A scorching hot summer in Zante

No, the airplane in the first photo didn't get entangled in my antennas!   It flew over the house and literally rescued our property from going up in smoke, like the pine trees in the second photo, where the plane drops 6.5 tons of water on the rapidly approaching fire front, less than 100 meters from the house (click on the photos to enlarge them). It was the 28th of August, and had the firefighter planes not arrived for another 10 - 15 minutes, all bets would have been off. It was the second close call this year for us. Such scenes have been extremely commonplace in my island during the last 25 years.

It's a sad reality that a vast pine forest area has been burnt to the ground during the last years, depriving Zakynthos of one of its greatest assets. Unfortunately, the great damage to the flora and fauna of the island will take many years to mend (if ever!). The planes and the firefighters on the ground (among them several volunteer radio amateurs) have saved many homes and possibly lives. We owe them all a big "thanks", perhaps more so to the pilots, who perform extremely dangerous aerobatics to deliver their payload with pinpoint accuracy.

The GaAsFETgate scandal in Zakynthos

Click on photo to enlarge.

GaAsFETs have really become ubiquitus in every situation one wants high gain and low noise figure in frequencies ranging from the low VHF to microwaves. The picture on the left is of a very popular transistor (although a bit dated now), the ATF 10136 from Agilent Technologies. The ceramic cap has been removed to take this photo (about 200X magnification). 

The chip is in the center, attached to the source strip. The diameter of the white ceramic material is about 1.5 mm. The drain is on the right and the gate on the left. Observe the thin gold wires that connect the chip to its carrier contacts (and to your circuits!). This particular transistor (from a low-noise 2-m preamp) had a cruel death: it was accidentally (and quite scandalously!) bombarded with high power on 144 MHz from the amplifier of an EME setup in a friend's station. The gate short-circuited to the source, and you may see that even the gold wires almost melted by the heavy current that destroyed the transistor (see the red arrow). Fortunately, nowadays those great transistors are fairly cheap to replace, and can be easily procured.  Thumbs up to Agilent (now Avago, and the other semiconductor manufacturers) that make our beloved toys!

Does your IC-E92D have any loose screws?

"It's the loose screws in my head!"

The IC-E92D is a very well constructed handheld transceiver, with a really solid feel of quality. I bought mine in 2008, in order to wet my feet in the new D-Star ocean. I also have the external speaker - microphone adaptor, which I think makes the rig a lot more pleasant to use.

The transceiver performed flawlessly, no problems at all, up to a few days ago, when I noticed that when I keyed the transceiver in medium and high power output on UHF using the provided rubber antenna, the display backlight would consistently and magically turn itself on and strange beeps and noises would emanate from the external speaker. The phenomenon was absent in the low and super-low power settings, so I reasoned that some kind of RF intrusion into the logic circuits was to be blamed. Removing the external speaker/mic cables changed things a bit (only full power produced the strange effects), but the goblin was surely still there. A quick search on the Internet revealed that other users have also reported similar problems with the display going blank or even getting inverted (!), so I was not alone out there. 

But what had changed to produce those effects? I hadn't changed anyhthing, the rig functioned with exactly the same accessories from day one. So, it was logical to think that the reason was internal.

Before opening the case, I studied the service manual a bit. I observed that the screws holding the transceiver together also had another very important mission: (especially the top two) pressed the main printed circuit board grounding spring contacts on the chassis. So these (and of course the other internal screws) are cleverly forming RF-tight enclosures within the transceiver. Could it be that some of those screws had gone loose, compromising this important function?

So, to take a first shot at it, I proceeded to carefully tighten the six screws that hold the transceiver together (they are at the back side, two of them near the top and four of them under the battery - you have to remove the battery to see them). Indeed, they took about 1/4 turn to feel nicely tight again (BUT DON'T OVERDO IT WITH THAT SCREWDRIVER, PLEASE!).

I am happy to report that the problem vanished immediately. I loosened the screws a bit again to see if it would come back, but it didn't, obviously because the contacts were not disturbed enough this way. My theory is that the screws gradually become a bit loose with normal use and thermal cycling, making the shielding / grounding contacts unreliable and "leaky". A bit of tightening and everything is back to normal again. Perhaps some day I will also have to open the case and tighten the internal screws, too. If the problem doesn't go away by tightening the externally accessible screws (especially the two ones at the top), that's the next logical step. This reasoning may also hold for other transceivers with the same shielding method. I must say I have certainly seen a lot of strange problems in other modern VHF/UHF transceivers go away when I tighten the screws that hold the printed circuit boards on the cast aluminum chassis!! They have a tendency of coming loose, mainly due to thermal cycling action.

Enjoy your IC-E92D and see you on D-Star!