Be careful when conducting 2 x tone tests.? You can easily manipulate / skew? the results by? manipulating the tone spacing.? ?Manufacturer's would do just that, years ago, to minimize IMD3 and IMD5....meanwhile higher order IMD was degraded.? That, and also manipulating the bias? to improve results.? Typ only IMD3 and IMD5 results were stated.?
My other issue with the 2 x tone test? is everything is in a steady state.? ?IE:? B+ / bias / screen voltage / fil V etc, etc...don't budge.? ?They are static, not dynamic.? ?Then toss in lousy ALC setups on some xcvr's.....which will further degrade IMD when ssb used.? The 25 ohms of DC resistance on each? grid choke in a SB-220? will result in a 3.75 V drop across each choke. (25 ohms dcr x 150 ma grid current per tube).? ?Ok, now the bias yo-yo's up/down? from 5 vdc (zener Vdc) to 8.75vdc, when driven.? That plus the instantaneous B+ will sag with full bore plate current peaks on ssb.? ?That mess will screw up the load line.?
IMO, you may be better off? with? just talking on SSB, and looking at the output on a SA (spectrum analyzer).? It's the higher order IMD products, like IMD 7-9-11-13-15-17-19? ?that cause the splatter.?
I got into it with JI, years ago,? about the tone spacing.? For his argument against ESSB he would use extreme wide tone spacings,? like 100 hz and 3200 hz on a MK-V? ( in DSP TX mode).......... or 50 hz and 5700 hz? on a modified MK-V.....(in analog mode with a pair of 6 khz filters installed).?
Try as hard as you can, but with normal speech, you can't achieve SIMULTANEOUS? lows and highs.? ? It's one or the other, but not both at the same time.? ?I tried every trick in the book, and no words, phrases will result in simultaneous highs + lows.? The only way to achieve simultaneous highs + lows is...... (A)? JI's convoluted 2 x tone tests, with extreme wide spacing.... or (B)? program material,? eg: rock and roll music fed into the xcvr.?
The 2 x audio tones fed into the xcvr will only test the xcvr.? ?With the linear amp in the circuit, the resulting IMD is no better than the xcvr.? The K3 is rated at -29db pep? (-23 dbc)? for IMD3...at 100 w pep out.? How the hell are you gonna test your L4B / SB-220? etc? ???? ?You can't.?
