[Zenith6S321]

I did an alignment using the B&K415 45.75 MHz output down converted by 20 MHz to generate the 25.75 MHz IF needed by the RCA 721TS. I then took pictures of the B&K415 scope sweep display, a Wavetek 1002 scope sweep display, a 25.75 MHz IF frequency VA62A 10 bar multiburst (0 MHz to 4.5 MHz detected video), and the CRT image of the VA62A multiburst. I used the same 75 ohm to 300 ohm matching pad (from the B&K415) on all of the equipment to connect their RF outputs to the 721TS tuner sweep alignment input test point. I also used the same 1X scope probe connected to the 721TS sweep alignment detected video test point.

The first picture is the down converted B&K415 scope sweep display. the markers are 21.25, 22.75, 23, 24, and 25.75 MHz (down converted by 20 MHz).

The second picture is the Wavetek 1002 set for sweeping the 18-28 MHz range with 1 MHz markers.

The third picture is the VA62A set to produce a 25.75 MHz IF video carrier frequency driving the same 721TS tuner IF sweep test point with the 10 bar multiburst pattern. The scope waveform of the detected video shows the sequence of bar frequencies 0, .5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5 MHz. The frequencies are shown on the scope waveform as the low to higher frequency square waves. By looking at the amplitude of each you can see the frequency response of the corresponding IF frequencies. 0 Mhz = 25.75, .5 = 25.25, 1.0 = 24.75, down to 4.5 = 21.25 MHz.

The fourth picture is the CRT image of the VA62A multiburst. It shows the vertical lines that the multiburst pattern produces on the screen. The brightness of the vertical lines is the maximum voltage on the scope multiburst waveform. The solid wide bar at the left is 0 Mhz, next is .5 MHz, and so on across the screen. So you can that the amplitude is about the same from 0 to 2.5 MHz but drops off at 3.0 MHz since that bar of vertical lines is dimmer the those to the left. This image on the CRT directly corresponds to the amplitude of the scope multiburst bars as well as the Wavetek IF sweep amplitude and the down converted B&K415 sweep amplitudes.

I am convinced that the down converted B&K415 works as well as the Wavetek 1002 as an alignment sweep generator. The VA62A is also useful ONCE YOU GET A GOOD SWEEP ALIGNMENT. You can the use its CRT image of the multiburst to tweak the IF adjustments that correspond with the multiburst bar frequencies to touch up the total tuner input to CRT image frequency response to what you are after. I have adjusted this 721TS for the RCA alignment procedure. But in the past I have also used the VA62A CRT multiburst patter to adjust the response to show bars out to 4 MHz. That resulted in a sweep pattern that showed higher IF amplitudes at the 22 MHz end of the spectrum. It also resulted in an overall lower receiver sensitivity. I guess its the gain-bandwidth product problem. You can have higher gain with a lower bandwidth, or a higher bandwidth with a lower gain.