Interstation Interference Stubs
From Contesting
From an email by K1RX on the YCCC Reflector, Nov 22, 2000
This list I found with some old notes from my days at the K1OX Multi-Multi.
| Band | Xmit Purpose | Design Frequency | Electrical Length | Physical Length (66% Vp/RG-213) |
|---|---|---|---|---|
| 80 | Null 40/20/10 |
2 waves @ 28.04 1 wave @ 14.02 1/2 wave @ 7.01 | 70.18 ft. | 46.32 ft. (Shorted) |
| 40 | Null 20/10 |
1/2 wave @ 14.025 1 wave @ 28.05 | 35.08 ft. | 23.15 ft. (Shorted) |
| 20 | Null 10 | 1/4 wave @ 14.025 | 17.54 ft. | 11.6 ft. (Shorted) |
| 20 | Null 15/40 |
1/4 wave @7.015 3/4 wave @ 21.045 | 35.08 ft. | 23.15 ft (Open) |
| 10 | Null 20 |
1/4 wave @ 14.025 1/2 wave @ 28.05 | 17.54 ft. | 11.6 ft. (Open) |
| 10 | Null 15/40 |
1/4 wave @ 7.015 3/4 wave @ 21.045 | 35.08 ft. | 23.15 ft (Open) |
I would suggest using a MFJ-259 device (or similar) to fine tune the performance. Hardline dimensions will be longer due to the higher velocity of propagation (typically 82 to 84%). Experiment, start longer than needed, then cut an inch or so at a time to get it right on.
