AmateurRadio.com

I am a strong believer that “if it ain’t broke, don’t fix it.” I also find that, particularly if it is anything to do with computers, the law “if something can go wrong, it will” operates with near 100% certainty. As a consequence, I an extremely reluctant to upgrade or update anything unless it fixes a problem I’ve experienced or am likely to experience, or provides new functionality that I actually need. I get anxious whenever the “Windows has new updates” balloon pops up, worrying about whether my computer is going to get screwed fixing some obscure vulnerability I don’t understand in some bit of Windows I may not even use.

One of the problems of getting old is that you tend to forget things and sometimes I do something having forgotten that the day before I had decided there was no point in doing it. And so, this morning, I decided to update the firmware in my Kenwood TH-D710 in order that it could identify from APRS packets newer radios like the VX-8G and TH-D72, regardless of the fact that I hardly ever use the radio’s own APRS display and the update would not affect the ability of APRSIS32 to identify these radios on my PC.

I downloaded the update software, browsed the help file that came with it and then ran the program and followed the instructions it displayed. The update went without a hitch. I was a bit concerned when the concluding instruction was to perform a full reset, which I thought would erase all my settings, but I had not seen any dire warnings about this so I went ahead. Sure enough, on completion the Kenwood was now in factory default mode, with all my settings and laboriously entered memory channels lost forever! Arrghh! If only there was a System Restore for real life!

Kenwood does provide a free memory management program for the TM-D710, MCP-2A, which can be used to edit, back up and restore memories and settings. However it needs a second serial cable attached to a different port to the one used for the built-in TNC. I had never got around to making up another cable as I don’t need computer control of the radio and storing channels in memory manually isn’t that hard so I don’t usually bother with programming software. Besides, all four serial ports on the shack PC were already used. So I had never tried it.

In the hope that it would save me time re-entering the settings and memories, which I could then back up, I installed MCP-2A and moved my serial cable from the radio’s control head (the TNC port) to the PC port at the back. But no matter what I tried, the program could not communicate with the radio.

Now I’m completely stumped. I’m using the same PC serial port and cable as I used to perform the upgrade and access the TNC, so the port and serial cable work. I tried the “Auto” baud rate setting and several manual selections and it made no difference. As this is the first time I have used it, I’m wondering if the rear PC port is actually broken. Have I overlooked something stupid? Is there anything else I could try to test if it works?

As the owner of a Kenwood TM-D710 I was interested to see that Anastasios, SV8YM, has developed a mod to fix the problem of the failing IF filters which causes these radios to go deaf after a couple of years. As explained in admirable detail in his original article describing the problem, it is caused by electromigration due to the fact that Kenwood omitted DC blocking capacitors on the input and output of the ceramic filters. This issue affects the TS2000 as well.

As you can see from Anastasios’ excellent photographs, the mod involves cutting some tiny circuit board tracks, bridging between pairs of them with wire, then soldering 0.1uF SMD capacitors between the bridge and the filter input. The TM-D710 has two receivers, each with two filters (one for wide FM and one for narrow FM) each of which has both an input and an output that needs to be treated. So that is 16 tracks that need to be cut and 8 tiny capacitors inserted. I’m afraid working with these tiny components is beyond me, which is a shame as it is now, while my Kenwood is still only a few months old, that it needs to be treated.

Thanks to SV8YM for sharing the details of the modification.

A couple of months ago I acquired a Kenwood TM-D710 dual band FM transceiver with APRS as it was the best solution to the problem of how to operate an APRS gateway without losing the ability to monitor for voice contacts on 2m when you do not have the space for two widely separated antennas. I have been quite pleased with the radio but rather alarmed at the number of reports of loss of sensitivity due to the failure of one or more of the IF filters. I asked on the Kenwood Yahoo group whether this was just a faulty batch of filters affecting radios of a certain age or a generic problem that was likely to affect any TM-D710 eventually and  was directed to this explanation in the blog of Tasos, SV8YM.

It has been a long time since I read such a well written explanation of a technical phenomenon and I’m sure you’ll find it interesting, especially if you own a VHF radio with 455kHz IF filters. In fact I’m sure many of you will find other articles of interest in this blog. I’ve added it to my regular reading list.