"Sampler??"

Also, you said the SRD was acting as an "impulse generator" when I assumed it was simply generating harmonics to boost the M/N loop output up in order to mix with the output of the YTO.

I recall these pictures. I was wondering if HP copied the general approach if not the patented design. Or licence it.

Jeroen correctly commented that "If it's Agoston's, it's a genuine time-domain short-pulse sampler, not an attenuator pick-off."

Joe Gwinn

I recall that the founders of Tek and HP met and agreed to cross-license their patents.

No, all I saw was the description.

They are really the same thing. An impulse train is a harmonic comb.

So we're just getting hung up on definitions? Fine, let's leave it at that.

Haha! No, neither of those things are going to happen, Jan. I'm still suffering from PTSD at having to toss a Tek 555 into a dumpster 20 years ago. Plus...... I've ordered *another* HP boat anchor to assist me to fix this one! You can never have too many boat anchors (although of course, I have). :)

Those old monsters were big, heavy, and immensely complex. Not so reliable.

Nowadays you can get a nice color digital SA with tracking generator for around $1300 from Amazon. The little handheld toys start around $60.

I think I'll order one for my new lab. Does anyone have suggestions? There's a 1.5 GHz Rigol for $1300 and a 3.2g Siglent for $2600.

One key point will be front-end preselection/image rejection. I've found that even the classic HPs had terrible spruious spikes, at harmonics of the input frequency. Tek made one SA plugin that had *no* image rejection. You had to figure it out yourself.

True, but when they go wrong, they're repairable without needing to be sent off at vast expense to the manufacturer to put right. That is no small consideration for the non-commercial users of these things.

The toys are phenomenal in terms of what they can do for the price, but all the key metrics of performance and accuracy aren't satisfied. After all, what can you expect for 60 bucks? But undeniably they're *great* for kids to learn with.

Dunno which model you're referring to there, but I've never had any such problem with the ones I've owned.

I moved overseas and couldn't hold on to everything, sadly. Didn't have time to find a museum either.

Yes, first thing I did. And replaced any suspect caps.

No, the input stage is fine. I can see all the local FM stations at their expected strength levels - but they appear to be about 20Mhz lower than they are!

Self-diagnostics have localised the fault to within the YTO loop and my subsequent investigations have narrowed down this issue with the 'greater "sampler" stage' putting out garbage. As I said further up the thread, either there's an issue with the 'sampler' itself or it's just doing its best with faulty input signals: garbage in/garbage out. There are 3 inputs to the section: fM/N, f20/30 and fYTO. All those signals are present and their power levels are fine. But I need to ensure their frequencies correspond to the charts provided in the manual and the relevant derivation formulas. If not, the loop has no chance to lock. My biggest problem is finding the time to fit it in!

On a sunny day (Fri, 2 Aug 2024 10:09:24 -0000 (UTC)) it happened Cursitor Doom snipped-for-privacy@notformail.com wrote in <v8ib8k$2p2d8$ snipped-for-privacy@dont-email.me:

The 'about' 20 MHz is susicous, as the IF is 21.4 MHz. Looks almost like a problem with the calibration On page 12 of the manual I see an internal reference output, is that 10 MHz correct? What happens when yu feed in 10 MHz from an other source? quote from that page: To lock the spectrum analyzer to an external frequency reference, set the FREQ REFERENCE Analyzer performance will be degraded unless frequency reference phase noise and spurious sign dBc single sideband (1 Hz) referred to 10 MHz at a 100 Hz to 10 kHz offset. To lock another spect the spectrum analyzer internal frequency reference, set the FREQ REFERENCE switch to INT

OK, we will wait and see. If all else fails, this was fun to create:

There are several IFs, none of which none are 21.4Mhz according to the notes in the text. They state the IF changes according to band, so it's

Yes.

What's your thinking in that suggestion? What difference could it make?

Well, I've just wasted several more futile hours trying to make sense of the figures given in the manuals. This thing is a *bitch* it is *so* complicated. I've never had to deal with something of this nature before in all my decades in the hobby. Much of the problem is having to rely on PDF manuals and HP having spread the relevant information over several different manuals covering thousands of pages. Nice work, HP!

Wow! What a lot of IFs!

They are indeed. And perhaps that's the best use for all these many and various HP manuals! :-D

I've got several hours tomorrow to look further into this, Jan. I have some useful info to apply to the problem........