Posts by PA3BYV

Hello all,

Recently I acquired a Nokia ex-UMTS PA, one with two BLD6G22L-150BN dual LDMOSFETs. As with similar PA’s one FET is in class AB and the other is a Doherty in class C. Its bias circuit is in part similar to the circuit DB8SDQ describes in his article about the PA with two BLF8G22LS (which are single FETs). DL8SDQ describes in detail how to disable the Doherty and make that FET linear. In order to find out how to disable the Doherty circuit I explored the bias circuit on my board and discovered a pad next to a ground pad labeled PEAK and AB.

I suspected this could mean exactly what it said, and I tried via a successive series of resistors to ground that pad. With zero resistance to ground the gate voltage rose to 2.1 V, similar to the gate voltage on the linear side. At the same time the current increased from 1.5 to 2.5 amps for the whole PA. So grounding this pad effectively disabled the Doherty and made it work in class AB. As Bert, PA3AOD has a similar PA we had a look at his bias circuit. He has a PA with two BLD6G22L-150BN/2. Its bias circuit is different from mine, but it has also two (unlabeled) pads at the same place in the circuit. He tried shorting these pads with exactly the same effect. So if you have one of these PA’s, shorting these pads should be enough to disable the Doherty. Disabeling the Doherty improved linearity and increased output, especially at lower outputs, as was to be expected.

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Hello Michi and others,

I was pleasantly surprised by the announcement of the Linux Transceiver. Thought it would be a welcome addition to my arsenal. Installed it according to the description on an Raspberry Pi 400 with a PiSDR card. It started with the opening screen, but didn't get any further after doing the configuration. Redid it on another SD card with latest Buster installed, same problem, but now I got as far as a spectrum and waterfall with multiple symmetrical peaks, updating once every two seconds. Burned a new SD card with 21-03-04 Buster, again same result. Used two different Pluto's (both rev B), and USB-Dongle. Audio loop worked, although with an annoying hum, RF loop didn't. Also the settings for the frequencies were lost every time at restart of the app. On install I didn't get any errors, only warnings about Jack daemon not installed. At startup also warnings that Jack server didn't startup. But Alsa worked, so probably shouldn't be a problem. I've been at it for 6 hours without result, so I could use some help here.

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These are at least two other variants of the board. One with wifi, the other without (as is mine). Courtesy PA2JSA.

Hi Adrian,

You have to ask Evariste for the password, don't know how they are different between devices or firmware. My device reported a fw version and a hw version prior to bricking. But as debricking resulted in also deleting hw version, I really don't know which version you would need. Sorry about that. At least, if your device looks like mine you would have the possibility to get into it by serial. On the other hand, telnet will give the same information if it is working. So best advice: don't brick it and ask Evariste, the wizard!

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With the new Pluto firmware from Evariste, F5OEO, Pluto, H.265 encoder box and OBS settings can be changed on the fly and simultaneous. So I recently ordered one of these boxes, but could not upload the firmware patch. Turns out this box has different firmware (ENC_V2.41.201231 instead of ENC_V2.38.201216). Evariste kindly offered to try to upload via internet. However, during this venture he accidentally bricked the device. Communication via its ethernetbus was not possible anymore. An internet search revealed that the main device (Hi3516) should have a serial monitor. However, was it brought out on the board? Probing with a voltmeter and a logic analyzer revealed indeed a signal resembling a 115200 baud serial tx on an unused pad on the board. Hooking it up to a PC via a level converter (3.3. to 5V) and a serial-to-USB adapter showed a typical linux startup on boot. It also reported a missing file and not able to start the application. Also the http-server did not start up and the device did not use DHCP anymore. So IP-address had to be modified by hand, which was succesfull in the end.

Here Evariste took over and was able to re-install the firmware and add the patch over the internet. So the device was unbricked and works again, although further tests have to be performed.

By the way, not only the firmware, also the hardware is different between these devices. Jaap, PA2JSA kindly sent me a picture of the board of his device with the .38 firmware and that differed significantly from the one shown below. Although the main device, the Hi3516 is the same.

In the picture below the two wires above the Hi3516 are TX (as seen from device) on the left, RX on the right. Third wire is ground. Level is 3.3V.

Hope this might be helpful for someone struggling with a bricked device.

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