Best Vertical Antenna For Portable Operation...DIY POTA ANTENNA

The efficiency of a 1/4 wave vertical antenna can be greatly improved by getting it up off of the ground. This "do it yourself" antenna covers 20M thru 6M. The lower frequency bands can be covered by adding a loading coil at the base. This antenna is easy to set up and does not require wires or tripods on the ground. A parts list is included in the video.

[@Inkling777]

My antenna mount is attached to a cargo rack mounted on the roof of my car. Rubber pads to prevent vibration electrically isolated it from my car, although there was some capacitive coupling. To improve the connection, I installed two stainless steel straps from the rack to my car body just inside door openings. That was done by drilling holes in both. The result seems to work well enough. I have SWR's of 1.4 or less with Hustler antennas on the 40, 30, 20, and 10 meters.

[@Jimscoolstuff]

Thanks for sharing this information.

[@craigmaxey4334]

Jim, your wisdom is very valuable…I now will strive for a 35 ohm match with similar vehicle setup.

[@Jimscoolstuff]

Thanks for your nice comment. 73,de KQ8E

[@DentonBramwellM]

Just figuring out my own POTA setup... found some good ideas in your video. Thanks for posting.

[@Jimscoolstuff]

Thanks for your comment. 73

[@traveller-nl]

Finally!! Jim, thanks for talking some sense into... oops, I mean about vertical POTA antennas. I love your coupling solution. Myself, I just braid-bonded it to the truck. Thanks for pointing out the 3/4 wave option and its higher radiation angles. Forgot all about it when operating the long skip on 20m. KX4UI

[@Jimscoolstuff]

Thank you for your comment.

[@dandypoint]

Excellent. Everyone seems to think they want minimum SWR with a quarter wave vertical! My trick on 160 meters is to make my inverted L (top loaded vertical) longer than 1/4 wave to get the R up higher then cancel the resulting inductive reactance with a Capacitor. That also gets the current peak higher on the vertical. Have you thought about how you could top or center load your system? I am using Hustler resonators. I also use the Hustler quick disconnect so I don’t have to screw the mast on each time. 73, de N4DJ

[@W1ZY]

Put a shunt coil from feedpoint to ground inside the box to perform final impednce match.

[@KC3UVF]

I love the idea of this mount! I've got a 10m rig in the vehicle and I've been thinking of swapping it out for one of my DX70's. I've been trying to figure out a mounting system for stationary operation that doesn't require me carrying around my pota antenna all the time. I've got a spare 17ft whip and a sunroof. Jackpot!

[@Jimscoolstuff]

Thanks for your comment.

[@randallstone2444]

…and key ‘til you feel better! Love it, thanks Jim. -Randall, K6RCS

[@Jimscoolstuff]

Thanks for your comment.

[@izzzzzz6]

Very good info. Some may want to add some thin plastic between the foil and the paintwork to increase slightly the thickness of the dielectric. One question. If I have a dipole around 73ohms in impedance and I wish to match it down to 35 ohms into coax. What ratio balun should I make? A 2:1 should be good?

[@Jimscoolstuff]

You will have a fairly good match using 50 ohm or 75 ohm coax. Many hams use a current balun (1:1) to prevent radiation from the coax. Thanks for your comment.

[@johndavidson1010]

Thanks Jim. I was thinking of using your idea in this way…. Make the foil patch and magnet to roof of my car but attach the wire to the SO259 to my antenna base mounted on a tripod. This will stop the need for wire counter poises and utilize the car body. ( no roof rack available) What do you think?

[@Mr4Brown]

Hi Jim, great video, I learned a lot. Honest question would a mag mount have given you similar results?

[@Jimscoolstuff]

Mag mounts are typically used for vhf . At high frequencies the small base area provides sufficient coupling to the vehicle. At lower frequencies more area (higher capacitance) is needed, or an actual physical connection is used. There is a type of mag mount that has 3 magnetic pads. This type of mag mount might work. Thanks for your comment.

[@Mr4Brown]

@@Jimscoolstuff Good to know. Thank you for the reply.

[@johnpeterson7264]

Great video !

[@off-trailseeking3965]

Thanks for a great explanation on an elevated 1/4 wave for POTA!

[@Jimscoolstuff]

Thanks for your comments.

[@DK5ONV]

💯Nice Video. 👍 Southwest Germany is waving a Hand. 🙋‍♂ 73 de Uncle Günter 👌

[@Jimscoolstuff]

Thank you for your nice comment.

[@dandypoint]

Did you calculate or measure what the capacitance value was on your foil/ rooftop capacitor? The reactance in ohms that you ended up with is really what I am wondering about. I am thinking if it was 15 ohms you would get the 1:1 SWR and as it goes down the SWR rises to the theoretical 1.42 at Xc =zero. If I did my math right Xc of 15 ohms is about 750 pf. So you would need about 1100 pf to get Xc down to 1 ohm. My numbers indicate if you had 12 inch square plate with dielectric K=2 and a spacing of 0.05 inches you would have about 1290 pf. I have no idea of the K value of car paint, but a K value of 2 seems to be conservative. I also think my 0.05 inch thickness is ultra conservative for car paint, but there may be a slight air gap below your plate so it could go either way. Your plate looks to be larger than 12 inches by 12 inches. So I am guessing your C is larger than 1200 pf.

[@Jimscoolstuff]

I used a 2 foot long by 18 inch wide piece of aluminum foil. That is an area of 432 square inches. I did not calculate or measure the capacitance.

[@dandypoint]

@@Jimscoolstuff thanks. That would give a very low reactance at 14 MHz for sure. I may try making some measurements on some of my mag mounts..

[@mikeramsey9747]

Very informative

[@Jimscoolstuff]

Thanks for your comment.

[@evertwenderpirt6328]

10 out of 10, Jim. 73 de ZS6AQW

[@Jimscoolstuff]

Thanks for the nice comment.

[@JohnHill-qo3hb]

Very clever Jim, thanks for sharing de ve7kkq

[@Jimscoolstuff]

Thanks for your comment. 73