Boom correction for
through the boom insulated elements on 2 meters & 70cm.
Proven accurate for boom diameters smaller than .055 wavelengths.
Formula: C = 12.5975*B - 114.5*B^2
| Correction for 2 meters G3SEK | ||||
|---|---|---|---|---|
| Boom diameter | Correction | Add | ||
| Inches | mm | Percent | Inches | mm |
| 0.750 | 19.050 | 10.56% | +0.792 | +2.02 |
| 0.875 | 22.225 | 12.14% | +0.1062 | +2.70 |
| 1.000 | 25.400 | 13.66% | +0.1366 | +3.47 |
| 1.125 | 28.575 | 15.13% | +0.1702 | +4.32 |
| 1.250 | 31.750 | 16.54% | +0.2068 | +5.25 |
| 1.375 | 34.925 | 17.90% | +0.2462 | +6.25 |
| 1.500 | 38.100 | 19.21% | +0.2882 | +7.32 |
| 1.750 | 44.450 | 21.67% | +0.3792 | +9.63 |
| Correction
for IØJXX's 2 meters antennas |
|
|---|---|
| Boom diameter |
Correction |
| mm | mm |
| 20 | +1.50 |
| 22 | +1.75 |
| 25 | +2.50 |
| 30 | +4.00 |
| 35 | +5.40 |
| 40 | +7.00 |
| Correction
for DJ9BV's 2 meters antennas |
|
|---|---|
| Boom diameter |
Correction |
| mm | mm |
| 20 | +2.00 |
| 25 | +3.00 |
| 30 | +5.00 |
| 35 | +6.00 |
| Correction for 70 cm G3SEK | ||||
|---|---|---|---|---|
| Boom diameter | Correction | Add | ||
| Inches | mm | Percent | Inches | mm |
| 0.787 | 20.000 | 25.00% | 0.1968 | +5.00 |
| 1.000 | 25.400 | 20.00% | 0.2362 | +6.00 |
| 1.125 | 28.575 | 24.50% | 0.2756 | +7.00 |
| 1.250 | 31.750 | 25.20% | 0.3149 | +8.00 |
| 1.375 | 34.925 | 25.77% | 0.3543 | +9.00 |
| Correction used by K1FO on 70 cm | ||||
|---|---|---|---|---|
| Boom diameter | Correction | Add | ||
| Inches | mm | Percent | Inches | mm |
| 0.875 | 22.225 | 28.98% | 0.2536 | +6.44 |
| 1.000 | 25.400 | 31.97% | 0.3198 | +8.12 |
| 1.125 | 28.575 | 33.49% | 0.3769 | +9.57 |
| 1.250 | 31.750 | 36.00% | 0.4501 | +11.43 |
| 1.375 | 34.925 | 38.00% | 0.5226 | +13.27 |
| Correction used by VE7BQH on 70 cm | ||||
|---|---|---|---|---|
| Boom diameter | Correction | Add | ||
| Inches | mm | Percent | Inches | mm |
| 0.630 | 16.000 | 22.94% | 0.1445 | +3.67 |
| 0.750 | 19.050 | 25.93% | 0.1945 | +4.94 |
| 0.875 | 22.225 | 22.50% | 0.1969 | +5.00 |
| 1.000 | 25.400 | 27.56% | 0.2756 | +7.00 |
| 1.125 | 28.575 | 31.50% | 0.3544 | +9.00 |
| 1.250 | 31.750 | 33.67% | 0.4210 | +10.69 |
| 1.375 | 34.925 | 33.33% | 0.4584 | +11.64 |
| Correction
for 70 cm IØJXX antennas |
|
|---|---|
| Boom diameter |
Correction |
| mm | mm |
| 20 | +5.7 |
| 22 | +6.2 |
| 25 | +7.7 |
| 30 | +10.0 |
| 35 | +12.8 |
| 40 | +15.1 |
|
Correction
for DJ9BV's |
|
|---|---|
| Boom diameter |
Correction |
| mm | mm |
| 20 | +5.00 |
| 25 | +7.00 |
| 30 | +10.00 |
| 35 | +12.00 |
Note: there is no difference in correction factor for round or square booms.
The following are some average
element diameter corrections for 2m to scale an antenna for a
different diameter element.
It is not so simple as just adding a simple linear correction as
the overall taper changes depending on the diameter of element.
As a consequence the correction varies from reflector to last
director. Eg: 6.25mm to 5mm diameter correction on a 10 el. DJ9BV
antenna is 2 mm at the reflector and 6.91mm at director 8.
The above was calculated using the YOC 5.0 scaling feature.
| Element diameter correction (2 meters) | |||||
|---|---|---|---|---|---|
| Diameter (mm) | 6.35 | 5.00 | 4.76 | 4.00 | 2.00 |
| Add (mm) | 0.00 | 4.50 | 5.00 | 8.00 | 12.00 |
| Correction
factor for Cushcraft and Cudee style mounted elements (2 meters) |
||
|---|---|---|
| Company | Inches | mm |
| Cushcraft | 0.25 | 6.35 |
| Cudee | 0.25 | 6.35 |
Dopt = (wavelength/2) * sin(beamwidth/2)
Good results can be obtained down
to 90 percent of the above formula if a smaller stacking frame is
desired.
Closer stacking than 90 percent of DL6WU's formula will result in
a degradation of G/T.