Thursday, 20 May 2021

SRH 789 (clone) antenna mod for hackRF Portapack

SRH 789 antenna modification

The Portapack

The Portapack (in my case, the H1) ist a great addition to the hackrf one. After I had damaged two hackrfs, my current setup now uses the version with a modified RF-frontend by Clifford Heath. This now works safely alongside my ham radio gear.

My portapack setup
It covers all ham bands from 160m to 6cm (any anything inbetween). In practise, it starts becoming useable at 80m up to 23cm. Beyond that, I don't own suitable antennas and/or preamps / filters.

VHF contest

Although the latest version of the Mayhem firmware now supports SSB-TX, I would not stand much of a chance in a contest with the portapack as main rig. But my trusty old 1980s FT-290 that I still like to use for portable operations, does not offer any of the luxuries that we came to expect from modern transceivers. So I like seeing the section of the band I am working on, on the portapack.
Not so this time. The strongest stations that were 59plus on the FT-290 barely showed up on the spectrum view.
The HackRF is not the greatest receiver there is with it's total lack of band filtering or preselectors and I suspected the nearby FM Radio tower to interfere.
The same disappointment a little later, when I was out, hunting a radiosonde that practically should have been on top of me. Something with my setup was very wrong.

The Antenna

I often used a 2m/70cm dual band antenna on the portapack, but a while ago I got a cheap clone of the Diamond SRH789 antenna, which should have been more than good enough for the job and does not poke through my backpack.
Not the original SRH789

So back home in the shack, I checked the SRH 780 against the dual band antenna and it became quite obvious that the problem did not lie with the HackRF this time.
Having nothing to loose, I took the antenna apart and was surprised to find a totally pointless plastic piece between the center connector of the SMA side and the telescopic whip. The copper wire that had once bridged the plastic piece had torn off when I rotated the antenna.
The antenna is obviously not meant to be treated that way, but with the portapack sitting on the ground, I need the antenna to point up, of course.
There is absolutely no L/C matching RF-magic going on in the antenna base. So there is no point in keeping that plastic bit there.
No RF will pass this
Fortunately it has M4 threads on both ends, so an M4 screw will be a simple, more RF friendly replacement.

M4 fits just fine. The copper wire can be removed
If you want, you can yank out the glued in center conductor, so the aerial can spin more freely. 
With a sharp pull, the center pin of the SMA connector comes loose

When I put it all back together, I took the antenna through it's paces with the NanoVNA. Not surprisingly, I got mixed results. This is to be expected from an antenna that is nothing but a piece of iron rod sticking out the back of the transceiver.
Radials? Counterpoise? GroundPlane? Nope.
The resonant frequency varied wildly with the surrounding conditions. i.e. me touching the VNA's case or leaning over my workbench. With some tuning you'll get an acceptable SWR all through the 100MHZ zo 1.1 GHz range. The impedance is a different story: While somewhere around 50 Ohms for 2m and 70cm, where the antenna works as a quarter wave, the impedance on the higher bands is all over the place.

Final word

This is not a great antenna. You can't expect miracles. Possibly because it is a fake/counterfeit product.The original Diamond antenna may be a better choice. Please leave a comment if you have one.
As a mainly RX-antenna with superb portability it is acceptable, but no match for TX-capable wideband discone (that will be significantly bigger and more expensive).

Thursday, 25 February 2021

Iphone 12 hearing aid compatibility problem

iPhone 12 bluetooth hearing aid compatibility issue (and a "works-for-me" solution)

More on that issue, including audio samples shortly on my YouTube channel.

No problems with iPhone 8

I had an iPhone 8 for the last 3 or so years, and just by the end of last year, I upgraded my hearing aid to the latest&greatest Li-Ion powered bluetooth connected version I could get my hands on.

Specs & hearing aid - no problem.
Things become tricky with a mask.

Apart from better hearing, the additional bonus of having a top quality, hands-free, near invisible headset for the numerous audio and video conferences that came with the pandemic was just a blast.

Until I switched to an iPhone 12.

The hearing aid

It seems that there is only a small number of actual manufacturers and a lot of brand names hearing aids are sold under. Mine are sold as SoniTon UP5 R Li with a CE 0543 mark that indicates it has been certified as a medical device in Denmark.

The actual manufacturer seems so be Unitron Hearing Ltd. in Canada. Other names/brands the device is sold under are: Vista DX 350 R Li, AudioNova DX 30 R Li, DX Moxi Move R 3, scala DX 350 R Li, excellence 2 V2 R Li

It is not specifically "made for iPhone", but can be used universally, so while the use as headset/headphones is generic, control is via Bluetooth LE and a "hearing remote" app.

The "hearing remote" app allows control via the iPhone

iPhone 12 problems

At first I didn't notice anything wrong. Podcasts and music were fine to listen to. But callers and team-mates complained about choppy, scratchy audio. Same thing on my side: distorted audio.

I went investigating and found that to be a common problem for people using the iPhone 12 series (mini, pro and "regular" alike). Even for hearing aids specifically "Made for iPhone. The sterotypical recommendation to use the latest iOS version as found on Apple's support and discussion pages were useless for me. Apple claims to have it solved for "Made for iPhone" with iOS 14.2.1, which left me on my own.

The solution

It appears, that the problem lies with "Adaptive Bluetooth". I am not sure which flavour of "Adaptive Bluetooth" that is, since both "adaptive frequency hopping" and "adaptive codec selection" (Qualcomm aptX Adaptive). If you know, please leave a note in the comments.

Disable Adaptive Bluetooth
Adaptive bluetooth can be disabled in the "remote hearing" app. The hearing aids have to be restarted after changing that setting.

With this setting changed, calls, voice recordings and video conferences are ok again. I am not quite sure whether or not I sense a very slightly reduced audio quality for music since then. It so, the codec chosen for compatibility might not be the best for music.

Sunday, 27 December 2020

Strange serial port issue with Arduino nano 33 sense ble

Serial port problems with Arduino nano 33 sense

Can't upload sketch / Can't connect via Putty or serial monitor

I gave myself a nano Christmas present: A brand new Arduino Nano 33 Sense BLE. Mainly because I wanted to try out machine learning with TinyML, but the book from O'Reilly is still in the mail.

Tiny, but with lots of sensors

So I started exploring Bluetooth LE, trying to master that skill first. It was a slightly bumpy ride because from time to time the Arduino IDE switched the serial port to COM5, while the Arduino clearly was on COM7 (these will very likely be different on your PC)

The nano 33 on COM7

I reset the arduino a couple of times, but I couldn't get it to communicate via COM7, although the port was clearly present in Windows.

Double click the reset button

More or less by chance I double-clicked the reset button. And - whatdoyouknow - I had the Nano on COM5. - How strange!

The nano 33 on COM5
Now I could upload sketches again. - Ok. But COM port assignments in Windows don't change without a good reason. Let's dig deeper.

USB device tree viewer

Uwe Sieber has published a great, free tool "USB tree viewer", that shows all the details of all attached USB devices. I can then copy both (the COM7 and COM5) configurations to Notepad++ and run the Compare-Plugin.

As expected, the double click on the reset button lets the nano 33 appear as a very different device:

While the Vendor ID is alwaysd 0x2341 (Arduino SA), the product ID changes from 0x805A to 0x005A. The device ID, revision number and sleep modes also change.

The device descriptor string 2 changes from "Nano 33 BLE" to "Arduino Nano 33 BLE" string descriptor 3 is the same, but padded with leading "0"s.

Looks like two different devices

No wonder Windows sees that as a new device. I have no idea what the point in all that is.

Please leave a comment if you have more info.

EDIT 20210107:
The behavior is actually documented in the documentation:

If the board does not enter the upload mode, please do a double press on the reset button before the upload process is initiated; the orange LED should slowly fade in and out to show that the board is waiting for the upload.

I still find the "nano 33 ble sense" rather unpleasant to work with because of that.

Friday, 25 December 2020

Macbook late 2008 SSD upgrade

Macbook SSD upgrade

With only 2GByte of RAM and an out-of-support El Capitan (OSX 10.11), the 12 year old MacBook is somewhere between "ready for recycling" and "too good to waste". Over time it had become unbearably sluggish. So with prior good results on Windows PCs from the same era, I decided to give it a go.

It is super easy and reasonably safe even for intrepid  beginners.

SSD selection

I tend to go for maior brands whenever affordable. Amazon had a 500GByte Samsung 860 EVO for cheap on Black Friday 2020, so that ist the SSD of choice. The person using the Mac as a mail and browse machine will never even come near the full capacity of that disk.

Preparations / backup

A full time machine backup on an external USB drive is all it takes to recover the installation to a new SSD.

Physical installation

These old devices are built to last and to be serviced: Just remove the bottom cover (unlock with lever). Remove the disk holder (black plastic bar) with a small Phillips screw driver and lift out the old disk by the pull-tab.

Carefully remove the SATA connector from the left side of the old hard disk.

Remove the four small bolts that held the disk in place and install them on the new SSD

Reconnect the SATA connector

Insert the SSD and fix it with the plastic bar.

Close the battery/harddisk cover.

SSD preparation

Attach the USB drive with the Time Machine backup to a USB port.

After a little wait, the MacBook will boot from the USB drive.

A menue comes up: There choose the hard disk utility and add a partition to the SSD (accept the first file system option).

Go back to the previous menu

Restore from Time Machine Backup

Choose your Time Machine Backup Disk and select the latest backup.

Wait for the restore to complete

Wait for the restore to finish and reboot

Tell the Mac where to boot from

It speeds up the boot process a lot when you set the new SSD as the boot device in the settings. Otherwise it takes a while to find bootable devices.

That relatively cheap upgrade saved the nearly unuseable machine from the junk yard. With only two 1GByte RAM modules installed, the next option is to go for more memory. With the last published firmware version, this machine supports up to 8GByte.

Friday, 4 December 2020

Inside an AMG8833 thermal imager

Very simple AMG8833 thermal imager

(I took it through it's paces in this video)

For years I had felt he need for a thermal imager or thermal camera to help me find faulty electronic components. But the price tag was prohibitive.

40mA - not very power hungry

I experimented with a single temperature sensor, sweeping a range with model servos. Interesting and entertaining, but not really useful. That was back in 2013. Even later, the cost for the simplest "grid eye" was still a bit on the high side for an experimenter. Until recently.

Bare bones imager

I then found this bare bones / no frills thermal camera here on Banggood. It comes without any matching documentation, let alone a manufacturer name.

PCB Version 5.1.2 from June2020

It has a resolution of 8x8 pixels and sports the "high gain" version of the Grideye. While "high gain" sounds like a good thing, it actually limits the sensor's thermal range to 0-80 degree centigrade.

The AMG8833

The Panasonic GridEye comes in different flavours that is easy to decipher from the part number:

The 88 stands for the 8x8 pixel resolution, the next digit shows the operating voltage 5 for 5volts, 3 for 3.3 volts. And finally a 3 for the "high gain" and a 4 for the "low gain" version, with the low gain version ranging from -20C to 100C. We don't have that in this device so on very cold days, the outside world looks like a blank sheet to the imager.

The next step up is the 32x24 pixels MLX90640 from Melexis, which has a -40 to 300C temperature range. Looking at what 8x8 pixels can do, 32x24 should be awesome. It comes at about twice the cost of the AMG8833 based imager, also from Banggood.

Electronics repair

It all boils down to the question: are 8x8 pixels sufficient to identify hotspots in a faulty device?

44c after just a few seconds
With it's 60degree field of view, working close-up gives enough contrast to identify individual hotspots. One thing to notice is that the colour scheme is autoscaling. So "red" just means warmer than the surrounding area, not necessarity hot. The colors are spread over the range currently detected by the sensor. The good aspect is that it always gives the best contrast possible, the downside is, that it can be very irritating.

The microcontroller

The GD32 ARM Cortex-M3 Microcontroller

Quite a capable little 32-bit RISC microcontroller from GigaDevice's "Value Line". See the data sheet here for details. The GD32F130F4P6 is the simplest of the DG32F130Fx family in the TSSOP20 package, sporting 16kByte of flash memory.
This thing appears to be pretty much a clone of the STM32F103x4 and might well be programmable with a ST-Link programmer. (haven't tested that).
The earlier 1.1 version, for which Banggood has a schematic diagram available, had a STM32F103C8, which essentially has the same performance, but more (64KBytes) of flash memory. So they obviously cut costs here a little on their way to Version 5.1.2

Final words

At a price point around 50 EUR/USD, this is not only a great experimenter's gadget, but very useful to track down thermal problems. Certainly no match for a full blown thermal camera, possibly even with a visual overlay - the cheapest models starting at three times the cost of this device.
The 0-80C temperature range can also be a maior limitation, depending on the intended use.
For me it is way better than sniffing out hotspots on PCBs or burning my fingers on them.

Sunday, 15 November 2020

RF-Power8000 - Power meter installation on Windows 10

RF-Power8000 Installation

Get the software

I got my RF-Power8000 here from Bangood. Unfortunately they didn't provide a download link for the software and manual. A quick google search at the time (Nov.2020) of writing revealed this source:
  • Software download from passion-radio LINK
  • Instruction manual from passion-radio LINK

Install the driver

The RF8000 communicates over a USB-to-serial bridge, that your computer might not immediately find the right driver for. In that case, you'll find a "serial" device marked with a "?" in the device manager.
The driver is provided with the software package (see above). As I don't like drivers that come with a setup routine, I recommend to use the "rightclick/update driver" function of the device manager.
Just point it to the "drivers_usb_CH340" folder and windows will find and install the driver.
At that point you should see another serial port in the device manager:

The meter shows up on COM6

Register MSCOMM32.OCX

Depending on other installations on your PC, starting the RF8000 software with the uninventive name of "english.exe" might result in an error message. In that case, MSCOMM32.OCX needs to be registered on your system.
To register the OCX, open an "elevated shell" (right click the start button and choose "Windows Powershell (Administrator)")
There type (with the path pointing to your rg_8000 directory):
 .\regsvr32.exe C:\Users\admin\Desktop\RFPower8000\rf_8000\MSCOMM32.OCX

Your path will be different

Configure the software

The program "english.exe" needs to be configured for both the COM-Port and the Baud Rage. It defaults to COM1 and 4800. While with some luck, your COM-Port might be "1", the baud rate ist not correct. Also: in "Model selection" choose "RF-Power8000"
Here are the correct settings:
  • Model selection RF-Power8000 (F3)
  • Port number: set that to what your device manager shows as Com Port. In my case COM6
  • Baud Rate: 9600
After that, I have to press the center button to start the meter.

No, it ain't pretty :-(

To set the frequency and the attenuator value (you absolutely need an external attenuator!) for the measurement, hit the "spanner and screwdriver" button.

Addendum 20201116:
This russian (?) RC enthusiast has written his own software for the RF-Power8000

And it looks good, too:

Saturday, 16 May 2020

Tello Motor Repair done right!

How to change a Tello Ryze Drone motor

Other instructions on the web

Before attempting the repair, I checked the web for tutorials. But found most of them pretty terrible, usually causing permanent damage or ugliness to that nice drone.
All except one from DroneZone, which I only found after having finished the repair :-(

That is what a decent job looks like

Tools required

While not really a tool, you need a replacement motor. There are several sources on the web, but they come with small weirdnesses like gears or plugs. Like so often, I got mine from Banggood. They come in two wire lengths (71mm or 87mm), but as a wire can never be too long, I went for the 87mm, although I needed to replace a front motor, where the leads are shorter.
These motors are properly keyed, so you can't confuse the clockwise and counterclockwise motors.

Other than that, good quality precision screwdrivers are a must. Poor screwsrivers ruin the screws. I currently use both a Wowstick, and traditional hand tools, depending on the job at hand.
And of course the wonderful, regulated Mini TS80 soldering iron. The first USB iron that doesn't suck. It does not come cheap, but during the building renovations, when I had no lab space, I learned to love it and won't go back to my old Ersa iron.

Other household items include
  • a pin to peel off the gunk that seals the solder points
  • wire cutters / needle nose pliers
  • Tweezers are handy, too

Problems encountered

If you follow my video (see here), you will find that I struggled at a few points

Cracking the case open

The plastic is very thin, so go around the edges carefully with a spudger.

Removing the gunk over the solder pads

This was a pain. I tried several methods. What worked best in the end was to peel the silicone-like gunk off with a needle. No great fun.


Desoldering needed more heat than I thought, given the delicate wires. That might have to do with the solder. I set the iron to 340 degrees centigrade. Later, when soldering the new wires to the board, the joints went dry immediately, so I replaced the solder. (Using solder wick)

Hotglue over the cable duct

Where the motor wire enters the body, there is a drop of hot-snot over the groove the wire runs it. This needs to be cleaned out.

Getting the motor out

That was not really hard. I could pull it out with my pliers, but the cable running through the motor holder gave quite a bit of resistance. So I smelled trouble getting the new wires in.
Motor arm

Putting the new motor in

The actual trouble is to get the new wires through the tiny hole in the motor arm. The trick is to bend the wires at an angle. You can see that in my video.

Final words

After the repair, I went through two freshly charged batteries. No problems. And other than in some repair videos, the drone does not look like it had been chewed up by a dog after the repair.