Re: Marconi Q meter exciter
Yes, I've found that out the hard way. It's back to the drawing board :-(
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Re: Marconi Q meter exciter
On Wed, 31 May 2023 3:02? Morris Odell wrote:
"I'm impressed with Peter's transformer design"
I claim no originality for the transformer - there are a couple of threads weaving in and out of the topic covering construction and performance, in particular from Jaques Audet and KN5L q.v.? Note that while these designs work well as low impedance voltage sources, the power transfer is very small.? They won't handle the 0.5W or so that the TF1245 (IIRC) requires, the ferrite will saturate.
PeterS??? ??? G8EZE
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Re: Marconi Q meter exciter
Hi all,
It's great to see this subject come up again!
The easy stuff first: The bonding bars are 340mm long and 8.7 mm in diameter with a 9 mm X 10 mm knurled slotted head at one end and a 1/4" BSW thread at the other. And I don't think there's anything special about the coaxial connecting cable other than its length. I saw a suggestion somewhere that the length was kept short to avoid transmission line effects at the higher frequencies but a wavelength in coax at 50 MHz is much longer than the cable so I doubt that it's a real issue.
Now the harder stuff: I don't want to modify the TF1245A because I have the VHF exciter and live in hope of finding a TF1246. The only modification I might consider is to replace the metering diodes with modern hot carrier diodes if necessary. My synthesized signal generator tops out at about 10 dBm so I need a bit more than that to compensate for inefficiency and losses in the coupling circuit
I have had mixed success making the exciter. I duplicated the amplifier from the HP 4342A Q meter and fed it through a 10:1 transformer made from a FT50-43 toroid but the results were not satisfactory at the extremes of the frequency range.? I'm not sure what ratio is needed for such a transformer. The output of the HP circuit is an emitter follower so it will have a low source impedance and it needs to feed the TF1245 input at 0.5 ohms. If I can get it to supply enough power over the entire frequency range I will work towards building in an ALC using a photoresistor optocoupler. I have recently picked up a power amplifier module on ebay that is rated at 2 watts (33 dBm) and will do some more experiments with it although it might need some modification to get down below 1 MHz.
I'm impressed with Peter's transformer design - it's a much better arrangement than what I have been using so I will try and duplicate it and maybe that will improve things.
More news as it breaks!
Morris
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Re: Marconi Q meter exciter
Has anyone got the essential dimensions for the bonding bars?
Pete G4GJL
Nigel,?
Thanks for the hint about accessing through the side panel, I will try that route.
I concur that the cable is nothing special, although the handbook implies otherwise - I wondered if managing the length was to do with managing the unwanted resonance effects between the TF1245 and TF1246 that the bonding bars are supposed to suppress.
PeterS??? ??? G8EZE
-----Original Message-----
From: nigel adams via <bristol.rell6l= [email protected]>
To: [email protected]
Sent: Tue, 30 May 2023 10:41
Subject: Re: [Test Equipment Design & Construction] Marconi Q meter exciter
Two comments if I may.
?
Easiest way to access a TF1245 is via a side panel. Avoids disturbing the front panel casting.
?
AFAIK the BNC cable from either a TF1246 or 1247 Oscillator to the TF1245 is nothing special apart from its short length.
Regards
?
Nigel Adams ¨C Marconi Instruments Heritage Collection
?
?
Peter, do you know if there is anything special about the official cable specified by Marconi to interconnect the source with the Q-meter main instrument?
?
On 29 January 2023 9:52? (message #1496) Morris Odell wrote:
"Now I only have a TF1246 HF exciter on loan and will have to return it soon so unless I can find a reasonably priced one I'll have to make something suitable."
It would be interesting to know how this worked out as I was never able to get adequate power transfer over the full low range bandwidth without stray currents and resonances. ?
If preservation of the TF1245 "as built" is not important, the following may be of interest.
I built a simplified 50:1 transformer on a FT50-43 toroid in a 15mm copper water pipe end cap with a 3mm tapped brass hexagonal pillar as the centre conductor.? Hooking this onto the TF1245A front panel with? some test inductors bypassing the injection terminal showed that about +20dBm into the transformer with a 50 Ohm shunt termination provided more than enough drive for the magnification? metering circuits from 50kHz to 50MHz+ (approximately 20mV injection voltage). I was able to take stable Q measurements by both delta-F and delta-C methods with good agreement, but I am not chasing ultra high or absolute Q. ?
I am planning to substitute the prototype transformer or a variant for the 20 milli-Ohm injection assembly and cable so the TF1245A can be driven by a (synthesised) signal generator. It looks as though the TF1245A will probably have to be completely dismantled to get access to the front connector, so it may have to wait until Autumn. ?
PeterS??? G8EZE
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Re: Marconi Q meter exciter
That one has a proper shield between the primary and secondary windings which would control unwanted capacitive coupling.? I have some UT-141 cable but could not find it at the time, my quick-look-and-see effort has just a 3mm tapped hex pillar screwed to the copper cup.? 50 turns of enamelled copper wire on a FT50-43 toroid and a piece of plain (no copper) FR4 board in the bottom of the cup to provide some separation between windings and metal.? I may build a "better" one in due course!
PeterS??? ??? ??? G8EZE
-----Original Message-----
From: Mikek <amdx@...>
To: [email protected]
Sent: Tue, 30 May 2023 11:00
Subject: Re: [Test Equipment Design & Construction] Marconi Q meter exciter
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Re: Marconi Q meter exciter
Nigel,?
Thanks for the hint about accessing through the side panel, I will try that route.
I concur that the cable is nothing special, although the handbook implies otherwise - I wondered if managing the length was to do with managing the unwanted resonance effects between the TF1245 and TF1246 that the bonding bars are supposed to suppress.
PeterS??? ??? G8EZE
-----Original Message-----
From: nigel adams via groups.io <bristol.rell6l@...>
To: [email protected]
Sent: Tue, 30 May 2023 10:41
Subject: Re: [Test Equipment Design & Construction] Marconi Q meter exciter
Two comments if I may.
?
Easiest way to access a TF1245 is via a side panel. Avoids disturbing the front panel casting.
?
AFAIK the BNC cable from either a TF1246 or 1247 Oscillator to the TF1245 is nothing special apart from its short length.
Regards
?
Nigel Adams ¨C Marconi Instruments Heritage Collection
?
?
Peter, do you know if there is anything special about the official cable specified by Marconi to interconnect the source with the Q-meter main instrument?
?
On 29 January 2023 9:52? (message #1496) Morris Odell wrote:
"Now I only have a TF1246 HF exciter on loan and will have to return it soon so unless I can find a reasonably priced one I'll have to make something suitable."
It would be interesting to know how this worked out as I was never able to get adequate power transfer over the full low range bandwidth without stray currents and resonances. ?
If preservation of the TF1245 "as built" is not important, the following may be of interest.
I built a simplified 50:1 transformer on a FT50-43 toroid in a 15mm copper water pipe end cap with a 3mm tapped brass hexagonal pillar as the centre conductor.? Hooking this onto the TF1245A front panel with? some test inductors bypassing the injection terminal showed that about +20dBm into the transformer with a 50 Ohm shunt termination provided more than enough drive for the magnification? metering circuits from 50kHz to 50MHz+ (approximately 20mV injection voltage). I was able to take stable Q measurements by both delta-F and delta-C methods with good agreement, but I am not chasing ultra high or absolute Q. ?
I am planning to substitute the prototype transformer or a variant for the 20 milli-Ohm injection assembly and cable so the TF1245A can be driven by a (synthesised) signal generator. It looks as though the TF1245A will probably have to be completely dismantled to get access to the front connector, so it may have to wait until Autumn. ?
PeterS??? G8EZE
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Re: Marconi Q meter exciter
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Re: Marconi Q meter exciter
Thanks Nigel. I have used an 'ordinary' lab patch cable 200mm long and observed?no ill effects.....just wondered!
Pete On Tue, May 30, 2023 at 10:42?AM nigel adams via <bristol.rell6l= [email protected]> wrote:
Two comments if I may. ? Easiest way to access a TF1245 is via a side panel. Avoids disturbing the front panel casting. ? AFAIK the BNC cable from either a TF1246 or 1247 Oscillator to the TF1245 is nothing special apart from its short length. Regards ? Nigel Adams ¨C Marconi Instruments Heritage Collection ? ? Peter, do you know if there is anything special about the official cable specified by Marconi to interconnect the source with the Q-meter main instrument? ? On 29 January 2023 9:52? (message #1496) Morris Odell wrote:
"Now I only have a TF1246 HF exciter on loan and will have to return it soon so unless I can find a reasonably priced one I'll have to make something suitable."
It would be interesting to know how this worked out as I was never able to get adequate power transfer over the full low range bandwidth without stray currents and resonances. ?
If preservation of the TF1245 "as built" is not important, the following may be of interest.
I built a simplified 50:1 transformer on a FT50-43 toroid in a 15mm copper water pipe end cap with a 3mm tapped brass hexagonal pillar as the centre conductor.? Hooking this onto the TF1245A front panel with? some test inductors bypassing the injection terminal showed that about +20dBm into the transformer with a 50 Ohm shunt termination provided more than enough drive for the magnification? metering circuits from 50kHz to 50MHz+ (approximately 20mV injection voltage). I was able to take stable Q measurements by both delta-F and delta-C methods with good agreement, but I am not chasing ultra high or absolute Q. ?
I am planning to substitute the prototype transformer or a variant for the 20 milli-Ohm injection assembly and cable so the TF1245A can be driven by a (synthesised) signal generator. It looks as though the TF1245A will probably have to be completely dismantled to get access to the front connector, so it may have to wait until Autumn. ?
PeterS??? G8EZE
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Re: Marconi Q meter exciter
Two comments if I may. ? Easiest way to access a TF1245 is via a side panel. Avoids disturbing the front panel casting. ? AFAIK the BNC cable from either a TF1246 or 1247 Oscillator to the TF1245 is nothing special apart from its short length. Regards ? Nigel Adams ¨C Marconi Instruments Heritage Collection ?
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From: [email protected] <[email protected]> On Behalf Of Pete_G4GJL
Sent: Tuesday, May 30, 2023 10:15 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Marconi Q meter exciter? Peter, do you know if there is anything special about the official cable specified by Marconi to interconnect the source with the Q-meter main instrument? ? On 29 January 2023 9:52? (message #1496) Morris Odell wrote:
"Now I only have a TF1246 HF exciter on loan and will have to return it soon so unless I can find a reasonably priced one I'll have to make something suitable."
It would be interesting to know how this worked out as I was never able to get adequate power transfer over the full low range bandwidth without stray currents and resonances. ?
If preservation of the TF1245 "as built" is not important, the following may be of interest.
I built a simplified 50:1 transformer on a FT50-43 toroid in a 15mm copper water pipe end cap with a 3mm tapped brass hexagonal pillar as the centre conductor.? Hooking this onto the TF1245A front panel with? some test inductors bypassing the injection terminal showed that about +20dBm into the transformer with a 50 Ohm shunt termination provided more than enough drive for the magnification? metering circuits from 50kHz to 50MHz+ (approximately 20mV injection voltage). I was able to take stable Q measurements by both delta-F and delta-C methods with good agreement, but I am not chasing ultra high or absolute Q. ?
I am planning to substitute the prototype transformer or a variant for the 20 milli-Ohm injection assembly and cable so the TF1245A can be driven by a (synthesised) signal generator. It looks as though the TF1245A will probably have to be completely dismantled to get access to the front connector, so it may have to wait until Autumn. ?
PeterS??? G8EZE
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Re: Marconi Q meter exciter
Peter, do you know if there is anything special about the official cable specified by Marconi to interconnect the source with the Q-meter main instrument?
Pete G4GJL
On 29 January 2023 9:52? (message #1496) Morris Odell wrote:
"Now I only have a TF1246 HF exciter on loan and will have to return it soon so unless I can find a reasonably priced one I'll have to make something suitable."
It would be interesting to know how this worked out as I was never able to get adequate power transfer over the full low range bandwidth without stray currents and resonances. ?
If preservation of the TF1245 "as built" is not important, the following may be of interest.
I built a simplified 50:1 transformer on a FT50-43 toroid in a 15mm copper water pipe end cap with a 3mm tapped brass hexagonal pillar as the centre conductor.? Hooking this onto the TF1245A front panel with? some test inductors bypassing the injection terminal showed that about +20dBm into the transformer with a 50 Ohm shunt termination provided more than enough drive for the magnification? metering circuits from 50kHz to 50MHz+ (approximately 20mV injection voltage). I was able to take stable Q measurements by both delta-F and delta-C methods with good agreement, but I am not chasing ultra high or absolute Q. ?
I am planning to substitute the prototype transformer or a variant for the 20 milli-Ohm injection assembly and cable so the TF1245A can be driven by a (synthesised) signal generator. It looks as though the TF1245A will probably have to be completely dismantled to get access to the front connector, so it may have to wait until Autumn. ?
PeterS??? G8EZE
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Re: Marconi Q meter exciter
On 29 January 2023 9:52? (message #1496) Morris Odell wrote:
"Now I only have a TF1246 HF exciter on loan and will have to return it soon so unless I can find a reasonably priced one I'll have to make something suitable."
It would be interesting to know how this worked out as I was never able to get adequate power transfer over the full low range bandwidth without stray currents and resonances. ?
If preservation of the TF1245 "as built" is not important, the following may be of interest.
I built a simplified 50:1 transformer on a FT50-43 toroid in a 15mm copper water pipe end cap with a 3mm tapped brass hexagonal pillar as the centre conductor.? Hooking this onto the TF1245A front panel with? some test inductors bypassing the injection terminal showed that about +20dBm into the transformer with a 50 Ohm shunt termination provided more than enough drive for the magnification? metering circuits from 50kHz to 50MHz+ (approximately 20mV injection voltage). I was able to take stable Q measurements by both delta-F and delta-C methods with good agreement, but I am not chasing ultra high or absolute Q. ?
I am planning to substitute the prototype transformer or a variant for the 20 milli-Ohm injection assembly and cable so the TF1245A can be driven by a (synthesised) signal generator. It looks as though the TF1245A will probably have to be completely dismantled to get access to the front connector, so it may have to wait until Autumn. ?
PeterS??? G8EZE
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This is from my son-in-law who is a internet security expert.
"By far the easiest option is for him to make a Google account and put all the files on Google drive. Then he can make the permissions such that anyone with the link to the files can download them.?
Google has a 15 GB limit per account but there's a $1 per month option to increase the storage to 100 GB. Way, way cheaper than operating a server and paying for a fixed internet connection. Also Google takes care of the "secure" part of his requirements list - he won't have to worry about his server getting hacked and used by attackers to conduct more attacks. Or chancing that an attacker can poison the documents and help the attacker gain access to computers that download the documents.?
Google and Google drive are definitely not as "techie" of a solution but keeping it simple is the name of the game.?
Hope this helps.?
Steve "
I would be willing to pay/contribute to the? 100GB option to make you data available to our HPAK guys. This option would allow you to keep your server private, but share the data, and provide you with a back up of your server. If you setup a PayPal account for the 100GB account, everyone that uses your info can contribute $1 towards the monthly fees. Just let us know when the account needs to be replenished.? The same applies to the other HPAK accounts. Each of the other owners can set up a PayPal account for each of the Google .io groups and send out a message when each account needs to be replenished, or when the account size needs to be larger - say another 100GB or more.? I would happily contribute $20-100/yr. to keep the info public and accessible to our members.
Don Bitters
On Sun, May 28, 2023 at 9:21 PM, bownes <bownes@...> wrote:
When I need to do this, I use a virtual machine, put it all on
it's own filesystem, mount the FS read-only, and shared it out
using http/https that has nothing but the shared files.
Bob
On 5/28/23 6:48 PM, Stephen Hanselman
wrote:
i have 20GB, about 8000 files, on components,and units that my
company, and it's predecessor, accumulated over 40 years.? In some
cases there are sever copies of the same file based on release
date.? true a good bit is available on MANY other sites but we
have it in one place. it's to much to copy to somewhere but i'd
like to make it available to others on this and other sites.? i
have a web server with a fixed IP address can someone point me at
methods to:
1. allow access to others
2. maintain a high level of security
Please PM with ideas
Steve
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Web servers that don't run CGI or otherwise process user input can be almost bulletproof.? ?You don't even need any .html files at all, just point the webserver?at the top level directory and make sure directory browsing is enabled.
On Sun, May 28, 2023 at 3:48?PM Stephen Hanselman < kc4sw.io@...> wrote: i have 20GB, about 8000 files, on components,and units that my company, and it's predecessor, accumulated over 40 years.? In some cases there are sever copies of the same file based on release date.? true a good bit is available on MANY other sites but we have it in one place. it's to much to copy to somewhere but i'd like to make it available to others on this and other sites.? i have a web server with a fixed IP address can someone point me at methods to:
1. allow access to others
2. maintain a high level of security
Please PM with ideas
Steve
|
When I need to do this, I use a virtual machine, put it all on
it's own filesystem, mount the FS read-only, and shared it out
using http/https that has nothing but the shared files.
Bob
On 5/28/23 6:48 PM, Stephen Hanselman
wrote:
toggle quoted message
Show quoted text
i have 20GB, about 8000 files, on components,and units that my
company, and it's predecessor, accumulated over 40 years.? In some
cases there are sever copies of the same file based on release
date.? true a good bit is available on MANY other sites but we
have it in one place. it's to much to copy to somewhere but i'd
like to make it available to others on this and other sites.? i
have a web server with a fixed IP address can someone point me at
methods to:
1. allow access to others
2. maintain a high level of security
Please PM with ideas
Steve
|
i have 20GB, about 8000 files, on components,and units that my company, and it's predecessor, accumulated over 40 years.? In some cases there are sever copies of the same file based on release date.? true a good bit is available on MANY other sites but we have it in one place. it's to much to copy to somewhere but i'd like to make it available to others on this and other sites.? i have a web server with a fixed IP address can someone point me at methods to:
1. allow access to others
2. maintain a high level of security
Please PM with ideas
Steve
|
Re: Can an antenna noise bridge be used to measure the antenna input port impedance on a receiver?
<forehead slap>
Yes, of course you are right! To the rear of the class I go!
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 5/22/2023 17:47, Dale H. Cook wrote: On 5/22/2023 7:03 PM, Tom Lee wrote:
I've never used one for that purpose, but you will likely need to add an attenuator, as most noise bridges will overload front ends. The problem is that the attenuator impedance will swamp the front end impedance.
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Re: Can an antenna noise bridge be used to measure the antenna input port impedance on a receiver?
On 5/22/2023 7:03 PM, Tom Lee wrote: I've never used one for that purpose, but you will likely need to add an attenuator, as most noise bridges will overload front ends. The problem is that the attenuator impedance will swamp the front end impedance. -- Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
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Re: Can an antenna noise bridge be used to measure the antenna input port impedance on a receiver?
On 5/19/2023 3:16 PM, Jeff Green wrote: Can an antenna noise bridge be used to measure the antenna input port impedance on a receiver? It can be, if it has enough sensitivity to keep from blowing up the front end. Don't expect to see 50 + j0 everywhere in its coverage range - you may be lucky to see that in only a few spots. The old saw is that antenna mismatch is a lot less critical in a receiver than it is in a transmitter. -- Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
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Re: Can an antenna noise bridge be used to measure the antenna input port impedance on a receiver?
I've never used one for that purpose, but you will likely need to
add an attenuator, as most noise bridges will overload front ends.
Give it a try and report back.
-- Cheers
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 5/19/2023 12:16, Jeff Green wrote:
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Show quoted text
I was given a Heathkit HD-1422 and a
Heathkit HD-1250 "Solid State Dip Meter." Both work fine, were
built with care and look like they were built yesterday.
?
Can an antenna noise bridge be used to
measure the antenna input port impedance on a receiver?
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Locked
Re: HP8711A Schematics A5
On Thu, May 18, 2023 at 12:32 PM, Frans van Empel wrote:
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
The HP/Agilent/Keysight group /g/HP-Agilent-Keysight-equipmentwould be a far more appropriate place to discuss getting manuals for HP test equipment. I'm locking the topic, as it really is off-topic of the group, and there is a better place to discuss it. Dave
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Pete_G4GJL
bownes
Dale H. Cook
Dr. David Kirkby, Kirkby Microwave Ltd