Central lesson: The radiator and return-current geometry create the radiation pattern. An ideal 4:1, ideal 5:1 or ideal lossless feed-point tuner does not independently reshape the normalized far field when the geometry and current distribution remain unchanged.
Two Realistic Education Profiles
| Profile | Geometry | Match evidence | What it teaches |
|---|---|---|---|
| Classic 4:1 field-reference | Full SS25 and four modeled 25 ft radial wires | Bob’s rounded third-party SWR curves | Fixed full-length broadband pattern progression |
| MPAS-derived 5:1 guide | Band-adjusted SS17/SS25 and one 25 ft counterpoise | MPAS Lite guide SWR starting points | Portable-burden and upper-band geometry trade-offs |
These are different complete profiles. Pattern differences must be credited to radiator and return geometry—not nominal transformer ratio.
The Most Important Comparison
The full SS25 model develops a 47° principal lobe on 10 m and 53° on 6 m. The band-adjusted MPAS guide geometry keeps the modeled principal lobe approximately 27–40° across 30–6 m. This is why a good SWR must never be presented as proof of the most useful DX takeoff angle.
Documented Match Starting Points
The two curves have different fixtures and evidence provenance. They are educational anchors, not a controlled head-to-head product specification. Real transformer, tuner, coax and common-mode losses remain additional quantities.
Classic Full-SS25 Pattern Gallery
Controlled R002 model: 7.62 m uniform vertical, four 7.62 m sloping radial wires, 0.1524 m feed point and declared average ground. Hardware, taper, coax, choke, network loss and common-mode current are omitted.
MPAS Guide-Geometry Pattern Gallery
Controlled R003 models: optional SS25 on 80/40 m; SS17 at 17 ft on 30/20/17 m; SS17 at 12 ft on 15/12/10 m; SS17 at 5 ft on 6 m; one 25 ft counterpoise.
Band-by-Band Reading
| Band | Classic full SS25 result | Operator interpretation |
|---|---|---|
| 80 m | −3.26 dBi modeled peak at 28° before complete-system losses | Electrically short and matching/ground-loss sensitive |
| 40 m | −1.16 dBi at 27° | Useful geometry; dedicated loaded paths are SS17 + M-COIL and SS25 + M25-COIL |
| 30 m | −0.45 dBi at 26° | Important CW/digital band omitted from Bob’s test but not from the antenna programme |
| 20 m | −0.26 dBi at 24° | Favourable portable-DX opportunity pending real network loss |
| 17 m | +0.01 dBi at 22° | Favourable modeled principal lobe |
| 15 m | +1.13 dBi at 18° | Strong low-angle opportunity with installation-dependent lobes |
| 12 m | +0.28 dBi at 16° | Lowest modeled principal-lobe elevation in R002 |
| 10 m | +2.37 dBi at 47° | Higher-order mode raises the main lobe; high gain is not automatically useful DX gain |
| 6 m | +3.92 dBi at 53° | Use the shorter guide geometry unless a specific full-length pattern is desired |
How to Interpret These Results
Use these graphics to compare pattern shape, principal-lobe elevation and relative realised gain within the stated model profiles. They are engineering decision tools for choosing a configuration and deployment—not laboratory certification of one guaranteed field result.
Actual performance changes with feed-network loss, tuner state, feed-line and common-mode behaviour, the selected radial or counterpoise system, soil, clearance and nearby objects. The Engineering Evidence Centre documents those variables, the current validation scope and the continuing measurement programme.
Evidence boundary: Every graphic on this page is NEC-4 simulation or evidence-anchored education. None is presented as a measured far-field product specification.
