DX-440 part question

[ka3jjz]

Yes, but please read the entire thread - thee is a possible condition that may mean you use something than diodes. Mike

 

[graywoulf]

Thank you for pointing that out Mike. Since the DX-392 has an RF gain pot on it, I assume then that whatever antenna I should choose or create can be controlled as far as the problem of RF overload. I think that the concept of the gas discharge element is very interesting. The first device of that kind that comes to my mind are those small what I call old style "front panel neon lamps". I might not be right in that choice though. All I want to do is have a small indoor antenna that will help my reception as I live in a very small town in the foothills of the Blue Ridge Mountains. There are no FM radio stations here and there are only three small local AM stations here as well. So, like I first said, all I want to do is not fry my radio this winter. Thank you for your time and help.

 

[ka3jjz]

Just by way of explanation for those that might not know; the pot in the circuit is a el-cheapo way to reduce the antenna gain for portables, for example, that don't have a RF gain control, or use a switch which sometimes results in too little or too much attenuation. You can safely leave it out entirely if you don't want or need it.

Mike

 

[Boombox]

Sorry for the slack reply.
I took two diodes, soldered them back-to-back (next to each other with reverse polarity) in the middle of a length of thin, flexible hookup wire which runs from the external antenna's solder pad (somewhere in the NE corner of the PCB, if memory serves) to the negative battery terminal. I wrapped the diodes and solder connections with a couple layers of clear shipping tape to keep any metal or solder from contacting the PCB.

I did the same thing with my DX-440, and I think I also did it with my DX-370, as I couldn't see any diode protection on the PCB.

The later Sangean models have internal diode protection (DX-398/ATS909, ATS505, I know for sure have it). I think the 909X has it also, from looking at the schematic.

If you use an external antenna, I'd also consider the project on this website, which looks simple to build, and does much of the same thing -- perhaps even better.

Hope this helps.

73
Boombox

 

[ka3jjz]

Yep, better to replace a couple of blown diodes in a box than to have to dig around the PCB...and as noted in the thread, there are other things you can use besides back to back diodes for static protection...Mike