Build a 23cm 1296 MHz Yagi Antenna
The 23cm band at 1296 MHz sits at the boundary between UHF and microwave — a band where EME (Earth-Moon-Earth) contacts are achievable with modest stations, tropo-ducting events connect operators over 2,000 km, and the short wavelength allows high-gain antennas of very manageable physical size. At 1296 MHz, a wavelength is just 23 centimetres — a 20-element Yagi under 70 cm long delivers 17–18 dBd gain. Construction at this frequency demands precision unfamiliar to most HF operators: element placement errors of 2–3 mm cause measurable gain loss, connectors matter enormously, and feedline loss can negate the antenna's advantage. This guide covers 23cm Yagi design principles, the established DL6WU long Yagi design, full element and boom dimensions with boom correction, N-type feedpoint assembly, weatherproofing, mast-head LNA installation, and SWR verification for fixed station and EME applications.
Why 23cm Construction Demands Higher Precision
Yagi design principles are identical at all frequencies, but at 1296 MHz several factors become critical that are negligible at HF and VHF:
The DL6WU Design — The Standard 23cm Reference
The DL6WU long Yagi design by Gunter Hoch (SK) is the most widely built and best-validated Yagi design for 23cm. Optimised for maximum forward gain over long booms, it was developed specifically for EME and has been built by thousands of operators worldwide:
Feedpoint Matching at 1296 MHz
The driven element of a 23cm Yagi presents approximately 25–35 Ω with significant reactance. Matching to 50 Ω coax requires both resistance transformation and reactance cancellation. Three approaches are used:
- Folded dipole driven element (recommended): a folded dipole presents 4× the impedance of a simple dipole — approximately 100–130 Ω. With a 2:1 balun, this transforms to 50–65 Ω. The folded dipole is naturally balanced, broadband, and the most reliable approach for a first 23cm Yagi build.
- Gamma match: a parallel rod connected to the driven element at a specific point with a tuning capacitor. Works well but requires careful tuning at 1296 MHz — more sensitive than at VHF.
- Hairpin (beta) match: a shorted parallel-wire stub across the driven element, combined with a series capacitor. Similar to gamma but symmetric. Used in many European 23cm Yagi designs.
- N-type connector mandatory: PL-259/SO-239 is not suitable at 1296 MHz — use N-type or SMA at every connection in the system. PL-259 adds 0.5–1 dB insertion loss per connector pair at this frequency.
Feedline Loss — Critical at 23cm
At 1296 MHz, feedline loss is the dominant system performance factor for most amateur stations. A high-gain Yagi connected with inadequate coax loses most of its advantage:
| Element | Type | Length (mm) | Length (inches) | Position from reflector (mm) | Position (inches) |
|---|---|---|---|---|---|
| 1 | Reflector | 117.4 | 4.62 | 0 | 0.00 |
| 2 | Driven element | 112.0 | 4.41 | 51.0 | 2.01 |
| 3 | Director 1 | 106.4 | 4.19 | 108.0 | 4.25 |
| 4 | Director 2 | 105.1 | 4.14 | 174.5 | 6.87 |
| 5 | Director 3 | 104.2 | 4.10 | 245.5 | 9.67 |
| 6 | Director 4 | 103.5 | 4.07 | 320.5 | 12.62 |
| 7 | Director 5 | 103.0 | 4.06 | 398.5 | 15.69 |
| 8 | Director 6 | 102.6 | 4.04 | 479.0 | 18.86 |
| 9 | Director 7 | 102.3 | 4.03 | 561.0 | 22.09 |
| 10 | Director 8 | 102.1 | 4.02 | 644.5 | 25.37 |
| 11–20 | Directors 9–18 | 101.5–101.8 | 4.00–4.01 | 729–1330 | 28.7–52.4 |
All dimensions for 4mm diameter aluminium elements on 12mm square aluminium boom with boom correction applied. Design frequency 1296.1 MHz. Verify the full 20-element table against the DL6WU calculator using your exact boom and element diameters before cutting any material.
Yagi 23cm Calculator
Materials for a 20-element DL6WU Yagi for 1296 MHz
Building the 20-Element DL6WU 23cm Yagi
Precision is the defining requirement at 1296 MHz. Print the complete element table from the DL6WU calculator before starting. Set up the drill press with a fence jig. Measure every element with the caliper after cutting. A carefully built 23cm Yagi delivers textbook performance — a sloppily built one produces mediocre results despite using the correct design.
Prepare and Mark the Boom
Cut the 12mm square aluminium boom to 650mm. Using a machinist's steel ruler and permanent marker, mark each element position along the boom starting from the reflector end at 0mm. Place a strip of masking tape along the boom face before marking — marks on tape are clearer and the tape prevents the ruler from scratching the surface. At each position mark, use a centre punch to make a small indent — this prevents the drill bit from walking when drilling begins.
After marking all 20 positions, verify each measurement independently using the caliper — measure from the reflector-end face to each mark and compare against the table. Any mark that is more than 0.5mm off must be corrected before drilling. Once a hole is drilled in the wrong position, the boom must be discarded or the error accepted.
Drill Element Holes and Install PTFE Insulators
Using the drill press with a fence jig to ensure perpendicular holes, drill 4.1mm holes through the boom at each element position. The drill press fence keeps all holes in a straight line along the boom centreline — a hand-drilled hole off-centre by 2mm causes the element to sit at a slight angle, slightly changing its effective electrical length.
Press the PTFE insulators into each hole — they should be a snug interference fit. Apply a small drop of cyanoacrylate to each insulator body before pressing in. PTFE insulators are essential at 1296 MHz: nylon and PVC have dielectric constants and losses that measurably shift element resonance frequency. If commercial PTFE insulators are unavailable, use a non-conductive boom material (fibreglass square tube) and mount elements directly without insulators — this also works correctly and eliminates the insulator requirement entirely.
Cut All 20 Elements to Precise Length
Cut all elements from 4mm aluminium rod using a fine-tooth metal saw or disc cutter. Cut each element 3mm longer than the table value, then file to exact length using a fine flat file, checking frequently with the digital vernier caliper. This file-to-final-length approach avoids the problem of cutting too short — once an element is too short it must be discarded:
Install and Centre Elements in the Boom
Insert each element through its PTFE insulator, centred so equal lengths protrude on both sides of the boom. Verify centring with the caliper: measure from boom face to each element tip on both sides — they must be within 0.5mm of each other. Build a simple centring jig from two small aluminium blocks set equal distances from the boom centreline — this makes accurate centring of all 20 elements fast and repeatable.
Secure each element with a minimal drop of epoxy or cyanoacrylate at the insulator-element junction. Use the minimum amount needed to lock the element in place — excess adhesive wicking along the element surface changes the element's effective electrical length. Allow adhesive to cure fully before proceeding to the next step.
Build the Folded Dipole Driven Element and Feedpoint
Build the folded dipole driven element from 4mm aluminium rod. The folded dipole is a rectangular loop with dimensions matching the driven element length (112mm) and with a 12mm spacing between the two parallel conductors, creating a narrow rectangle. A 5mm gap at the centre of one long side is the feedpoint:
Verify SWR at 1296 MHz
Connect the NanoVNA-H4 to the N-type feedpoint connector. Hold the Yagi horizontally in free space — at arm's length, away from metal surfaces, your body, and the floor. At 1296 MHz, nearby objects within 30cm significantly affect the feedpoint impedance. Sweep 1270–1320 MHz:
Mount, Install Mast-Head LNA, and Weatherproof
Mount the Yagi on the mast using a non-conductive standoff — a 15cm fibreglass or PTFE rod between the boom and the mast bracket keeps the metal mast away from the antenna's rear elements and prevents the mast from disturbing the radiation pattern and impedance. Orient the Yagi for horizontal polarisation (elements horizontal) for terrestrial contacts, or vertical polarisation (elements vertical) for EME where your counterpart uses the same polarisation.
Install the mast-head LNA immediately at the N-type feedpoint — connect with the shortest possible N-type jumper (under 15cm). The LNA dramatically reduces the system noise figure regardless of feedline length. Power the LNA via a bias-T at the shack end of the feedline — 12V DC through a 100 µH RF choke in series with the coax centre conductor, with a blocking capacitor at the shack end. Weatherproof the N-type feedpoint connection, the LNA enclosure, and all outdoor coax connections with self-amalgamating tape and silicone sealant.
EME on 23cm — Moonbounce for Modest Stations
The 23cm band is the most active EME band in amateur radio. More operators have worked moonbounce on 23cm than on any other microwave band, making it the best entry point for EME:
- Minimum station: one 20-element Yagi (17 dBd), a 0.5 dB NF mast-head LNA, 50–100W transmit, and JT65c or Q65 digital mode. Many operators have made their first EME contact with exactly this setup.
- Digital modes: JT65c (traditional 23cm EME) and Q65 (newer, more sensitive) both decode signals 10–15 dB below the noise floor — making EME practical with modest antennas and power levels that would be totally inadequate on CW.
- Expanding the system: two phased Yagis add ~3 dB, opening up more stations. Four Yagis add ~6 dB. A 1-metre dish produces ~24 dBd — equivalent to a large array. The EME journey on 23cm has a clear progression from first contact to serious DX station.
- EME activity windows: the moon is above the horizon approximately 12 hours per day. The EME2 and moonbouncers.com forums coordinate activity and allow pre-scheduling contacts with specific stations.
Terrestrial Operation — Tropo, Aircraft Scatter, and Weak Signal
Beyond EME, the 23cm band offers several terrestrial propagation modes that reward a high-gain Yagi:
- Tropospheric ducting: at 1296 MHz, tropo events regularly extend range to 500–2,000 km. During strong ducting anticyclones, stations 1,500 km distant are routinely worked on SSB with a single Yagi at 50W — an experience that is simply impossible on VHF bands during the same conditions.
- Aircraft scatter: passing aircraft reflect 23cm signals over paths of 300–800 km that are otherwise blocked. Aircraft scatter contacts at 1296 MHz are brief (seconds to minutes) but reliable and predictable — using ADS-B flight tracking, you can pre-calculate when an aircraft will be in the common scatter volume for a planned contact.
- Beacon monitoring: many 23cm beacons operate around 1296.8–1297.0 MHz across Europe and North America. Monitoring beacon signals reveals propagation conditions in real time and provides a concrete test of your system's receive capability.
- Frequency coordination: 23cm calling frequency is 1296.1 MHz (SSB), with JT65c/Q65 EME activity centred on 1296.100 MHz. Local and regional contacts use 1296.1–1296.5 MHz by convention in most regions.
| Symptom | Most likely cause | Diagnosis | Fix |
|---|---|---|---|
| High SWR across entire 1270–1310 MHz sweep | Driven element shorting to boom — no PTFE insulators; or N-type connector wired incorrectly at feedpoint | Ohmmeter from N-type centre to flange — should read ~100 Ω (folded dipole resistance), not 0 Ω | Install PTFE insulators at driven element position; verify N-type centre connects to one side of gap and flange to the other, not both to the same side |
| SWR minimum 20–40 MHz above 1296 MHz | Boom correction not applied — elements too short; or driven element folded dipole too narrow | Verify boom correction was added to all element lengths from the calculator; measure folded dipole width | Add 1mm per side to folded dipole; if directors are also short, the boom correction formula was not applied correctly — recalculate all element lengths |
| SWR minimum below 1270 MHz | Elements too long — boom correction over-applied or design frequency was set incorrectly in calculator | Measure driven element folded dipole total width; compare to table value | File 1mm per side from folded dipole; verify calculator was set to 1296.1 MHz design frequency |
| Gain appears very low — signals weak compared to other 23cm stations | Feedline loss without mast-head LNA; or element position errors across the array | Measure SWR at antenna directly vs at shack — large difference confirms feedline loss; check element positions with caliper | Install mast-head LNA immediately; upgrade to LMR-400 feedline; verify all element positions are within 1mm of table values |
| NanoVNA shows flat response — no variation across sweep | NanoVNA model does not cover 1296 MHz — original NanoVNA covers only ~900 MHz | Check NanoVNA model specs | Use NanoVNA-H4 or NanoVNA-V2; or borrow a microwave VNA from a local 23cm operator or club |
| SWR changes when mast is nearby | Metal mast too close to rear of antenna — coupling into rear elements | Compare SWR handheld vs on mast — large change confirms mast coupling | Add non-conductive standoff (fibreglass or PTFE rod, 15cm minimum) between boom and mast bracket; verify mast is not running parallel to elements |
How many elements for EME on 23cm?
A single 20-element Yagi (17 dBd) with a 0.5 dB NF mast-head LNA and 100W at JT65c or Q65 is the practical minimum for EME contacts. This allows working other single-Yagi stations and large-array stations. A 24-element Yagi (18 dBd) is more comfortable and makes noticeably more contacts. Two phased Yagis adds approximately 3 dB and significantly expands the reachable station pool. Most operators start with one 20-element Yagi, make their first EME contacts, then decide whether to expand the antenna system.
Why must I use N-type connectors at 23cm?
PL-259/SO-239 connectors have 0.5–1 dB insertion loss per connector pair at 1296 MHz plus significant impedance discontinuity. On a 23cm system where every 0.1 dB affects EME capability, PL-259 connectors waste a meaningful fraction of transmit power and degrade receive sensitivity. N-type connectors are specified to 11 GHz with under 0.1 dB insertion loss at 1296 MHz. SMA connectors are even better. There is no acceptable substitute for N-type or SMA on the 23cm band. Using PL-259 at 1296 MHz is simply incompatible with competitive EME operation.
Is a dish better than a Yagi array on 23cm?
A 1-metre dish at 1296 MHz produces approximately 24–25 dBd — equivalent to eight or more 20-element Yagis. For serious EME and long-distance work, a dish is ultimately the highest-performance approach. However, it requires a precision feed, accurate az-el tracking mount, and more complex installation than a Yagi. A 4-Yagi phased array (adding ~6 dB over a single Yagi) is often a better second step than going straight to a dish — it builds experience with 23cm while significantly improving performance. Once you have worked 100+ EME contacts with a Yagi array, you understand what a dish adds and whether it is worth the investment.
Can I use my regular NanoVNA for 23cm?
The original NanoVNA and NanoVNA-F cover only to approximately 900 MHz — insufficient for 1296 MHz. The NanoVNA-H4 and NanoVNA-V2 cover to 1.5 GHz and work well for 23cm SWR measurement. Before using any NanoVNA for 23cm, verify its upper frequency limit in the specifications. The NanoVNA-H4 is widely used by 23cm operators and costs approximately $60–80. Many amateur radio clubs also have members with microwave VNAs who will help verify antenna SWR at 1296 MHz.
What transmit power is needed on 23cm?
For local and regional line-of-sight contacts, 10–25W with a high-gain Yagi is fully adequate. For EME, 50–100W is the recommended starting point with a 20-element Yagi — this enables contacts with well-equipped stations during typical conditions. 200W opens up more of the EME contact pool. Power amplifiers for 23cm are available from Kuhne Electronics, SSB Electronics, and similar suppliers, or homebuilt using LDMOS or GaN transistors. The transmit chain — radio, amplifier, and feedline — is typically the most expensive part of a 23cm EME station.
How do I get started on 23cm if I know no one on the band?
The 23cm calling frequency is 1296.1 MHz. Running JT65c or Q65 with WSJT-X during EME activity weekends (check the ARRL contest calendar and EME2.net for dates) produces contacts with distant stations on a first outing even with a modest antenna. The moonbouncers.com and EME2.net online chat systems allow pre-scheduling contacts and announcing your presence before getting on the air. The 23cm community is active and extremely welcoming to new operators — posting on these forums before your first session is the fastest path to making a first contact and getting experienced help with your station setup.