Friday, September 30, 2022

QDX is an excellent digital modes transmitter (and very good on receive).

Recently I've been tinkering with antennas here and one of the resonant dipoles I put up is for 20m. I normally run digital modes on the IC-7300 which conveniently connects to a linux computer via a single USB cable but thought I'd get out the QDX again.

The QDX from QRP Labs is an excellent little transceiver for travel or portable operation. It's a bit hard to compare reception as conditions change so frequently but my impression is that it's almost (but not quite) as good as the IC-7300.

What is astonishing is how good the transmit is. On a single 2 minute transmit over just now on 20m I was spotted by 79 stations all over the world.

Here's the graph of spots over a 24 hour period.

The little triangles on the graph are transmit spots. This is a new feature of WSPR Watch that should be in the App Store (free) in a few days.

The reason that QDX transmissions are so well decoded is, I think, because it does direct frequency generation by measuring the audio frequency rather than mixing the audio up to RF. It's a very pure signal.

All over the world on a pocket sized transceiver.

I wrote a small review for the Macedon Ranges Radio club here by the way.


Robbie said...

I’m not sure what you were using today, but it you were picking up my (very compromised) attic antenna, 5W WSPR from the UK, which is mighty impressive to me (there’s so much noise where I am that receiving anything outside Europe is rare for my station). 73 from M7SXB

Peter Marks said...

I'm still running the QDX. Looks like I received you quite a few times in the past 12 hours. Best SNR was -20dB.

Amazing for a transceiver that fits in a shirt pocket.

Note that I am in a very low noise location. The antenna is nothing special, just an inverted V dipole cut for 40m.