I'm wanting to figure out how much gain, in dB, coupling a Select-A-Tenna and utility groundwire is adding to my radio's built-in loopstick. I've tried doing barefoot vs enhanced comparisons looking at the dBu on my Tecsuns, but that's not foolproof. The stronger stations desense the radio, skewing the readings. I've seen stations with only "25 dB" gain and others with a little over 50. In one case I briefly saw a ~28 dBu station flash 98 dBu when I added the big antennas, until modulation on a local (80 dBu barefoot) signal desensed it by about 20 dB or so.
I also tried noting overload characteristics at home with the big antennas, vs. near a transmitter, but until this past week I don't think my comparisons weren't really valid. (I would test the same station at different distances, but be unable to get close enough to the tower to duplicate the behavior, or would be able to duplicate it but with different stations.)
My preferred method would be to find a place where the strongest signal, when enhanced, still wouldn't overload the radio, but I'd probably have to go to the Arctic shore of northern Canada at midday for that. (Unless someone has a better way that won't require traveling far out of town, or using an expensive FIM or communications receiver?)
Meanwhile, though, I recently made a couple comparison videos of my PL-398mp's reception of 760 KFMB.
One video was recorded at 32° 50' 33.70" N,117° 1' 31.65" W near CA-52 and Mast Blvd in Santee, CA, using just the PL-398mp's built-in lopstick last week. I was parked on the eastbound onramp.
The other video was recorded at 32° 45' 43.55" N,116° 56' 45.00" W near Fuerte school near my house, using the PL-398mp plus SAT & utility groundwire last night.
You may notice, like I did, that the overloading on 760 was equally severe in both videos, and the dBu reading on 1520, the 2nd harmonic, was about 81-83 dBu. I was thinking, since in both cases the radio behaved virtually identically...
If I could calculate the field intensity at both places, I could hopefully get a decent estimate of antenna gain by figuring the difference. It should be fairly straightforward to use the charts (or better yet Radio-TimeTraveller Bill's Field Strength Calculator - although it won't do multiple-conductivity paths, it's ok for this example) to calculate the strength near Fuerte School, which I'm guessing to be around 120-140 mV/m or so. (I'm on my phone so can't calculate exactly, but am basing my figure on a comparable strength station that's already been calculated.)
How would I calculate the field at the coordinates listed near CA-52 & Mast Bl, though? I think if I had this info I could estimate the antenna gain. If I was to make a wild guess, I'd figure on something like 100-300 V/m or so, but I'd like a more accurate calculation if at all possible. (A 70 dBu gain, like I mentioned in a previous example whose results I didn't trust, would mean going from 130mV to about 400V. For those of you worried about RF safety, FCC 1.1310 specifies general population maximum exposure as 614 Volts/meter at 760 kHz, and I was way beyond the fence in a publicly accessible area.)
Or, is there a better and more accurate method of calculating inductively-coupled antenna gain that doesn't involve purchasing any additional equipment, or traveling too far outsde the San Diego area?
I also tried noting overload characteristics at home with the big antennas, vs. near a transmitter, but until this past week I don't think my comparisons weren't really valid. (I would test the same station at different distances, but be unable to get close enough to the tower to duplicate the behavior, or would be able to duplicate it but with different stations.)
My preferred method would be to find a place where the strongest signal, when enhanced, still wouldn't overload the radio, but I'd probably have to go to the Arctic shore of northern Canada at midday for that. (Unless someone has a better way that won't require traveling far out of town, or using an expensive FIM or communications receiver?)
Meanwhile, though, I recently made a couple comparison videos of my PL-398mp's reception of 760 KFMB.
One video was recorded at 32° 50' 33.70" N,117° 1' 31.65" W near CA-52 and Mast Blvd in Santee, CA, using just the PL-398mp's built-in lopstick last week. I was parked on the eastbound onramp.
The other video was recorded at 32° 45' 43.55" N,116° 56' 45.00" W near Fuerte school near my house, using the PL-398mp plus SAT & utility groundwire last night.
You may notice, like I did, that the overloading on 760 was equally severe in both videos, and the dBu reading on 1520, the 2nd harmonic, was about 81-83 dBu. I was thinking, since in both cases the radio behaved virtually identically...
If I could calculate the field intensity at both places, I could hopefully get a decent estimate of antenna gain by figuring the difference. It should be fairly straightforward to use the charts (or better yet Radio-TimeTraveller Bill's Field Strength Calculator - although it won't do multiple-conductivity paths, it's ok for this example) to calculate the strength near Fuerte School, which I'm guessing to be around 120-140 mV/m or so. (I'm on my phone so can't calculate exactly, but am basing my figure on a comparable strength station that's already been calculated.)
How would I calculate the field at the coordinates listed near CA-52 & Mast Bl, though? I think if I had this info I could estimate the antenna gain. If I was to make a wild guess, I'd figure on something like 100-300 V/m or so, but I'd like a more accurate calculation if at all possible. (A 70 dBu gain, like I mentioned in a previous example whose results I didn't trust, would mean going from 130mV to about 400V. For those of you worried about RF safety, FCC 1.1310 specifies general population maximum exposure as 614 Volts/meter at 760 kHz, and I was way beyond the fence in a publicly accessible area.)
Or, is there a better and more accurate method of calculating inductively-coupled antenna gain that doesn't involve purchasing any additional equipment, or traveling too far outsde the San Diego area?