HP C, 3586A manual Tuning a SSB Signal Using the NOISE/DEMODULATION Mode

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10.TUNING A SSB SIGNAL USING THE NOISE/DEMODULATION MODE

10.1General – The A and B versions of the HP-3586 have SSB channel modes that speed the setup of the instrument for reception and measuring of SSB signals. Unfortunately the C version doesn’t have these modes but can still be configured to tune SSB signals using the method I described previously in Chapter 9. The noise/demodulation mode was designed for measuring noise and copying SSB signals on telephone channels. The demodulation feature is very useful for tuning SSB radio signals but I haven’t found much use for the noise feature.

The noise/demodulation mode is basically the same as the low distortion selective mode except it automatically selects the instrument’s widest band pass filter and sets its frequency display to show the SSB signal’s carrier RF frequency or the RF frequency of a tone used to find a SSB channel on a phone line. This last feature is useless for our radio type measurements. But the carrier frequency display mode is very useful since this is the usual way of defining radio SSB signals.

10.2Instrument Setup - Configure your HP3586 by pressing [NOISE/DEMOD] on the measurement mode sub panel to configure the instrument for demodulation of SSB signals. Press one of the channel select buttons [LSB] or [USB] located under the frequency display to match the sideband used on the band you’re tuned to.

10.3Determining a SSB Station’s Frequency – I’m going to use the same CCA net example of chapter 9. First press [CARRIER] on the frequency/entry sub panel if it’s light isn’t on to read the SSB carrier frequency of the SSB station. You should now see the CARRIER annunciator on the frequency display on. Then confirm the net is on the air and it’s approximate frequency using my 75A4. I next tune a frequency close to the net control operator using my HP3586 by setting it for proper side band and using the entry keyboard. Then fine tune using the frequency control knob on the HP3586 and the procedure described section 4.11 of Chapter 4. Since the Fo oscillator output is always tuned to my filter’s center frequency it will still not be the same as the frequency on my LED frequency since I’m in the carrier tuning mode for the SSB channel measuring modes. But after tuning for best audio in the noise/demodulation mode I can easily change modes to move the center of my filter’s band pass by changing modes. Just go to the measurement/mode sub panel, press [LO DIST]. Notice the display frequency doesn’t change but the CARRIER annunciator goes out and the CENTER one goes on. Now I have moved my Fo output frequency right onto the net control’s carrier frequency. I now will turn down the volume of the HP3586 speaker and use my 75A4 receiver to copy the net and proceed to check into the net.

10.4Measuring the Strength of a SSB Station – After tuning in a SSB station for best audio in the auto 10db mode, while in the entry range limit setting mode press [100db] under the analog meter to use the 100db range for more for stable and reliable radio signal level measurements. To slow down the display variations and better represent the received station’s average power, turn on averaging or be sure the [AVE] button’s light is on below the measurement display. Choose the units you want the measurements in, you can choose dbm or use an offset and db.77V to make the readings more like that of a S meter and referenced to 100uv as previously explained in section 9.4 of Chapter 9. If we now look at the instrument’s level measurement display while receiving a SSB station we should see it deflecting upward every time its operator talks. If you get an OL or UL on the level display, increase or decrease the 100db range’s upper limit setting to get into an accurate measuring range.

With some A and B versions there is an additional WTD noise filter in series with the 3100Hz filter usually used for SSB on telephone lines. You may want to switch to the widest filter without WTD for more accurate level measurements. However, it really doesn’t make a great difference because it’s very hard to do precise level measurements on a varying SSB radio signal. If you are doing comparative measurements, just make sure you use the same filter for all measurements.

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Contents Version 2.0, September Table of Contents Introduction Description of the HP3586 Page Selective Signal Connections Front Panel Description and Initial SET UP Page Page Setting and Measuring Frequency Page Power Level Measurements Using the Selective Mode Page Voltage Level Measurements Using the Selective Mode Measuring Carrier Signal Strength Tuning SSB Signals Using the Selective Mode Filter Band Width Carrier Offset Tuning a SSB Signal Using the NOISE/DEMODULATION Mode Measuring Audio Noise Using the Wideband Mode Measuring Impulse Noise Measuring Audio Harmonic Distortion Page Passive and Active Network Analysis Page Measuring a TRANSMITTER’S Spurious Emissions Page Selection of Measurement Modes and Other Considerations Page Page Understanding the Decibel Ratio Measuring System Appendix aNumber Ratio Power DB Ratio Page Appendix B HP3586 Error CodesAppendix C Schematics for Useful HP3586 Accessories
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B, 3586A, C specifications

The HP C3586A and C3586B tape drives are notable components in the realm of data storage solutions, primarily designed for enterprise-class environments. These SCSI (Small Computer System Interface) tape drives are regarded for their efficiency, reliability, and capacity to meet the growing demands of data backup and archival processes in businesses.

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