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Paranoia or what?
On 2/4/2015 1:39 PM, Jerry Stuckle wrote:
On 2/4/2015 2:02 PM, John S wrote: On 2/4/2015 11:57 AM, Jerry Stuckle wrote: On 2/4/2015 12:26 PM, John S wrote: On 2/3/2015 2:17 PM, Irv Finkleman VE6BP wrote: I haven't seen a post on this group since the 27th of January. Was it something I said, or what? Just gotta make sure this newsgroup is still working! :-) de Irv, VE6BP Hi, Irv - I did not think you were interested in some of my research projects because they are in the 70cm band. If it does interest you, let me know and I'll describe my project. Cheers, John N1JLS John, There are definitely people interested in 70cm band projects. Please - post away! Thanks for your reply, Jerry. History: My thought was to have a remote transmitter for measuring rainfall. Yes, I can buy one, but then I don't have a reason to do all this. I decided to use a Silicon Labs si4420 device for both receiving and transmitting. I would use the 70cm band and include my call sign on every transmission. It would be inside the base of a very old tipping bucket rain gauge using a 3-cell AAA supply. The trigger is a momentary contact when the bucket tips, indicating .01 inches of rainfall. Present: Okay. Well, it turns out that the si4420 wants a 27+j136 balanced load seen at its terminals. This is where the antenna investigation comes in. So, I need to show a balanced input of 27+j136 from an antenna separated from the chip with two traces of some impedance (TBD) to the chip. Some lumped matching components can be used, but I have tried to minimize them for home construction purposes. I don't have the room to put in very many cm of micro strip transmission line. My goal is to make it as simple as possible and be able to make it in my shop by hand. Thanks, Guys. John N1JLS John, I've looked at similar chips with the idea of building an expensive single-channel 440 Mhz FM rig. Not that the existing rigs aren't cheap - just something to do. You might want to look at a couple of PDFs on the silabs website: https://www.silabs.com/Support%20Doc...Docs/an422.pdf https://www.silabs.com/Support%20Doc...Docs/an421.pdf The first is a datasheet on the 4420 (and others); the second has all kinds of good information including PC board antennas (see figures 2.7 and 2.8). Silicon Labs has a lot of good information on their website. However, there's so much sometimes it can be hard to find exactly what you want Thanks, Jerry. I have those documents and have read them. Good stuff there. |
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