A 5/8 wave is not 50 ohms and has a lot of reactance present...thus a matching
coil is needed for proper matching to 50ohm feed. The coil makes the 5/8 wave
look like a 3/4 wave electronically thus presenting a 50ohm feed point. It also
allows it to operate as a 1/4 loaded on 6m. I've done this with NMO150s for
decades..of course a decent groundplane is required for proper operation
Chris WB5ITTTrustee W5APXWRXZ789 GMRSSociety of Broadcast Engineers Vice
Chairman and Frequency Coordinator, SBE134 SE TX and SW LA
On Friday, November 28, 2025 at 11:50:18 AM CST, Gary Sitton via BVARC
<[email protected]> wrote:
On 11/28/2025 10:35 AM, Daniel Poirot via BVARC wrote:
I tried the 5/8ths wave and couldn’t get it to tune until it was cut down to
1/2 wave!!!
:-/
On Fri, Nov 28, 2025 at 10:29 AM Gary Sitton via BVARC <[email protected]>
wrote:
Dan: I made both a 2 mtr and a 20 mtr version of the flower pot vertical.
There's also a 5/8 wave version using both 50 and 72 ohm coax.
Gary, K5AMH
On November 28, 2025 9:22:05 AM Daniel Poirot via BVARC <[email protected]> wrote:
Howdy y'all,
Thinking of our new friend Jose and all of the folks with constrained spaces,
I have just the thing!
The 'flowerpot antenna' is an end-loaded, half-wave vertical. It takes up no
space at all, may be deployed for use and hidden away after, is easy to build,
and is cheap!
The parts list is simple: 10' or longer 1/2" PVC pipe 10' or longer 50 Ohm
RG-58 coax patch cable electrical tape and box cutter knife.
The antenna itself may be threaded inside the PVC at the end load coil, or
just taped to the outside, depending on just how stealthy you need to be.
The wavelength of 2 meter frequencies is 2 meters. A half wave is 1 meter,
and a 1/4 wave is 50 cm. Simple math!
A premade coax feedline is a great way to start, as the pesky BNC is already
fitted. Lop off the end you don't need.
Measure down 1/4 wavelength. almost exactly 50 cm. Longer is better. We will
tune for length. Cut around the outside and through the braid, and strip off 50
cm of the shield braid and the 'outside'. Leave the inner insulator for
protection from the elements.
Tape the stripped end to the end of the PVC, leaving 3" or so for tuning.
Tape along the length of the stripped portion and the next 50 cm. Make several
turns of tape 1 meter down to anchor the antenna part of the coax.
At this point, wrap nine (9) turns of coax tightly for the end load. Wrap
this all in plenty of tape to keep the turns from separating. Add several turns
of tape at the end of the coil to anchor the coil.
Done. That was easy. It actually took longer to read than it does to make.
Using our handy, dandy SWR meter, tune the stripped portion to length. Mine
ended up shorter than 50 cm. but with a nice 50 Ohm matching resistance.
The 10 feet of PVC makes for a suitable mast, the tail of the coax can reach
the HT, or you can extend EACH as necessary.
The performance easily beats the antenna shipped with the HT. I hope it
lights a fire in you to build another antenna! ;-)
For a video of the exercise, see the YouTube:
https://youtu.be/4EhUau841jk?si=LWWBV8fhqdQ4zYjX
73, y'all
Dan KJ5IZK
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ClubBVARC mailing
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--
Gary Sitton, K5AMH
[email protected]
SDR/DSP Consultant,
"Have FFTs, Will Travel."
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