#EK07

[ptiautiste]

Finally...

I was looking for a really good shortwave receiver for at least a decade -an old tube equipped one of course. The problem getting one nowadays is that they were only produced in small numbers half a century (or more) ago, since then most are scrapped, botched, altered or corroded cause of bad storage -or all together. So if you have the chance getting one today you most likely will buy a 'construction site', needing hundreds of working hours for restoring it in a good working condition.

But after a looong search finally i had real luck. A big wooden crate was delivered on a pallet.

In this crate was one of the -for my opinion- ugliest shortwave receivers ever built, but at the same time also one of the best ones: a Rohde + Schwarz EK07.

Built in 1958 this one was a storage unit from the German Army. Well stored, regularly maintained and serviced, not altered, not botched, never used. So it is in nearly mint condition. It wasn't cheap but getting my hands on this was just sheer luck. Without doing anything: it's in perfect working order. No potentiometer, no switch crackles, every tube checks new -of course you can check all the tubes in the radio itself without removing them.

The manufacturer is more known for it's precision Lab-Equipment and less for it's shortwave receivers. This is also because their receivers weren't consumer or amateur gear, this was pro gear by any means. They were used in applications like coast guards or military surveillance and such. Always things where equipment costs doesn't matter -only the outcome. So back in 1958 when this unit was manufactured you could buy at least two brand new cars for the same amount of money. In exchange for this you got a masterpiece of german engineering and craftsmanship -and also an electro-mechanical nightmare if anything fails and you're not absolutely familiar with it's guts.

Fancy? No, there's absolutely nothing fancy on these. These are absolute workhorses, designed for doing an important job 24/7/365 for decades. Just take a look to that bandswich gear in the photo above. How often you have to switch over the bands until this would be worn out? Millions and Millions of times... And nope: this dark residues at that drum on the left and box below isn't mold or such. These are completely silver plated so it's just the darkened silver.

As you may see, most of the structural parts are made of die-cast and aluminum, so from the materials used it's relatively light weight. But all that built-in sturdiness and shielding adds up to staggering 147lbs/67kg. It's only a receiver, not a transmitter or a power amplifier.

Tubes... and more tubes

If you're not familiar with tube radios: your average AM (and shortwave) Radio from the 50's or 60's used 4 tubes (without the rectifier if this was a tube). Your trusty Hammarlund or Yaesu shortwave receiver from that time would have somewhat from 8 to 12 tubes -and these were quite good and sensitive receivers! This Rohde + Schwarz counts 28 tubes.

Some tubes here, some there, all fully shielded. But why the hell that much? The answer is quite simple: stability. On every count. Constant and stable gain over all bands and for a looong service time, stunningly stable VFO frequencies and all that stuff. No, they used no consumer tubes like in your TV or such. All of them are out of the 'commercial'-tube-series with a guaranteed service life of at least 10000 hours like in every aircraft of that time or such. Failing was not an option, this HAD to work.

Speaking about stability and accuracy:

this of course isn't digital stuff -it's purely analog. In the pictures below you can see the dials. Just add both frequencies and you know where you are -here on 29.630MHz or 29630kHz.

As you see: your readout is easily accurate down to less than 500Hz. So you can read at least 500Hz out of 29630000Hz. With other words the accuracy of your readout is 0.001687% in this case. Your average modern digital multimeter would be proud if it came only near to this 65 year old contraption.

Of course that large dial in the picture on the left isn't the only one. There are 12 of 'em, mounted on a drum and rotating according to the selected band. Giving you a simple S-Meter like in other shortwave receiver was of course also not possible.

Instead they provided you with a Voltmeter which displays directly the input voltage at the antenna input -and the threshold voltage for the 'Squelch' (if you have set that) which isn't a normal squelch. If activated it doesn't cut your Audio, it reduces the Gain instead with a settable time constant, so it acts more like a active noise cancelling between any signal -also between any dash and dot if you're receiving CW (Morse Code). Besides that you can choose your IF-Passband between 150Hz and 12kHz, have a absolutely stable BFO, a good Envelope Detector for AM-Reception and a perfect Audio Stage - that's all.

Speaking of the Audio Stage: 2W undistorted output power from a single end class-A is more than you need with a good speaker. McIntosh ® would call that circuit 'Unity Coupled', further a E88CC for the Audio-Preamp. We're talking about an Shortwave Radio, not an 'High-End' Audio Amplifier. Wanna take recordings of what you hear? No problem: here's your Line-Output, symmetric, 600 ohms, transformer coupled and with +10dBm (if you want) and in accordance to all Studio-Standarts. Sound quality for AM Broadcasts? With a passband switchable up to max. 12kHz for the IF better than the majority of stations can provide.

Precise?

So far so good, but what's about the heart of every shortwave receiver: the Oscillator or VFO? How stable and precisely does it beat after 65 years?

In your trusty -and quite good- Hammarlund or Yaesu amateur Radio from these days the VFO usually is equipped with two tubes: the Oscillator itself and the buffer amplifier -both sometimes also united in one bulb. If i hadn't lost track here they used 12 -and tons of other stuff. So that frickin VFO has a component count which is easily about the order of a complete shortwave receiver.

What the hell is all that stuff about -and wtf they had for breakfast back then? The answer is again simple: precision and stability.

As i said: this thing is 65 years old and i touched nothing. Of course I checked how much it's 'off' in terms of the frequency. After warming up for 20 Minutes i checked it every 1000kHz from the bottom to the top of its range. It was a bit different between all points, at some less than 50Hz and about 1kHz worst case.

My Lab-Equipment is quite good and precise, but for these low errors the tolerances of the measuring equipment has absolutely taken into account. So i made a separate measurement only for 10MHz -with the aid of a frequency standard sourced from an atomic clock. So this was 'the real thing'. After warming up for an hour i measured for 15 Minutes. The deviaton was between -717 to -722Hz. Including the error of the dial. This means frickin' 71.7...72.2ppm. PPM -parts per million! 65 years after manufacturing.... Just absolutely stunning -and with what freaking kind of equipment they had calibrated this back then??? Just have in mind: this is pure analog goodness, not a modern PLL. How the f***k they got there? Here's the clear link between a manufacturer of high-grade Lab Equipment and a shortwave receiver. I'm just stunned over the knowledge of the engineers who designed that circuit back then and the precision this was built.

All without doing anything and all it's original capacitors. Yap, i could realign that but tbh it's just wayyy to less been worth the effort. So it will stay as it is.

Nope,

you're not provided with that fancy stuff your new digital or SDR may have on board. There's no notch filter, no panoramic display -not even SSB! Why the hell they just 'forgot' all these things? The answer is easy: it's modular. The EK07 is just the 'mainframe', everything else you wanted to have can be added as external components you had to buy separately -also for tons of money of course.

Wanting SSB? Just add this:

35kg/77lbs and 18 Tubes more -to mention it's also a synchronous detector for AM is not worth the effort. Panoramic display, digital frequency counter, Teletype Adaptor, a remote control for controlling that beast over a telephone line? FM? Diversity reception?? No problem, you had just buy it. Everything of course with the same standards for precision and build quality.

The outcome...

Yea, i spent a good amount of money getting this -but in my opinion it was worth every dime. I wanted a good tube receiver and i got a really good one. Compared to upper class modern Radios it's still a very good radio. So the only thing I have to add is an external SSB/AM-Synchronous Detector. The originals are nearly impossible to get today, so i decided to build one. It's on the way and i will give you the results later. So stay tuned...

[carobd2unit]

XTOOL OBD2 Products Software Upgrade Notice - April 2021

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Currently of extreme competence key programmer tablet in OBD2 market are there tools like Xtool X100 PAD3, Xtool A80 Pro, etc. They are great tools and have got high praise from the customers worldwide, especially in the European area.

Here below is the page link of XTOOL car professional products in cardiagtool.co.uk e-shop:https://www.cardiagtool.co.uk/wholesale/brand-xtool/

📷

1.MAJOR CAR DIAGNOSIS TOOLS UPDATE

HONDA – HONDA                                                          V11.40

New special functions for engine, anti-lock, four-wheel drive and smart key in new modes to further improve special function coverage and fix fault codes and data flow problems in the Accord, CRV and Odyssey.

New special function "Motor rotor position correction" for the engine system.

New action test “regulator venting” and special functions “brake pressure sensor group”, “sensor group”, “steering angle sensor neutral setting” and “bleed warning system” for the anti-lock brake system. steering angle sensor neutral point setting” and “bleed warning system”.

Adaptive cruise control system with new action tests “throttle opening angle”, “brake booster 1”, “brake booster 2”, “brake booster 3”, “brake booster 4”, “brake booster 5” and “brake booster 6”. Brake Booster 3”, “Information Display”, “CMBS Brake” and “Indicator Check”.

4WD Free Control System new actuation tests “Shift solenoid oil pressure test”, “Drive train test” and special functions “Drive train calibration”, “Drive train calibration”, “Drive train calibration” and “Drive train calibration”. “Drive train calibration”, “Drive oil life Resett” and “Calibration data clear”.

Smart key entry system with new special functions “Ignition knob change”, “All keys lost”, “Add 1 key”, “Resett key” and “Custom key”. key setting” and “customization”.

New special function “ECM/PCM Resett” for the electronic cable control system.

7、The FCVSCM system has a new action test “H2 line pressure release mode”.

8、The CAN gateway system has a new action test “F-CAN bus connection unit check”.

New special functions "High voltage battery diagnosis", "SOC pResettting” and “IMA ECU replacement” for the electric drive system.

New special functions for the instrumentation system "Maintenance reminder device (US market)" and "Maintenance reminder device (European market)".

New special function “PAWS unit replacement” for the precision four-wheel steering system.

Hyundai – KIA                                                              V13.0

New Hyundai Elantra, MISTRA, Encino, Fiesta Pure Electric and other new models with basic features, further leading model coverage

Add 3 new models: MISTRA (DU2) 2021, 7th generation Elantra (CN7C) 2020, MISTRA electric (DU2 EV) 2021, etc. Read fault codes, clear fault codes, read data stream, action test, version information and other basic functions.

New: Encino electric (OSC EV) 2021, Sonata X (DN8C) 2021, Fiesta electric (SQ EV) 2021, New generation ix25 (SU2) 2021, MISTRA (DU2) 2021, 7th generation Elantra (CN7C) 2020, MISTRA electric (DU2 EV) Special features for engines, transmissions, anti-lock, power steering, etc. for the 2021 model year.

New special features for engines, transmissions, anti-lock, power steering, etc. for K3 EV (BDC EV) 2021, K5 (DL3C) 2021, new generation KX3 (SP2C) 2021, etc.

VW - All models                                                            V12.10

New system unprotection functions for Skoda models 15 airbag system, 09 central electrical system, 56-radio, etc.

New system unprotection functions for some Volkswagen Audi models 56-radio, 57-TV tuner, 84-night vision system, 8F-left front seat belt tensioner, etc.

New system unprotection for Skoda models 15 airbag system, 09 central electrical system, 56-radio, etc.

New system unprotection functions for some Volkswagen Audi models 56-Radio, 57-TV tuner, 84-Night vision system, 8F-Left front seat belt tensioner, etc."

FORD - FORD USA/FORD EU/FORD AUS/FORD CHANGAN/Lincoln                    V12.90

Ford Diagnostics new model upgrades to 2021.

Ford offline programming upgrade to 2020.

New Ford 2021 new model year basic features.

New Ford 2018-2020 new vehicle model programmable module installation features.

New Ford Taurus (Taurus), Fiesta (Fiesta), Lincoln MKX and other models Smart Link programming, RF keypad learning process, ATC barcode input, cable adjustment mode, EVAP test and other special features.

SAIC GM - BUICK/Chevrolet/Cadillac                                           V15.00

The first to release a VIN number repair function.

New CANFD models (New Corvette, GLU, Encore, Genesis) diagnostic basic functions and special functions.

New one-touch brush hidden frame number repair function, including engine, body

instrumentation, power steering, electronic brake and airbag modules.

New one-touch repair function for hidden transmission hardware number."

Changan - Kuayue                                                              V5.10

New X1, X3, X5, D5, KY5, new KY5, KY5MINI, KY10, mini3 models

V3, V5, T3 models, some basic functions modified, new special functions  Add” New X1, X3, X5, D5, KY5, new KY5, KY5MINI, KY10, mini3 models, support Changan Kuayue(China National Ⅵ Emission Standard) diagnosis

DONGFENG - XIAOKANG/FENGGUANG                                          V7.60

New diagnostic support for C51, C52, Ruichi EC31, Ruichi EC35II, Ruichi EC35III and Ruichi EK07S

First release of DONGFENG Fengguang brand

New support for reading version information, reading fault codes, clearing fault codes, reading data streams, reading freeze frames, action tests and special functions for the following models: C51, C52, Ruichi EC31, Ruichi EC35II, Ruichi EC35III, Ruichi EK07S

New DONGFENG Fengguang"

CHERY – KARRY                                                             V9.52

New support for Karry pickups

New Karry pick-up truck (first release)

2.MAJOR KEY PROGRAMMING UPDATE

SAIC Maxus                                                               V26.32

Support all smart keys to read the anti-theft password

Add pin code reading for all models with smart keys

BAIC – SENOVA X55/ D70/ BJ40L/ EC3/ EC200/ EU400/ EU5/ EU7                     V27.10

Add pin code reading

GEELY - BOYUE/BOYUE PRO/XINGYUE/BINYUE/ HAOYUE/JIAJI/ NEW YUANJING        V27.24

Add pin code reading

DONGFENG - FENGXING S50EV/ S500EV (2017)/ S50EVD (2018)/ S50EVB (2018-2020)/ S50 EVC (2018-2020)/ CM5EV (2017)/ CM5EVA (2018)/ CM5EVB (2019-2020)/ SX1EV (EX1)      V26.51

Supports key matching for EV models

Add pin code reading for models after 2017

Chery – EQ5/ XINGTU TX                                                     V27.21

Support all key lost

Add key matching for DAMAYI(EQ5) smart keys

Add key matching and ECU matching for XINGTU TX smart keys

JMC -YUHU 5/ YUHU EV/Teshun L500EV                                        V26.31

Add remote key matching for YUHU 5/YUHU EV/TESHUN L500EV

JAC – Sailor/ Gallop                                                        V27.03

Add remote key matching for Sailor T6

Add remote key matching for Gallop

Toyota                                                                   V26.75

Support all key lost

Support all key lost for Toyota Chip 88 smart keys

Toyota US - RAV4                                                          V26.16

Support all key lost

Add key matching for 2019 all key lost

BMW – All Models                                                         V27.71

Support part F chassis gearbox wipe reset

MEVD174K, MEVD17KW engine: Read ECU information/Read & write ISN/Write VIN

DME8FF_R engine: Backup & reset code

8HP transmission for F series chassis: Reset & update EGS

M35080(Odometer for E series chassis): Read & write data, mileage correction

M35128(Odometer for F series chassis): Read & write data, mileage correction

M35160(Odometer for F series chassis): Read & write data, mileage correction

MSV90 engine: Read ISN

EWS IMMO system: Key enable & disable

Hyundai/ KIA                                                       V27.26/ V27.36

Support password-free reading of 8A chip after 2019

Add pin code reading for 8A chip after 2019(KIA K3, etc.)

GM - Buick Velite 6/ Chevy Blazer                                              V27.83

Support all key lost

Add smart key matching

Instrument Cluster – Trumpchi/ Nissan/ Ford/ Land Rover/Maserati                  V30.00

Add mileage correction for GAC Trumpchi GS7/GS8/GM8 digital display(35XX)

Add mileage correction for 2019- Nissan Altima digital display

Add mileage correction for 2017- Ford Mondeo dual digital display

Add mileage correction for 2017- Range Rover Sport full LCD display

Add mileage correction for 2005-2006 Maserati Quattroporte and 2018- Ghibli/Levante/Quattroporte

KC501 – Honda/ GM/ BMW                                                  V10.06

Supports BCM reading for 2019- Honda Civic

Supports BSM3 reading for GM

Supports CAS1 reading for BMW

Supports footwell module reading for E series chassis

Supports reading & writing for M35080/M350160 chip

3.MAJOR SPECIAL FUNCTIONS UPDATE

Maintenance Light Reset (America) - CADILLAC                                  V28.05

Add 2020 CT4, CT 5 Maintenance Light Reset function

Maintenance Light Reset (America) - CHRYSLER/GM                              V28.10

Add Maintenance Light Reset and auto scan function for CHRYSLER/Jeep/Dodge

Add Maintenance Light Reset function for Chevrolet Onix (2020 model), Tracker (2021 model), Chuangku (2021 model)

Maintenance Light Reset (China) - GWM/CHERY/GEELY                            V29.10

Add Maintenance Light Reset function for JOLION, ORA Good Cat

Add Maintenance Light Reset function for CHERYEQ5

Add Maintenance Light Reset function for Haoyue

Maintenance Light Reset (China) - DONGFENG Glory/MAXUS                      V29.10

Add Maintenance Light Reset function for ix7, ix5, E3

Add Maintenance Light Reset function for EG50, T70, V90, EV90, EV30, EXTENDER, G20, EUNIQ5, EUNIQ5 PLUS-IN, EUNIQ6, EUNIQ6 PLUS-IN, EV30 OVERSEAS

Maintenance Light Reset (China) – GWM                                       V29.11

Add Maintenance Light Reset function for Haval third generation H6, tank 300, Haval big dog

SAS reset (China) - GWM/GEELY/ CHERY                                         V8.43

Add for JOLION, ORA Good Cat.

Add SAS reset function for GEELY Hao Yue

Add SAS reset function for EQ5

SAS Reset (China) - GWM/CHERY/JMC/BAIC MOTOR/SAIC MG/ROEWE/JAC/Hunter/DONGFENG FENGXING/CHANGAN                                                       V8.43

Add SAS reset function for GWM.

Add SAS reset function for CHERY New Tiggo 7, New Energy ArrizoE

Add SAS reset function for new JMC tiger, tiger 5

Add SAS reset function for new SENOVA brand new D50, brand new D50 (China National VI).

Add ZS yaw rate sensor calibration function for MG6 (2014).

Add SAS reset function for MG EZS, EMG6, IP32P_CN6

Add steering wheel calibration function for ROEWE 360 (1.5L)-.

Add yaw rate sensor calibration function for ROEWE i5, ei5, i6, ei6, RX3.

Add SAS reset function for ROEWE ei6 Plus, Marvel X "

Add JAC Refine M3-1.8VVT, Heyue A30 GCC, Pickup T8, Micro Card X200SAS reset function.

Add electronic stability system for Refine M4, M6

Add hunter X5, X5 pure electric SAS reset function.

Add SAS reset function for DONGFENG FENGXING DONGFENG FENGXING CM5EV (2017-2020), SX1EV(EX1), S50EV/S500EV (2017), S50EVB/S50EVD (2018), S50EVB (2019-2020), S50EVC "

Add SAS reset function for CHANGAN Ruicheng CC

DPF - HONDA                                                              V6.70

Add DPF for Honda

DPF - Benz /GWM /JMC /GEELY /MAXUS                                        V6.60

Add DPF function for Mercedes-Benz hatchback SPRINTER 906, Mercedes-Benz hatchback VITO/VIANO (VITO/VIANO) 639, Mercedes-Benz hatchback VITO/V (new Vito/V-class) 447 (after 2016), Mercedes-Benz hatchback SPRINTER 909

Add DPF function for GWM car Fengjun 5 (China National VI), Haval H2 (China National VI) and other models

Add the DPF function of JMC cars N800HP China VI and N806 models

Add the DPF function of GEELY Automobile National VI

Add DPF function for MAXUSD60 and other models

EPB Reset (America) - GM                                                   V23.56

Add EPB Reset for Chevrolet (China) Chuangjie, Sail EV, CADILLAC (China) CT4, CT5. Chevrolet Corvette, Cheyenne, SS, Spark EV, Lumina, CADILLACELR, Holden Capaci 5, Capaci 7

EPB Reset (China)- GWM/ROEWE/MAXUS                                      V23.87

Add EPB function for Hover Big Dog, JOLION, Tank 300, ORA Good Cat

Add EPB function for new energy ei6 Plus

Add EPB function for D60, G10, G20, G50, V90, EV80, FCV80, EUNIQ5 (pure electric), EUNIQ5 PLUG-IN (hybrid), EUNIQ6 (pure electric), EUNIQ6 PLUG-IN (hybrid), EUNIQ6 PLUG-IN( Hybrid).

Gearbox Match – KIA /GWM                                                 V16.35

Add Gearbox Match function for Haval CHULIAN

New Asia car series Kia K5 (2020-2021) Gearbox Match

Throttle Match (Asia) - KIA                                                   V28.47

Add throttle matching function for Freddy (ND), K4 (PFC), K5 (JFC)-(2020 models)

Add throttle matching function K2(UC)-(2019-2020 models)

Add throttle matching function K3 (BDC), K5 (DL3C), KX5 (QLC)-(2021 models)

Add throttle matching function K3 PHEV (BDC PHEV), K5 HEV (JFC HEV), K5 PHEV (JFC PHEV), KX1 (QE), KX7 (QMC), PEGAS (AB)-(2020-2021 models)

Add throttle matching function for a new generation of KX3 (SP2C)-(2019-2021 models)

Add throttle matching function for Kaizun (VG), Witkey (VQ), Cee'd (ED), Cerato/Fredi (TD), Ophelias (GH), Far Ship HEV (TF HEV), Far Ship (TF), Picanto (TA), Shuer (AM), Hybrid (TF HEV), Opitma (TF/QF), Maxima (JB), Sorento (XMA)

Add throttle matching function Cerato/Freddy (YD)-(2014-2017 models)

Throttle Match (Asia) - Proton/SUZUKI/SSANGYONG                              V28.47

Add throttle matching function for Proton ARENA/JUMBUCK, GEN2, EXORA, PERSONA, PERSONA ELEGANCE(DOM), SAGA, SAGA BLM, SAGA FL, SATRIANEO, SATRIANEO GTI, WAJA CAMPRO/IMPIAN, WIRA/PERSONA EXPORT, EXORA BOLD, PREVE, SAGA FLX, SUPRIMA S, INSPIRA

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Throttle Match - DONGFENG XIAOKANG/DONGFENG Glory/ MAXUS /GWM /JAC /JMC /GEELY /SOUEAST                                                               V28.57

Add throttle matching function for XIAOKANG D51, D52

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Add throttle matching function for MAXUSD60, EUNIQ5 PLUG-IN (hybrid), EUNIQ6 PLUG-IN (hybrid), G50, G20, T60 (D20 engine), G10 (D20 engine), D90, G20, T70, EXTENDER (Thailand version T70), V90, V80

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Add throttle matching function for classic Yuhu, new Yuhu, Baodian series, Baowei series diesel C63 system, Yuhu 5, Yuhu 7, Yuhu 9, Baodian series (new) and light truck series N600HD5, N720, N806

Add throttle matching function for GEELY Vision X3 (2019 models), Vision X6 (20 models-Type 2), Vision S1 (2019 models-China V), new Vision (2019 models), Emgrand GS-15TD, Emgrand S1 (2019 models)

Add throttle matching function for Throttle Match matching function for Delica and Futura

Throttle Match - GWM/ JAC                                                  V28.58

Add throttle matching function for GWM Harvard Big Dog, WEY Tank 300

Add throttle matching function of JAC Jiayue X7 and Si Hao X7/X8

Throttle Match - CHERY                                                     V28.58

Add throttle matching function for X70, X70M, X70 COUPE, X70S, X90, X95

Don't forget to contact us at:

Email:  sales@CarDiagTool.co.uk Skype: cardiag.co.uk Whatsapp: +86 15002705698

Or leave a message at https://www.cardiagtool.co.uk/

to tell us what suggestions or questions you have about our products.

Source:http://blog.cardiagtool.co.uk/xtool-obd2-products-spftware-update-notice-april-2021/

[ptiautiste]

AM-Detection -the not easy way

Sometimes quite simple things can be a real nightmare if you take a closer look. One of those is AM detection. Your worst enemies are distortion and fading (the latter results in the first). The AM-Detector is only one little part in a receiver, exactly that kind of part usually no one thinks about. "It works, so what should be wrong with?" -a lot and sometimes there's more wrong than right.

A good part of that distinctive AM-Sound we all know is because of the Detector, even under the best conditions. If you're listen to shortwave or the broadcast band during the night then you also have to cope with Fading. Shouldn't be that problem, the automatic gain control takes care of that, right? Ehmmm... Yes. Sometimes. Why the sound gets so distorted when the signal goes down? Just because it's very often 'Selective Fading' and not just Fading -and your Detector doesn't like it.

Really good AM-Reception has a lot in common with High-End-Audio: if it shall work well EVERYTHING has to be well. So let's just talk a bit about Detectors...

Basically the Detector just splits the Audio Signal from the received and amplified Signal. Sounds easy and in fact it is -up to some degree. If you want more than this things getting complicated -really complicated. In at least 999 out of 1000 AM-Receivers for the Detector a small circuitry called 'Envelope Detector' is used, it's just a small Diode (Tube or Semiconductor), a few Resistors and small Capacitors. So, from the view of the Development Engineer: just put half a dozen cheap Components together and Bob's your Uncle. To tell the Truth: compared to the expense that thingy works surprisingly well. Because of this it's the 'Gold Standart' for this task since at least the mid 30s. But as good as it is, it absolutely has it's Limitations. Up to about 15...30% Distortion at a 100% Modulation Level is one, the inability to detect a signal with different sidebands (>selective Fading!) properly another.

To overcome these Limitations a thing named 'Synchronous Detector' was developed many Decades ago. This kind of Circuit has many advantages over the Envelope Detector, but to make one the complexity and the component count of those is just hilarious compared to the Envelope Detector. If only the result counts and nothing else: that's the way to go. We'll talking later how this exactly works, but before this you have to know that in a receiver with a Synchronous Detector also an Envelope Detector is needed: just for tuning in. So first we'll have a closer look how we can get the most ideal Envelope Detector.

Basically it's quite simple: want to have low overall Distortion? Feed it with at least 'a few' volts RF at it's input for having a high ratio between the input voltage and the 'forward voltage' of the Diode. Want low Distortion at low modulation levels? Use a Diode with low Impedance and a load Resistor with a value as low as possible. Want low Distortion at high modulation levels? Just make the input Impedance of the following Stage as high as possible for having the highest possible Ratio between the Resistance of the Load Resistor and the input Impedance of the following Stage.

The Receiver i wanted to use (R+S EK07) has an IF output, meant for exactly such things, the IF Level there's about 250mVpp @ 300kHz. So having everything above in mind -and just adding a 700mVpp IF output for the Synchronous Detector and an additional AGC-Circuitry, then we're coming to this:

The EK07 is a fully tube equipped receiver, so i also want to use tubes as far as possible and -like in the EK07- in a way which guarantees 10k's of Service hours. If at one point a Semiconductor may perform muuuch better -ok, so then. First of all i want high performance. So what tubes may perform optimal here?

For the first IF-Amp (IF1) not much is needed, the Gain is only about 3, the output voltage low and besides that it has to be an remote-controlled type. Selectivity isn't needed or desired, so no IF-Can, only a Broad-Band setup. Nearly every IF-Tube with a Transconductance of at least about 3000mhos (3mA/V) would do that job. To have better performance i took the EF805s, which is a Special Quality Version of the EF85 -or 6BY7.

Transconductance is about twice what's needed, so we'll have Gain to spare, anyway, it's getting controlled with the AGC so it will work with less current which adds greatly to the service life. So no problems here.

For the second IF-Amp (IF2), things aren't exactly that easy. First: the output for the Synchronous Detector is placed between both Amps and has to deliver a constant voltage, so for the 2nd IF we need an Amplifier with an fixed Gain. A STABLE fixed Gain over long time periods. Further we want to have a relatively high and undistorted output voltage which calls for quite a bit of gain. Wait: there was also that thing with the low-value Load Resistor in the detector itself -so we also need a quite reasonable amount of output power from this stage. In Addition we want to have a stable gain for a time as long as possible. A IF-Tube like the EF805s could also handle this, but then we have to 'beat the crap' out of this thing. Not a good start for a long and stable service life, also not with Special Quality Tubes.

Because of all that my choice was a kinda 'special'-Special-Quality type: the E81L.

The datasheet calls this a 'Long range, Special Quality Tube for the use in Telephone Equipment'. Telephone Equipment? Like an answering machine?? Nope, by far not. Back in these days telephone companies needed to have Amplifiers for pushing the calls through loooong cables for long range service. But: this was all multiplex service, so they pushed dozens and dozens of calls simultaneously through one pair of wires or a Coax. The same way like for cable TV. THIS was these bulbs were meant for. For this task every company employed tens of thousands of such tubes 24/7/365. If a single one failed -most likely somewhere in nowhere of course- they had a problem. So they absolutely had to last.

These little bulbs are designed for about 4.5W plate dissipation at 20mA, the Transconductance is 11000mhos (11mA/V)-so it's about twice an usual IF Tube in every respect. So that's exactly what's needed here: a tube especially designed to last, quite powerful, so we can drive it with comfortable low settings, enhancing service life and stability much further.

Because we need some amount of power the usual Broad-Band Amplifier arrangement (still: selectivity is not wanted or desired) with just a plate Resistor isn't good here, a suitable inductor works way better here. This has the further advantage that we can build it with a Tab like an Autotransformer -we don't need that much voltage it could deliver with that inductor by far, so this adds further to a good SNR and lower output Impedance. 300kHz trough a transformer? Yep, no problem. Just use the right core. Here it's not a laminated iron core but a ferrite one instead. Cause it's a single-A Amplifier of course we must add an air-gap, preventing saturation.

In a penthode stage the gain depends nearly exclusively on the Transconductance of the tube used, have to much just cut it down. The E81L has a quite high transconductance, about 3 times more than needed -and in the same order than big output tubes like the 6550, EL34 or 6CA7. For cutting that down to the desired level just put a Resistor or Pot in series to the bypass cap of the cathode Resistor. This acts as an series feedback so it also enhances linearity and long time stability greatly. Yap, i thought quite a while about which tube i should use here.

So after all Amplification is done now, we need a Diode for the Envelope Detector. Back in the Octal-Days this was the 6H6 / EB34, later in the Miniature-Days the 6AL5 / EAA91, both with two separate diodes in one bottle (or Can for the 6H6). These were not A DIODE, these were THE DIODE, so there's not much to choose from. Both are kinda close to each other, but are these ideal for what we want? They both can handle a reverse voltage of several hundreds of volts, so waaaay more than we need here. Both having a Plate Resistance of 600-something Ohms per System which is quite low -could be lower, even with both Systems in parallel. Of course these would be work well, no doubt about. But still.... Hey, this should be High-end so we're whining here at a very high level!

Basically we can use EVERY TUBE as a diode: just take the control grid as Anode, the Cathode as what it is and everything else as Shielding. We don't need hundreds of Volts reverse Voltage, nor high current, so also no big Cathode. We only want to have an internal Resistance as low as possible, so a close spacing between the Grid and the Cathode. This calls for a small Tube with a high Gm (or Transconductance) -like the 6AK5 / EF95. Can it handle the reverse voltage we need? Datasheet says 50V, so at least twice of what's needed. So just take one, put some current trough and take the voltage drop. Result: 210 ohms -way less than that what one of the double-diodes would provide, even with both Systems in parallel. Fits very well!

This is the soviet-military version of the 6AK5W / E95F. Special Quality. See these 'trenches' in the bulb? And the microscopic rivets holding the Plate together? The Soviets literally ruggedized the heck out of this tube! Why? Just because they used it widely in their Fighter Planes, ICBM's, Tanks and so on. Doubts about the soviet built quality? Hey, they wanted to win WWIII with them -so: nope. If you ever saw a ruggedized tube: this it is.

After the Detector itself is done, we come to last part of our little contraption: the buffer Amplifier. At the output of the Detector we have the AF as well with the overlayed AGC-Voltage and we want to have an input Impedance as high as possible for the Buffer Amp. Voltage Gain isn't needed -we have plenty of both from the Detector- so we just can use a Cathode Follower for the buffer. Ideally the Buffer should handle both voltages simultaneously, but then the output will be negative with respect to Ground. How to....? Simple: just put that thing between a positive and a negative supply rail. Then the output can swing freely between every positive or negative Potential as desired. Further: we don't need a Grid Resistor! The Grid just follows any voltage swing of the Detector, this also adds to a high input Impedance.

This Circuit will provide us a very high input Impedance, but this is High-End! So: what tube will be the best for? Because of the lack of any Grid Resistor the input Impedance depends now largely on the contact potential of the grid. So we want a tube with low contact potential which calls for a tube with a low Transconductance. Further we want a tube which needs only a low bias voltage for it's Grid, 'cause we'll loose any bias-volt in our AGC-Output voltage. This calls for a tube with an high Gain. Low contact potential and low Transconductance? High Gain?? That's the 12AX7 / ECC83! Ok, it's of course a double Triode, but we still can use the second system for something else -like for the Line-Output Amp. In that Stage there's not much needed so it also will perform well enough there -we're still talking about AM!

So let's put everything neatly together, adding adequate shielding and so on -and we get this:

So now it's time to have a closer look we did everything right. Just put a 300kHz-Carrier in, 100% modulated with a triangle-signal. We should get a perfect Triangle at the AF-Output -if physics are with us. Due to the Triangle Signal any Distortion can easily be spotted on the Scope.

Looks promising! But somehow... Is the beam defocused? Let's take a very close look:

No, it's not. Those are just the very small remnants of the Carrier, so we actually have a look how the Detector works on a nearly 'microscopic' Level. I could take a measurement how much distortion we have left, but the Flanks of the Triangle are perfectly straight, so the Distortion will be really small -like 1% or so worst case. At least for the moment it's not worth the Effort. Compared to the usual 15...30% Distortion at a 100%-Modulation level this works really well, there's no doubt about.

So finally: we wanted to have a Envelope-Detector as good as possible and here we are. Ok, tbh it's better than needed, cause finally the REAL Detector will be a synchronous one. So why i took this that far? Easy: because of mental peace. Now i never have to think about if that part of the whole final thing could work better. As i said before: it's High-End.

Will update you if the next module is ready. But i fear this here was just the more easy part of the whole thing. From now on things may get a bit more tricky...