Merovingian
Member
- Joined
- Sep 17, 2006
- Messages
- 206
I finally got one of those NanoVNA's people have been talking about. I have never used one before so I have been playing with mine for the last hour or so, just seeing what I am getting as far as SWR and Impedance goes on my three SDR/scanner antennas. As I expected, my Diamond discone and Siro UHF discone do better on some frequency ranges and a little worse on others. The surprise came when I hooked up my Wellbrook loop antenna and did a sweep from 0.1 MHz to 30 MHz. The SWR and Impedance was bad to terrible on all frequencies and some parts it was horrendous (see the attached screenshot).
I have been using my loop for about a year now and in my limited "year" experience with receiving SW with the loop I thought it had been doing well. I am not an expert with all of this but I consider an SWR of 2.0 or less to be "good" and 1.5 or less to be "very good". Anything above 2.0 I would think the antenna was stepping into "bad matching" territory, maybe I'm being overly conservative, I'm not sure. . . When the Loop's best SWR measurement of 3.54:1 at 22 MHz and an impedance of 14 ohms and its worst SWR of 11:1 at 18.47 MHz and impedance of 710 ohms, being fed through a 50 ohm cable makes me wonder how it can receive anything at all. I wasn't expecting the range of frequencies the loop can receive to be perfect or anything nor to have an SWR below 2.0 for everything but 11:1? and an impedance well below 50 and well above 50?
So, is this being measured correctly? The loop seems to work so maybe all of this isn't very critical at these low frequencies? I'm also guessing this is how all loops like this are?
Thanks
I have been using my loop for about a year now and in my limited "year" experience with receiving SW with the loop I thought it had been doing well. I am not an expert with all of this but I consider an SWR of 2.0 or less to be "good" and 1.5 or less to be "very good". Anything above 2.0 I would think the antenna was stepping into "bad matching" territory, maybe I'm being overly conservative, I'm not sure. . . When the Loop's best SWR measurement of 3.54:1 at 22 MHz and an impedance of 14 ohms and its worst SWR of 11:1 at 18.47 MHz and impedance of 710 ohms, being fed through a 50 ohm cable makes me wonder how it can receive anything at all. I wasn't expecting the range of frequencies the loop can receive to be perfect or anything nor to have an SWR below 2.0 for everything but 11:1? and an impedance well below 50 and well above 50?
So, is this being measured correctly? The loop seems to work so maybe all of this isn't very critical at these low frequencies? I'm also guessing this is how all loops like this are?
Thanks