JUMA Amateur Radio Forum

Yes, you are correct, the TRX-1 is Double-Sideband Transceiver, and therefore you will indeed be transmitting both an upper and a lower sideband in PSK31, and indeed in any other mode except CW. Now, whether this 'upsets' anyone or not I'm not sure - I'm sure that the purists would object to this 'w...

Hi, Leo, As other commentors have said, you do not need a lot of test equipment to set up the TRX-2. Certainly at least a good 3-1/2 digit accurate mutlimeter is a basic essential, and yes, a frequency counter would also be useful, but even that is not essential by using a little ingenuity. The most...

Hi, Larry, The TRX-1 PA uses the IRFR110 power MOSFETS, and these are fairly rugged devices. When mounted on a PCB, as they are in this case, the maximum disspation is limited to 2.5W. Assuming an overall DC to RF efficiency of 50%, fairly typical for small solid-state amplifiers, then with 10W DC i...

I got my spare connectors from the Juma parts company. They are also available from the UK electronics parts shop Maplin, known as 'Kyosho Race Pack Connector' used for model radio controlled cars. The Maplin part number is: GZ98G, and in the UK it costs 2.29 UK pounds, or about 3 Euro. Try http://w...

OK, let's try and answer some of your questions. Filters The Juma has three receive filters available, Narrow, medium, and Wide. The bandwidths of these receive filters are user configurable both in the original firmware, as well as in my modified firmware. There is a single transmit filter whose ba...

By way of illustration, examine the attached JPEG image of a chip from the Juma TRX-2 Filter Module, you can clearly see the 45 degree chamfer on the left-hand side, pin 1 is at the top left-hand corner.
73 Adrian, 5B4AIY

I have now replaced C27 with two 100pF 500V silver mica capacitors. With these in place operating the amplifier for an extended period of time into a dummy load at 100W output they remain cool, and showed not the slightest sign of heating. If you are experiencing this problem, then I would strongly ...

You will fnd the latest build on this website in the section: "Juma Firmware by 5B4AIY", in this section, there is an entry entitled: "Juma PA-100D & Elecraft KX3 - New Firmware v1.05h" and at the bottom of this is an attachment which can be downloaded, a ZIP archive containi...

There is now an updated version of the firmware for the Juma PA-100D, version 1.05h Build 17. Please see the details in the section related to my firmware.

NOTE: This is NOT an official Juma release, but simply more refinement to my modifications for this excellent 'afterburner' !

Adrian, 5B4AIY

There is now a new version of the firmware for the TRX-2, version 1.09b. This fixes a minot bug, and enhances the display. Please see my firmware section for full details.

NOTE: This is NOT an official Juma release! It is simply my latest version of my modified firmware.

Adrian, 5B4AIY