Tuesday, April 14, 2009

New arrival

There's a new arrival in G4ILO's Shack, rather an unexpected one. It's a Juma TRX2 HF SSB/CW transceiver designed by OH2NLT and OH7SV and built by Gerd, DF9TS.

The Juma was a bit of an impulse acquisition. I was surfing the web looking at QRP transceiver kits and happened to come across the Juma website, which I had not heard of before. I was very interested in the TRX2, which seems very good value for money for us here in Europe, better than an Elecraft K2 to which it is broadly comparable. But I was put off building it by the fact that it is an SMT kit. There are a lot of SMT parts to solder!

However, I kept on thinking about the TRX2, and kept on going back to the site, browsing the wealth of information and photos of the transceiver, and reading through the forum. There I came across a posting from Gerd, DF9TS, who was advertising a TRX2A (that's the all-band version) ready built for less than the cost of an unbuilt kit!

To buy one ready built would really be cheating. In any case the post was about three weeks old. I thought that he would probably have sold it, but it wouldn't hurt to enquire. Well, he hadn't sold it, and what's more he offered to send it to me to evaluate on a try before I buy basis. That was an offer I couldn't refuse, and the result was that the transceiver was delivered to me this morning.

I am going to take some time trying it out and comparing it with my various other radios, but here are some initial impressions.
  • The receiver sounds fabulous. There is a sweetness and clarity about the audio that reminds me of the tube based analogue radios of a few decades ago. It sounds even better than the K3, and it seems to hear weak signals just as well as the K3 does, too.
  • There are quite a lot of birdies, many of which are not audible even with an antenna connected. They don't bother me, but some people seem to get very wound up about them.
  • There are only three filters, common for both SSB and CW. They are not as flexible as those in the K3 or most other radios because the low side is fixed at 300Hz. This means that if you want a 400Hz CW filter the high side would be at 700Hz, so the tone frequency would have to be 500Hz.
  • The sound even using the narrowest filter is much easier on the ears (without the harsh, 'ringing' sound) of those in the K3.
  • SSB transmit audio sounds very nice with the speech processor switched out, but a bit gritty and distorted with it switched in. But conditions are poor at the moment and the TRX2 only produces 10W out, so the only SSB contacts I have made so far have needed to have the processor switched in.
  • There is no DATA mode for sound card data operation, and no SSB VOX. Actually, I haven't even figured out how to connect the TRX2 up for data mode operation yet (I'm not sure if there is even a fixed level audio output.)
  • The front panel is minimalistic, there are not many controls, but there is everything you need, making the TRX2 pleasingly easy to use.
  • The connections make rather an excessive use of 3.5mm stereo jacks. The use of one for the front panel mic connector is particularly perverse. But at least they are cheap and do the job.
  • Similar to the Elecraft K2, a lot of the functions of this radio are controlled by firmware. But unlike the K2 the firmware is open source and provided for download. You can compile it using the standard Microchip C compiler. I shall probably be having a go at this later.
I really like what I have found so far. The rig does need some setting up - the S meter is far too generous and the power metering also is a bit optimistic - but this is something I can do once I have finished just playing with it.

Watch this space. I'm sure I'll be writing more about the Juma TRX2.


German said...

I recently built a Juma TRX2, it works fine but sensitivity drops from 20m. On 15 and 10m a preamplifier is strongly recomended.

Do you have the same problem?

Unknown said...

I decided not to buy the TRX2 from the German ham who built it after all. Unfortunately, at the time I tested it, due to solar conditioons there was no activity on the bands above 20m so I am unable to comment on the sensitivity.