5:1 Baluns/Ununs

5:1 CUBE™ Unun – Model CU-5-1500 (50:250 Ohm, 1.8-61 MHz, 1.5KW PEP)

Application. For traveling wave, end fed or portable 20-31 foot vertical antennas the 5:1 unun makes a good transformer for converting 50 ohm coax to a 250 ohm feed point. If you use the antenna on multiple bands, the feed point impedance may not always be 250 ohms and use of the unun at high (>350 ohms) or low (<100 ohms) will require reduced power input or the unun may have its power ratings exceeded and damage to the unun may occur. The (5:1 conversion ratio will change for loads other than 250 ohms unbalanced.

Typical application:

CU 5 1500 antenna - 5:1 Baluns/Ununs

Also available as a balanced output – CB-5-1500

Portable operation is fun but also brings challenges to the radio operator concerning receiver “noise” levels, RF interference from adjacent sources including close by transmitting stations, and RFI from portable generators. A typical scenario and some suggested Palomar product solutions are shown in the picture.

Portable Operation RFi Reduction Picture png - 5:1 Baluns/Ununs

Portable operation is typical of ham radio operating events such as Field Day, Summits on the Air, Route 66 events, National Parks on the Air, California QSO party, DXpeditions, and emergency operation command posts, etc.

Suggestions

Each low power operating station with a generator should have:

  1. Generator RFI Kit (Part # RFI-GEN) with FSB31-1 ferrite filters at each end + Nylon ties for security
  2. Transceiver RFI Kit (Part # RFI-XCVR)
  3. Laptop RFI Kit (Part # RFI-1C)
  4. Coax Cable Noise Filter (Part # CMNF-1)
  5. Bullet-55 portable HF end fed antenna system


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