I have had some success with very weak signals. A few years ago I tried tvfool reports for my location by zip code, address without height, and address at 5 ft height. I also did a recent update with NMs for 5 ft, which is the height of my antenna because it is in the common area, not my controlled area.
Code:
Real tvfool-zip tvfool-address address 5 ft Update 5 ft 5/7/2015
CH dBm path dBm path dBm path NM(dB) dBm path
7 WTPC -41.9 LOS -74.0 2Edge -81.0 2Edge 9.9 -81.0 2Edge
9 WSKY -58.1 LOS -88.2 2Edge -95.5 2Edge -4.6 -95.5 2Edge
11 WGBS -73.8 LOS -98.9 2Edge -114.6 2Edge -23.8 -114.6 2Edge
13 WVEC -38.6 LOS -71.1 2Edge -78.0 2Edge 12.8 -78.0 2Edge
16 WHRO -32.4 LOS -62.3 2Edge -72.2 2Edge 18.6 -72.2 2Edge
17 WKTD -50.0 LOS -87.9 2Edge -95.4 2Edge -4.6 -95.4 2Edge
20 WUND -93.8 2Edge -117.9 Tropo -117.9 Tropo -27.0 -117.9 Tropo
22 WRIC -57.9 LOS -87.7 2Edge -94.3 2Edge -3.5 -94.3 2Edge
25 WTVR -60.4 LOS -90.1 2Edge -96.5 2Edge -5.6 -96.5 2Edge
26 WRLH -58.5 LOS -88.5 2Edge -95.1 2Edge -4.2 -95.1 2Edge
29 WVBT -32.7 LOS -69.2 2Edge -77.5 2Edge 10.6 -80.2 2Edge
31 WAVY -32.8 LOS -66.2 2Edge -75.6 2Edge 15.2 -75.6 2Edge
33 WTVZ -33.3 LOS -63.4 2Edge -73.2 2Edge 17.6 -73.2 2Edge
40 WTKR -33.9 LOS -64.4 2Edge -74.0 2Edge 16.9 -74.0 2Edge
42 WCVE -62.1 LOS -92.6 2Edge -98.7 2Edge -7.9 -98.7 2Edge
45 WNLO -55.3 LOS -93.4 2Edge -101.7 2Edge -10.9 -101.7 2Edge
46 WPXV -35.4 LOS -67.0 2Edge -76.4 2Edge 14.4 -76.4 2Edge
50 WGNT -34.8 LOS -69.6 1Edge -79.3 1Edge 8.5 -82.4 1Edge
What prompted me to make some tests, was that I had been asked if there was a way to hunt for and measure channels that had been missed during a tuner scan. If the tuner doesn't pick them up, we don't know why, and what could be done to receive them.
For the first test I connected my CM4221 antenna, which is outside close to ground level, to my Sadelco 719E signal level meter (SLM) with a short coax jumper (SCJ), and took some readings of my channels.
CM4221 > SCJ > 719E SLM
For the second test I added my CM7777 preamp to see if I could read the weak channels.
CM4221 > SCJ > CM7777 > SCJ > CM0747 Power Supply > SCJ> 719E SLM
Code:
Real Test 1 Test 2 Amp Gain
RF Equiv Equiv
CH dBmV dBm dBmV dBm dB
16 -6.9 -55.7 +19.0 -29.8 25.9
9 -10.2 -59.0 +13.1 -35.7 23.3
31 -12.2 -61.0 +12.1 -36.7 24.3
33 -9.0 -57.8 +14.8 -34.0 23.8
40 -9.0 -57.8 +15.1 -33.7 24.1
46 -19.9 -68.7 +6.2 -42.6 26.1
50 -22.0 -70.8 +2.9 -45.9 24.9
Amp Gain is the difference between the two tests and
varies because the signal strengths changed between tests.
I was able to measure a few weak ones that don't always show up after a scan with the preamp:
Code:
Signal Strength at Antenna
Terminals before 24 dB Preamp
dBm
17 NA NA -10 -59 NA -83
19 NA NA -26 -75 NA -99
22 NA NA -20 -69 NA -93
42 NA NA -25 -74 NA -98
45 NA NA -8 -57 NA -81
Antenna enclosure on porch for CM4221 and folded dipole for VHF-High in attachments. The signals have to travel through the openings in the decorator blocks on their way to the antenna. Not much attenuation for UHF, but a lot more for VHF. The openings act like a high-pass filter, as their size is related to wavelength.