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I did the 2999(D) mod on the Uniden 858 chasis (Radio Shack) and it certainly improved the small signal digout on SSB, almost brought it to the level of listening performance of the adjacent ICOM 745 (858 had been aligned previous), using a 1/2 wave dipole inverted V resonant at ch 38. On AM...

I used a 2sc2999-D which has a current gain (beta) similar to the original. The high gain -e is hard to find anyway, and the noise floor reduction was most noticeable in 3KHz wide SSB mode.

To updatge this thread.....the 745 decided to work in FM mode only RX/TX after testing that function with an old RS Patrolman scanner. I removed the FM board and the front panel to look for somewhere to start, and started to realize that ICOM packed this chassis so full of electronics, ribbon...

I put a 2sc2999-D in my realistic TRC 458 and it made a definte improvement in SSB receive capability, on weak signals. I didn't retune or anything, just the swap. Carefully ensure your orientation is correct (E-B-C). I compared it to my IC-745 on 11 meter receive and that mod brought it closer...

Anyone here go through aligning their receive sides of these radios? Athough my 745 is working very well, and is more sensitive on 11 meters than my TRC 458 realistic, I haven't done anything to it except verify the PLL lock voltages for the different bands. They were about 0.07 v off. Tried...

Well, I'm convinced this was a good modification to make, at least with the 'D' version. The TRC 458 was always great on SSB, getting good reception to the western US and Europe, depending on time of day, but not quite as good as the TRC 433 base in side to side comparisons on local (-200 mile...

I made the swap today, using a Sanyo 2SC2999-D. Has about the same Hfe range as the original 2SC1730L, but lower noise figure. Have not changed the detector diodes. The 2SC2999E is hard to find. On the generator, had a couple more dB C/N at 7.8 Mhz, and picked up 1/2 an S meter reading, from...

The 1 KHz (or 400 hz) signal I'm referring to is the one you measure the S/N ratio on. Thats the post detection audio signal, which is present at the speaker terminals, and back at the right side of the am detector diodes. The pre-dectection C/N ratio would be measured in the I/F stages, for...

The 400 Hz tone is at the low end of the designed in frequency response for the TRC 458, and the upper end is at 3500 Hz. I didn't make an exact fall off plot for mine, but the spec is 6dB down at a nominal 450 Hz on the low side. If you had, with a given volume control, RF gain, and modulation...

Here's a simple spreadsheet where you can change the dBm (power level) to see what the equivalent uV is.

I'm wondering the same thing, so have ordered the low capitance detector diodes and a lower NF RF first stage amp. I should have my results in a couple of weeks. Mine is a Realistic 458. A couple of other factors, besides these, are at play. One is the background environmental noise at 11...

Sorry about the half explanation- dB is completely relative term, so that if something is twice something else (like voltage), it is 3dB greater. This is because the common log of 2 is 0.3. Named after Bell, it is called a Bell. Not too clean, so they came up with dB (decibel...or 1/10th of a...

The whole HP early Spectrum Analyzer AP Note lineup is at- Spectrum Analysis AN150 The 150-11 AP Note describes how to convert signal and related harmonics into THD in %.

I use a 1971 HP Low Frequency Spectrum analyzer plug in (8556B) for audio distortion measurements. Works very well when aligning foster seeley FM demods for lowest distortion in FM stereo tuner work. HP put out a great note on it, starting on page 12...

Nice views. Can you display in Log 10 mode versus linear with that tool ? It will bring up the harmonics in the display some for THD. Also, can you pull the data from a file and reprocess versus remeasure? For a handy table to print out for 50 ohm systems-...

Robb, Intrested to know if you could measure what the S/N was with the 1uV RF input at 100% modulation with that tool. With a 1 KHz test tone I measured a little over 50 dB S/N with a 1 mV RF input, which is 30dB over threshold. Of course I measured it with the LF section of the HP 8556B...

Here's more context on App Note 150 to round out the discussion on noise power and noise figure, and how to measure the NF of the SA- "At room temperature and for a l-Hz bandwidth, kTB = -174 dBm. We know that the displayed level of noise on the analyzer changes with bandwidth. So all we...

No it won't...think about this scenario-no inline preamp with a lower NF used. Hypothetical carrier measured at peak - 0 dBm (1 mW). Perfect ideal carrier with no bandwidth. The ideal case. All carriers have some BW, the case is still valid. Adjacent noise floor (per unit hertz) is 60 dB...

Your last included"The S/N ratio of the noise you are trying to measure against the noise inside the analyser will not improve/change with a change to a narrower RBW. This is because both the noise contribution from the analyser and the noise signal of interest BOTH have to pass through the same...

I appreciate your posting those pictures. I could not locate any of the quotes you sighted in the HP 150 Ap Note. I tried everywhere in the text to find your two quotations. I cut and paste below text from the bottom of page 59 and the top of page 60 (pdf page # and document # agree) of...