QRSS Rigs

Seen below is a general view of what is currently (left to right) the 160/80m TX, a QRP Labs GPS unit housed in a black box, the 40m TX, the 28Mhz TX and finally my 5w amplifier that boosts 50mw to 500mw from the 10m rig. The 40m/10m rigs are from he old QRP Labs U2 series and the 160/80m rig is a QRP Labs U3 DDS type. When these rigs were built there were no official QRP Labs housings available, so everything was custom built. All the rigs incorporate a built in PSU and 160-10m ATU. They all have their own separate GPS units for timing and frequency discipline. The antennas are just bits of wire in the attic directly connected to the loudspeaker terminals provided for output. (No RF sockets as such).

A closer view of the 10m rig, general view and inside view. The FT240-61 toroid is part of the T match ATU design used elsewhere.

The QRP Labs rigs have given excellent service over the years. Here's a few note for users. The power amplifier stage. The kits allow up to 3 x BS170 FET's to be fitted. They are very cheap (about 10p each) and quite robust. On the lower bands, having 3 of them should give a healthy 1.3 watts output at 9v. By the time you get to about 20Mhz the input gate capacitance is quite high, and you'll find that you get better results using only one BS170 in the output. At 9v you should easily achieve 450mw output. I do not recommend using more than 9v at any time on the output stage. Heat sinking the BS170's, well I'm not overly convinced it's worth it. On the DDS PCB's there is a blue potentiometer. Set this for maximum output. It's a fine adjustment, especially on 28Mhz. Drift on 28Mhz can sometimes be a problem. Effective thermal control is necessary. Sometimes a fan to disperse air currents reaching the reference xtal helps. Or sticking some thermal mass on to the xtal. It's usually a painful trial and error if you're unlucky.

Firmware upgrade / Atmel 328P IC repair. Firstly I prefer to use AVRDUDE, a command line program. It's available for most operating systems. It's very easy to use. On Linux you'd normally installs through your package manager. For Debian, Ubuntu,Linux Mint and many others you install it with "sudo apt-get install avrdude" command.

FIRMWARE FLASHING AND OPERATING MANUALS

U3S firmware. Last version for the U3S was v3.12a and the IC used is an Atmel 328P. First you set the configuration fuses, and then burn the actual firmware. On the U3S you now only need a .hex file to flash the IC.

Setting the fuse uses the command:

avrdude -c usbasp -p atmega328p -U lfuse:w:0xf7:m -U hfuse:w:0xd9:m -U efuse:w:0x04:m -U lock:w:0x0f:m

If it says -

avrdude: safemode: efuse changed! Was 4, and is now fc

Would you like this fuse to be changed back? [y/n] n (answer no)

Flashing the firmware uses the command:

avrdude -c usbasp -p atmega328p -U flash:w:v3.12a.hex

When finished - Power up the U3S. The screen will have a row of blank squares. Press the left hand side menu button. You will now enter the set up mode. Proceed to enter your desired configuration settings. Done !

Firmware files, handbook etc can be found here.

U3 firmware. Last version for the U3 (DDS only version) was v3.09f and the IC used is an Atmel 328P. First you set the configuration fuses, and then burn the actual firmware. On the U3 you now only need a .hex file to flash the IC.

Setting the fuse uses the command:

avrdude -c usbasp -p atmega328p -U lfuse:w:0xf7:m -U hfuse:w:0xd9:m -U efuse:w:0x04:m -U lock:w:0x0f:m

If it says -

avrdude: safemode: efuse changed! Was 4, and is now fc

Would you like this fuse to be changed back? [y/n] n (answer no)

Flashing the firmware uses the command:

avrdude -c usbasp -p atmega328p -U flash:w:v3.12a.hex

The .hex file , operating manual and building notes can be found here.

U2 firmware. Uses Atmel 328P. Requires both the .eep and .hex file to be written.

Setting the fuse uses the command:

avrdude -c usbasp -p atmega328p -U lfuse:w:0xf7:m -U hfuse:w:0xd9:m -U efuse:w:0x04:m -U lock:w:0x0f:m

If it says -

avrdude: safemode: efuse changed! Was 4, and is now fc

Would you like this fuse to be changed back? [y/n] n (answer no)

Flashing the firmware uses the command:

avrdude -c usbasp -p atmega328p -U flash:w:Ultimate2.07.eep

and

avrdude -c usbasp -p atmega328p -U flash:w:Ultimate2.07.hex

Firmware files, operating manual and construction notes can be found here.

U1 firmware and docs.

If you have an ancient U1 then the files are here. Use U2 style settings to burn the Atmega 168.

AVRDUDE ERROR MESSAGES

Avrdude may complain that it cannot write a file because it detects the incorrect IC in the programmer. This is because there are several minor variants of the same IC. It's nothing to worry about. For example a -PU version indicates that it is a low power consumption version. Either use the -F option to force the file to be written or change the IC same in the command line to match the exact version that you have. For official QRP Labs files see here.

The command line assumes that you are using the common USBASP type interface. Your may vary. If you use anything different then you need to specify it.

GUI FOR AVRDUDE

If you prefer a GUI then look here. It's a Python app, and runs fine on Linux Mint 19.3 (tested) and on Raspbian etc. Being Python should also mean that Windows users with Python set up can use it, but then there's already AVRDUDESS for Windows users anyway. Direct link for G4DUDE on Sourceforge is here. The fuse descriptors used are different (not HEX) so the following use these instead: L=F7, H=D1, E=FC and anything else leave unactivated.

GPS UNITS

For info regarding the QRP Labs QLG gps unit, NEO6M's or the Reyax UP501's click here.

Note - the usual connector used on GPS modules for the antenna is a called a u.fl connector or an IPEX connector. I think I've seen two sizes in common use too, so take care when purchasing spare parts.

There is also the QRP Labs GPS kits that work very well. There is the QLG1 (retired) and the QLG2 (about to be released at the time if writing). There are a few minor differences in their operation with regards to some older QRP Labs kits which are best explained by Mr QRP Labs himself in this forum message. The salient points are quoted below.

All current kits work, with all firmware versions (All firmware versions of QCX-series, Ultimate3S, VFO, Clock and ProgRock kits). As far as I can tell, No firmware change is needed, to correctly handle the QLG2 output.

Older Ultimate-series kits have a problem. I went back and looked in my archives at all the old source code I could find, with the following result:

Ultimate: http://qrp-labs.com/qrsskitmm.html - all firmware versions will not work with QLG2 because it seeks sentence $GPRMC

Ultimate2: http://qrp-labs.com/ultimate2.html - all firmware versions will not work with QLG2 because it seeks sentence $GPRMC

Ultimate3: http://qrp-labs.com/ultimate3/u3.html - firmware 3.03 and below will definitely not work because it seeks sentence $GPRMC; firmware 3.06 and above will work because they are looking only for $xxRMC (don't care about x). I am not sure about 3.04 and 3.05 because I could not yet find where I hid the source code for those ;-) The v3.09f firmware chip for Ultimate3 is already available in the QRP Labs shop or for download so anyone with a very old Ultimate3 firmware version could upgrade to make it compatible with QLG2 if they wish.

On this website I have created a folder with new QLG2 Version 1 information here. I will add more as required in due course. The new QLG2 looks extensive in capabilities and it will take some time to discover all that it can do. Official website is here.

ISSUES WITH NEO6M GPS MODULES

Poor performance has been noted even on new modules that are really old stock. The button cell for Almanac back up fails and goes short circuit. This appears as a zero ohms load across an on board regulator, and it looks like it the current is being sinked into the zero Ohm load. This appears to steal current from the main GPS receiver module and the result is poor performance. Remove the cell entirely and throw it away !

RF GETTING INTO THE U3S (OR OTHERS) VIA GPS CABLES INTERCONNECTS

Not normally a problem, but sometimes it happens. Another transmitter in your shack inducing RF into the cable between the GPS and your U3S etc rig might cause some oddities, such and random resets, or in my case the TX frames would change timings, and yet there was no changes in the menu settings. I seemed have this problem whilst using a random wire close the rig, especially 10/15m. Solution = wrap the end of the interconnect closest to the U3S around an old ferrite rod, you knew the sort of thing that used to be used in old AM broadcast radios years ago, about ten times. Any rod will do, they all have a very high Mu (permeability).

WSPRNET MAP SHOWS LOCATOR SQUARE ERRORS

WSPRNET seems to want to default to a 4 digit grid sqaure rather than a 6 digit one after some years of not receiving a log file from your callsign using the official software with YOU using it. The trick is to upload a log as if you are using wspr.exe or wsjt-x via the wsprnet database. G0UPL documented a way to do that easily here - http://qrp-labs.com/images/appnotes/AN002_A4.pdf or failing that I have kept a copy of it here. Also read the notes here.

BETTER STABILITY FOR THE U3S.

As supplied the U3S is pretty good, assuming that you properly enclose it and ensure no miscellaneous air currents are present to effect the 27Mhz crystal in the reference oscillator. Stability should be good up to 30Mhz for QRSS and WSPR. But microscopic temperature changes can occasionally reveal some wobbles. For a very small price I recommend purchasing the TXCO option, that you attach to the supplied daughter board synth unit. Note. DO NOT fit the supplied 27Mhz crystal if you want to use this modification. When fitted, you will need to set the reference frequency in the U3S menu to 25Mhz instead of 27Mhz. Then allow the GPS to fine tune it. (The TXCO option was actually produced for the QCX series of transceivers, but soon got adopted by U3S owners.

There is also some advisors claiming that you can stick some kind of heatsink on xtals etc. My advice, don't bother ! I've tried it, and I have not seen anything worthy of note.

U3S PA ARRANGEMENT

I also own pair of U3S transmitters. The best arrangement for the BS170 power amp is this. Use the single winding RF choke. Use ONE BS170 (remember that on the PCB there is one BS170 for PA switching, and one for the actual RF PA. Use 12v on the PA. Adjust bias control for a maximum of 560mw output on 28Mhz. This pretty much gives the maximum SAFE output.. Power output will range from about 200mw on 50Mhz to 1 watt from about 14Mhz and below. Do not solder the PA onto the PCB but use what we call "turned pins" so that you can plug in a new BS170 if it fails. Note - there is one BS170 used as the PA switch, and next to it is a one BS170 used for the PA. (There are spaces provide for another two, good for lower bands but ruins 20Mhz and above due to the fact that it increases Gate capacitance, and lowers the output on the upper bands).

It is also possible to use a BS270 in the PA although I have not personally tried it. The spec looks almost identical. I noted that the package type is slightly different.Listed Drain current = 400ma versus 500ma for the BS170. It's a bit more elongated to accommodate a different clip on heatsink, but the max drain current is rated at 400ma vs 500ma for for BS170. In a U3S or similar rig this is probably not relevant since even at 1w output and using 12v @ 200ma is the maximum that you're likely to see. For other PA designs using the BS170 like a QCX etc then this needs to be reconsidered. (I don't have such rigs so I don't know).

I have also seen that the spec sheet for a BS170 that shows an 860mw dissipation is rather conservative, it's more like 2400mw absolute max, ASSUMING that this in to a matched load. Remember that this is the DC input, and RF output will vary across the frequency spectrum. You must add the reflected power to the dissipation figure. For example if you're putting 1 watt of DC power in to the device, but have an RF reflected power of 500mw due to a bad SWR then you are using the device at 1.5w ! And never allow a device to be hotter than what your finger tip will allow you to touch for a long time without burning your finger.

POWER SUPPLIES.

Blocks on your display, or can't get past the splash screen on a QRP Labs kit ? Chances are that you THINK you have a good 5v DC supply to the module, but you have not ! Yeah so you checked the voltage, about 5v etc. Nope, you need to look deeper. Even a miniscule of ripple will effect processors like the Atmel 328 or an STM chip. Solution, build a supply with a fixed voltage regulator like an 7805 and build it to the manufacturers spec sheet. That means having a 0.33u at the input and 0.1uf at the output end. Other values don't work. I also advise having a 1000uf across the input too. Even if you use a pure DC source like a battery for the feed, the voltage regulator can still have an initial spike, and that 1000u cures it. Remember that these regulators don't provide reverse polarity protection, so add that idiot diode in the positive BEFORE anything else. Get it wrong, or over volt your kit and it's usually a totally write off. You've been warned. Do not use floating earth PSU arrangments. They often cause problems. everything must be properly grounded.

The above photo's show the tiny TXCO retrofitted on the synth PCB. It might be best to click and save these pics and then re-open in a viewer for a closer inspection. On the SYNTH PCB there are some spare pads for adding your own surface mount TXCO, but these alone are difficult to obtain and fit on the pads. It's better to purchase from QRP Labs a ready made TXCO and use three stiff wires to connect to those pads. It can be purchased here http://shop.qrp-labs.com/tcxo On the synth unit you will see four pads, and we use three of them. 3.3 Volts, ground and RF signal input. Later versions of the synth unit allow an a slightly neater arrangement of the TCXO.

RUNNING SLOW HELL

For typical use, use a speed of about 20 and FSK size, 003.