9:1 UnUn (SDR or QRP)


SKU: LMK-003 Categories: , Tags: , , ,



This product has been updated for 2021 following feedback from several happy users. The internal transformer has changed from an Iron core to a new ferrite core which provides improved impedance matching from 1MHz up to 30MHz. It is also now supplied with all Marine Grade A4 Stainless Steel hardware and is fully potted to ensure a long service life.


This high quality 9:1 UnUn was made to team up with an SDR receiver such as the SDRPlay RSP range to provide an effective impedance matching network for an end fed long wire antenna. I use one myself for holidays and weekends away and it works great.

The UnUn is hand wound with 25 SWG (0.5mm) enamelled wire on a ferrite core so could also be used for QRP transmit. I’ve not tested this but should be OK for 5W or under.

The enclosure is a genuine high quality Hammond with 2 flanges to allow for multiple fixing or hanging methods and measures 35mm wide x 76mm high (including mounting lugs) x 20mm deep. The connection studs are all marine grade A4 Stainless Steel with wing nuts for the antenna and ground to allow an easy install and quality coax connectors are used on both versions. The antenna output is marked with a dot on the side of the unit to allow for quick and easy identification. The box is fully potted to ensure excellent weather protection and provide a long service life.

You can choose between two different connectors:

  • BNC
  • SMA

Each unit is individually tested and is supplied with 2 x 4.3mm insulated ring terminals.

Recommended wire element lengths (feet):

35, 44, 49, 53, 59, 71, 89, 98, 124, 146, 162 & 174.

Please note that all of my products are hand made in my own workshop and may be subject to slight manufacturing variations.

Additional information

Weight 0.12 kg
Dimensions 7.6 × 7.5 × 2 cm



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