The first picture is the spectrum of the B&K 415 RF output from about 38 to 49 MHz. Its varies about 3 dbV.
The second picture shows the downconverter output with a 20MHz sine wave to shift the 45.75 MHz sweep down to 25.75 MHz (45.75 - 20 = 25.75). Other harmonics show up, but the TV IF only amplifies its IF range signals (19.75-27.25 for this case). This downconverted output also varies by about 3 dbV.
If your old TV has a different IF range you calculate the value to enter into the sine wave generator by taking the 45.75 - your_TV_video_carrier_frequency = sine_wave_frequency. In the case of this TS721 its 45.75 - 25.75 = 20MHz.
The third picture shows the display of the B&K 415 scope XY outputs with the downconverter RF connected to an RCA 721TS tuner converter sweep input test point and with a direct probe (a scope probe set to 1X) connected to the video detector sweep test point. Yes, the B&K 415 markers all work since they are added by the B&K after the signal comes from the TV and the B&K then drives the scope H&V inputs.
The scope I am using is my new Digilent Analog Discovery USB scope. It's limited to a 50 MHz bandwidth, but it includes a bunch of features like a spectrum analyzer (FFT), a logic analyzer, an I2C and SPI serial protocol analyzer and a lot more. Here is a link if you are in the market:
http://www.digikey.com/en/product-hi...FRGBswodfAoO-Q
Be sure to get the BNC adapter as it expands the input frequency range when using scope probes instead of the fly-leads:
http://www.digikey.com/product-detai...073-ND/4840860
I thinks it's a great value for $280.
The fourth picture is the IF spectrum input to the video detector. It makes it easy to get the traps tuned to exactly 21.25MHz.