80m Resonance of the 807-xx is determined by choice of RMU
... NOT by adjusting the overall length of the antenna.
Changes to the overall length might improve 80m, but it
will affect the resonanceon on higher (harmonic) bands.
DO NOT CHANGE THE LENGTH OF THE ANTENNA !!!
Aerial-51 offers a choice of 4 different RMU's
for setting the resonance of the 807-xx antenna;
| RMU-R1 | RMU-R2 | RMU-75 | RMU-CW |
(The photo is intentionally fuzzy ... to confuse the copy cats.)
The RMU itself is very small and light as a feather, yet handles 1 kW of power in SSB/CW. It was co-developed be DJ0IP and DF4SA.
The printed circuit board has wires with solder lugs attached to both ends and is then encapsuled in heat-shrink tubing. Once encapsuled, they all 4 look alike.
Spiderbeam now has RMU circuit boards in stock
for ALL FOUR versions of the RMU.
Here are the approximate Resonant Frequencies*:
* Specifically, these are the frequencies where minimum SWR occurs on 80m. The actual "resonant frequency" for each is slightly lower than the frequencies shown here. Resonance can vary slightly from one QTH to the next and with height above ground.