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« on: July 24, 2016, 0028 UTC »
As the OP on this thread, I thought I would give you an update on my experiences with the RA0SMS mini-whip active antenna. I actually ordered two of them because I have an antenna phasing unit and wanted to try some phasing experiments with them. My order arrived in only two weeks – much faster than I expected! Unfortunately, I haven’t been able to mount them properly (high and far from the house) yet. My first experiences were with them located indoors (bad idea!). I’ve been battling RFI for some time now in my listening area. I use common-mode chokes and a galvanic isolator on the antenna lead-in. The antennas are definitely sensitive to local RFI sources as expected, they make great RF sniffers! I briefly moved one outside (onto a wood fence) and compared it to my indoor mag loop antenna. The station signal levels were similar but the active was still picking up RFI (from somewhere) pretty well! The receiver noise floor when using the antenna is fairly low – can be higher or lower than the mag loop depending on the frequency. One interesting (bad) thing I discovered with the active antenna was the presence of images from a strong local AM station on 1230 Khz (1 KW, 1 mile away) – these were at harmonic frequencies (e.g. 4920 and 6150). Those are not seen with the mag loop so I am calling them images. I hope to get at least one of the mini-whip antennas mounted outside better in the near future. With proper installation and grounding, I’m sure they could be a reasonable choice for someone with limited real estate and/or finances. Hopefully I will have more information to share later.
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