I know that one of the measures of success of a small transmit loop antenna is the high Q (and thus narrow bandwidth), which leads to good Tx efficiency. According to the Mazzoni data sheet, the bandwidth of the Baby Loop on 20 meters is 6 KHz. I think I have installed my antenna according to their instructions (2 meters above the ground surface). I have a NanoVNA, which can measure the VSWR profile right at the antenna (i.e. not going through any other station gear). My VSWR plot on 20 meters is about 31 KHz. wide (between points where the VSWR is 2.6:1), which is about 5X as wide as they say in the data sheet. Has anyone else measured the VSWR bandwidth of a Baby Loop? I am not too alarmed that my SWR is a little higher than their plot in the data sheet, but to have 5X the bandwidth makes me worry that my radiation efficiency is taking a huge hit for some reason. At Mazzoni's recommendation I installed eight radials under the antenna, out to about 2.5 meters from the mounting pole. Didn't seem to make much difference, but they are probably useful. The antenna is mounted at least 10 meters from any homes. I don't see any suspicious conductors near the antenna. The antenna is guyed with non-conductive rope. Adjusting the position of the coax and other cables doesn't make much difference to the BW. Any comments? Has anyone else measured the VSWR bandwidth of their Baby Loop antenna? I'm using the antenna, and it works fine on all bands. I just want to make sure it's not broken, or installed improperly, or maybe I'm interpreting the Mazzoni spec wrong. -- Tom, W7GT
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