Simple QRP projects, 10m, 8m, 6m, 4m, FT8, 160m, WSPR, LF/MF, sub-9kHz, nanowaves and other random stuff, some not related to amateur radio.
15 Jun 2017
Top Band Loft Antenna
Some years ago, at the old QTH, I was looking for an easy 160m antenna, mainly for local use and WSPR. This antenna was the result. It exceeded all expectations.
Yes, this type of antenna can be VERY effective. Most hams do not recognise that the radiating part of the antenna is where there is RF current, and everything you can do to get the RF current up in the air helps. I have also made such an antenna, on 40m, but designed the loading-coil and capacitance of the top-hat (several large diameter coffee-cans) to be a resonant series circuit at the freqency required. This then top-loads the antenna, with a low impedance, and small reactance (if resonant) and makes the up-feed radiate very well. I made a roughly 1/4 wave vertical like this, top-loaded and high-Z fed at the bottom. i did not require huge radials, the radiating part of the antenna is at the top and it worked a treat! resonant top-loading is the way to go!. See http://users.tpg.com.au/users/ldbutler/ReverseFeedTopLoading.htm for an interesting read. Cheers, Hugh G6AIG
Yes, this type of antenna can be VERY effective. Most hams do not recognise that the radiating part of the antenna is where there is RF current, and everything you can do to get the RF current up in the air helps. I have also made such an antenna, on 40m, but designed the loading-coil and capacitance of the top-hat (several large diameter coffee-cans) to be a resonant series circuit at the freqency required. This then top-loads the antenna, with a low impedance, and small reactance (if resonant) and makes the up-feed radiate very well. I made a roughly 1/4 wave vertical like this, top-loaded and high-Z fed at the bottom. i did not require huge radials, the radiating part of the antenna is at the top and it worked a treat! resonant top-loading is the way to go!. See http://users.tpg.com.au/users/ldbutler/ReverseFeedTopLoading.htm for an interesting read.
ReplyDeleteCheers, Hugh G6AIG