AmateurRadio.com

When using a hand held radio with a long whip antenna for more gain I often prefer to use a speaker mic so I can hold the radio in a steady, upright position. I have a speaker mic for the Kenwood TH-F7E (which fits the old TH-205E as well) and I have one for the Motorola GP300. But needless to say neither of them fit the Intek H-520 Plus 10m rig because the wiring and pin spacing is different. The official Intek speaker mic is rather expensive so I looked on eBay and found a speaker mic for “Alinco Icom Standard 2-pin” with the correct pin spacing for less than £7 including postage from Hong Kong.

When it arrived I decided to check what the audio sounded like by listening on the K3 while I made a call. The mic keyed the radio up but there was no audio. To make troubleshooting easier I swapped the antenna for a dummy load and audio was then heard!

I then tried a variety of different antennas and power levels and was soon pulling my hair out. I would hear audio with the dummy load connected and none as soon as I switched to an antenna. Eventually I tried the very short antenna supplied with the H-520 on the lowest power setting, 0.1W and I heard audio. It was looking very much as if the presence of radiated RF was somehow interfering with the audio. But the amount of RF required to cause the problem must be small as 0.1W on any of the larger antennas resulted in no audio from the speaker mic.

I didn’t know whether the RF was causing a problem with the microphone or the radio. I tried clamp-on ferrites at both the mic end of the cable and the plug end but neither made any difference so I was none the wiser. This particular made-in-China speaker mic is held together with screws that require a nonstandard five pointed key to undo so I couldn’t look inside to see if it used screened cable. I decided to give up on that speaker mic and do what I could have done in the first place if I hadn’t thought spending seven quid would be an easier solution.

In my junk box was the business end of another cheap Chinese speaker mic from which the cable had been ‘borrowed.’ I noticed in the past that the curly cables used for these speaker mics are often not screened. I happened to have a length of stereo audio cable with each channel separately screened. I wired this up to the spare speaker mic and attached suitable 2.5mm and 3.5mm jack plugs to the other end. When I tested it I now had transmit audio even on high power with the 4 foot telescopic whip!

At this time I don’t really know whether the mic I bought was at fault because I don’t have another radio that uses the same size plug spacing to test it with. Given that I have been less than impressed with other aspects of the H-520’s performance I wouldn’t be surprised if it wasn’t the radio that has inadequate filtering for RF picked up on the speaker mic cable.

I’m not paranoid, but I think everyone is out to get me!

I ordered some connectors from eBay seller m0jpm and, because I have been thinking about getting a radio that has N type connectors on it, I decided to order a couple of BNC to N-type adapters so I could use the much easier to obtain BNC plugs on my antenna cables. The listing I ordered from is shown below.

The package arrived this morning and when I opened it, to my dismay I found that the adapters were the reverse of what I wanted. As you can see, they are for attaching N-type plugs to BNC sockets.

It has sometimes happened that I ordered the wrong thing by mistake, so I was relieved when I checked the eBay listing and saw that this time it was the seller’s mistake not mine. But my relief turned to anger when I emailed the seller to inform him of the error and received the reply: Dear g4ilo, Hi we have send you what you have ordered, as this is the only n-type to bnc we have listed. but if you not happy send it back for a refund.

Is it really necessary to insult my intelligence by telling me “we have send (sic) you what you have ordered”? I will send the adapters back for a refund (and no doubt be out of pocket for the postage) because they are no use to me. But I shan’t be buying anything from m0jpm again.

In a comment to my previous post Ricardo CT2GQV said that I should give up buying on the Internet. I wish I could, but if I did I would have to give up the hobby because it is not possible to buy radio stuff round here.

I’ve bought loads of radio and electronic stuff from Hong Kong and China on eBay and most of it has been okay. But I’ve had the occasional duff purchase, like the stubby dual band antenna allegedly made by Diamond which I’m pretty sure was a fake.

I bought a Motorola GP300 radio body at the Blackpool rally a couple of weeks ago but I needed accessories like a battery pack, charger and speaker mic. Ebay was the obvious place to look for them. The 1800mAH NiMH battery pack was fine, and a good price. The speaker mic is obviously a clone of the original Motorola design but a lot less solidly made, but I have received good audio reports using it so no complaints there. However I was a bit suspicious about the “overnight charger” purchased from RadioFactory because after 6 hours of charging the battery pack was really hot.

The GP300 battery ran out while I was on Watch Hill this afternoon so I need to charge it back up, but before I do I thought I would take a look inside. The case is conveniently designed so that you can pull it apart after pushing back four flexible plastic clips. The circuit board then just lifts out. I got quite a surprise after I did!

The top of the circuit board is printed with component outlines but most of the components marked are not present, and many of the components that are there don’t correspond with the outlines. In the middle of the board is an unidentified component that looks as if it has overheated.

On the underside of the board, again, most of the components that are supposed to be there are missing. Some of the tracks are bridged together with solder blobs or a wire link. I haven’t got the time or, more importantly, the clarity of mind to work out exactly what the circuit on the board actually is, but it doesn’t look much like something capable of charging a 7.2V battery pack from a 12V wall wart.

I’m not quite sure what to do about this. I have the plastic case and the charger contacts, which as I know from the charger I made for the TH-205E are the hardest parts of a battery charger to make. So I could simply make up another constant current charger circuit on Veroboard and put it into the existing case. Or I could simply cut my losses and buy another Motorola charger from a reputable source. I’m sure that one of my readers will know of one.