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Re: S11 and S22 comparisons on 8753
Peter Gottlieb
And I'm sure the thing is completely unrepairable except by Agilent, schematics are not available, and once it goes out of support that is basically the end of that.
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On 12/24/2012 8:38 PM, J. Forster wrote:
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Re: S11 and S22 comparisons on 8753
J. Forster
Agreed.
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Note that the 8754A(?) computer based VNA that went to 18 GHz cost prehaps $80,000 in 1970 (a guess). Probably more w/ options. That's $450,000 in today's deflated dollars, so $700,000 is not such a bad deal. I don't have quite $800k to blow this week after buying Christmas presents. LOL. -John ==================== On 25 December 2012 00:24, J. Forster <jfor@...> wrote:You can use a SNA for quick and dirty tests, comparing a known, highAgreed. That is why I was surprised when someone said a scalar one was |
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Re: S11 and S22 comparisons on 8753
David Kirkby
On 25 December 2012 00:24, J. Forster <jfor@...> wrote:
You can use a SNA for quick and dirty tests, comparing a known, highAgreed. That is why I was surprised when someone said a scalar one was more accurate. The only regime where they are used today, AFAIK, ia at frequencies aboveAgilent sell a VNA for 110 GHz. At $691,437 for a 4-port model, I don't expect Agilent sell too many of them! If you buy all the options, it will be over $800,00. Dave |
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HP5328a Fan upgrade
Hi Folks,
I've been thinking on upgrading my HP5328a's fan wich is so noisy that I cannot make any QSO while it's on. Anyone ever thought about replacing it with a DC Brushless Computer Fan like ADDA Model AD0812HS? This fan is quite the same in dimension, it is even a little thinner. Any thougths anyone? Bas. |
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Re: S11 and S22 comparisons on 8753
J. Forster
You can use a SNA for quick and dirty tests, comparing a known, high
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quality, component to the DUT, especially if you have a Storage Normalizer, but in no way is an SNA a substitute for a VNA. The only regime where they are used today, AFAIK, ia at frequencies above those practical for VNAs, over 40 GHz or more. FWIW, -John ================= On 24 December 2012 21:11, laurens_db <laurens101@...> wrote:A well calibrated VNA is the best way of measuring S11/ S22.That was my belief too - at least in the context of typical test |
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Re: S11 and S22 comparisons on 8753
David Kirkby
On 24 December 2012 21:11, laurens_db <laurens101@...> wrote:
A well calibrated VNA is the best way of measuring S11/ S22.That was my belief too - at least in the context of typical test equipment. I would not be surprised if there other techniques applicable to standards labs, which are not too practical for commerical or amateur use. I just opened this book: and looked up scalar network analyzers. By the very title of the book, you can see it is mainly devoted to VNAs, though there is a bit of discussion about scalar network analyzers. To quote: "Scalar network analyzers has the attribute of being very simple to use, with almost no calibration or setup required. The scalar network analyzers were designed to be quite flat in frequency response, and a typical system consisted of one and the input and one at the output of the DUT. However, for measurements of input or output match, or impedance, the scalar network analyzer relied on a very high quality coupler or directional bridge. If there was any cabling, switching or other test system between the bridge and the DUT, the composite matches of ALL were measured. There was no additinonal calibration possible, to remove the effects of the mismatch. As test systems became more complex and integrated, scalar network analyzers started to fall from favor and there are virtually none sold today by commercial instrument manufacturers" As far as I can tell, the error correction of a VNA offers the ability to compensate for errors than the scalar network analyzer simply does not. A broadband cal kit load is as close to 50Ohm as HP can make it.Yes, although because of the limitations of broadband loads, sliding loads are often used at higher frequencies. To once again quote from Joel Dunsmore's book: "The load standard is usually the most difficult to produce. <snip lots> The sliding load, which should more properly be called a sliding mismatch, is constructed from lengths of precision airline, The centre conductor of the airline is typically created in such a way that it can slide into place while the outer conductor is not yet mated, to allow a beadless connection. The load element is typically not resistive element, but is more commonly a tapered bead of lossy material, that essentially makes the airline look like a lossy element. It is designed to have an impedance which is not quite 50 Ohms, normally in the range of 26-40 dB return loss. <snip> "As the sliding load is moved, so its apparent impedance rotates around the Smith Chart" There's a diagram showing a full circle on the Smith chart, almost, but not quite in the centre.It slightly spirals in, as the frequency (and so loss) is incresed. "The difference between the computed centre and the actual centre of the Smith Chart determines the directivity error term" I think is should be obvious what I stated earlier, that sliding loads are impractical at lower frequencies. Looking at the manual for the 85054A 'N' cal kit, the minimum frequency of the sliding load is 1.999 GHz. At 100 MHz (lambda = 3m), the load would need to be 1.5 m long to get a complete half-wave on a Smith Chart. I suspect you can get away with less than a full circle, as it only needs 3 points to make a circle, but I think accuracy would suffer a lot if you could not get an appreciable part of a circle. Dave |
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Re: HP Oldies.
Nothing special by today's standards but in 1952 it was. I'll see if I can dig up the information that was sent to me.
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Here is a description of the last of the series the H/J -pete --- In hp_agilent_equipment@..., Peter Gottlieb <hpnpilot@...> wrote:
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Re: HP Oldies.
Peter Gottlieb
What was so special about the 202? Are today's generators as good?
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On 12/24/2012 6:27 PM, petepdx1955 wrote:
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Re: HP Oldies.
I've been adding to my collection of HP acquisitions, from what
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I've been able to find in the search of patents BRC had some interesting on creating FM modulation. Their 202 series FM generators were the 'standard' for anyone doing work on VHF FM which in the 60's for telemetry was a big money maker. And if you were designing for consumer FM you bought a 202. And of course the Q-Meter was a big seller. --- In hp_agilent_equipment@..., "Richard Knoppow" <dickburk@...> wrote:
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Re: HP Oldies.
There were two companies with Boonton in their name
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Boonton Electronics. Now a division of a British company boonton.com if interested. Their two biggest contributions were a C and L bridges that ran at 1 MHz, and a power meter head using diodes. Boonton Radio Corporation or BRC. These are the guys HP bought. The Q-Meter is prob the biggest contribution, but they did a few other things very well one of which was generators that could FM better then any one else at the time. The area around Boonton was quite the concentration, all basically springing from a company called Ferris Instruments. Ballentine was another off shoot. Another company not into instruments but in the same area was Aircraft Radio Corp, or ARC. --- In hp_agilent_equipment@..., Dave Daniel <kc0wjn@...> wrote:
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Re: HP Oldies.
A couple weeks ago was a very very clean 250-A, have you checked the completed items. The seller was only asking something like $50 for it.
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Was listed at least the first time with no bidders, didnt see if it went the 2nd time. 260-A's come up at least ever 3-4 months. My spare parts 260-A's came free from a ham swap meet. I'd just wait, they will show up again. -pete BRL 250-A, HP 250-A, HP 250-B. --- In hp_agilent_equipment@..., "Max Robinson" <max@...> wrote:
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Re: S11 and S22 comparisons on 8753
laurens_db
A well calibrated VNA is the best way of measuring S11/ S22.
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A broadband cal kit load is as close to 50Ohm as HP can make it. A slight mismatch at the end of an air line will allow you to normalise the return loss measurements, but not a full correction (the port match and directivities are not resolvable with this method IIRC) --- In hp_agilent_equipment@..., Brooke Clarke <brooke@...> wrote:
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Re: S11 and S22 comparisons on 8753
David Kirkby
On 24 December 2012 19:23, Brooke Clarke <brooke@...> wrote:
Hi:I don't claim to know much about scaler network analyzers, so what I say might be wrong. I don't see how you can consider a *scaler* network analyzer able to characterise S11 and S22, since both S11 and S22 require both magnitude and phase information. I believe the things you refer which have an impedance close to, but not exactly 50 Ohms are generally known as sliding loads, though I suppose they might have other names. I do have a few precision airlines which are machined very accurately. I've got a couple of 50 Ohm ones, and a couple which are stepped from 50 Ohms to 25 Ohms. These are part of VNA *verification* kits, so they need to be very accurate. I understand the weak point of calibration kits is the loads - hence sliding loads are used at higher frequencies. Dave |
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HP 3456a was Re: HP 3478A general questions
marvgozum
If both DMM meet your needs, then the chance it will work coming from unknowns via eBay, and easier to maintain DIY is your goal, the 3456a. If you need more updated features including amps but are willing to risk requiring a factory cal, repair and the costs it requires, 3457a.
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3468a is not a system class DMM, but a general purpose DMM very much like he 3478a but is much cheaper as it doesn't support the GPIB bus but uses the then popular HP calculator interface. The 3479a is not a DMM, AFAIK. --- In hp_agilent_equipment@..., Jeff Machesky <jeff@...> wrote:Of the two meters, 3456 or 3457 which would be the smarter purchase ? |
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Re: S11 and S22 comparisons on 8753
Hi:
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The most accurate way of characterizing S11 or S22 is to use a scalar network analyzer with a bridge and precision air line. The cal load is a precision load that's just slightly off from 50.0 Ohms but how much off doesn't matter. It's far more accurate than a VNA. The key idea is that the air line is exactly 50.0 Ohms and the mismatch causes ripple above and below that so the center of the ripples is where the location of 50.0 Ohms. Have Fun, Brooke Clarke hp_agilent_equipment@... wrote: Re: S11 and S22 comparisons on 8753 |
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HP 3456a was Re: HP 3478A general questions
The HP3468A can be programmed via the HP-IL -- the proprietary Hewlett Packard Interface Loop -- so it can attach to calculators (HP-41C), printers and storage devices.
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--- In hp_agilent_equipment@..., Jeff Machesky <jeff@...> wrote:
SNIP |
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Re: S11 and S22 comparisons on 8753
Dave,
Is that the same data you are supposed to back up to a floppy? TheYes, backing up on floppy will save those calibration constants (and other stuff as well). That way, if you have to replace the processor board, you don't have to recalibrate everything. You can replace the board in a few minutes and restore the constants. No need to send the analyzer in. In the case of the 8720D, there is a set of cables available (AgilentYou can do the internal calibration with those cables, but also with other cables or omit one of the cables altogether. Whatever you pick as your default cable setup will then become the calibrated state when you power up the analyzer. I assume several of the internal cables were selected to give it thisThe 8510 had top notch hardware and relied on it for pretty good raw performance at the plane of the test set ports on the front panel. So, if you connect something to either port directly, you can get a decent measurement of return loss even without a cal. For S21 and S12, you need a test cable, and that cable is an unknown until you do a calibration which is similar to the user cal on your 8720. In the back of the test set, you can attach a pair of delay lines that are hopefully of similar length to your test port cables. That's as close as you can get on the 8510 as a default state. The 8753 and 8720 are newer designs, and they made more use of digital correction and non-volatile memory, thereby allowing for less expensive hardware. The main provision is that you need stable hardware, and that is the case. At least on my 8720D, I'm sure it is nowwhere near 55 dB as one of theIf you were to send the analyzer for a "Internal Calibration" (this is the factory/service center job) and you asked them to use your supplied cables and calibration standards, in theory you would get the analyzer to have perfect calibration when you turn it on and test it with your cal standards. You would not need to do the manual calibration. In practice, connectors are not perfectly repeatable, and you might see something like 40-50 dB of return loss or even better, depending on repeatability. However, remember that your measurement is only comparing the unknown against your calibration standard. Hence, seeing 60dB of return loss only means that the unknown is almost identical to the calibration standard you used. In practice, you could have calibrated the analyzer with a poor load that is 45 Ohms instead of 50 and the analyzer would "think" that a 45 Ohm unknown is a perfect 50 Ohms. The "internal calibration" procedure is in the service manual for the 8753, and I assume that it's also in the manual for the 8720. I don't have an 8720, so I am speculating. If you find it, you will see that a portion of the procedure is quite similar to the regular cal that you do all the time. Vladan |
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Re: 3586A encoder question
This is a good point too, Thanks.
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Antonio I8IOV --- In hp_agilent_equipment@..., Steve Reeves <steve_reeves@...> wrote:
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