Building Low Budget Antennas - DIY Stacked J-Pole Antenna(s) for a 70 cm DMR Repeater (Part 1)

I do not like buying antennas if I can build my own that works just as well as a purchased antenna.  Throughout my amateur radio "career" I only purchased two Diamond X50 antennas.  One needed refurbishing after two month.  See article HERE.  Living by the sea takes its toll on any antenna if it is not very well constructed.  This is why I prefer to build my own antennas.  Be as it may this is my choice.  Others might prefer to purchase commercial antennas which is also fine. 

In this article we will be looking at building two  low budget antennas -  The DIY Stacked J-Pole Antenna(s) for a 70 cm DMR Repeater. Currently only a two stacked antenna as I will later add the other two that will result in a 4 element stacked J-Pole antenna.  The idea for this antenna was derived when I saw a product pamphlet in the shack of Nico ZS4N of  Hy-Gain's 4 Element 2 Meters Stacked J-Pole Antenna. I searched the Internet and only found copies of the advertising pamphlet on this 2 meter antenna and none on a 70 cm version of this antenna.  So I decided to roll my own.

Now why a J-Pole Antenna?  Glynn E. "Buck" Rogers Sr (68 years as K4ABT) tells us more:

The J-POLE has been around since the early days of HAM Radio, and is a direct descendant of the "Windom" Like the Windom or ZEPP, the J-POLE is a spin-off, or a modified WINDOM for VHF and UHF. One of the first articles I wrote about the J-Pole was in HRC magazine in 1958. Since 1958, I've written several j-pole articles in other HAM Radio publications.

Here, my references are to the early, 1923 (version) Windom (Article by Loren G. Windom September 1929, QST magazine) . If you look at the feed of the early Windom that was fed with a single wire, you may soon see the similarity between the Windom, ZEPP, and the J-Pole.

Look close at the configuration of the Jpole and the Windom, and you will understand why in many of my articles in CQ Magazine and other publications, that I often refer to the Jpole as a Windom, with the short section folded back on itself to form the parasitic element. It is for this reason that I feel these are two of the best antennas ever designed.

Having said this, you will also note that the Windom (and the Jpole) are powerful antennas that provide outstanding performance on all bands above the band for which they are cut or designed for. The reason these two antennas perform so well (as Multi-Band antennas; Windom for HF & lo VHF, Jpole VHF & UHF), is because they operate at harmonics of the fundamental or lowest frequency for which they are cut/designed. To add additional feeders (ladder-line), other than 50 ohm coax or UNUNs is a waste of RF energy. Only 50 ohm coaxial cable and a BALUN at the feed-point is all that is necessary. Anything more, adds losses into the equation that cannot be overcome after-the-fact.

Remember the axiom:

"When you have reached perfection, anything more becomes a point of diminishing returns." Enough said!

Trust me on the above paragraph, as I have experimented with every Windom and J-pole concept or design that can be imagined. Having built and sold thousands of these two antennas, I've found that
It's difficult to improve on perfection.

• For now, let's look at some of the features of our J-Pole, whether for; 140-150 mHz, or 430-450 mHz
• the J-Pole is easy to erect
• the J-Pole needs no radials
• the J-Pole has low angle radiation
• the J-POLE has greater bandwidth.
• the J-Pole has greater immunity to terrestrial noise
• the J-Pole is great for local nets or distant repeaters
• the J-Pole has more gain than most Ground Planes
• the J-Pole is more durable than most Ground Planes
• the J-Pole meets most "stealth" antenna restriction agreements
• the J-Pole has less static-charge noise, and static-charge build-up
• the J-Pole is a end-fed half-wave dipole 

The J pole antenna uses the stub to provide a good match to 50 Ohm cable. The feed point is moved up or down the stub to provide the best match, and adjustment can be made once the antenna is in position if required.

The main disadvantage is that it can be a little more difficult to adjust than some other forms. The reason for this is that impedance matching has to be accomplished by altering the trimming length of the stub.

Thanks, Buck  K4ABT!

Now I needed a 70cm Stacked J-Pole Antenna and the only information that I have was the two images above and the info from Buck K4ABT,   No measurements or images for a 70cm version!  I decided to design my own 70cm version from scratch and sorry Buck I might have transgressed the axiom here?

I looked at the second image depicting the two meter version above.  I decided to "invent" my own way of building the 70cm version of the Stacked J-Pole Antenna.  I used an online calculator to calculate the 70cm dimensions.  However the final dimensions for my version of this antenna differ significantly from the calculator which is fully understandable as the feeding arrangement and parts used is completely different to the traditional version of the antenna.  Up to now I could not find any information about this Stacked J-Pole Antenna for 70cm.  I however now have all the information at hand after constructing two of these antennas.  

The dimensions for the antenna was calculated using a free antenna calculator program (available for download from here). I set my frequency to 438.260 MHz. The resulting calculation is shown in Figure 1 below. 

 

The above dimensions did not work for the upside down J-Pole antenna for 70cm.  Here is the dimensions that worked for me.

Herewith the small amount of info that I have about the antenna:

The antenna is a high performance all driven stacked array of vertically polarized dipoles (J-Poles) that presumably delivers 6-9 dBi (or 4-7 dBd) or more omnidirectional gain.  Uniquely designed phasing and matching harness maintains a perfect parallel phase relationship and is center fed to minimize beam tilting for better low angle radiation.  The driven element maintains an extremely broad band response and effective isolation from the supporting mast only if the correct distances is set.  Open construction minimize failure due to moisture and condensation.  The entire antenna is DC Ground for static removal and lightning protection. Feeds with a good 52 Ohm coaxial feed-line.

Electrical Specifications:

Gain:  6-9 dBi (or 4-7 dBd) (2 x Phased Stacked J-Pole Antennas)

Power Limit: 1 Kw PEP

VSWR (at resonance):  1,1:1  Note:  Using the NanoVNA not connected to the computer I obtained a 1:1 SWR but using the NanoVNA Saver program the SWR was reflected as 1.4:1 and 1.2:1.  Why is still a mystery.

Impedance: 50 Ohms

Mechanical Specification:

Mast Height:   To be calculated 

Isolators:  Stauff  Gr 2

Mast Diameter:  50 mm

Wind Survival:  100 km/h

With all the information now on paper, I was ready to move onto the next phase and that was to gather all the materials I was going to need.

Materials that I used for one antenna:

1 x 200mm x 38mm x 38mm x 2mm Aluminum Angle Iron

1 x 12mm x 2mm x 2.5m Aluminum Round Tube  (The thicker the wall thickness the better. 2mm is rather thin.)

1 x 1 meter x 10mm x 2mm Aluminum Round Tube

1 x 30 mm x 10mm Wooden Dowel 

2 x 22 mm Plastic End Caps to fit into the 25mm Boom ends.

1 x SO239 Connector (Optional)

2 x Electrical Eye Lug (Terminal)

1 x 12mm Stauff Clamps (Insolaters between boom and elements.)(See images)

2 x 45mm x 5mm Stainless Steel Bolts + Washer + Lock Nuts

2 x 40mm x 4mm Stainless Steel Bolts and 2 x Lock Nut

2 x 6-16mm Stainless Steel Hose Clamps

2 x Stainless Steel TV - U Clamps

1 x 150mm x 80mm x 5mm Aluminum Flat Plate to mount antenna to boom.

1 x 100mm x 3mm Solid Copper Wire

Odds and Sods:

Hot Glue Sticks

Self Amalgamating Tape

Solder

Solder Paste

Marine Silicone Sealant

Heat Shrink Tubing

 

Tools:

 

Metal Punch

Drill

Various Drill Bits 3mm - 8mm

Hack Saw 

Hot Glue Gun

Soldering Iron

Screw Driver (Small flat)

Alen Keys 

Spanner Set

Small Pipe Bender (See images)

 

Test Equipment:

 

SWR Meter

Antenna Analyzer (If you have one but not compulsory)

Amateur Radio Transceiver

Coax Patch Leads

Mast (Non conductive)

Coax feed line cable  10 m  RG58CU 50 ohm

Power Supply for Radio 

Bending the J-Pole Element:

(Click on images for larger view.)

Now how did I bent the 180 Degree bend of the antenna?  I used a small pipe bender.   The 10mm aluminum tubes are cut to 1 x 565mm length.  I made a mark at 465mm on the long side of the antenna.  On the short end I measured 120mm and made a mark.  The first mark on the long side is placed on the 0 | 0 mark of the pipe bender.  Now start bending until the 0 on the top lever reaches the 180 mark on the bottom lever.  You now have a 180 Deg bend and your J-Pole antenna element.

I am not going to go into detail how I further constructed my version of the antenna. I will however describe my findings in constructing and testing the antenna.  The images below provide good detail of how I constructed the 70cm Stacked J-Pole Antenna.

My build observations and findings:

I used the material that I had in my "Junk" Box.  The aluminum was left overs from other antenna projects.  Measurements is absolutely crucial and feed point connections must be short as possible for obvious reasons.

I used the outer braid of RG58CU Mil-Spec to connect the 3/4 wave element.  The 1/4 wave radiator is connected using a short piece of 3mm Solid Copper Wire.

Tuning the J-Pole correctly is very important:

Tuning a J-pole antenna involves two main steps: adjusting the overall length to set the resonant frequency.  With this upside down J-Pole the one feed point (tap point - 3/4 wave element) and the joint between the 10 and 12mm is tuned to achieve a 50-ohm match and 1:1 SWR, all while using an SWR meter or antenna analyzer for precise readings at your desired frequency. You adjust the lengths of the main radiator and the stub (shortening to raise frequency, lengthening to lower it) 

Tools Needed

• SWR Meter or Antenna Analyzer
• Coaxial cable
• Tools for cutting/adjusting wire/tubing

Tuning Steps

1. Initial Setup: Mount the J-pole at its final operating height, away from ground/obstructions if possible, and connect your SWR meter/analyzer between the radio and the antenna's feed point.
2. Find Resonance (Length):
   • Measure the SWR across your desired frequency range.
   • If the lowest SWR dip is below your target frequency, the antenna is too long; trim a little from the ends (main radiator and stub).
   • If the lowest SWR dip is above your target frequency, the antenna is too short; add length.
   • Repeat trimming/adding in small increments until the resonant frequency (lowest SWR dip) is at the center of your band.
3. Match Impedance (Feed point):
   • With the antenna resonant at your frequency, find the point on the 3/4 wave element and the 1/4 wave radiator for the lowest SWR and 50-ohm match point.
   • Once you find the right points for the lowest SWR and 50-ohm impedance your antenna is now tuned.
     
4. Add Common Mode Choke: Install a choke (ferrite beads or a few turns of coax) at the feedpoint to prevent common-mode currents, which improves performance.
5. Final Check: Re-test across the band to ensure good performance and bandwidth.

Key Considerations

• Two Adjustments: J-poles need both length (frequency) and feed point (impedance) tuning.
• Bandwidth: J-poles have narrower bandwidth than dipoles, making precise tuning crucial.
• Material: Use bare wire or tubing for best results; insulation affects performance

Theoretical Performance of a 70cm stacked J-Pole Antenna:

A 70cm stacked J-pole antenna, essentially two J-poles combined (often a 2x5/8 wave design), offers increased gain over a single J-pole, pushing into the 6-9 dBi range (or 4-7 dBd)

, providing a lower take-off angle and better range for 70cm (UHF), ideal for repeaters and long-distance simplex, but its performance depends heavily on precise construction and stacking distance for optimal phasing. 

What to Expect with a Stacked J-Pole:

• Increased Gain: Stacking elements (like two J-poles) concentrates the radiation pattern, adding gain, often resulting in 3-6 dB more than a single unit, pushing it from a typical 3-5 dBi J-pole to higher figures.
• Lower Take-Off Angle: This design provides a lower angle of radiation compared to a simple dipole, which is excellent for FM voice communication and hitting distant repeaters.
• Performance: You can expect good range, with some users reporting success reaching distant repeaters or even simplex contacts (e.g., 40-80 km) with modest power (3W+).
• Construction Matters: For dual-band 2m/70cm stacked J-poles, the 70cm performance often involves a 2x5/8 wave design, requiring careful tuning and phasing for both bands.

Typical Gain Figures:

• A single J-pole is often around 3-5 dBi.
• A stacked 2x5/8 wave 70cm J-pole can reach 6-9 dBi (or 4-7 dBd), depending on the design and how well it's stacked.

In Summary: You're looking at a medium-to-high gain antenna for 70cm when you stack J-poles, making it a significant upgrade for FM and weak-signal work on that band.

Finally:

I really did not go into a full-out testing and use of this antenna at this stage.  The only testing I have been doing is using one J-Pole at a time with the Nano VNA.  See images below for the test results.

The next step will be to stack and co-phase two of the antennas and then test it again with the NanoVNA and also installed on a mast. I will provide more feedback and details in a future article on how the DIY Stacked J-Pole Antenna(s) for a 70 cm DMR Repeater performed.  Stay tuned!!

Images:  (Click on images for larger view.)

Destructive Fire destroy and damage homes, cars and wild-life in Mossel Bay (6 - 10 January 2026)

2026 was off to a fiery start in Mossel Bay in the Garden Route with various fires gutting homes, destroying vehicles and vast tracts of prime land and fynbos. The fire that started in open veld next to the N2 and spread to several areas as listed in the image below.

During the period 6 - 12 January 2026 the ZS Link Network Amateur Radio Group kept abreast of the fire and all related developments via WhatsApp Group and live Amateur Radio Nets in the event that amateur radio emergency communications were called upon.  Another first is that the fire fighters were supported by OM Jan ZS1CBS, a radio amateur and farmer who assisted in fighting the fires with his own fire fighting equipment.  Well done to Jan and a big thank you for assisting our community in times of need!!  (See images below)

The fire in Aalwyndal, Vakansieplaas, Island View and surrounds saw an enormous outpouring of solidarity – it was a tenacious community against a raging fire. Special thanks to the neighbourhoodwatch groups (Community Policing Forum), NSRI and the farmer’s associations from all over the greate Mossel Bay.
On the afternoon, 8 January 2026, when numerous flare-ups occurred due to persistent, strong and ever-changing winds, threatening adjacent areas like Sonskynvallei, Hartenbos Heuwels, Renosterbos and Num Num - more than 30 bakkies and small trailer tenks with water were, as well as trucks with water tanks were deployed. Here are some of the videos of the volunteers who added tremendous value to the firefighting effort.

Hannelie Marias, Chairperson of the Da Gamaskop Community Policing Forum writes (translated from Afrikaans):  “𝐼𝑡’𝑠 𝑢𝑛𝑏𝑒𝑙𝑖𝑒𝑣𝑎𝑏𝑙𝑒 ℎ𝑜𝑤 𝑝𝑒𝑜𝑝𝑙𝑒 𝑐𝑎𝑙𝑙 𝑎𝑛𝑑 𝑎𝑠𝑘, ‘𝑊ℎ𝑒𝑟𝑒 𝑑𝑜 𝐼 𝑓𝑖𝑙𝑙 𝑢𝑝 𝑤𝑖𝑡ℎ 𝑤𝑎𝑡𝑒𝑟?’ 𝐴𝑛𝑑 𝑡ℎ𝑒𝑦’𝑟𝑒 𝑜𝑓𝑓! 𝑇ℎ𝑒𝑦 𝑑𝑟𝑖𝑣𝑒 𝑤𝑎𝑡𝑒𝑟 𝑜𝑢𝑡 𝑎𝑛𝑑 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛 𝑡ℎ𝑒𝑚𝑠𝑒𝑙𝑣𝑒𝑠 𝑎𝑡 𝑠𝑡𝑟𝑎𝑡𝑒𝑔𝑖𝑐 𝑝𝑜𝑖𝑛𝑡𝑠 𝑠𝑜 𝑡ℎ𝑎𝑡 𝑡ℎ𝑒 𝑏𝑎𝑘𝑘𝑖𝑒𝑠 (𝑝𝑖𝑐𝑘𝑢𝑝𝑠) 𝑤𝑖𝑡ℎ 𝑎 𝑠𝑢𝑏𝑚𝑒𝑟𝑠𝑖𝑏𝑙𝑒 𝑝𝑢𝑚𝑝 𝑎𝑛𝑑 𝑚𝑜𝑡𝑜𝑟 𝑡𝑜 𝑠𝑝𝑟𝑎𝑦 𝑤𝑎𝑡𝑒𝑟 𝑐𝑎𝑛 𝑗𝑢𝑠𝑡 𝑟𝑒𝑓𝑖𝑙𝑙 𝑎𝑛𝑑 ℎ𝑒𝑎𝑑 𝑏𝑎𝑐𝑘 𝑖𝑛𝑡𝑜 𝑡ℎ𝑒 𝑓𝑖𝑒𝑙𝑑. 𝑌𝑒𝑠𝑡𝑒𝑟𝑑𝑎𝑦, 𝐼 𝑚𝑦𝑠𝑒𝑙𝑓 𝑚𝑎𝑛𝑛𝑒𝑑 𝑎 𝑓𝑖𝑟𝑒 ℎ𝑦𝑑𝑟𝑎𝑛𝑡 𝑜𝑛 𝑡ℎ𝑒 𝐴𝑎𝑙𝑤𝑦𝑛𝑑𝑎𝑙 𝑅𝑜𝑎𝑑. 𝑇ℎ𝑒 𝑚𝑒𝑛 𝑠𝑡𝑜𝑝, 𝐼 ℎ𝑎𝑛𝑑 𝑡ℎ𝑒𝑚 𝑡ℎ𝑒 ℎ𝑜𝑠𝑒 𝑎𝑛𝑑 𝑜𝑝𝑒𝑛 𝑡ℎ𝑒 ℎ𝑦𝑑𝑟𝑎𝑛𝑡. 𝑇ℎ𝑒𝑦 𝑎𝑟𝑒 𝑒𝑥ℎ𝑎𝑢𝑠𝑡𝑒𝑑, 𝑤𝑜𝑟𝑛 𝑜𝑢𝑡. 𝐴𝑔𝑎𝑖𝑛, 𝐼 𝑠𝑡𝑜𝑜𝑑 𝑖𝑛 𝑡𝑒𝑎𝑟𝑠 𝑏𝑒𝑐𝑎𝑢𝑠𝑒, 𝑤𝑖𝑡ℎ 𝑡ℎ𝑒 𝑔𝑟𝑒𝑎𝑡𝑒𝑠𝑡 𝑟𝑒𝑠𝑝𝑒𝑐𝑡, 𝑎 𝑦𝑜𝑢𝑛𝑔 𝑚𝑎𝑛 𝑤𝑖𝑡ℎ 𝑎 𝑝𝑟𝑜𝑠𝑡ℎ𝑒𝑡𝑖𝑐 𝑙𝑒𝑔—𝑦𝑒𝑠—𝑐𝑙𝑖𝑚𝑏𝑠 𝑜𝑢𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑎𝑘𝑘𝑖𝑒, 𝑐𝑙𝑖𝑚𝑏𝑠 𝑜𝑛𝑡𝑜 𝑡ℎ𝑒 𝑡𝑟𝑎𝑖𝑙𝑒𝑟 𝑤ℎ𝑒𝑟𝑒 𝑎 𝑤𝑎𝑡𝑒𝑟 𝑡𝑎𝑛𝑘 𝑖𝑠 𝑚𝑜𝑢𝑛𝑡𝑒𝑑, 𝑎𝑛𝑑 𝑜𝑝𝑒𝑛𝑠 𝑡ℎ𝑒 𝑡𝑎𝑛𝑘 𝑙𝑖𝑑. 𝐻𝑒 𝑚𝑢𝑠𝑡 ℎ𝑎𝑣𝑒 𝑐𝑜𝑚𝑒 𝑡𝑜 𝑟𝑒𝑓𝑖𝑙𝑙 𝑎𝑡 𝑡ℎ𝑒 𝑤𝑎𝑡𝑒𝑟 𝑝𝑜𝑖𝑛𝑡 𝑎𝑡 𝑙𝑒𝑎𝑠𝑡 10 𝑡𝑖𝑚𝑒𝑠. 𝑁𝑜𝑤 𝑡ℎ𝑒𝑠𝑒 𝑎𝑟𝑒 𝑡ℎ𝑒 𝑠𝑡𝑜𝑟𝑖𝑒𝑠 𝐼 𝑤𝑎𝑛𝑡 𝑡𝑜 𝑡𝑒𝑙𝑙.”

Videos:  Mossel Bay Advertiser and EWN 

 

 

𝗨𝗣𝗗𝗔𝗧𝗘 – 𝗛𝗨𝗠𝗔𝗡𝗜𝗧𝗔𝗥𝗜𝗔𝗡 𝗔𝗜𝗗 - 12 Jan 12:25 🙏 THANK YOU, Mossel Bay! Your generosity during the Aalwyndal, Vakansieplaas & Island View fires has been overwhelming. Crews are no longer stationed in the fire zone, but remain on alert for flare‑ups. 🚫 No more perishables accepted – the active operational period has ended. 🧴 Toiletries & household items still welcome (see list below). 💳 Financial contributions remain open to support affected families. Drop‑off: Generosity, 3 Watson Street, Voorbaai Donate online: edenprotocol.co/mossel-bay-fire-relief 🧴 Needed Items * Soap, facecloths, toothpaste, toothbrushes * Shampoo, conditioner, roll‑on, spray * Sanitary towels, lotion/aqueous cream * Razors, hairbrushes, combs * Toilet paper, washing powder, fabric softener * Handy Andy, bleach/Domestos, dishwasher liquid * Washing pegs, scourers, broom, mop, dustbins

Images:  Robert Crous + Mossel Bay Advertiser (Click on images for larger view.)

 

Images:  Working on Fire, Kishugu Aviation and Mossel Bay Advertiser  (Click on images for full view.)

Images below:  Jan ZS1CBS, Radio Amateur and Farmer getting his fire fighting  equipment ready before moving in to fight the fire which at that stage was threatening the Hartenbos Heuwels and other areas.  Jan, thank you for the community service you provided free of charge.

Images and video below:  The editors son also assisted in fighting the fire after his normal daily work schedule.  Thank you son for the service that you rendered to the Community of Mossel Bay!

 

End.

I cannot access the Aasvoëlkop Repeater (145.625 Mhz) from Heuningklip. What is the reason?

On Saturday the 27 December 2025,  Jakobus ZS1JDJ visited his father in law OM  Jan ZS1CBS at Heuningklip near Herbertsdale.  He carried out some tests from the QTH of Jan to ascertain why Jan ZS1CBS cannot access the 145.625 Mhz Aasvoëlkop Repeater which is situated about 22.8 km away from the farm as the crow flies.  Now why would they not be able to access the repeater?  I looked into the matter and here is some interesting information that I found.  Please note that the data is analyzed as I received it.  Slight differences might exist.

• The repeater could not be accessed with 20 Watts RF Power
• Using a 11 element Yagi they were able to open the repeater but the audio was unintelligible.  Lots of rain on the carrier signal.
• The topography showed that there are quite a few small mountains around  the QTH of ZS1CBS. 
• The antenna was tilted upwards and also pointed at the mountains around the QTH (in all directions) to look for a possible reflected signal towards the repeater.
• Topographic images confirm that the QTH is situated between mountains.
• Jan ZS1CBS can however access the 145.650 Riversdale Repeater (See image why.)  No mountains in the way.  Opening through a valley?
  
• The "range" of mountains in the way from the QTH to the Aasvoëlkop Repeater is clearly visible in the red circle in the image below as well as the Radio Path Study Image.
• Signal distribution images (Radio Mobile) showing that there is no signal propagation to the Aasvoëlkop Repeater. (No green or yellow reflections.  White - No signal distribution) 
• Riversdale Repeater signal distribution present.  (1 - 10 Micro Volts and more.)
• The Radio Link Study 1 as with regards to the Aasvoëlkop Repeater reflect the fade margin as -5.07 dB and 28.52 dB in respect of the Radio Link Study 2 aka Riversdale Repeater.  Significant difference!

Comment:  With the "ground work" now done it is clear that Jan ZS1CBS has currently better access to the Riversdale Repeater than the Aasvoëlkop Repeater.  Further tests with different antennas and antenna polarization need to be done.  A high power radio (50 Watts) should also be tested.  

Conclusion:  There are several other options available to "get onto" the Aasvoëlkop Repeater from the QTH and these will be looked at once we are sure that there are no path to the repeater with any VHF Radio equipment.  

A big thank you to Jan ZS1CBS, Jakobus ZS1JDJ, Johann ZS1AAC and Viv ZS1VIV for providing the data that enabled me to evaluate the different radio paths as listed below.

Images:  (Click on images for larger view.)

 

Videos: