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Ham Radio General Class Lesson 6.2, Dipoles, Ground-planes, and Random Wires


Here’s your video introduction to Ham Radio General Class Lesson 6.2, Dipoles, Ground-planes, and Random Wires from the ARRL License Manual. For details, please see www.ke0og.net/general.

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  • For wavelength to frequency calculations, I was taught; Metres X Mega-Hertz = 300. (Re-arrange to suit your application)
    So: 300 / 150 MHz = 2 Metres: 300 / 7.5 MHz = 40 Metres: 300 / 430 Mhz = 0.7 Metres = 70 cm, etc.
    I can use metric and imperial measuring systems, but radio is in metric, so I use metric.


  • As a guy that passed my general several years back and lost a bit of interest, I have found your videos very useful as I get back into the hobby. Thank you!!


  • Greetings from Sweden 🇸🇪.
    Awesome channel!
    God bless you for all the great work you do.

    This helped me a lot!

    73!


  • I don’t understand the dipole mirror analogy. Do we actually sink a 1/4 wavelength dipole under the earth & leave 1/4 above grade?


  • Oh my you have many issues with this video…. first, an easy calculation to go from meters to feet is simply multiply by 3 and then add 10%. For example, to convert 10m to feet multiply by 3 to get 30 feet, then add 10% to get to 33 ft. Very simple and more than 99% accurate. The true length would be about 32.833 feet.

    Secondly, to say that all mobile antennas are way too short is obviously wrong. What about 1/4 wave whips? Those are not too short. Some people even use 5/8 waves which in some cases are too long (for best performance like in places where there are lots of obstructions such as tall houses or buildings close to the road that mobile station is driving on).

    I expect way more accuracy from a seasoned ham to not make slips ups like this.


  • Awesome video!
    Thanks so much!


  • L GL G

    Author Reply

    Very helpful video on antennas, one of your best.


  • Good stuff. Makes understanding the book much easier.


  • Like & Subscribe
    Wonderful Review // Thanx for
    sharing. Peace.


  • Another great video David. Quick question though: How do you relieve tension at the tuner end of a random wire antenna? If the length is long and the end is tied up high somewhere, I would think it would pull quite a bit on the tuner so what would you suggest? Thanks David. Matt / KF4ULD


  • the mirror example is too good sir


  • Dave what is the advantage or dis advantage of an off center long wire. Monty KN4GTW, thanks


  • Tell me one source where I could get all my doubt clarified as a one stop solution.


  • Tell me some thing about array factor.
    I am a beginner and having a lot of doubt in the analysis of antenna pattern.
    How much important is the antenna pattern in antenna design.


  • How much liquor do you drink before making these kindergarten videos that you claim are for General Class candidates? None? Well then you must be shooting up heroin. These videos are a terrible waste of time. You make us real hams laugh…


  • Dave can you talk about printed antennas such as Bluetooth antennas on PCBs? that would be greatly appreciated!


  • Good or for bad I use YouTube a lot to research ideas and how to's. I think I am pretty good at sifting out the BS. And I also don't judge based on fancy presentations. I have to say if there was a measuring tier on YT on bang for the buck how-to, content, understandability…your vids would be at the top of heap. Which brings me to my point' you do have idiots that watch your videos. And I know this because there are actually viewers that give you an occasional 'thumbs down'. In my wildest dreams I can't imagine why? Jealous, maybe, or just plain idiots. That's my vote. Keep up the great work, 1,000s of people like me need great instructors like yourself and greatly appreciate it.


  • Dave, you are the best. Love these videos. Would love to see your video setup in a future video!
    I'm currently studying for both the Technician and General License exam that I hope to pass this coming Saturday.
    I have a single story house with a balcony on top. What can I expect in the way of performance if I were to put an Inverted "V" on the (flat) roof? I figure it's out of harms way, but would be approximately 10-12ft off the ground. Would this affect it's performance?


  • Good evening i enjoy your videos
    please what is your email address
    thank you


  • Great intro to antennas. Thanks! 73 KM4UQU


  • Love your videos Dave, they helped me earn my General Class and I'm waiting on my call sign from the FCC now.  My question is about multi-band end fed antennas like the ones PAR electronics makes.  They have a 9:1 UNUN transformer and are typically much shorter than regular dipoles.  Is grounding and RF as big of an issue with these since they are fed to the transceiver via coax rather than straight in like a random wire?  Thanks!


  • Great video ! Can you tell me if ,for example, a MFJ-2010 Wire dipole would need to be grounded ? Thank you ( don't have my license yet but i'm one big SWL fan for now… )


  • The mirror analogy for the 1/4 wave being half a dipole was very good.


  • MattMatt

    Author Reply

    What about random wire and outdoors? and linking antennas in to 1/4 wavelengths? 


  • One of the best videos I have ever seen on ham radio. Thanks!


  • should the feed point always be in the center of antenna??In the case of long wire you just attached the feed point to one end of the wire??


  • Doing my RAE exam next week. These tutorials are excellent for newbies like me. Thank you for sharing. 


  • I love the explanation with the mirror, maybe basic for some, but for new operators I will remember forever. thank you. looking forward to the extra videos 


  • Great Course


  • Crear course General Class
    Congratulación


  • Reply to HM Dickson: Thanks for the tips on electric fence wire and Nolox. But I don't share your cavalier attitude about RF safety. Lesson 8.2 will cover RF safety in more detail.


  • I pay little attention to RF. For years i maintained television transmitters. There was so much RF that all the 26 florescent lights in the building burned constantly! I run 2 watts on QRP now. Never give RF a thought 🙂 Gold or silver wire would be the best although a bit pricy! Try electric fence wire. Cheap, strong, made for the elements. A bit of "Nolox" at the connections will take care of corrosion. If you put RF just outside with coax, do you think wood walls will protect you? LOL!


  • Can the coax be used for the feed line from the antenna tuner to the random wire?


  • thanks for replying so quickly 🙂 sounds like it will be more worthwhile to buy some copper wire considering i'm not putting out many watts


  • Yes, but your wire losses will be slightly higher, meaning some of your signal will become heat instead of RF radiation. But not by much. The biggest issue to look for is corrosion from the joint of dissimilar metals. One way to avoid this is to use stainless steel nuts and bolts to hook wire together.


  • can you use steel wire, like garden garden wire or does it have to be copper?


  • The technique you describe isn't covered in the book or on the test. Given these are training videos for helping students pass the test, I don't usually include much extra material. In this case, I confess I haven't heard of the technique you describe. Can you provide me with some references to articles? I can post these in the About section above and also on my website. 73, Dave


  • Once I get the metric wavelength I divide that in half. Then I generally add a a few centimeters to that. I prefer to have my dipoles longer so I have room for adjustment. My 10 meter aluminum dipole is easy because I am using telescoping elements. Adjustment is just a matter of loosening a hose clamp and sliding the elements in or out. I get good SWR all over the band. Conveniently the antenna can be shortened for 6 meters.