Telefunken SW Radio

[6AL5W-Martin]

The collection of boatanchor radios makes possible to study what the old engineers have done the reach a maximum of effiency in receive. The radios are well described in their documents, all.

We have to different between 2 kind of radios only:
1.) a radio with budget. The maximum possible for a fixed money
2.) money is not important ! The maximum we can build.

The green radio, Siemes E309, what is upside in the tower, is a 1.), but well build. There are a lot of radios from other manufacturers what are good to compare with this. We find them oftenly, really fine radios what make enjoy to listen short waves.

The Collins 51j4 (R388A/URR), also here, is also a 1.) radio. We see that in the fact that the count of moving slugs is only the half of the 30 bands. Around 1000 US$, and it use 3 of the amazing mechanical filters. A greatful radio, but it have a noise, and a lower sensitivity in and of the scale, typical for a massive moving slug.

The Rohde+Schwarz EK07D, in middle of the tower, and a second downside in the tower, is a 2.) radio. R+S asked for a money what is enough to buy 4 pcs. of the collins from that. The weight class ist also another, we have to handle 66kg. Look inside, silver plated all over... a dream of engineering. The large revolver drum have contact rings made from a massive silver alloy, build for 100 years of good life. All tubes are SQ, except the audio power. It have a much lower own noise then the E309, related to the sensitivity. But there is. It is a high classified SWL, also today they are mostly expensive to buy.
51j4 will loose in comparement to a EK07. This is allready.

E104Kw4/7 , later was a E104Kw8 and a E104Kw10, they are nearly the same with some differents, Kw8 and Kw10 have 18 Bands and 3 various IF frequencys in the first stage, also a PSU with regulating by a tube where the Kw4 use the cute big gas Stabi..
E104 is a 2.) radio, of coarse. Today always expensive when one is to sale, they are rare. It is the most amazing radio of germany. It is for study, what is possible with tubes.
The own noise of that amplidiers is so low that it can listen the cable noise of a RG58. So you have to use the thick 60 ohms cable by R+S to connect the radio to the antenna.

I always thougt, when there are tubes, there is a noise, this comes from glowing.
Now, I see there is another world. Made with a simply EF805s (that is a SQ of EF85)
When you restorate one, remember to the good old english tubes mady by mullard, there was to buy CV2493 what is a "poor noise selected" E88CC. I use them oftenly in the first stages of old scopes, have some of them here- this is the idea. Select the first tube for the E104 from a lot of them, for the smallest own noise ! Get to know, there is a little wires R, adjustable, in the filament of this V1. Do 5,9V RMS there. Then replace the gate resistors in the tuner chassis to metal films. Test him now, with a well calibrated signal generator of 60 ohms and attenuators, a not modulated signal of < 0,12µV will be answered with a loud beep from the BFO. Here you see where is the own noise floor of a E104.. we must save them, so this engineering will not go in forget and forgotten.
The practical use of that sensitivity is today not realitic, the noise of the world ist to high, special in the low bands. But in 20m, 10m, have fun with that outperformer, a lot of modern radios can be afraid for a comparement with the oldie E104.

It have no mechanical filters, this is the problem. 3 crystals are there to provide 6 bandwiths, but the 51j4 can do that better.
And the accuracy of frequenca adjustement, bec. it use various center frequencys in the first IF it was not possible to print Hz/kHz Marks on the fine tuning dial. 51j4 have that !
E104 adjust <1kHz in the scala, thats all.

About the adjustement of the tuner.
The radio use 3 tuned coils in the pre selection, 4 in the 1. IF, 1 in the second oscillator.
So in the revolver drum are 17x (3+4+1) coils.. full ceramic made parts, gold plated contacts. Also there are 15 crystals + 15 fixed adjusted coils for them, the osc. 1.

The are not only a lot of filter cans, you see also cans made from magnesium alloy (this what is mostly so bad oxydated), in each of this magnesium cans are L-C Filters, choking all over ! The first is in the power line, and the last is the headphones an the speaker.. and allover between also..

The last what I found amazing is the management of the ground.
E104 is build in 5 part chassis. Tuner+1.IF+osc. - second IF a, - second IF b, - BFO+audio, - PSU. When you take a good look to the screwing, there are isolating plates ! Also in the rotating mechanik are isolatings. Of coarse, all chassis are groundet, but strong in plan, not all over. The only direct case grounding point is the antenna jack.

There are some side boxes to collect, a side band selector and a RTTY apparatus, both have a CRT. I need them. EK07 knows that also, but other second IF.

R+S components ca be used by converting the 525kc IF to 300kc with a external home brew. Also swapped, EK07 can use TFK by converting 300kc to 525..

The Long Wave Communicatios Receiver, E108Lw4, have also the second IF of 525kHz and can use the Sidebamd and RTTY boxes of E104.

Last word, the handling..
E104 and E108 have a weight of 90kg in case, with only 2 handles.
It is a good idea to put them on the table with 3 persons !

Enf the story, now I will look what will be the next restoration

greetings
Martin

[turretslug]

The points about the difference between "built to price" and "built to specification" are significant and perennial aspects of equipment construction. Also, the recognition and pursuit of the fact that what may appear to be grounded screens/chassis may actually become low-impedance coupling elements if care isn't taken, especially at higher frequencies. The pioneering HRO receiver became notorious for oscillator radiation, no doubt the use of pentode mixing with signal and oscillator on adjacent grids didn't help and the use of plug-in integral aerial/2x interstage/oscillator coil-packs with common metallic base-plate also sounds like a coupling liability. The famous (and still widespread and highly-appreciated in the UK) AR88 made a cursory nod towards isolation with separately-screened oscillator box but otherwise the construction is simple and inexpensive mass-production orientated with no other attempts at restricting coupling currents. This radio is an excellent example of your type 1.), using up-to-date electronic developments but pressed and folded mild steel casing and relatively simple gear-box and scale, suitable for factories and work-force accustomed to domestic production. I'm not familiar with the comparable and contemporaneous Telefunken E52, but I've heard that considerable care was taken with modular isolation and single-point earthing to minimise unwanted effects such as oscillator radiation and spurious responses. No doubt, the equivalent cost was several times that of an AR88, with the extraordinary micro-scale and magnified/projected precision scale being labour-intensive. Definitely a type 2.)!

It has been most interesting to see this thread's dissertation on the the efforts taken to produce superlative performance by R + S and Telefunken- even if the technology is now long in the past, the principles are still important building-blocks.

[6AL5W-Martin]

the Siemens E 309...

the little bulb there in the middle of the scale will be mechanical moved up and down to light up the band what is selected
Pic 1: restorated, Pic 2: band selection in the scale, Picture 3: dirty, . The radio rotate the complete scale.
The radio have 3 empty crystal sockets for favorite channels also. The revolver drum: contacts are to polish, each one, sorry for a lot of work, a budget oldie.

btw. E309, EK07, E104 and E108 have the rotating switch "tubes tester". I think it was here a military requirement to have that.