Hello -

I am setting up an antenna for receive only SW listening purposes - to be used with a SDR and several old boat anchor radios.

I am building a new-old-stock Mosley SWL-7 trap dipole antenna I bought on eBay. The antenna comes with 100 feet of 75 ohm balanced-line for the feed line (very thin/small) and a direct connect between antenna and feed line at the center, no balun.

The antenna by design is resonant on specific SW broadcast bands.

My question is - do I need to use the full 100 feet of feed-line to keep the antenna resonant, or can I shorten the feed line to fit my space without impacting antenna resonance?

I believe that if I had a balun and coax, the feed line length would only matter due to loss of signal strength on longer coax runs, but with the balanced line and no balun, I am concerned with changing the antenna's characteristics if I shorten the line.

Please let me know.

Thanks,

John