EEVBlog #261 Marconi - Page 1
Forum section: electronics / general

author: tecman
author_rank: Frequent Contributor
timestamp: March 22, 2012, 05:53:33 pm
content: Dave, you're slipping.In the power supply, the metal band on the transformer is not mu-metal, but copper. Much more effcetive than mu-metal at high freqs. Also you pointed to the "output caps, but they are actually the input caps. Note the 250 volt ratings !paul

author: SeanB
author_rank: Super Contributor
timestamp: March 22, 2012, 07:12:02 pm
content: Dave, do you want some of the optional output protection and conversion adaptor units. I have some that are unused, and will not be using them really. They use a 50ma wire in fuse that does introduce a slight loss, but which protects from feeding back RF into the unit. Cheaper than that output protection built in, and saves you from oopsies. Converts from N to BNC and such.

author: ei6iz
author_rank: Newbie
timestamp: March 22, 2012, 11:05:27 pm
content: Dave,The 'penetrators' between the lower and upper sides of the RF board are decoupling caps (possibly also with some series inductance ) to keep stray noise out of the RF bits (& stray RF out of everything else )The copper tube is Microwave hard-line, used quite a bit in RF test gear. it's big advantage here is that the screen (being solid copper) is superb. Coax, even double screened and semi-rigid types leak too much for this kind of application.there are so many screws , RF gaskets and bits of finger stock required because by the time you get to 1GHz a couple of Cm is a significant distance in terms of RF wavelength and RF Impedance to ground climbs very rapidly with distance. an accurate Dynamic range of around 150dB over the full range of 9Khz to 1.2GHz is quite the feat of RF engineering and as a result detail matters ;-)I have to say, I'm a fan of Marconi Instruments RF gear (& indeed the racal stuff too)If you want a decent 10MHz external frequency reference to drive this, look for a 'thunderbolt' on ebay.Rubidium units are not so good as they can have fairly poor phase noise performance. The 'Tbolt' locks to GPS so you get the stability along with decent xtal oscillator phase noise specs. price is right too..If you can get your hands on one, you might wish to do a tear-down on a Racal RA17 receiver. They were the no expense spared pinnacle of Britsh 'hollow state' (tube) Radio receiver design from the 1950's, not bettered in terms of RF performance by solid state until around the mid 1980'sTakes a bit of work to keep em running like new but when they are in good shape they hold their own in terms of performance.There are a lot of similarities to the modular design approach and attention to RF details and it would provide an interesting comparison to the modern high end stuff.regardsBrendan EI6IZ

author: rolycat
author_rank: Super Contributor
timestamp: March 23, 2012, 12:19:17 am
content: This was painful to watch.The manufacturing date of this beautiful signal generator coincides neatly with the last days of GEC under Arnold Weinstock, who innocently handed over the company which he had spent over thirty years building into an engineering giant to the egregious George Simpson in 1996.Within five years Simpson and his accomplice John Mayo wrecked one of the world's great manufacturing companies with a repulsive mixture of greed and arrogance, backed by the financial Masters of the Universe who, as an encore, did their utmost to destroy the economy of the entire planet.There's not much electronics left that isn't made in China; almost nothing that's "Made in England", but maybe with inspiration from the boundless enthusiasm of people like Dave we can reclaim some vestige of occidental engineering excellence and start building things of real value again.

author: gregariz
author_rank: Frequent Contributor
timestamp: March 23, 2012, 01:35:17 am
content: Actually the tube is semi-rigid. Hardline is more akin to something like heliax. The penetrators are feed-thru caps/filters as mentioned. What your seeing is a cross between UHF and microwave construction. You wouldnt be able to get away with as much lumped component design in a higher microwave application. What strikes me is that apart from the uC control circuitry, not much has changed in design terms.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 23, 2012, 01:40:50 am
content: I want one!!British Engineering at its best!--Although they did have to put in a bit of quirky design with the cutouts that don't allow you to reach the screws!Dear old "Macaroni" made some marvellous stuff,as well as some "not so marvellous",& some downright evil!They were never quite as consistent as HP with their RF stuff,but even the "evil" stuff worked ,& was pretty reliable.The top level stuff like the one reviewed,could hold its own with anything made,anywhere!The GEC connection--Never had a lot to do with them,but their RF UHF RT links back in the '60s (first generation solid state) were beautifully constructed.The East-West Broadband microwave system was originally all GEC valve stuff.The guys who fixed that system also looked after the STL link for ABW2,& quite a few of the original Marconi modules in the STL were replaced with GEC ones--The Marconi link was pretty much an "orphan".The TV Transmitters at ABW2 were Marconi,& remained in service from about 1960 to 1990----not a bad run!We had an IFR spectrum Analyser at my last job.(Made in South Korea)It was a very nice unit,but had a few bugs.One was that a carrier which changed frequency fairly rapidly appeared as multiple carriers---not good when you are looking for a PLL fault.The other was that you could control it from a PC,but the only way to send displays to the PC was by using a floppy disc---& this thing was new in about 2005!

author: Kozmyk
author_rank: Regular Contributor
timestamp: March 23, 2012, 05:36:17 am
content: Hey Dave! That's? a neat little power driver you're using in the vid. What make is it?

author: EEVblog
author_rank: Unknown
timestamp: March 23, 2012, 05:38:47 am
content: Quote from: Kozmyk on March 23, 2012, 05:36:17 amJust a One Hung Low brand crap cordless screwdriver from Bunnings.Dave.

author: Kozmyk
author_rank: Regular Contributor
timestamp: March 23, 2012, 06:04:01 am
content: Quote from: EEVblog on March 23, 2012, 05:38:47 amCheers.I hadn't noticed them getting so small.Now that they have, and Li-Ion too, I think I'll get me one.Bosch IXO4 looks nice with it's Easy Access adapters 3Nm £39 ...just noticed that the Black&Decker KC460LN has more torques though 5-7Nm £26 ...Ho hum decisions decisions.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 23, 2012, 06:07:07 am
content: Quote from: vk6zgo on March 23, 2012, 01:40:50 amThe mechanical engineer was probably coming from the British automobile industry

author: EEVblog
author_rank: Unknown
timestamp: March 23, 2012, 06:11:48 am
content: Quote from: Kozmyk on March 23, 2012, 06:04:01 amI wanted the Bosch, but found it didn't have variable torque settings, so got the OneHungLow instead.Turns out the OneHungLow's lowest slip torque setting is still too high for the job of screwing the board on my uCurrent boxDave.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 23, 2012, 06:31:22 am
content: Quote from: rolycat on March 23, 2012, 12:19:17 amI looked athttp://en.wikipedia.org/wiki/Marconi_Companyhttp://en.wikipedia.org/wiki/Marconi_Communicationshttp://en.wikipedia.org/wiki/Marconi_Electronic_Systemsandhttp://en.wikipedia.org/wiki/General_Electric_Company_plcIt is hard to follow how often Marconi was merged, demerged, split and reorganized, and where "the real Marconi" did end up.QuoteLooking at all the mess Marconi went through maybe one big mistake was to favour national, British solutions over international, heaven forbid, European, ones. At a time when China was already gearing up and was preparing to steal the lunch of every electronic manufacturer in the world.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 23, 2012, 07:09:27 am
content: Quote from: EEVblog on March 23, 2012, 06:11:48 amThe old "Wrist Mk1" will probably still do it!

author: Kozmyk
author_rank: Regular Contributor
timestamp: March 23, 2012, 07:25:26 am
content: Pologize in advance for the departure from topic.When yer MkI Wrist is as decrepit as mine you save it for more delicate work.

author: rolycat
author_rank: Super Contributor
timestamp: March 23, 2012, 07:39:25 am
content: Quote from: BoredAtWork on March 23, 2012, 06:31:22 amIndeed. By 1996 GEC had swallowed a lot of other famous names, including big chunks of Ferranti, the creators of the world's first commercial computer and more importantly the rather splendid ZN414 radio-in-a-TO-18-can which was one of my very first electronics projects as a schoolboy.Ferranti also made the early ULAs used by 80s computers like the Acorn BBC micro and the Sinclair Spectrum - more examples of good engineering vanquished by short-sighted management - although of course Acorn gave birth to ARM, who by playing well with the international semiconductor giants are one of the few remaining British success stories in electronics.I guess its pointless to get misty-eyed over this ancient history. Time to get back to designing new stuff, and maybe hunting down great test gear like the 2023...

author: Kozmyk
author_rank: Regular Contributor
timestamp: March 23, 2012, 08:44:59 am
content: Quote from: EEVblog on March 23, 2012, 06:11:48 amFor baby torque jobs I got one of these from HobbyKing.http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7031It's uncalibrated but there is a scale on it so I cal'ed it myself using a milk bottle of water on the end of a lever.That was fun ... filling up the water until the clutch slipped then working out the torque each time.Jeez I hope I haven't lost the result sheet or I'll have to do it all over again

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: March 23, 2012, 10:54:07 am
content: Pardon me barging into this thread but what price tag would such a piece of kit have had on it?Who would have bought one and for what purpose?Oh and Dave, I too exclaimed "phworrrrrr" when the lid came off the RF board.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: March 23, 2012, 10:58:45 am
content: I nearly forgot to ask what is the beryllium used for?

author: Bored@Work
author_rank: Super Contributor
timestamp: March 23, 2012, 12:19:52 pm
content: Quote from: Ed.Kloonk on March 23, 2012, 10:54:07 amSome of these strange "used test equipment sites" claim the list price was once USD 5775. But one can't really trust these sites.QuoteThat is a little bit like asking who buys screwdrivers and for what purpose. Because such a generator wasn't build for a dedicated purpose. There are other types of generators build for special purposes, e.g. TV pattern generators. But not this one.Therefore the answer is those who need one for generating the kind of signal the generator can generate. That might be an engineer working on some communication system using such frequencies, or a scientist needing such signals for some experiment.

author: Psi
author_rank: Super Contributor
timestamp: March 23, 2012, 12:22:58 pm
content: Quote from: Ed.Kloonk on March 23, 2012, 10:58:45 amIt's got really good thermal conductivity for a non-metal.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: March 23, 2012, 12:32:19 pm
content: Ah. Thank you.

author: markus_b
author_rank: Regular Contributor
timestamp: March 23, 2012, 12:40:57 pm
content: Quote from: BoredAtWork on March 23, 2012, 12:19:52 pmIf you look on Ebay then you'll see them starting at $300 and going to $2000, depending on the built-in options (e.g. high-precision oscillator).

author: vk6zgo
author_rank: Super Contributor
timestamp: March 23, 2012, 12:56:17 pm
content: Quote from: Kozmyk on March 23, 2012, 08:44:59 amNow THAT'S Engineering!

author: kb2vsq
author_rank: Newbie
timestamp: March 23, 2012, 01:30:58 pm
content: Dave --- I disagree with your analysis on the top side. I think that is a multisection attenuator and that's why you have the multicolo(u)r ribbon going from the RF section to the connector -- as you said, it's DC control.I would liked to have seen more analysis of the RF sections, but hey, can't have too much fun now...

author: rolycat
author_rank: Super Contributor
timestamp: March 23, 2012, 02:25:18 pm
content: Quote from: Psi on March 23, 2012, 12:22:58 pmJust to be pedantic, although beryllium does indeed have really good thermal conductivity, itisa metal.I suspect Psi meant beryllia (beryllium oxide), which also has good thermal conductivity but is an electrical insulator.

author: tecman
author_rank: Frequent Contributor
timestamp: March 23, 2012, 03:03:02 pm
content: In electronics beryllium is most often found as beryllium-copper, which is a very good spring material, with the conductivity close to copper.paul

author: robrenz
author_rank: Super Contributor
timestamp: March 23, 2012, 03:10:59 pm
content: Quote from: Kozmyk on March 23, 2012, 06:04:01 amI have one of these and it has worked very well under heavy use.http://www.amazon.com/dp/B000WI9CIG/ref=asc_df_B000WI9CIG1947795?smid=ATVPDKIKX0DER&tag=hyprod-20&linkCode=asn&creative=395093&creativeASIN=B000WI9CIG&hvpos=none&hvexid=&hvnetw=g&hvrand=4822794381295520853&hvpone=&hvptwo=&hvqmt=

author: T4P
author_rank: Super Contributor
timestamp: March 23, 2012, 03:17:54 pm
content: Quote from: rolycat on March 23, 2012, 02:25:18 pmShort question ,Is it beryllium that is a heavy metal or does it turn into a heavy metal being a oxide of it's own product ?Sorry , did well at chemistry while in school but none of that made sense .

author: IanB
author_rank: Super Contributor
timestamp: March 23, 2012, 03:37:39 pm
content: Quote from: Dave.S on March 23, 2012, 03:17:54 pmBeryllium is not a heavy metal. Nobody even mentioned heavy metals in this thread.Although it has not been fully explained, I believe the use of beryllium oxide in that device was as heat sink compound.The cautionary note is because beryllium is quite poisonous and must be handled with care.

author: SeanB
author_rank: Super Contributor
timestamp: March 23, 2012, 03:46:31 pm
content: Beryllium is either added to brass to make it harder, but with a larger elastic modulus. Makes it springy and able to survive many cycles of operation, but it breaks in a few cycles if actually bent. Makes a great pressure gauge.The other use is as an oxide, where it is a better heat conductor than any other electrical insulator, and can be used in thick washers to reduce capacitance while still handling a large heat flow. Thus you can have good high frequency response with high dissipation, good in RF amplifiers. Drawback is that the dust is a carcinogen, and it is very bad if inhaled. Normally you can tell a beryllia washer by it being a pale pink colour, as shown in the video. Nice washers, no need for heatsink compound in many cases with smooth surfaces, just a thin coat of silicone grease, but you do need to be very careful not to exceed the recommended tightening torques on them. Brittle buggers though if mishandled.

author: wkb
author_rank: Super Contributor
timestamp: March 23, 2012, 03:49:14 pm
content: Quote from: IanB on March 23, 2012, 03:37:39 pmBeO is used for isolation in e.g. HF powertransistors. And today I have received a 150W 50ohm BeO-isolated resistor that is destined for a HF dummyload.In dustform BeO is harmful, see for more info:http://en.wikipedia.org/wiki/BerylliosisSo do not indiscriminately grind down things you do not know much about.... Yes, that also applies to the EEVblog teardown-ers around here!

author: T4P
author_rank: Super Contributor
timestamp: March 23, 2012, 04:27:34 pm
content: I always knew that if a metal was harmful , it's a heavy metal .But it looks like in dustform it's a carcinogen ,But when ingested it is a carcinogen too .But yes , beryllium is a heavy metal ,http://www.osha.gov/SLTC/metalsheavy/index.html

author: Lightages
author_rank: Unknown
timestamp: March 23, 2012, 04:51:06 pm
content: Beryllium is NOT a heavy metal. It is #4 on the periodic table. It is classified as an alkaline metal. The link provided for OSHA has the word "heavy" in the url, but beryllium is included in the list as a toxic metal only.Beryllium is a commonly used alloying agent for copper and aluminum. It adds strength and raises the melting temperature while also raising the high temperature strength of the alloy.It is believed that Beryllium in its pure form is quite toxic if inhaled in dust or powder form and there have been reports of people dying within days of this kind of exposure. If it is contained in an alloy it is generally accepted as safe to freely machine in an open environment. If one is machining Be in its pure form then many rather strict safety procedures are to be followed.In one of my earlier lives I had the need to know such things as I was designing equipment that made use of Be and other rather uncommonly used elements.

author: T4P
author_rank: Super Contributor
timestamp: March 23, 2012, 05:30:51 pm
content: Quote from: Lightages on March 23, 2012, 04:51:06 pmAw man ... poor me didn't read.

author: Neilm
author_rank: Super Contributor
timestamp: March 23, 2012, 05:41:32 pm
content: Quote from: Ed.Kloonk on March 23, 2012, 10:54:07 amI have seen quotes for that sort of signal generator of upwards of £15k new (for the options we wanted).I was trying to replace a signal generator that is even older than that one. Unfortunately, we did manage to get the old one fixed so no new toy to play withThe sig gen is used in our in house EMC testing facility. We do in house testing on all our equipment.Neil

author: w2aew
author_rank: Super Contributor
timestamp: March 25, 2012, 01:38:14 am
content: Quote from: BoredAtWork on March 23, 2012, 06:07:07 amNo, I don't think so - there wasn't a puddle of oil under it!

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2012, 09:52:04 am
content: No, it judt means the oil ran out a while ago........Kind of like flying on a Dakota - no oil do not get in, because it has all left. Thick like treacle syrup before flight, thin as water afterwards. To refill you might need a putty knife to help it pour from the cans.