-------- In message <[email protected]>, Bob kb8tq writes:
>>> The HP3336 with its outstanding level-control is a much >>> overlooked bargain for this kind of stuff. >> >> I looked for the manual, and it seems to have ROM feeding values to a DAC. >> Is that not DDS? That is for the level control, not for generating the signal. The level control has a custom HP-chip with two matched thermal converters, so you can compare the power of two signals with it. One signal is the RF output, the other comes from a DAC. The 3336 is as far as I know one of the the most precise instruments when it comes to amplitude, and it was built specifically for the last two generations of the Carrier Frequency Coax telephone network (L4 and L5) where up to 10.800 4kHz telefone channels were stacked over each other in a single coax cable. Because the top frequency were near 70 MHz, they needed a repeater for every mile of cable which is up to 4000 repeaters for a call across the US. If every one of those repeaters had a systematic dip of 0.01dB at the same frequency, That would amount to 40dB attenuation in total, so the amplitude tolerances were almost insane, in order to keep the amount of equalizing manageable. Google: bstj53-10 site:archive.org It's an amazing story... The HP3336 and the HP3586 level meter go together to measure these lines: The 3586 measures the received signal and when it is done it tells the 3336 to step 4kHz up to the next channel. The crucial trick is that the 3336 produces the exact same output level for all 10800 channels. See: HPJ May 1980. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
