9/1 (450 Ohm to 50 Ohm) UNUN as “pre-match unit” for use with multiband endfed non resonant longwire antennas.
The endfed multiband “longwire” antenna is a popular and simple wire antenna that is often used to be QRV rapidly on several different amateur radio frequency bands.
Depending on the on-site possibilities, different wire lengths can be chosen. Lengths can vary between some 9 meters until the longest length feasible. Longer wire lengths give some gain, and allow more efficient use of the lower amateur radio bands. Wire lengths of roughly 9.5,13,19 and 38 meters are popular.
Mostly, the antenna wire is installed in an “Inverted L”, “or “slooping” configuration.
The feedpoint impedance of such a “random” wire length (referred to ground) varies widely, depending on the frequency used and the setup shape of the antenna.
In order to transform the average feedpoint impedance of the antenna within the comfortable tuning range of an good a-symmetric antenna tuner, a 9/1 UNUN impedance transformer is often used.
This transformer thus acts as a “Pre-Match Unit”.
Often, some experimenting is needed to achieve a good compromise and optimum results.
Optimum results can be expected when the transformer is installed near the ground, with its “cold” side connected to a good RF ground. (i.e. earth stake with radials).
- Impedance transformation ratio: 9/1
- Frequency range: 1.5 to 30 MHz.
- Maximum power: 1200W PeP @ VSWR < 2,0/1 , (ICAS)
- Insertion loss: < 0.2 dB.
- Intrinsic VSWR: <1.4/1
- Tamper proof, UV resistant polycarbonate housing.
- Coaxial connector potted internally.
- Aluminum mounting bar.
- M6 SS connection terminals.
Price: 98 Euro.
- Option N-connector (N-connector instead of SO239): + 6 Euro.