Friday, August 21, 2015

Kenwood TM-D710 reboots at transmit/deaf possible fix!

The D710 was the radio I bought when I got my Tech license in the fall of '09...so it is about 6 years old.

I haven't really had any trouble with it, but starting a year or two ago on VHF at High power the radio would reset/reboot when I keyed up.  If I lowered the power to Medium then it would not reboot (I assumed some sort of low voltage condition).  More recently I noticed that it was getting deafer, unable to hear repeaters that should be in range.

I probably wouldn't have done anything, but I found a couple of websites describing a design flaw of this radio (and maybe it's sister the D700) having to do with some filters.

Here are the links I found.

http://sv8ym.blogspot.com/2010/10/lift-withering-spell-off-those-ceramic.html
http://www.sv1jrf.eu/2014/06/kenwood-tm-d710-repair-toko-filters.html
http://www.4x4ham.com/showthread.php?518-Kenwood-710A
http://www.eham.net/reviews/detail/6871

I ordered mine from PacParts for $25 with shipping.


I followed the directions on the previous links on how to disassemble the radio but I didn't feel comfortable attempting to disconnect the center antenna pin from the main board...luckily all I had to do was rotate it 90deg and I could access both sides of the board to remove and replace the filters.

Note, my mainboard had the filter name silkscreened to the board to make it harder to put the wrong filter in.  Also note, the actual filter name is only the 50G, 50E, 55G, and 55E...the part number on the replacement makes it a bit more confusing than it needs to be, but not difficult.  I have the vacuum powered desoldering system, so removing the filters (5 tiny pins) was not difficult.

Fast forward.  I got it all back together and tested a local VHF repeater using High power, worked fine and radio did not reboot.  I did not get a chance to test the UHF part until I drove home from a radio meeting last night.  I had the radio scanning the 'local' repeaters for my drive and I picked one up that sounded clear so I joined in the middle of a net checking...oops I had not heard the net part.  But they kindly gave me a signal check and said audio was clear but a bit scratchy...then after I told them my position they told me I was 65 miles from the repeater, and due to the terrain, not line of sight...So apparently the UHF is fine, and also the propagation was good last night.

If you have an older radio, and any symptoms like I listed, I would swap out those filters.

Monday, June 8, 2015

MDSR Software IF interface ... and Asus T100...continued

(newer info at bottom)

I got a mobile device audio adapter for the Asus T100...

Mobile devices that have microphone inputs now use a single conductor jack. (common, L,R, Mic).  I got an adapter that had a 4 conductor 3.5mm jack, and the output is a pair of 3.5mm stereo plugs, one for headphone out, one for audio/mic in.  (I got mine through Amazon... search for 3.5mm 4pin splitter)




I needed that so I could use the audio for digital modes.  First some screenshots of the digital modes in use on the Asus T100, and then screenshots of settings for the audio devices.



Messy desktop with JT65-HF and MDSR running...note all the decoded contacts listed.



With Fldigi  and the MDSR-SA on the desktop...attempting to tune in some CW and have Fldigi decode.



Now the sound inputs (Recording).   With theses settings I can hear the audio with headphones plugged into the adapter, and the digital mode decoders have audio to decode.





And the Audio Output (Playback) settings.






Note:

Apparently the audio input on the Asus T100 is only mic level.   So some attenuation is needed. (I haven't added that yet)

Alex Schwarz (one of the MDSR designers) has a diagram of an mic input attenuation circuit at the MDSR Yahoo Group.

This web page also has some examples.  I will have to dig through my resistor drawer and see what I have available.

These shots are to prove the setup works, and maybe help with the settings.


Addendum:
I have found the audio input to the T100 is very flakey.  I don't know what criteria it uses to decide if an external mic is plugged in vs the internal mic...but I have plugged a standard mobile phone earbud/mic set and the T100 recognized the mic.  I plugged that adapter at the top in with my headset/mic which uses two plugs (that match the 2 plugs on the splitter).  The T100 kept the internal mic installed, even if I unplugged and plugged in a few times.

What that means is the audio in from the Xonar card isn't going in...so I can't use a digital mode decoder.

In addition the MDSR software is no longer working correctly.

At this point it is a problem with the T100 and Win8.1.   If I plug the USB cord into my laptop, and plug the mic in, it all works just fine there (Win7).

So for me, I don't think I will pursue MDSR on the T100...


Part 1.

Thursday, June 4, 2015

MDSR Software IF interface with FT-857d through Xonar U7 usb sound card, and Asus T100

This is going to get complicated.  My plan for this blog entry, (or maybe a couple) is to explain the what and how...I do this a lot, but this one is particularly complex (not difficult) and it took me a while to decipher the docs and troubleshoot.

MDSR
MDSR Yahoo Group

Background is there are a number of SDRs (software defined radio) out there with costs from $40 for a receive only dongle (RTL-SDR) to $3000 worth of Flex-Radio or the equivalent.  But there isn't much in between.


Some very smart folks figured out that you could pull (in many cases) a 455kHz IF (intermediate frequency, a tool the radio uses to give it multi-band capability...and probably other reasons an EE could explain) from many lower cost commercial amateur radios.

With the IF output, you now have all the audio for whatever band the radio is on...the radio does the heavy lifting, and you play with the output.

The folks at Modulator-Demodulator Software Radio created some circuitry and software to take that IF output, bring it down to around 12kHz and then let the software create the waterfall effect and other things (like filters).  Tuning through the bands looking for signals is more fun with a waterfall display.  (uses Omni-Rig and my CAT cable for the interface)


The RX hardware is called Lif2014, it can be used stand alone (that is as far as I have gotten).  The TX part is called BiLif, and the Lif plugs into it for RX/TX capability.  With this hardware, you don't need TNCs or other hardware to use digital modes.

The software is called MDSR.

1) Radio

Here is my setup.  A Yaesu FT-857d to supply the IF.  I got a short chunk of small coax with a BNC on one end.  for the other end, I bought a 4 pin header with 2mm spacing.

The easy part (and one reason I bought this radio) is there are two blank plugin spots for filters.


The coax center conductor is soldered to the 'inside' pin (left pin of the set of 4 in the above picture) and the ground shield is soldered to the 3 outboard pins of the header...then header plugged onto filter pins.  So no permanent mod to the radio.



By wiring it up that way you enable the filter in the radio menus...so you can turn the mod on and off.  One possible drawback would be that you lose audio out of the radio speaker while the filter (IF output) is engaged...disengage it again, and you have normal use of the radio audio output.


Note that the audio will be supplied by the IF converter and your sound card...so voice modes are still available, just through the computer speakers (or headphone jack).

2) IF converter (Lif2014)

This kit (available on the MDSR website) is a fairly easy build with no testing equipment required (other than a voltmeter).  The labeling on the some of the components was hard to decipher, so I will include my notes on that.  The unit requires 12vdc, I am using a 500ma wall wart for now.  (note, mine is the 2012 version, but the circuitry/operation/software is identical...just the layout changed a tiny bit)



3) Sound card

Here is where it starts getting tricky.  To use the equipment I have listed so far, you can simply plug the Lif output into your computers sound card and have at it.  If you want to transmit, you will need a good sound card.  If you want to use digital modes also, you will need a second sound card.

The solution to all that is the Asus Xonar U7, a USB sound card.  The MDSR folks have tested it and found that it is within limits for transmitting, so you can use it as your audio out...in addition it adds a sound card, so you can use your internal sound card (for example in a laptop) for digital mode decoding, and the Xonar for the MDSR software work.

This is the biggest headache I had on this hole job...getting my desktop sound card line inputs to work properly...I haven't tried it on a laptop yet.


So I have a standard mini stereo jack going from the Lif 12kHz output to the Xonar linein/mic input.  On the back of the Xonar I have a RCA to mini stereo cable going to my desktop line-in port.



(missing in the above pics are the input properties...where you select "Listen to this Device" and the output you want to use)

Again, this is so MDSR software can have the audio out of the Xonar, and programs like Fldigi can have the audio out of the computer sound card.


4) Software

Of course the Xonar required its software and drivers, but it works well, no problems with installation or use.
MDSR  has to be installed with the latest updates.  And some digital mode software if you want to play with that.


The MDSR software itself is functional, but it relies on java, and is sluggish (on my fast desktop).  They are working on an all new software package, that should solve those problems.



If you made it this far...I have successfully run this setup on my Asus T100 Transformer.  I don't have a USB hub handy, so I haven't used the CAT control with it (only one USB socket), I also have not put audio into the Transformers sound card...and I am assuming it has an audio in...

to be continued...  Part 2

BTW here is the screen shot that all the above closeups came from...