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Re: BNC Frequency Limit

 

In the past, I have fed 13GHz into one of these Agilent scopes that use BNC inputs and it displayed the 13GHz signal (from an old HP 83752A generator) just fine. There was some loss, but that is to be expected in the cable and the scope front end as it was a 13GHz rated scope. It was probably less than 3dB loss but I can't remember now.

These 13GHz BW scopes (40Gsa/s sample rate) have a fixed 50 ohm input via the BNC connectors on the front panel. They are quite old scopes, there has been one at work for many years and I use it now and again for TD stuff.



I'm not sure what the upper frequency limit would be for these custom BNC connectors if they were used for a counter rather than a 13GHz scope. It's going to be a bit more than 18GHz but it might not manage 22GHz...
Re: BNC Frequency Limit

 

¿ªÔÆÌåÓý

There was an option to move the high frequency input to the rear panel, leaving only a BNC on the front panel. Might that be what you have?

Steve
WB0DBS
EM17iq09ao


On Jun 29, 2024, at 2:54?PM, Jinxie via groups.io <paul666@...> wrote:

?6054B and I can't post any pictures right now I'm afraid. It doesn't appear that the BNC has been changed from SMA; looks original and why would anyone do such a thing anyway? Does seem an odd choice!

Re: BNC Frequency Limit

 

I'd expect a 22GHz counter to typically use a 3.5mm connector, but it could also use SMA or N connectors at a push.

Note that the highest (frequency) rated BNC connectors I've seen are rated to 18GHz but these are specials made by Agilent. These connectors look just like a BNC and can mate with a standard BNC connector but they are gold plated and have a precision inner connector made with better defined dimensions and a better mating technology compared to a standard BNC connector. These special BNC connectors could be used as the main channel inputs of a 13GHz scope for example.
Re: 3562A Help/advice

 

It's worth knowing that the variant of the display in the 3562 is different from most other 1345A units. The 3562A service manual includes schematics and these are the best ones to use.? Foolishly I started with (several different)1345A manuals which were excellent from a general understanding point of view of the interface and commands but quickly throws up lots of specific differences on the boards.

The self test (just remove the IDC cable) with Pikes Peak is a very good place to begin.

Alan
Re: BNC Frequency Limit

 

Chuck, it absolutely *cannot* have been an N type at any time in its life or there'd be a ring of some sort around the BNC as they're smaller than the hole an N type needs.
Re: BNC Frequency Limit

 

6054B and I can't post any pictures right now I'm afraid. It doesn't appear that the BNC has been changed from SMA; looks original and why would anyone do such a thing anyway? Does seem an odd choice!
Re: BNC Frequency Limit

 

Forgot to say, the 2442 goes to 26.5GHz.
Re: BNC Frequency Limit

 

First:
BNC and N WILL NOT mate properly. while the main dimensions of the center parts are the same (they are 7mm class connectors) the center pin of the N connector is lrger than the BNC center pin. If you push a N male onto a BNC frmale you can damage the BNC.

I am also very surprised that any commercial frequency counter would use a BNC connector for a 8 GHz input never mind at 20GHz. All 7mm connectors are limited to 18GHz for predictable performance. Most N types got to 12GHz but special precision versions go higher. As an example the 20GHz Marconi 2440 counter uses a precision N type for the microwave input. The otherwise identical 2442 uses a 3.5mm (like an SMA but air dielectric).

What model is the counter? Can you post a picture of the connector niclding the area around the connector?
Re: BNC Frequency Limit

 

The 6054 has a BNC for its low band (200MHz) input, but
uses an N for its microwave input.

-Chuck Harris


On Sat, 29 Jun 2024 11:26:05 -0700 "Board via groups.io"
<board@...> wrote:
Is it the 6054?

Are you sure there is no SMA - BNC adapter on it? Perhaps someone
modified it...

On 6/29/24 11:22 AM, Jinxie via groups.io wrote:
No, it's the standard 50 ohm BNC output socket. I just checked and
it's actually up to 24GHz according to the front panel just above
that socket. It's a Systron-Donner counter if that helps at all.
Re: BNC Frequency Limit

 

I thought I knew the S-D lineup pretty well, and yet I don't
recall an instance where they used a BNC on microwaves.

What model do you have?

-Chuck Harris


On Sat, 29 Jun 2024 11:22:40 -0700 "Jinxie via groups.io"
<paul666@...> wrote:
No, it's the standard 50 ohm BNC output socket. I just checked and
it's actually up to 24GHz according to the front panel just above
that socket. It's a Systron-Donner counter if that helps at all.
Re: BNC Frequency Limit

 

HI? Just? curious which came first the "N":? connector? or the? ? b"N"c? ,
? I suspect the "N"? but an "N"? and a BNC? will mate together ( gender allowing )? so where is the great frequency difference? ??? just asking..
?cheers? mike Pinfold? ZL1BTB

On Sunday 30 June 2024 at 06:22:44 GMT+12, Jinxie via groups.io <paul666@...> wrote:


No, it's the standard 50 ohm BNC output socket. I just checked and it's actually up to 24GHz according to the front panel just above that socket. It's a Systron-Donner counter if that helps at all.

Re: BNC Frequency Limit

 

¿ªÔÆÌåÓý

The word "limit" should not be interpreted as a fixed, discrete boundary that separates "useful" from "useless". The world is analog, so it's best to consider what is really meant in a given circumstance.

For a frequency counter to function properly, all you need is to preserve the zero crossings and some minimum amplitude, so that's a fairly forgiving application. That said, I am surprised to hear that your counter's 22GHz input uses a BNC. High-frequency counters often have a couple of connectors, one covering up to a couple of GHz and another above, but I've never seen or heard of a BNC being used in a commercial instrument for 22GHz -- could you let us know the instrument model? Or is it a homebrew counter?

That aside, in other situations you might need to worry about impedance mismatch. And that's where a typical BNC connector has unfavorable characteristics as you increase frequency. The instability of the ground connection is also a problem (particularly in mobile applications, where the modulation of impedance can cause the BNC to act as a surprisingly good vibration sensor). BNCs are also manufactured to fairly loose tolerances, so if the application demands accuracy and precision over a wide frequency range, BNCs aren't going to be a good choice.

So, it's not as if signals abruptly stop emerging from the BNC once you go above, say, 4GHz. It's more complicated than that. And whether a BNC is useful or not in a given circumstance depends very much on what performance you need in that particular case. The frequency "limit" will vary accordingly.

-- Cheers
Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 6/29/2024 10:58 AM, Jinxie via groups.io wrote:

Hi all,

According to this site:

50 ohm BNC connectors are only good up to 4GHz and 75 ohm ones to 2GHz maximum. And yet - to take just one example - my best frequency counter, which accepts and can measure signals up to 22Ghz, uses 50 Ohm BNC sockets and seemingly works just fine with them. And yet it's not just the Historytools website which claims BNC is only good up to a few GHz; plenty of other sources say the same thing. What's going on here?

Thanks,
J.

Re: BNC Frequency Limit

 

¿ªÔÆÌåÓý

Is it the 6054?

Are you sure there is no SMA - BNC adapter on it? Perhaps someone modified it...

On 6/29/24 11:22 AM, Jinxie via groups.io wrote:

No, it's the standard 50 ohm BNC output socket. I just checked and it's actually up to 24GHz according to the front panel just above that socket. It's a Systron-Donner counter if that helps at all.

Re: BNC Frequency Limit

 

No, it's the standard 50 ohm BNC output socket. I just checked and it's actually up to 24GHz according to the front panel just above that socket. It's a Systron-Donner counter if that helps at all.
Re: BNC Frequency Limit

 

¿ªÔÆÌåÓý

The frequency counter can't measure amplitude. Using BNC above 4 GHz causes losses due to reflection, but the frequency counter will still work even if your signal is 10dB lower. If you use BNC connectors with a spectrum analyzer, you'll see that the amplitude of your signal is now lower since you used BNC instead of SMA or N.

If you get a VNA, you can also see that the input of the frequency counter is no longer 50 ohms at 22 GHz.

I am also not aware of any frequency counters that go that high that use type BNC connectors. Perhaps it uses an N connector, and you have an adapter?

On 6/29/24 10:58 AM, Jinxie via groups.io wrote:

Hi all,

According to this site:

50 ohm BNC connectors are only good up to 4GHz and 75 ohm ones to 2GHz maximum. And yet - to take just one example - my best frequency counter, which accepts and can measure signals up to 22Ghz, uses 50 Ohm BNC sockets and seemingly works just fine with them. And yet it's not just the Historytools website which claims BNC is only good up to a few GHz; plenty of other sources say the same thing. What's going on here?

Thanks,
J.

BNC Frequency Limit

 

Hi all,

According to this site:

50 ohm BNC connectors are only good up to 4GHz and 75 ohm ones to 2GHz maximum. And yet - to take just one example - my best frequency counter, which accepts and can measure signals up to 22Ghz, uses 50 Ohm BNC sockets and seemingly works just fine with them. And yet it's not just the Historytools website which claims BNC is only good up to a few GHz; plenty of other sources say the same thing. What's going on here?

Thanks,
J.
Re: New doc about 180 oscilloscopes

 

Gianna this is incredible!? I'm currently working on a 182T with a 8557A plug-in.? Can I be greedy and ask for a Spectrum Analyzer section for this beautiful document?
Re: New doc about 180 oscilloscopes

 

Buonasera Gianni,?

ho iniziato a leggere il suo lavoro, a pagina 4 mi sa che deve correggere l'unit¨¤?di misura delle dimensioni?, sono cm , non mm

By the way, ho lavorato?in HP Italia dal 1976 al 1985 come tecnico service, prima nel settore RF / MW e poi on site, avevo un 180 sul tavolo e ora da pensionato ne ho uno?nel mio lab...

Bei ricordi.

Se trovo?altre parti da?sistemare la avverto.

Un caro saluto.

Il giorno ven 28 giu 2024 alle ore 18:20 Gianni Becattini via <Giovanni.becattini=[email protected]> ha scritto:

I continue with my perhaps-senseless activity of documenting old stuff.

This is the draft about the 180/181 oscilloscopes:

Any contribution/correction welcome.



--
Roberto Vegliach
Cell. 351 5920130

ScreenHunter 414.png

Re: New doc about 180 oscilloscopes

 

Some notes from my repairs;
Some of the metal film resistors used in the voltage divider/feedback circuits in the PSU and the horizontal amplifier can drift high in value, or go open.
The 4-071 transistors used in the older scopes do go bad occasionally, sometimes they also fail intermittently & drive me up the wall, trying to figure out which is to blame.

Double check the plug-in connector pitch against the Tek scopes you referred to, they are a different pitch as far as I know, the HP scopes used the Amphenol Blue Ribbon or McMurdo Red Range with barrier polarization, Tek used dowel pins for polarization, buying the wrong type for extender cables could be an expensive mistake.

There was a warning of PSU over-voltage faults causing damage to some plug-ins, testing & repairing the PSU without the plug-ins installed is recommended.

The dates for the storage scopes need checking, the 141A (round CRT) is first seen in the 1966/67 catalog, the 181A doesn't appear until the 1968 catalog.

The 141T mainframe you have is a late one, with the oscilloscope beam finder switch & calibrator removed, intended for the spectrum analyzer plug-ins..
Something should be added to inform of how easy it is to damage the storage CRTs in the 141 & 181 series as explained here;

The newer timebase plug-ins such as the 1825A, can suffer from the plastic edge of the rotary switches cutting through the PCB traces, I've seen this in other scopes, such as a 1715A.

The 182A doesn't have the internal flood gun in the CRT, it uses external lamps for illumination, later 182C & 182T use a CRT with the flood gun, it's slightly longer as a result.

David
Re: New doc about 180 oscilloscopes

 

Thank you for doing the work on this. I was working for -hp- when the 180 came out. It was almost a world beater but not quite.
I suppose I am more oriented toward "old stuff" because I am old.

On 6/28/2024 9:20 AM, Gianni Becattini via groups.io wrote:
I continue with my perhaps-senseless activity of documenting old stuff.
This is the draft about the 180/181 oscilloscopes: <>
Any contribution/correction welcome.
_.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
6841 - 6860 of 151493