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Re: HP8711A Schematics A5
Hi Sam, Thanks ! Since?I am looking for the difference between the 50 Ohm and 75 Ohm version, maybe a CLIP of the HP8713A? will be more helpful. The A5 module probably ( and hopefully ) only will contain a better frontend and directional coupler. 73, Frans? ?PA0FVE Op do 18 mei 2023 om 04:35 schreef Sam Reaves <sam.reaves@...>: You might try Artek Manuals as they have a clip for the HP8711B which IIRC is just an upgrade of the CPU/Video board. They have a complete set for 19.00USD |
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Re: Accurate RF field strength Measurements
On Thu, May 18, 2023 at 12:29 PM, Jeff Green wrote:
I will not remove the topic. If it's being dealt with somewhere else that's fine, but I would have to have a very good reason to delete a thread, and that's not one of them. Dave (group owner) |
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Re: Accurate RF field strength Measurements
Jeff, ? First, the type of antenna you need to use is dependent upon your frequency range of interest.? And from that if you are looking for accurate field strength measurements you have to use ?an antenna with a known antenna factor (AF) or to put it basically, a known gain figure to know what signal level it is giving you.? This is usually obtained by comparing your subject unknown antenna under test (AUT) against a known gain antenna on either an open test range or in an anechoic chamber. ? There can be more simpler approaches (somewhat including theoretical) determining the antenna factor but all depends upon what you are using for your test environment, reference antenna or other means to obtain a known field strength measurement at your AUT location.? Any of these approaches with loose field strength data will give you loose results when trying to obtain the antenna factor. ? If you are planning on using a specific antenna for relative (comparison) measurements I wouldn¡¯t be as worried about an accurate antenna factor.? But if you are doing absolute signal level measurements then you ?need to have reasonable accuracy in order to determine the field strength you are measuring. ? Aside from this the gain of an antenna is not necessarily flat over its usable frequency range.? Manufacturers of EMC (Electro Magnetic Compatibility) test range antennas will usually provide a curve indicating the AF over that range of frequencies. ? I have basically leaned on the side of very accurate antennas in this note.? And from looking at some of the antennas in the links below you will find that they are manufactured to very high standards.? This is primarily because these antennas are required to take measurements that are used to provide test results in accordance to very stringent government and industry standards (i.e. FCC, IEC, VDE, CSA, etc.) ? Below are few reference links regarding antenna calibration plus some examples of manufacturers and distributors who provide calibrated antennas for precision measurements that are sometimes very esoteric.? Don¡¯t be shocked by what you see in the way of antennas.? These are utilized for highly accurate measurements but will give you an idea of the style that are used for various frequency ranges when employed in a precision test environment. ?
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? I hope this helps. ? Greg |
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Re: HP8711A Schematics A5
Thanks a lot Sam ! It is an open door to stress the importance of having access to the proper schematics... I do hope that HP did not make a mistake by putting the only HP8711B module into the HP8711A? Component-Level Information Packet. 73, Frans? ?PA0FVE Op do 18 mei 2023 om 03:35 schreef Sam Reaves <sam.reaves@...>:
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Re: Determining the impedance of an unknown cable:
¿ªÔÆÌåÓýThanks. ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ? From: [email protected] [mailto:[email protected]] On Behalf Of Ed Breya via groups.io ? No equations to remember - just rules of thumb. The higher the Z, the lower the C. I don't recall the exact numbers, but I think 50 ohm cable is about 30 pF/foot, while 75 ohm is about 25 or so, and so on, as Z increases. there are all kinds of data and tables and such with precise numbers, but the trend is that Z mostly determines C (and L too), regardless of dielectric constant and velocity of the insulators and such. |
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Re: HP8711A Schematics A5
You might try Artek Manuals as they have a clip for the HP8711B which IIRC is just an upgrade of the CPU/Video board. They have a complete set for 19.00USD
Search on 8711 Sam |
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Re: HP8711A Schematics A5
I sent you a private reply but I did find my original scan on my laptop. The index for the CLIP shows only the 50 Ohm version so unfortunately that is all that I have. I also uploaded those to KO4BB.com
Sam |
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Re: HP8711A Schematics A5
I scanned that original manual for HP and they put it up on their site several?years?ago. I scanned every page that was in the manual. I still have the manual but will have to get it back from the person I loaned it to and verify if I missed a page. This will probably take a couple of weeks. Best regards, Sam ? Sam Reaves
ARS W3OHM
Owner / Moderator of: LeCroy Owners Group on Groups.io Sencore Owners Group on Groups.io Sprint Layout Group on Groups.io?? Pulsonix EDA Group on Groups.io LPKF Owners Group on Groups.io
Electronics and Mechanical Hardware Design Engineering Manager Staff Scientist Andritz Rolls Global Research Center (RETIRED) |
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HP8711A Schematics A5
I am looking for the schematics of the A5 Receiver Assembly for an HP8711A.
HP's relevant Component Level Repair Service Guide ( # 08711-9004) is giving the wrong information.
There the schematics are given for the 50 Ohm version ( 08711-60105 ) instead of the required 75Ohm version (-08711-60070 ).
73,
Frans? ?PA0FVE
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Re: Determining the impedance of an unknown cable:
For those who want the equations, here they are:
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1) The capacitance per length is 1/(Zo*v), where v is the speed of light in the cable. For RG58, v is 2/3 the free-space speed of light, so you get 100pF/m, just as Ed says. The way I always remember it is that the ZoC time constant is just the one-way time delay, length/v. If you are trying to work out Zo from capacitance measurements, use Zo = 1/(C_per_length*v) 2) The inductance per length is Zo/v, so you could also infer Zo from inductance measurements if you wanted to do it that way for some reason. The L/Zo time constant is again just the one-way time delay, length/v. -- Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 5/16/2023 21:34, Ed Breya via groups.io wrote:
No equations to remember - just rules of thumb. The higher the Z, the lower the C. I don't recall the exact numbers, but I think 50 ohm cable is about 30 pF/foot, while 75 ohm is about 25 or so, and so on, as Z increases. there are all kinds of data and tables and such with precise numbers, but the trend is that Z mostly determines C (and L too), regardless of dielectric constant and velocity of the insulators and such. |
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Re: Determining the impedance of an unknown cable:
No equations to remember - just rules of thumb. The higher the Z, the lower the C. I don't recall the exact numbers, but I think 50 ohm cable is about 30 pF/foot, while 75 ohm is about 25 or so, and so on, as Z increases. there are all kinds of data and tables and such with precise numbers, but the trend is that Z mostly determines C (and L too), regardless of dielectric constant and velocity of the insulators and such.
Ed |
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Re: Determining the impedance of an unknown cable:
¿ªÔÆÌåÓýEd.? I¡¯m afraid I don¡¯t remember all of my transmission line equations.? Please tell us how it¡¯s done. ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ? From: [email protected] [mailto:[email protected]] On Behalf Of Ed Breya via groups.io ? You can also do it by measuring the capacitance, if you know the length. |
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Re: This PDF shows one way to perform a simplified measurement of an audio amplifier:
¿ªÔÆÌåÓýThe reactive part of the impedance of resistors of this value is unpredictable at best.? Of course for RF amplifiers the value would have to be scaled down quite a lot.? Even so resistors still have self-inductance as well as shunt capacitance.? A satisfactory measurement could be made over a narrow frequency range if the resistor could be characterized over the range. ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jeff Green ? This PDF shows one way to perform a simplified measurement of an audio amplifier: ? I realize this almost certainly will not work for RF...but it might...any ideas? ? Jensen is a major player in extremely high end audio transformers. Their application notes are very informative. i |
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Re: Low noise high reverse isolation low distortion RF Amplifier
Once you determine the signal levels, from the amplifier sample port, as presented to the SpecAn, simulate that input with two isolated signal generators (Combined via 3dB hybrids and isolating pads) to make sure the measurement result is not dominated by Specan internal IM generation.
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Lester B Veenstra K1YCM M?YCM W8YCM 6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1) lester@... 452 Stable Ln Keyser WV 26726 USA GPS: 39.336826 N 78.982287 W (Google) GPS: 39.33682 N 78.9823741 W (GPSDO) Telephones: Home: +1-304-289-6057 US cell +1-304-790-9192 Jamaica cell: +1-876-456-8898 -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of G8HUL Sent: Tuesday, May 16, 2023 3:57 AM To: [email protected] Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier In order to measure the IMD levels, unless the performance of the amplifier is terrible, it will have to be operated near it upper limit otherwise the IMD products will be so small as not to be visible on a spectrum analyser; so the signals concerned will not be that small, certainly in the range where very poor connector and cable non-linearities might play a part. Regards Jeff -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Brooke Clarke via groups.io Sent: 15 May 2023 20:07 To: [email protected] Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier Hi Jeff: The paper on Gore's web page is talking about high-power, multichannel systems. The Langford paper is talking about the second order intercept of an active antenna and the feed line that comes after it, i.e. very low power levels. But details are missing, like what length of line and how the measurement was made. -- Have Fun, Brooke Clarke, N6GCE axioms: 1. The extent to which you can fix or improve something will be limited by how well you understand how it works. 2. Everybody, with no exceptions, holds false beliefs. -------- Original Message -------- I would disagree with Tom regarding " Properly functioning cables and connectors" not being non-linear. There is always some non-linearity, it just depends on the level. Even the slightest amount of contact resistance in the braid or at connector interface will cause unwanted products, perhaps at an extremely low level but they will be there. There is a lot of info on the subject on the web, but here is one example: < > <> Regards Jeff G8HUL -----Original Message----- From: [email protected] <mailto:[email protected]> <[email protected]> <mailto:[email protected]> On Behalf Of Tom Lee Sent: 14 May 2023 12:28 To: [email protected] <mailto:[email protected]> Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier I agree with Jeff. Properly functioning cables and connectors are not nonlinear and thus cannot produce the effects that Lankford reports (assuming that he has achieved a proper match to eliminate the obvious length-dependent effects). A 20dB degradation in intercept sounds like the result of a tarnished connector to me. -- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 5/14/2023 01:42, G8HUL wrote: I think that the coax cables, and connectors, should be investigated in isolation, Non-linearities in cables and connectors are a well-known phenomenon. 73 Jeff G8HUL -----Original Message----- From: [email protected] <mailto:[email protected]> <[email protected]> <mailto:[email protected]> On Behalf Of Jeff Green Sent: 14 May 2023 01:19 To: [email protected] <mailto:[email protected]> Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier The best I can do is to refer you to this web page PDF, Dr. Lankford's concept of best small antennas. ,%20LW,%20And%20SW%20rev%202.pdf Here is some of the text" "While studying active whip intercepts some time ago I discovered, much to my amazement, that long coax (50 feet) lead often degrades 2nd order intercepts of active whip antennas by 20dB |
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Re: Low noise high reverse isolation low distortion RF Amplifier
In order to measure the IMD levels, unless the performance of the amplifier is terrible, it will have to be operated near it upper limit otherwise the IMD products will be so small as not to be visible on a spectrum analyser; so the signals concerned will not be that small, certainly in the range where very poor connector and cable non-linearities might play a part.
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Regards Jeff -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Brooke Clarke via groups.io Sent: 15 May 2023 20:07 To: [email protected] Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier Hi Jeff: The paper on Gore's web page is talking about high-power, multichannel systems. The Langford paper is talking about the second order intercept of an active antenna and the feed line that comes after it, i.e. very low power levels. But details are missing, like what length of line and how the measurement was made. -- Have Fun, Brooke Clarke, N6GCE axioms: 1. The extent to which you can fix or improve something will be limited by how well you understand how it works. 2. Everybody, with no exceptions, holds false beliefs. -------- Original Message -------- I would disagree with Tom regarding " Properly functioning cables and connectors" not being non-linear. There is always some non-linearity, it just depends on the level. Even the slightest amount of contact resistance in the braid or at connector interface will cause unwanted products, perhaps at an extremely low level but they will be there. There is a lot of info on the subject on the web, but here is one example: < > <> Regards Jeff G8HUL -----Original Message----- From: [email protected] <mailto:[email protected]> <[email protected]> <mailto:[email protected]> On Behalf Of Tom Lee Sent: 14 May 2023 12:28 To: [email protected] <mailto:[email protected]> Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier I agree with Jeff. Properly functioning cables and connectors are not nonlinear and thus cannot produce the effects that Lankford reports (assuming that he has achieved a proper match to eliminate the obvious length-dependent effects). A 20dB degradation in intercept sounds like the result of a tarnished connector to me. -- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 5/14/2023 01:42, G8HUL wrote: I think that the coax cables, and connectors, should be investigated in isolation, Non-linearities in cables and connectors are a well-known phenomenon. 73 Jeff G8HUL -----Original Message----- From: [email protected] <mailto:[email protected]> <[email protected]> <mailto:[email protected]> On Behalf Of Jeff Green Sent: 14 May 2023 01:19 To: [email protected] <mailto:[email protected]> Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier The best I can do is to refer you to this web page PDF, Dr. Lankford's concept of best small antennas. ,%20LW,%20And%20SW%20rev%202.pdf Here is some of the text" "While studying active whip intercepts some time ago I discovered, much to my amazement, that long coax (50 feet) lead often degrades 2nd order intercepts of active whip antennas by 20dB |
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Re: Low noise high reverse isolation low distortion RF Amplifier
¿ªÔÆÌåÓýHi Jeff:The paper on Gore's web page is talking about high-power, multichannel systems. The Langford paper is talking about the second order intercept of an active antenna and the feed line that comes after it, i.e. very low power levels.? But details are missing, like what length of line and how the measurement was made. -- Have Fun, Brooke Clarke, N6GCE axioms: 1. The extent to which you can fix or improve something will be limited by how well you understand how it works. 2. Everybody, with no exceptions, holds false beliefs. -------- Original Message --------
I would disagree with Tom regarding " Properly functioning cables and connectors" not being non-linear. There is always some non-linearity, it just depends on the level. Even the slightest amount of contact resistance in the braid or at connector interface will cause unwanted products, perhaps at an extremely low level but they will be there. There is a lot of info on the subject on the web, but here is one example: Regards Jeff G8HUL -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Tom Lee Sent: 14 May 2023 12:28 To: [email protected] Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier I agree with Jeff. Properly functioning cables and connectors are not nonlinear and thus cannot produce the effects that Lankford reports (assuming that he has achieved a proper match to eliminate the obvious length-dependent effects). A 20dB degradation in intercept sounds like the result of a tarnished connector to me. -- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 5/14/2023 01:42, G8HUL wrote:I think that the coax cables, and connectors, should be investigated in isolation, Non-linearities in cables and connectors are a well-known phenomenon. 73 Jeff G8HUL -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Jeff Green Sent: 14 May 2023 01:19 To: [email protected] Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier The best I can do is to refer you to this web page PDF, Dr. Lankford's concept of best small antennas. ,%20LW,%20And%20SW%20rev%202.pdf Here is some of the text" "While studying active whip intercepts some time ago I discovered, much to my amazement, that long coax (50 feet) lead often degrades 2nd order intercepts of active whip antennas by 20dB |
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Re: Low noise high reverse isolation low distortion RF Amplifier
I would disagree with Tom regarding " Properly functioning cables and connectors" not being non-linear. There is always some non-linearity, it just depends on the level. Even the slightest amount of contact resistance in the braid or at connector interface will cause unwanted products, perhaps at an extremely low level but they will be there.
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There is a lot of info on the subject on the web, but here is one example: < > Regards Jeff G8HUL -----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Tom Lee Sent: 14 May 2023 12:28 To: [email protected] Subject: Re: [Test Equipment Design & Construction] Low noise high reverse isolation low distortion RF Amplifier I agree with Jeff. Properly functioning cables and connectors are not nonlinear and thus cannot produce the effects that Lankford reports (assuming that he has achieved a proper match to eliminate the obvious length-dependent effects). A 20dB degradation in intercept sounds like the result of a tarnished connector to me. -- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 420 Via Palou Mall Stanford University Stanford, CA 94305-4070 On 5/14/2023 01:42, G8HUL wrote: I think that the coax cables, and connectors, should be investigated in isolation, Non-linearities in cables and connectors are a well-known phenomenon. |
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Re: Low noise high reverse isolation low distortion RF Amplifier
Well, everything is nonlinear to sone degree, but that¡¯s pedantry and not useful engineering. We¡¯re looking at a claimed 20dB degradation in intercept. That¡¯s well beyond anything that can be attributed to a proper cable/connector system.
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Cheers Tom Sent from my iThing; please forgive the typos and brevity On May 14, 2023, at 09:34, G8HUL <g8hul@...> wrote: |
Dr. David Kirkby, Kirkby Microwave Ltd
Sam Reaves
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