Not just the pilot only, but the pilot or any spot on the whole signal that you want.
When I use my old Sadelco 719E signal level meter (SLM, originally designed for analog signals but usable for digital) and manually tune through the 6 MHz 8VSB DTV signal, I notice a slight increase in signal stength at the lower end of the channel which is caused by the pilot.
I do not use the pilot for signal strength readings, I make a reading at center channel. My Sadelco DisplayMax 5000 SLM (designed for analog and digital, OTA & cable) also uses center channel for a reading of digital 8VSB & QAM.
The readings for NTSC signals are made, of course, at the picture and audio carrier frequencies.
My Sadelo DispalyMax 800 can read digital signals two ways:
1. It scans the digital channel and then gives an average power reading derived from many readings across the channel. The display looks a lot like a spectrum analyzer display, and I can see if the top of the signal is flat or not.
2. The second way is to tune the meter to center channel for a reading. This gives me a real-time reading without having to wait for a scan that can be used for immediate feedback to help aim an antenna for max signal. It only gives a relative reading in that mode, so after aiming I can switch to the scanning mode for an accurate power reading in dBmV. Besides giving immediate feedback in the single frequency mode, the meter is more sensitive then down to about -35 dBmV VS about -20 dBmV in the scanning mode. The meter refuses to give a reading below -20 dBmV in the scanning mode.
The attachments show you what the display on the 800 looks like.
If the signal has enough SNR to decode, then you will see the pilot. I don't see any point in focusing on measuring the pilot to the exclusion of the rest of the signal.
Finding channels missed by tuner scan, Part 1 of 4
Good; that one is easier.
Ooops! I thought you were going to use an old field strength meter.
I made a few tests today using my old Sadelco 719E (less expensive version of the FS-4 that I bought when I retired in 1988) that showed me it is possible to hunt for, detect, and measure the missing weak channels. It was necessary to use my CM7777 preamp to read the weak ones, but I was able to do that without preamp overload because my strongest signals are weak enough to avoid overload. I used my 719E because it makes it possible to turn the tuning knob through the channels manually, just like a spectrum analyzer automatically would during its scan.
Here are the two meters. The one on the left is the Sadelco 719E; the upper knob is for UHF, the lower for VHF-lo, FM, and VHF-hi. The one on the right is the DisplayMax 800. I repeated the image in the attachments in case the link to my image host is broken.
If you are going to use the Sadelco DisplayMax 800, you will not be able to manually tune slowly through the freqency range, it will be necessary to enter the desired frequency on the keypad. You can, however, hop thru the range in fixed frequency increments of 125 KHz; the measurement bandwidth is 280 KHz. If you are going to use the pilot (see attachments), that frequency is just above the lower edge of the channel:
There is another problem. With the 719E I am able to listen to the noise of the channel as I tune through it to see if it rises above the noise floor. I don't know how that will work with the 800, but will try some more tests with it to develop a measuring technique.
I will post the data from the first tests that used the analog meter when I have more time, followed by a report on using the 800.
If you try to buy an old used Sadelco meter, make sure you get one that does VHF and UHF. The ones described as VHF and Super don't do UHF.
Finding channels missed by tuner scan, Part 2 of 4
In earlier posts retiredengineer asked a very intelligent question: Is there any way to hunt for, and measure channels missed during a scan? If there is, then it would be possible to know if simple improvements would enable the tuner to decode the signals, or if reception is impossible at that location.
I told him that even if he was able to find those weak channels, they might not have sufficient SNR or signal quality (few errors) to be decoded by the tuner. He said that it would be sufficient for now just to be able to find and measure them, so I made some tests using the equipment that I have.
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 UHF channels.
CM4221 > SCJ > 719E SLM
For the second test I added the UHF section of my CM7777 preamp to see if I could read the weak channels.
CM4221 > SCJ > CM7777 > SCJ > CM0747 Power Supply > SCJ> 719E SLM
Real Test 1 Equiv Test 2 Equiv Amp Gain RF CH dBmV dBm dBmV dBm dB 16 -6.9 -55.7 +19.0 -29.8 25.9 29 -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 * CH 40 pilot measured -7.0, 2 dB stronger; measurement bandwidth is 500 KHz ** CH 40 pilot measured +17.0, 1.9 dB stronger 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 with the preamp that usually don't show up after a scan. 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
I will make another test later with a tuner to see how many channels it can capture during a scan that day.