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[KB6NU] Would you buy alligator clips from this company?
KB6NU's Ham Radio Blog /////////////////////////////////////////// Would you buy alligator clips from this company? Posted: 26 Sep 2017 12:55 PM PDT http://feedproxy.google.com/~r/kb6nu...m_medium=email This appeared in my inbox about an hour ago: Besked fra afsender: â—Ž â—Ž forget the above information ★★★★★★★★★★★★★★★★☠…★★★★★★★★★★★★★★★★⠘…★★★★★ Nice day, dear friend- Hope this email find you well- This is Ana, a girl from China shenzhen, manufacturer of audio connectors, dc connectors, alligator clips, test cable,Â*and rf connectors for 13 years. After saw your website, I thought you might be interested in our product as below picture showed, https://ae01.alicdn.com/kf/HTB1b2G.S...Xq6xXFXXXV.jpg would you like to get some samples for testing , my friend ?We still have many other models, i can send you our more information if its okay for you,Â*ODM & OEM available since 2001 dear friend -Im here waiting for your reply- all email send to and and Contact person : Ana whatsapp :+86-18126184197 E-mail: wechat: yibaokeji121 Skype : michael.zhaoyanhui web : www.koko-go.com ★★★★★★★★★★★★★★★★☠…★★★★★★★★★★★★★★★★⠘…★★★★★ forget the below information â—Ž â—Ž So, would you buy alligator clips from this company? Im tempted to ask for samples, just for the heck of it. Another odd bit of info is that the sender of this email is . danhostel.dk, as the name might imply, is a chain of hostels, offering holiday accomodations in Denmark. The post Would you buy alligator clips from this company? appeared first on KB6NUs Ham Radio Blog. /////////////////////////////////////////// Why 50 ohms? Posted: 26 Sep 2017 12:02 PM PDT http://feedproxy.google.com/~r/kb6nu...m_medium=email I often get asked by newcomers why we use 50Â*Ω coax in amateur radio, while cable TV uses 75Â*Ω coax. I didnt really have a good answer until I read the following tweet from GB, KG4GVL, and the reply from Dave, KJ8U: GB HoytÂ*@KG4GVL Can anyone give me a sound electrical reason why we design antenna systems around 50 Ohm impedance? DaveÂ*@KJ8U Long answer microwaves101.com/encyclopedias/… The executive summary of the long answer on Microwaves101.Com is that for coaxial cable with an air dielectric, the lowest loss is at about 77Â*Ω. Air-dielectric coaxial cable can, however, handle the most power whenÂ* its characteristic impedance is about 30Â*Ω. Youll find all the math at the Microwaves101.Com link above. Hams want coaxial cables to both handle a fair amount of power and have relatively low loss, so whoever chose 50Â*Ω as the amateur radio standard did so because it happens to be about halfway between 30Ω and 77 Ω. Nowadays, we rarely use air-dielectric coax. Instead, we use coax with a polyethylene dielectric. This increases the power-handling capability of the coax. Not only that, a coaxial cable with polyethelene dielectric has the least loss when the characteristic impedance is 51.2Ω.Â* How lucky is that! By the way, this line of reasoning also explains why 75Â*Ω is the standard for video and cable TV. These cables dont have to handle a lot of power, so minimizing loss is the most important consideration in these applications. The post Why 50 ohms? appeared first on KB6NUs Ham Radio Blog. |
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