Thank you for the report of your test with the FM dipole; sorry to hear that it didn't give you 2 and 4.
There are two factors involved. The antenna might not be long enough to give the gain that you need for 2 and 4. My test of the FM dipole showed that it had about 11 to 12 dB less gain than a folded dipole 88" long using THHN 14 gauge wire.
The other factor is the noise level, which is very high on channels 2 and 4 from electrical interference. Your indoor antenna needs to be located where the noise level is as low as possible.
My tests have shown me that the noise level with the FM dipole is also lower by about the same amount as the signal, giving the same SNR. This means that the FM dipole might have enough gain for the signals, but there isn't enough difference between the signal and the noise.
I made some more tests yesterday to compare tbe 88" folded dipole with the FM dipole, using the channel 3 output of a Channel Master converter box as a test signal and my Sadelco 719E signal level meter. The meter has a speaker so that I can hear the sound of the noise and the video carrier of the signal, in addition to being able to measure their strength. I used the meter on the left:
88" folded dipole
signal: -3 dBmV (-52 dBm)
noise: -13 dBmV (-62 dBm)
The signal is 10 dB stronger than the noise. A digital signal needs to be at least 15 dB stronger than the noise for reception. I could have used a stronger test signal to make the difference greater than 10 dB, but it didn't matter for this test to compare the two antennas for gain.
FM folded dipole
signal: -15 dBmV (-64 dBm)
noise: -26 dBmV (-75 dBm)
The signal is 11 dB stronger than the noise with the FM dipole.
The 88" folded dipole has 12 dB more gain than the FM folded dipole.
There are two thngs you can try:
1. Build an 88" dipole like I did
2. Try to find a location that has less electrical noise interference
The second one will require trial-and-error by you because you don't have a meter to measure the noise. You can suspect interference from CFL and LED lamps. You can also use a portable radio operating on batteries that will tune the AM broadcast band to hunt for noise sources. Tune it to a vacant frequency at the low end and at the high end of the AM broadcast band. Sometimes a high noise level on the broadcast band will also indicate noise on VHF channels. It doesn't need to be an expensive radio. I use a Jensen MR-550 AM/FM Portable radio. Use it on AM not FM; it works better on AM to hunt for noise. The built in AM loop stick antenna acts as a direction finder.
Maybe you could also set up a temporary antenna outside as a test.
What balun did you use to connect the FM dipole to your TV?