it too serious. Ideas are in the wide open space waiting to be realized. They are in the mind, can not be sold or stolen.

You will find technical stuff, schematics, antenna ideas, small Sunday-projects, and stories about ham radio, hiking, or anything else produced by my crazy mind.

Have fun!

Frank

I would say sorry for the language I use in this blog. In any case of missing world ask google translator or someone from down under. :)