Editor note – Please enjoy this guest post from Jeff Bourgeois VE7EFF.
Today, September 6, I hope to POTA activate Inonoaklin Provincial Park CA-3626 in Southern BC, Canada, located on the shores of the Lower Arrow Lakes. On this activation, I will be using my novel experimental homebrewed Coaxial-Sleeve Dipole. The results were surprising!
We have been wanting to come back to this park since a brief visit to the area last summer. I especially wanted to come back because, at that time, it had never been activated by anyone. I had plans to activate another park in the area that day. Unfortunately, I was beaten to the draw just a few weeks ago by another ham.
The other reason I didn’t get here sooner was because it is a 3-hour drive east from our home in Kelowna, BC. 3-hours is pushing the limits of how far I’m willing to drive on daytrips, especially in mountainous areas. We rarely, if ever, do overnight trips.
We left the house very early in the morning on Sept. 6, 2024. While the countryside is very beautiful enroute to the Arrow Lakes, I kind of dread the drive as the roads are often narrow, twisty-windy and up and down steep mountain passes. At times it felt like being on a roller coaster.
We arrived at the park shortly after 9 AM. Inonoaklin Park is a small day-use only park and we are the only people here today, so far. What a beautiful location. We can see a couple of small house boats moored in the lake.
There are no paved parking lots here, just sand and gravel. I found a suitable spot to park my Subaru Forester. While there are a couple of picnic tables a couple hundred feet away, I decided I wanted to operate closer to the water.
The first order of business is to deploy my antenna system. Until recently, I used my Gigaparts antenna mast tripod to support the Gigaparts Premium 34 ft. Carbon Fiber Telescoping Antenna Mast. But there are times when setting up a tripod isn’t the best option. For example, if I want to activate in a park parking lot area, the ranger may not approve of that setup. Recently I decided to buy the Chameleon CHA Porta Mount, Wheel Mount. I thought I would use it today, just out of convenience. I have used it in two other parking lot situations before and I’m quite happy with it.
Last year, all my activations were done using my N9SAB dipoles with good results. But dipoles can be more work to set up than end-feds or verticals. Telescopic verticals are on my bucket list to try but I just haven’t got there yet.
I know that End-Fed antennas are very popular and successful, and one day I will give it a try, but I’m kind of hung-up on the idea of having to use a counterpoise wire to make it tune or work effectively. The counterpoise wire seems in essence to really just be the other half of a dipole, laying on or just off of the ground. And I understand that in many cases, the coaxial transmission line kind of takes the place of the counterpoise.
For this activation I will be using my recently designed and built vertical or sloping ½ wave coaxial sleeve dipole antenna. It’s the one coiled-up in the top-center of the photograph below. Keep in mind that this is an experimental antenna for me, and I haven’t documented precisely the construction details. I have written a rough description later on in this report. It will be operated as a slightly sloping vertical coaxial sleeve dipole.
Whether I’m using a dipole or sloping vertical, I try to situate the antenna such that it will provide optimal propagation to the SE direction. Because I’m in the Pacific Northwest, I seem to get good propagation results when setting up the antennas to maximize radiation to the USA South-east. That’s my theory anyway.
I now have the top-end of the coaxial sleeve dipole tethered to the tip of my mast and sloping down at about a 20 degree angle. The other end is supported by the Gigaparts mast tripod. It has nothing else to do today, so why not put it to work.
There are a couple of good reasons why I have the dipole sloping away from the mast, other than the mast being tilted due to being parked on a bit of an incline and the wheel mount shims being a bit sloppy today.
-
- I almost always have mountains obstructing part of the horizon view. So, raising the angle of apparent maximum radiation helps maximize the signal just above the mountains for best skywave propagation. (That’s the theory, anyway)
- My carbon fiber dipole is much more conductive than I would expect; it substantially detunes the vertical dipole when draped vertically parallel directly next to the mast. So I slope it away to reduce the mast detuning and signal absorption. That seems to do the trick.
The dipole bottom-end is defined by the location of the toroidal choke, through which the coax loops for 13 turns. This choke blocks the dipole RF from travelling back towards the transmitter. Its location also determines the antenna’s overall length.
This shows the 20m antenna construction in limited detail. This particular version is built using RG-8X coax from DXEngineering.
It is interesting to note that the dipole bottom-half is acting as both a 50-ohm transmission line and the bottom ¼ wave radiator for the dipole. This is due to the magic of RF skin effect on the outer conductor of the coaxial line. You can learn more about this antenna concept by searching on “coaxial-sleeved dipoles” on the Internet.
The coaxial-sleeved dipole is typically used for vertical VHF/UHF antenna design. And I built one for my home 2m transceiver. I actually built 3 versions using different sizes of copper pipe. They seem to work really well. So then I thought, why not try this on the HF bands? This 20m coaxial-sleeve vertical dipole was my 1st attempt at this using RG-8X coax. I also built another 20m version using RG-174 coax for backpacking POTA activations.
Ok, enough antenna talk. So, how did it work? Let’s find out….
One funny side note here.
About halfway through the activation, a brief visitor called over to us and asked: “Are you catching any fish?” Well, I guess from the picture below, it does kind of look like a deep-sea fishing pole. As we are nowhere near the ocean, I don’t think there are any blue marlin or tuna in this lake. 😊 But, then again, perhaps I am fishing…. Yes, I will be fishing for POTA Chasers! All I have to do is bait the fishing antenna with a few good CQ’s and wait for the bites! 😉
Today I’ll be operating CW with my KX3 at 10W, powered by a Bioenno 4.5 Ah battery. I’m keying with the KXPD2 paddle. It works just fine, but I’m finding that I need to burnish the contacts after every few hours of ops. The handy little table is another fine product from Helinox.
Most of the next 6-hours are spent trying to make POTA contacts.
I did take a lunch break, and later another break to go for a walk to stretch my legs. Such a beautiful day with beautiful scenery. There is also a waterfall just a few hundred meters from here.
The results are in. The first two 20m contacts are P2P with KI7QCF and W4LOO; both in Utah, at 17:57 UTC (10:57 PDT). The next 25 minutes are filled with 15 more 20m contacts in the states of CA, CO NC, MA, WI, ID, ON, TX, CA, KS, NM, NY, and OR. Yes, I know Ontario isn’t a state 🙂
The real action today was on 17m and 15m bands. So, let me jump around the bands and timelines before I report the best results. On the 12m band, I bag 4 contacts in TX, ON, IL, and GA, beginning at 20:11 UTC (13:11 PDT).
Near the end of the day on the 30m band beginning at 23:24 UTC I logged just 3 contacts in MI, MT, and BC. I never get much action on 30m during daytime. And at the end of the day on the 40m band beginning at 23:53 UTC, I scooped-up my last two contacts in OR and BC. I never get much action on the 40m band during the day either. So, now for the real action, 17m and 15m were hot and cold. It was just a matter of patience and persistence.
17m Band, Round-1:
I actually had two goes at the 17m band first starting at 18:41 UTC (11:41 PDT). In the first go-around I logged 13 contacts including the states of CA, TX, NY, TN, CO, PA, and NM. But there was one bonus DX contact with SM3NRY in Sweden; sweet!
17m Band, Round-2:
After spending time on 12m and 15m, I came back to 17m to see what more was happening there. It was even better this time around. Beginning at 21:52 UTC (14:52 PDT) I logged 15 more contacts starting with FL, and followed by CA, NY, NJ, ME, VA, MO, and KS. This time I’m awarded with 3 more DX contacts including EC1R in Spain, F4ILH in France, and EA2BD also in Spain.
Going back in time to 15m, I also had two go-arounds.
15m Band, Round-1:
This first 15m band round begins at 19:16 UTC (12:16 PDT). This first round only harvested 5 contacts in the states of CA, MO, MI, TX, and IL.
15m Band, Round-2:
The second round of 15m brings in 9 more contacts including the states of IL, MI, MO, FL, and OH. And 3 more bonus DX contacts in Belgium, Italy, and France with ON4VT, EC1R, and F5MDY.
It’s been a long day of CW ringing in my ears. My last contact was at 23:56 UTC (16:56 PDT). Time to pull the plug.
Tip: Click on the photo to enlarge the resolution for a closer look.
In summary, this was my most successful POTA day ever in terms of numbers of contacts and DX. Perseverance, hopping bands and calling CQ for over 5 hours helped get the numbers up. 15m and 17m were the superstars of the day. It also helps that we are at or near the solar maximum, too. I don’t win any awards for the most contacts/hour. Generally, I typically only average about 10-12 contacts/hour on all my activations. What I lack in speed, I make up for it in perseverance and hours on the air.
So, how much credit should I give to my experimental coaxial sleeve slanted vertical dipole?
Who knows; chalk it up to luck, solar cycle, band conditions, the antenna, operating QRO at 10 watts, or all the above? So many variables, who can say….
Alexis had an enjoyable day reading, sketching, and going for walks along the lakefront. I had a productive and successful day achieving a total of 68 contacts; 8 of which were DX to Europe.
Time to pack-up and make the 3-hour rollercoaster drive back to Kelowna.
Thank you for reading,
Jeff – VE7EFF and Alexis – VE7LXE
Equipment List:
Elecraft KX3 with internal antenna tuner
Bioenno 4.5 Ah LiFePo4 battery
Chameleon CHA Porta Mount – Wheel Mount
Gigaparts Telescopic Mast, 34ft, Carbon Fiber
20m Coaxial Sleeve Slanted Vertical Dipole, home brew, experimental,
Did you have multiple dipoles or did you just let the tuner do its magic on all bands but 20? Was the antenna matched on 20 without the tuner? Cool experiment!
73, Kevin K3OX
Hi Kevin,
I only used the one antenna for the whole activation.
I initially tuned the vertical dipole for 20m in my back yard tethered to the carbon fiber mast. The mast was perfectly vertical there. I quickly realized that the carbon fiber mast was significantly pulling down the resonant frequency. When I pull the bottom of the antenna away from the mast a by a few feet, it then resonates between the 20m and 17m bands.
At that time, I left the tuning as is as I didn’t have more time for retuning.
The KX3 and KX2 have great ATU’s. So, my KX3 tuned across all bands with no issues in terms of SWR matching.
Since this activation at Inonoaklin Prov. Park, I have retuned the vertical dipole for 17m (partly because the antenna was a little short for optimal 20m tuning). It seems to perform much the same as when tuned for 20m, except that it is optimized for 17m. If I remember correctly, the 17m tuned version had a best SWR of about 1.9:1 when measured on my analyzer. So, it could be operated without a tuner on a single band, if you don’t have a tuner.
I think a fiber glass mast wouldn’t have near the same detuning effect as a carbon fiber mast. I hope to get one for this purpose in the near future.
Cheers/73,
Jeff
Great write up Jeff. Would like to know more about the coaxial-sleeve dipole that you made out of RG-174. I also do POTA with the KX-3. Looks like some I would like to try.
W0HL
Hi Dennis, thank you for your feedback.
I believe coaxial-sleeve dipoles were originally developed as vertical VHF/UHF solutions to not require radials or a center support. And that is how I built and used my first VHF vertical antennas.
To be honest, I haven’t heard of anyone else using this concept on HF (perhaps they are, I just haven’t heard of it). But, I though it would be an interesting experiment.
I haven’t tabulated any solid numbers for construction. I just used the standard calculation of 468/F in mHz to determine the initial 1/2λ length in feet for band desired (i.e. 20m, 17, etc). Then cut the coax a foot or so longer to give you room to trim the tuning, preferably with an antenna analyzer if you have one. You also need a little extra coax length before the toroidal choke to act as your input feed-line pigtail with BNC connector.
Sorry if I can’t be a little more explicit; but this was a bit of an whim experiment that seems to have some promise.
I’m sure if you Google on coaxial-sleeved dipoles you will find more technical discussions from which to work (even though most references are concerning VHF/UHF applications – but the concepts are generally the same for HF).
Cheers/73,
Jeff (VE7EFF)
Thanks for the info, Jeff. Appreciate it
W0HL
Jeff and Alexis,
Great article on your HF coaxial dipole! And that sounds like a great location to operate. I’ll bet your noise floor was excellent. I have family in Peachland, so next time I am visiting, I’ll get in touch.
I have experimented with the same basic antenna last fall. I modeled it with EZ-NEC and found that it has about a 13 degree main lobe take off angle with 3db width of 16 degrees. The ideal height above ground is about 6 feet from the choke end. More or less than that raises the angle of the main lobe. The amazing part is that the gain, takeoff angle, and the main lobe change very little over about a doubling of frequency from the design. That is drastically different from a horizontal dipole. So, as you found out, as long as your tuner can match the change in impedance, you can expect very similar performance on all those bands.
I used a 17 meter version of this antenna for the SOTA S2S trans Atlantic event last fall. It worked fantastic on 17, 15, 12, and 10 meters. I used a KX2 on CW for that outing. As you found out, it is a very good DX antenna. I use a fiberglass push up mast, so I don’t have the problem with detuning. I typically wind the antenna loosely around the mast so the mast does not bend over.
As far as making it over those mountains, I don’t think those reach the 5 degree angle, so I don’t think the slope of the antenna makes any significant difference. Certainly, band conditions and this high part of the solar cycle make a big impact, but I think you will find this to be a very good dx antenna. If you want shorter range, then an inverted V or a dipole will do better. But the neatest thing in my book is the ability to use multiple bands with similar performance.
I wrote this up in https://www.skyviewradio.net/newsletter/ for December 2023 in more detail. Unfortunately I am not at home right now so I can’t copy the article. You might be able to have K3JZD find it for you.
72/73,
Dan, NM3A
I noticed that you used a toroid choke to define the lower end of the dipole. That is another key to using it for multiple bands. Some articles on this coaxial sleeve dipole suggest using coiled coax for a choke. That will work okay- for a single band. For other bands than the design band it won’t work well.
Dan, thanks for your feedback. What noise floor? 😊
That’s the joy of operating out in the boonies away from power lines – no, or low QRN.
Good info from your EZ-NEC analysis. (I still need to learn to use it, when I get the time.)
I’m definitely going to get a fiberglass mast to eliminate the detuning effect on the vertical dipole. The carbon fiber mast I have is great for my horizontal and inverted-vee dipoles, but now that I’m experimenting with vertically oriented antennas, fiberglass is obviously necessary for best efficiency.
And for those operating backpack or away from the car, just hoisting the top of the dipole into a tall-enough tree (using a throw bag and line) is a great no-mast-required solution for the vertical sleeve dipole, too – which I have talked about in one of my recent past article posts, and in an upcoming post, too.
I’ll contact skyviewradio .net to see if I can get a copy of your article on the coaxial sleeve dipole that you wrote about.
Cheers/73, Jeff (VE7EFF)
Hi Dan ~ Can you please share the presentation you gave to your Skyview radio club on January 22nd on how you built your sleeve dipole antenna? I saw it referenced on Facebook.
Many thanks,
John – W3JED
John,
I am on the road, but I will share when I get home in a couple weeks.
Thanks Jeff for the details about your experience with the sleeved dipole. I have only used such antennas for mono-band operation (in fact, my main home antenna is a horizontal sleeved dipole, https://gavare.se/radio/sleeved-dipole.html#20mHome ), so it was interesting to read about how they work with a tuner for multi-band operation.
73 de SM6VNO Anders
Anders, thank you for your feedback. Much appreciated.
The KX3/KX2 ATU’s have been so valuable in allowing me to use single band antennas in multiband scenarios.
I really like the idea of coaxial-sleeve dipoles because they don’t require a counterpoise. And as with any antenna, elevation is our friend – the higher the better (except for NVIS).
I just read your coaxial-sleeve dipole experiments on your website that you listed above. Very interesting read and good documentation of your experiments. I followed similar experimentation paths as you did.
I just purchased a spool of RG-58C to do some more experiments with. I think I will use it to build and test a 30m band version similar to what you did. From my experience with the N9SAB 30m dipole, it tuned quite well across 40m – 10m with my Elecraft KX3 ATU. So, I’m hoping I will perhaps have similar good results with a 30m coaxial-sleeve slanted vertical dipole.
As well, I have some RG-316 on order with which I will also do some similar experimenting with.
73, Jeff (VE7EFF)
Here is some more information from my experimentation. https://www.nelis.net/K3JZD/Files/Skyview_Newsletters/Skyview%20Q5er_202404.pdf
See page 10
And: (From my PowerPoint presentation. I can email you a pdf that includes all the illustrations if you like- email me direct.)
HF Portable Antenna
Skyview Radio Society
20 February 2024
Dan, NM3A
HF Portable Antenna
Typical Types
PEFHW
PEFNRW (non-resonant wire)
PVertical 1/4 wave
PDipole
`Horizontal
`Inverted V
`Vertical
PYagi-Uda
HF Portable Antenna
Requirements for (my) Portable Use
PLightweight
PEasily Portable
PEasily Erectable
PEasily Transportable
PEffective
PInexpensive
HF Portable Antenna
My Latest Antenna Trial
Vertical Sleeve Dipole (VSD)
PVertical (End Connected)
Sleeve Dipole (aka Flowerpot)
`Electrically a Center-Fed Dipole
but physically end-fed
`Takes advantage of the different
properties of the inside and
outside of the coax shield
`Can use an actual shield outside
of coax> Choke not as important
HF Portable Antenna
Ten Meter VSD Dimensions
PWire half dipole – 95 inches 22 ga insulated
PCoax half dipole – 84 inches RG58 100% shield
PLower end HAT – 6 feet
PChoke Guanella 1:1 (or coil coax / ferrite beads)
PCan support 100 Watts easily
PSupport:
`Push up fiberglass mast (SOTABeams TravelMast)
`Rope support from tree (or PackTenna)
HF Portable Antenna
100 W Choke
Dipole
HF Portable Antenna
How to Isolate Antenna
PGuanella Balun/Choke
`Smaller
`Light weight
`Allows for easy
extensions for other
bands
PCoiled Coax Choke
`Simpler
`Cheaper
`Easier to Adjust
`Single band?
10 W Choke
HF Portable Antenna
PAdjust sleeve/coax & wire for lowest SWR
`Wire end is easy – just add or subtract wire.
`Coax end:
– Guanella Balun:
– Disconnect wire from coax
– Trim Coax and/or Wire
– Resolder wire to center conductor
– For extra bands, use jumper coax between antenna and choke
and wire clipped to end of wire end of antenna
– Coiled Coax:
– Simply move coil to add or subtract from antenna
– Trim wire separately
– For extra bands, use coax connector at center of antenna and
wire clipped to end of wire end of antenna
HF Portable Antenna
PEasily scaleable up to V/UHF or down in HF
PEasy to add extensions for 12, 15, 17, or 20 M
`Wire end: Alligator clips for extensions
`Coax end:
– Short pieces of coax with connectors
– Add to choke end of antenna for Guanella balun version
– Add to center for coiled coax choke version
`Modeling 20 M version shows very similar patterns
for higher frequency bands, so with a wide range
tuner, a 20 M antenna will work well through 10 M.
HF Portable Antenna
EZNEC Modeling Vertical Dipole
PAdvantages:
`Low radiation
angle
`Lightweight
`Portable
`Easy to erect
`No radials
needed
HF Portable Antenna
EZNEC Modeling 2 Element Beam
PAdvantages:
`Gain
`F/B
`Low radiation
angle
`Relatively easy
to erect
`Lightweight
`Portable
HF Portable Antenna
Real world testing with
local and European
stations agrees with
model predictions
HF Portable Antenna
SWR
Similar for Dipole or
2 Element Beam
Less than 2:1 from
below 28.0 to 28.8
Generally will not
need antenna tuner
for a single band
Fixed or Portable V/UHF Antenna
PWorks well as a lightweight portable antenna
for high deployment in a tree
PGood for lousy locations for public service
PEncased in PVC, works well as an indoor or
a permanent outdoor antenna
PGain over ground wave 1/4 wave
PEasy to make and tune
HF Portable Antenna
Selected References
PAndrew (VK1AD),
“10m Flowerpot Antenna”
,
vk1nam.wordpress.com/2022/12/02/28-mhz-antenna-project-10m-flowerpot-
antenna/
PAdamczyk,B, Pearson,A (KD8WYR),
“Sleeve Dipole Antenna Design and
Build”
, incompliancemag.com, 31 Oct 2019
PMcCormick,C (M0MCX), DX Commander Antennas, May 2017
PTaylor,JE (W2OZH), QST, Aug1991,
“RFD-1 and RFD-2: Resonant Feed-
Line Dipoles”
PBishop,JC (VK2ZOI),
“Half-Wave Flowerpot Antenna”
,
vk2zoi.com/articles/half-wave-flowerpot/
PHunt,S (G3TXQ),
“High Performance Common-Mode Chokes”
, pp 32-39,
May 2015, RadCom Plus
PFlower Pot Antenna Calculator,
nomonsuhendar.blogspot.com/2020/12/flower-pot-antenna-calculator.html
PHeffer,R (G4NSJ), Flowerpot Antenna and How it Works,
Dan,
Thanks for the link to your article published in Skyview newsletter last April. All very good info.
That was a good layman’s video you linked to about G4SNJ Flowerpot Antenna and how they work. Very well explained for the layman unfamiliar with the topic of coaxial sleeve dipoles.
I’ve been having lots of fun experimenting with my variations on the coaxial-sleeve dipole.
I originally built my first ones back in 2018 for the 2m VHF band. I built 4 versions. Each one with different size copper pipe ranging from 1/4″ to 3/4″ copper pipe. Similar to G4NSJ and yours, but I used the same diameter pipe for the upper and lower half of the dipoles. I feel that keeps the dipole more balanced with equal size conductors top and bottom. They all worked very good. The 1/2″ copper pipe version is still my primary 2m VHF base station antenna.
As well, I still use the same coax and outer shield for the upper portion of my HF coaxial-sleeve dipoles. For the top half, I just solder the outer shield to the center conductor, just past the separation of the bottom half shield. My thinking is that this keeps the dipole more balanced with equal shield conductors top and bottom.
Anyway, the experimentation continues on…. so many variations to try…
73, Jeff (VE7EFF)
Anders,
There is one very big difference between a vertical and a horizontal dipole (whether sleeved or regular feed) and that is the main lobes. With a horizontal dipole those lobes change wildly for different frequencies and with electrical or physical height above ground. With a vertical dipole the lobes do not change much with different frequencies. Height above ground does make more of a difference, but it still is not dramatic until you get very high.