Reducing power output of TRX2

General discussion

Reducing power output of TRX2

Postby WI3CK » 01 Jun 2012 16:24

The nominal power output of the TRX2(A) is specified as 10W. Many QRP clubs require power output not to exceed 5W.

Is it possible to lower the transmit power somehow through the configuration? I'm currently running firmware v1.07u.


Regards,
Jan
WI3CK
 
Posts: 9
Joined: 23 Mar 2012 06:44
Location: USA

Re: Reducing power output of TRX2

Postby 5B4AIY » 01 Jun 2012 18:09

Hi,
The output power of the transceiver can be adjusted by means of the carrier level control R28 on the main board. It is normally set to give an output of 10W, but this can easily be reduce to 5W by re-adjusting this potentiometer if you wish.

The output power can also be set with the on-board attenuator. This is set by selecting the TUNE mode, press the PTT switch, and then press and hold the PWR button whereupon you will be able to adjust the output power by inserting or removing steps of the fixed attenuator. The step setting will be stored in the EEPROM for future use.

You say you are using my firmware version 1.07u, there is now a new version, 1.07x that has a number of improvements that you may wish to install, along with an updated user manual. Drop me an email to: adrian04@cytanet.com.cy and I'll be happy to send you this latest version. There is also a new version for the PA-100D linear amplifier, if you have that equipment as well.
Regards,
Adrian, 5B4AIY
5B4AIY
 
Posts: 214
Joined: 13 Nov 2011 09:22
Location: Cyprus

Re: Reducing power output of TRX2

Postby WI3CK » 01 Jun 2012 20:00

Adrian,

thank you for your quick reply. I guess my R28 was a little off. Now I can use the internal attenuator just fine to adjust between 5W and 10W. That's perfect.

I would certainly give the new 1.07x firmware a try. While at it, first a big THANK YOU for doing all that custom firmware work. Second, it so happens that I do have the free version on the Microchip IDE and MP-Labs C compiler installed in another VM to play with some PIC18F2550 code. I presume that I should be able to compile the TRX2 firmware from sources too. The way I do things with the 18F2550 is that there is "protected" HID bootloader code, that loads the actual firmware via USB. The Michrochip bootloader is written in a way that it can't destroy itself, so I'm not too worried to send something to the PIC. Even if it doesn't run at all, I can start the bootloader by setting a certain bridge on my board and just flash another version. Is your TRX2 firmware working similarly?

My email is JanWieck@Yahoo.com


Regards,
Jan
WI3CK
 
Posts: 9
Joined: 23 Mar 2012 06:44
Location: USA

Re: Reducing power output of TRX2

Postby 5B4AIY » 02 Jun 2012 06:30

Hi, Jan,
I forgot to mention R26, which adjusts the gain and hence the output power on the SSB modes, my apologies. R28 sets the CW carrier level, of course. By adjusting these two potentiometers you can easiy set the transceiver up for no more than 5W in either CW or SSB modes. The fixed attenuators are really there to equalise the output power across all the bands, and this is most easily accomplished using the serial test suite's Auto Equalise feature. I'll send you the latest versions today. Again, my apology for forgetting R28.

If you are operating RTTY/PSK-31, then you can also set the output power in this mode by adjusting the indput drive level as well. When the input source of the Juma is set to LINE and with the speech processor turned off, the input sensitivity is somewhat low and you will have to use a fir amount of drive, but this also means it is hard to really over-drive the power amplifier. I use mine with the excellent NUE-PSK self-contained modem, and when using this its output jumper has to be set to the HIGH position to provide sufficient drive, but it also means that the Juma is relatively insensitive to RF pickup.

73, Adrian 5B4AIY
5B4AIY
 
Posts: 214
Joined: 13 Nov 2011 09:22
Location: Cyprus


Return to Juma Discussion

Who is online

Users browsing this forum: No registered users and 24 guests

cron