Trekstor Surftab wintron 7.0

It should be more correct, the system was not running anymore, so it was changed.

The disaster with the Trekstor tablet since November has now come to an end. Even after the second inspection of the device - shortly after it came back from the 1st - at Trekstor no error could be found. My subsequent in-house inspection revealed that the battery is no longer providing enough power to power the SDR and WiFi adapters. Unfortunately, the battery is excluded from the warranty, permanently installed and obviously not available as a spare part. Even an external current hub is no longer useful.

The device is still functional and useful for other purposes, but unsuitable for the remote station. The dream of a functioning station based on low power consumption has to be redesigned. The solar-powered 12 V DX system needs a new heart.

About the progress of my efforts to build a small but nice station in the garden, I will continue to report when I have found and tested appropriate devices.

Maybe I'll get new ideas and suggestions at Ham Radio.

Until then, the break screen remains here.

I wish all of you reading this a great time - and maybe you'll see each other in Friedrichshafen!

73, Willi

After long experimental sessions with the tablet I discovered more good reasons to use the tablet in my remote station. The background why I did long tests is the circumstance I can only use 12 V solar power and need a low Ah consumption gear.

As I mentioned the other day listening and recording with the ELAD FDM-SW2 software was only possible with a limited bandwidht set to ~192 kc/346 kc, which is beyond my needs. The ELAD FDM-SW2 software consumes more resources than the tablet could provide. Recordings stuttered. Now I was testing the Studio 1 software and was able to record and listen stutterfree with ~1500 kc bandwidht. This is enough to record the whole MW Band e.g.

So my complaints are now going to the software developers. Studio 1 is fine, lets say very fine, but not able to record automatically at a certain time, ELAD FDM-SW2 does but is not able to record ~1500 kc bandwidht.

Another issue with the tablet is that it connects only through USB2 (and not USB 3) with the ext. HD. At some times the audio hangs for 1-3 sec. which does not affect the recording in most of the cases, but in some. The tablet can use a 128 GB microSDXC-Card which could be much more faster. I did not test this now because I need more than 128 GB of space.

As I wrote the other day recordings and listening through the HD are possible if connected through a USB-Y-Cable to a seperate batterie charger. The Trekstor Surftab is not so bad as thought here. It is suitable to run the station.

Before reading this: you have read all articles in this blog about this tablet?

Listening with the Trekstor and ELAD-SW2-Software is fine if you accept the bandwidht limitation of 192 kHz. There are two things you have to know.

(1) With a connected FDM-S2 the power consumption is high. After 2 hours or so the tablet will shut down if the FDM-S2 is not connected to a seperate power supply. All works fine with this seperate connection and is durable.

(2) Recordings with a separate HD are not possible. The recordings will stutter. So the only chance to record something is with the tablet itself is on the inbuilt disc or on microSDHC-card.

After testing and testing the Trekstor under different problematic situations, I came to the conclusion that this tablet is not suitable to run durable as a remote station. The other day I wrote about problems with the HDD. They are solved. The irregularity was a somehow wrong USB-Y-Cable. After attaching another one the HDD runs smooth. The other issue is the small bandwidth. The tablet resp. the ELAD Software stutters if the bandwidth is not set to 153,6 kHz. That's too less for longtime operations and recordings. I have no idea if this issue can be solved. The tablet comes with 1GB RAM, has a 1.33 MHz processor and there is only 1,3 MB free space left on a disc that comes with 16 GB. Much of it is covered by the operating system. I don't run a lot of additional software. As I wrote in a futher article about 1228,8 kHz bandwidth I cannot confirm this anymore, the devil knows why I came to this result. Only 153,6 kHz bandwidth is left now! The issue might come from the power supply with the SAVAKE USB-cable. If no charging is running in the background the bandwidth could be set to 614.4 kHz. But recordings may be disturbed by lite stutters, as you can hear during listening. If you switch the SAVAKE cable to charging it is possible to record with 614,4 kHz bandwidh for a while until stuttering begins again. The same with 307,2 kHz. If the ELAD FDM-S2 is connected directly as a single device with a single cable to the only USB port 614,4 kHz is possible. And yes 1228,8 kHz sometimes too. It's irregulare.

A SATA-disk on the hub or directly on the OTG cable can not be operated continuously, I realized. I suspect when charging begins on the tablet, the connection is disconnected. The hard drive needs 1A, probably do not get as much from the hub or cable. The connection to the FDM-S2 is stable, if the hard disk is not connected. An alternative would be a microSD card, but does not reach far, if you want to do hours of recording. I think a hard drive with an external power supply may be chosen only, without a hub. Or a USB 3.0 Dual Power SuperSpeed cable ("A" plug on micro "B" connector). As a test later shows it is possible to have permanently operation of the HDD if it is connected through a y-cable to an external power supply. So, all is working well together. Now the Tablet is usable for all needs. Big hurray on the remote station!

As I wrote previously, additional steps were necessary. Restarting the system was sufficient to determine that everything can run smoothly. FDM-SW2 CPU use now was 15%, total CPU usage at 23%. The data aquisition frequency of the software was set to 1536 kHz, the bandwidth of the recording is at 1228 kHz. This is the maximum amount of bandwidth to record stuttering free. After rebooting also Audioengine D1 was detected. The driver must be set in the FDM SW2 settings previously. Sometimes a restart of the software is required.

After some searching and testing weeks, I have the right OTG cable found that works in both directions. A SAWAKE 4 Port Hub is doing its battery service and ensures that the data flow in both directions. This is a milestone on the way to my remote station. The OTG hub cable combo running at the moment still in test mode. Connected are an external hard drive and the ELAD FDM S2. The hard drive is powered by a power hub with the SAVAGE 4 Port Hub. Audioengine D1 is apparently not supported by the USB output.

However, an unsolved problem always means that more arise.

Even without Power Bank possible

How does the tablet with mobile solar power? Connected was a RAV Power 15 W solar charger under the most favorable conditions: sunshine. There were used the ELAD FDM S2 / SW2 recorded files. The tablet ran under load with Wi-Fi, bluetooth and 100% display illumination. The test conditions showed that this use is quite possible for some hours. The solar charger provided through enough power to operate continuously.

As I wrote the other day, first tests with recordings on the ELAD FDM-S2 shows a limitation of the bandwidth to 2457.6 kHz. More is not stutterfree.

The picture shows another useful device to operate on the Tablet, a Logitech MX Master bluetooth mouse. The device can be programmed in many ways. It is, for Instance possible to change by keystroke between different types of modulation and to adjust the volume.

66 Min for free

No external AC power, the tablet can only with battery operated. The test environment is set to these values:
98% charged battery, Power saving mode, off screen: never, 0% brightness, volume level 100%, Bluetooth and WLAN off.
During operation, the USB connector must sit well, otherwise breaks the connection to the SDR. FDM-SW2 was set at a fixed frequency. After 40 min., the remaining battery life is reduced to 24%. After 60 min. is at least 6% of battery life available. After 66 min. with 5% left, the system will shut down automatically. The waiting time until the full charge is 2 hours with mains charger.

I didn't come to any solution working with this ext. powered hub. The Tablet didn't charge and run the ELAD FDM-S2 at one time. Following a tip I cut the ground line of the mini-USB-connector, but this didn't work either. It's reconnected again. I tried to connect 470 Ohm resistors in both data cables of the connector. (As described in Perseus_SDR Group)
According to the Perseus_SDR Group link the resistor should be set only between line A und B, but this does not work with the Tablet either. Connecting 124 kOhm and 36,5 k Ohm resistors (from: ... searchtips) in the same way did not work either. May be it's all bullshit.

At this time I dont see any chance to charge and run the ELAD FDM-S2 in parallel with this Trekstor Surftab wintron 7.0.