Confused about Frequency Counters

I'll pass..... I'd first have to rob a bank anyhow, in order to pay for it, and I think the bank clerks would just laugh when I pointed a soldering gun at them... (Or maybe a glue gun, or a caulking gun) :)

Reply to
oldschool
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Overpriced. Look at the prices of the sold listings:

I have two R2001D boxes parked in my palatial office waiting for the mythical "spare time" needed to fix them. One has most of the red LED's on the right bashed in by someone dropping something heavy on the front panel. The other has a very weak CRT display, which is probably an HV power supply problem. Both have lock problems, which means it's time for a tantalum transplant. They've been sitting there for about 3 years. If I wait long enough, maybe the owner will forget I have them.

I have a few other service monitors. There are three SSI/Wavetek 3000 series service monitors in this photo, plus one more I recently acquired. Typical cost was $300/ea: In the middle left, is an IFR-1500 service monitor (with an intermittent power supply). I paid $1500: There are several cell phone specific service monitors hidden in various corners.

Yep, service monitors are a good thing to have an use, especially in the field or on mountain top radio site. It has everything that you might need to work on radios including a counter. All have TCXO or OCXO reference oscillators for accuracy. At home, I have a home made GPSDO for even more accuracy.

However, there's a catch. All the stuff in the photos is from the

1980's which means that components are starting to fail. It's a continuous battle to keep these things running and usable. If you decide to invest in an older service monitor, be prepared to occasionally dive in and do some repairs.
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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

I am now the owner of a C&C 150. For the price, and considering the specifications, I just took a chance in the dark (literally), since I drove to a local WIFI at midnight and from my car, I bought it. I had a feeling it would be sold if I waited until today.

I did find one of those discussion groups on the web, in which they were discussing it. Some guy bought one (on ebay) for around the same price I paid, and he was pleased with it, but did not know how to use a lot of the features and controls. Someone in that discussion posted a URL for the manual. (Not the same one you posted). This one:

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(I bookmarked the URL).

This is the manual that's upside down, which I posted about....

(Apparently, others like this have been sold on Ebay recently). The discussion occured about a month ago). (There actually was another one being sold on Ebay, but for about $20 more, with shipping).

All I got to do now, is wait for it to arrive.... Till then, I'll read the manual. (and wont have to stand on my head to do it).

Thanks for the help!

Reply to
oldschool

Congrats on getting the counter. I downloaded the manual and found that *ALL* of the pages were inverted. No problem. Fire up PDF-Xchange and click on the "Rotate CW" button at the top of the screen. That should fix all the pages. Then do a: File -> Save As to replace the original with something readable.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Yes, that seems to describe it.

Google for Sanjian Studio (which is on the PCB) and you'll find an English translation of the manual. That had assorted URLs to

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where the many stages of this project's development was discussed. You have to log in to see the schematics. I subscribed, but my account seems to have now expired (I didn't get the spam that I expected from this subscription). So I only have the assorted files I downloaded, see here:

Yes. High gain is a problem too, causing spurious transitions.

Yes, except it's meant to be (and mine are) and MB506.

Good idea.

Earlier schematics show two 4-bit counters before the PIC, which by itself does not have a 60MHz counter.

Clifford Heath.

Reply to
Clifford Heath

I assume the MB501 was 2c cheaper than the MB506 that the project was designed with. Find one of the many versions that actually use the MB506 instead.

Reply to
Clifford Heath

snipped-for-privacy@tubes.com wrote on 5/28/2017 1:43 PM:

Just curious, is the manual a series of images of pages or is the text selectable?

I received a PDF document of an old PDP-11 listing from someone who wanted help typing it in. I realized when I clicked my cursor over the text it would select even though it was clearly created from images. Seems some software in the path (possibly my reader) was doing optical character recognition on the document. Most of it came through ok, but once in a while the slightly out of adjustment printer characters would be misread like a 9 for a 0, or a 0 for an O. Still, it saved a lot of time.

Anyone else see scanned documents showing selectable text?

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Rick C
Reply to
rickman

Got it and thanks. Nice the way the download is packaged as a single ZIP file. The docs are in Chinese. I haven't tried Google translate on it yet. The new schematic is very difficult to read the text. I'm also having problems decoding the "forum description". It's readable imported into MS Word as Unicode-8. The photos of the PCB seem to be the old design, which lack the extra divider chips. This is going to be a challenge.

It also says MB506 on both the old and new schematics. That's odd because it's a divide by 128 or 256 that goes up to 1.6GHz. At 2400MHz, divide by 128 yields 18.75MHz. I originally thought that it would need to use all of the 60MHz counter frequency range, but now I'm not certain. The PIC used is apparently slow, and won't go that fast. 18.75MHz seems about right for the PIC16F628a where the data sheet says it quits at 20MHz. The ForumDescription.txt file says that it's divide by 64 on the first page, but then claims that the low channel goes to 75MHz, and later claims that the prescaler is an MB501. Kinda looks like the ForumDescription.txt file is a mixture of the old and new designs.

Looking at the new schematic, I see that one bipolar front end transistor was replaced by a dual gate mosfet. However, it doesn't look like the gates were tied together on the schematic. The original schematic is tiny, but after enlargement, I don't see a dot where the wires cross.

Also, if you follow the signal path through the prescaler chip on both the old and new schematics, the higher frequency range input goes through the prescaler, into the DG MOSFET, and then to the PIC counter. If there is a sensitivity problem, it would only be on the lower frequency range input, which goes to the DG MOSFET directly.

Probably correct, but I can't tell what those are. Also, I think you have it backwards. The older schematic shows no dividers, while the new schematic shows what I guess are dividers.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Searchable text is a standard PDF feature, even with bitmapped text. PDF-Xchange has built in OCR (optical character recognition) that will read through the graphical text, do its best to convert it to ASCII text, and save the combined file. After that, you can use the search, select, edit, functions: The free version will do all that except edit and save the resulting text. For that, you need the registered version.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

I missed the translated user manual (in English). It shows a sensitivity graph for the high frequency range with the following comment from Pg 12: It is noted that the UHF channel allows measurements up to about 450 MHz. This path comprises a divide by 64 stage claimed to be able to operate to 2.4GHz according to the published specifications. It is therefore surprising that the sensitivity fell as quickly as it did. Looking at the schematic and layout, my never humble opinion is that the designer didn't know anything about RF design and layout.

The schematic shown on Pg 13 is quite different from either the old or new versions of the design that I previously mentioned. Instead of the extra divide by 4 packages, it has a 2nd DG MOSFET in front of the PIC counter. It also lists the prescaler as an MB506 which is divide by 128/256, not 64. It also shows that the gates of the DG MOSFET are NOT tied together.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

I'm not sure what "standard" means. I was viewing a document full of imaged text the other day and none of the permissions were set to preclude anything. Yet I couldn't select any text as it had not been OCR'd.

I assume the OCR has to be done at capture time. Are you saying a reader will convert images to text?

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Rick C
Reply to
rickman

That was my conclusion also, and that (plus the earlier published versions) is why I said "advanced hobbyist". Not even very advanced, certainly not RF-experienced :)

I don't know what frequency the PIC counter input is capable of, but I know that the AVR counter is clocked; so you can only count at half the CPU clock frequency. Bah, humbug.

Both my units have MB506.

The units I have have both pairs of protection diodes, and the inputs are joined only at the connector. I cut the trace and soldered a bit of co-ax onto the prescaler input capacitor.

I don't have a good RF source (yet - currently building, see

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so I can't evaluate the sensitivity.

Clifford Heath.

Reply to
Clifford Heath

The clock crystal is 4MHz on the old version. I can't read the numbers on the schematic of the new version. That doesn't look very promising for measuring 60MHz inputs or even with /4 at 15MHZ.

Oh swell. So the PCB wiring might not follow the schematic. I suppose it doesn't matter since the DG MOSFET seems to be badly biased anyway.

I was having nightmares last night from thinking about this counter. Maybe I should give up while I'm still sane?

Before you reinvent the wheel, there are AD9851 based DDS generators available on eBay. along with the associated LCD display: However, those only go up to about 70MHz and the output looks distorted above 30MHz. If you're going to test the counter all the way to its rated maximum frequency (2.4GHz), you're going to need a better generator. DDS has benefits for a function generator and arbitrary waveform generator, but is limited to lower frequencies.

This looks interesting (and tempting):

137.5MHz to 4.4GHz signal generator in 10KHz steps. Looks ok to about 1GHz, but drops in output and increases in sidebands at higher frequencies. Looks like the same board, but in a shielded box: Or maybe this thing: Or maybe something computah controlled via USB: Or maybe a real RF generator from HP, TEK, Fluke or others that can actually be calibrated and trusted. This is the cheapest HP I could find: I have an HP 8656A but prefer to use an HP 8540B. Top right:
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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Bad choice of words. I meant that the PDF standard: includes searchable text as part of the standard. I'm too lazy to look up the chapter and verse.

Yep. If you scan text as a bit map image, and save it in PDF format, it cannot be text searched. You have to feed it to an OCR program, which is capable of attaching the OCR text to the PDF, save it, and then you can search.

No. It can be done at any time with any reasonable document. I usually make some effort to realign the text and improve the contrast to make it easier (and faster) for the OCR program to do it's thing.

If the images look like readable ASCII characters, yes. I don't think size makes much difference, but I haven't done much experimentation into how badly I can butcher the text and the OCR will still work. I also haven't tried to edit the text after reading to correct OCR errors.

Maybe a demo will help. Note that the initial scan and file saves were done in Irfanview, while the OCR and subsequent saves were done in PDF-Xchange:

Original document scanned to JPG using Irfanview 4.44: This is not searchable.

Same document saved to PDF using Irfanview 4.44: This is also NOT searchable.

Same document in PDF-Xchange 6.0 build 322.4 after OCR: This one can be searched.

PDF-Xchange screen grab showing a typical search result:

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Here's how to edit OCR errors using Adobe Acrobat: I'm still trying to figure it out using PDF-Xchange Editor.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

But I don't think the PIC has a clocked counter anyhow. I assume that the AVR does it to (sometimes) avoid the need for a low-pass filter.

The xtal on mine is marked "SCK451C" and "TC,A.426", whatever that means. It was about 15ppm slow, but seemed quite stable, based on measurements taken with an HP5386A.

Quite a few people have patched in a TCXO to these units.

I don't understand why they used a DG MOSFET, nor why, since they did use one, they didn't use the upper gate for gain control. It seems they're feeding the signal into the upper gate, so won't get the best bandwidth from the cascode behaviour.

I haven't found the schematic of the current-manufacture.

I think it's fixable, perhaps with an additional front-end. It would still be easier and cheaper than building from scratch.

Who do you think designed those? People like me :) I have a bit of that Jedi "build your own light sabre" thing going on.

Plus there's no accessible used test equipment market here in Australia. Whenever nice gear comes up at bargain prices, merchants buy it up and slap a stupid price on it.

That's exactly what I'm using for development. They have all copied a flaw in the output filter design, leading to very low output at higher frequencies. Some impedance problem, it's not designed to drive 50ohms. I'll add a buffer.

I loathe and detest both PICs and those 16x2 displays. I'm building one with 320x240 colour touch screen.

The Arduino also has TTL-level RS232, so add a $2 USB module and you have USB control.

I expect to incorporate an ADF4351 also, and possibly two AD9851's, to give quadrature (but still cheaper than AD9854 or whatever the multi-channel DDS chip is).

E.g.

The ADF351's have the same problem as most of those VCO synthesisers, that they won't sweep cleanly. Changing the frequency makes them jump wildly about until they stabilise again.

The Arduino clone and TFT Touchscreen LCD cost me $AU14 all up. Add the $30 ADF4351, a $17 $AD9851, and USB and you have a nice bundle for half what the above costs.

"Does not ship to Australia"

I have to give this HP5386A back, but not in a hurry - my friend also has mountains of test equipment. He worked in sat-comms, so has contacts who call him before dealers get there - but he loves to hoard it all :(

Clifford Heath.

Reply to
Clifford Heath

...

Other people have also given you a method, but I thought it was worth mentioning that the standard OSX (Mac) Preview app does PDF natively, and it's trivial to invert, shuffle, delete, etc. Just show the page thumbnails on the left, click on one, type Command-A to select all pages, and hit Command-L twice to rotate. Command-S saves the rotated file.

You can also select and delete individual pages, re-order pages, and even drag pages in from another document. It's nice, and it's standard.

Clifford Heath.

Reply to
Clifford Heath

It is so easy to be misunderstood. I'm talking about the text showing up in the PDF document. I receive d a document that was clearly a scanned image in a PDF file. But the text was selectable and copyable. The two options are the image was scanned and OCR when the PDF was made, or the PDF viewer had OCR scanning built in. Since I couldn't select the text in another scanned image PDF it must be the former.

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Rick C
Reply to
rickman

The example I provided was how to do the latter. I scanned the image in one program, and added a searchable text layer with a PDF viewer.

There are scanning programs that will seem to do the process in one step such as Nuance Omnipage, Paperport, Adobe Acrobat (NOT reader), etc. To the casual user, it looks like the process is being done in one step. In reality, it first scans to a bitmap. Next, the OCR software reads the bitmap to produce the searchable text layer. It then saves the result as a PDF file. To the best of my limited knowledge, none of the available software does the OCR step *WHILE* scanning, but I might be wrong about that.

I never did figure out how to display and edit the OCR text in PDF-Xchange Editor. Looking through their feature list of other versions, it seems to be something at only the more advanced and expensive versions will do. Bummer.

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

I'm still not getting through. I'm not looking for ways to make PDF images text selectable. I'm reporting on what I saw.

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Rick C
Reply to
rickman

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