Trev, I watched your video bye the way.
Lawrence.
Lawrence.
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Simple micro transmitter
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11-12-2016, 08:25 PM
Hi.
One further thing I'm trying out, as most MP3 players have a low impedance output I think I'll try a step up transformer to feed the modulator valve rather than using the pre amp. I have an old Magnetic pick up head matching transformer out of an old radiogram I scrapped many moons ago. This was to match a low impedance cartridge to a valve input. I'll give it a try tomorrow and see if it's a worthwhile mod.
11-12-2016, 08:28 PM
(This post was last modified: 11-12-2016, 08:37 PM by Mike Watterson.)
The details of 1j42a construction:
http://www.radiomuseum.org/forum/142_photos_curves.html In general it's similar to the 1j24b, but the two g1 plates are not connected together internally. Also the spacing, anode and Joe Sousa writes [my comments] Quote:This rod pentode was designed for operation with 6V at the anode and screen grid, while drawing only 15mA from 1,2V at the filament. Other Russian rod pentodes were designed for at least 45V. As with any other tube that is designed for operation at low voltages, the internal mu of the 1j42a is low µg1g2=2.5 at 6V in triode connection and the total intrinsic gain in pentode connection is µg1A=16 for Anode voltages between 3V and 12V. However the Anode I/V curve has a flat spot at 6V, where the total intrinsic voltage gain from g1 to Anode should be some 10x higher, which is to say, more than 100. This flat spot is located where one would find the tetrode kink. The transconductance is nominally 400µS with g1=0V and g2=A=6V, g3=0V. Despite the low voltage operation, the data sheet still specifies the input resistance as 60kΩ at 60MHz, but the equivalent noise resistance is specified as a relatively large 90kΩ at 30MHz. This noise resistance is substantially higher than the 6kΩ equivalent noise resistance of the 1j24b. Joe's article is slightly misleading, the g1 is always plates, not rods. It's g2 rods that have become two slots. I don't know why the two anode plates are now wedges, perhaps due to low HT and close spacing. Regular Rod Tube (not 1j29b, 1p22b, 1p24b) Note that the 1j37b is essentially the 1j18b with the link between the two g1 plates cut. ALL the rod pentodes use plates either side of filament for g1. The 1j37b lacks some screen rods to reduce capacitance. The 1j42a, also top view The 1j37b has flat anode plates and two pairs of rods for the g2. You can see that g2 has become two slots instead of two pairs of rods. This increases the effect of any differential voltage on g1a and g1b! All the elements are much closer to allow low HT, 6V to 8V is best! The two anodes are triangles instead of plates. Thus the polarity of g1a and g2 doesn't matter! ANY mis-match will deflect the two beams away from the slot, reducing Anode current and gain. However the g2 triode gain will increase. Normally g1a and g1b "pinch" the space charge and thus reduce the Anode current, g2 and g3 are Electrostatic focus. ALL Rod pentodes. But on 1j37b and 1j42a the two g1 plates are not internally connected, thus just like X or Y on an electrostatic CRT / Scope tube, any differential voltage will deflect the beam! Thus it's a sensitive full wave rectifier to the differential voltage on g1a and g1b. The common signal on both is amplified in the normal way to the anode, or indeed g2, if there is a differential voltage! A full wave rectifier is either a detector or a frequency doubler purely based on having low pass or high pass filter on the anode! The differential signal and "common" signal is also thus multiplied (mixed). Not separate signals on g1a and g1b, except fortuitously. For MAXIMUM mixer action one signal (Frequency A) must be equally applied to g1a and g1b, the other signal (Frequency B) must be applied in antiphase to g1a and g1b (or simply applied to only g1a OR g1b!). The 1j37a works the same, but is designed for 45V (works at 22V) and takes MUCH more filament. The 1j42a and 1j24b take similar filament currents, 11mA to 15mA. Russian Electrometer using 1j42a as input (g1a and g1b tied!) and two 1j24b as amps. The only known application circuit for 1j42a doesn't even use its strange behaviour. For completeness, top view of the 1j24b and 1j29b, showing that the 1j29b is really two rod pentodes in parallel. The 1j24b is later enhanced 1j18b, the 1j37b based on 1j18b. The 1j42a was the last. Special low voltage design. The 1j29b is doubling the 1j18b design to get twice gain and 0.5W or more. The 1p22b is short life for proximity fuse radar, the 1p24b is enchanced version that can be 1W long life or 800W peak repetitive pulses for proximity fuse (by definition, a short life!)
11-12-2016, 08:39 PM
Hi Michael.
What is the difference between the 1j42A & 1j42B? I have many of the other types (around 200) but only 10 of the 1j42A and was wondering if the "B" type is a worthwhile valve to buy?
11-12-2016, 09:22 PM
(This post was last modified: 11-12-2016, 09:26 PM by Mike Watterson.)
There is no 1j42b only 1j42a,
This http://www.radiomuseum.org/forum/summary...todes.html lists all known Rod pentodes, using Russian databooks and sources. Only the 1j42a has been found since that was written. There is supposedly a 1j30b "mixer", which is 15mA filament like 1j42a rather than 59mA of the 1j37b. No-one has seen one. Various Russians and Ukrainians have the list on that page and all the main Rod Tube sellers have been contacted. The one seller of 1j42a claims to have "plenty". All seem to be dated 1984! Russian Rod Pentodes The ONLY Rod tubes that can be bought, they are also very plentiful. Model Cyrillic fmA Ik Max HT Application (Very Obsolete) 1j17b 1Ж17Б 49 5 60 Oldest type 1j18b 1Ж18Б 24 5 60 g3 connected to cathode/filament internally (Last Generation Rod Tubes Most are 1975 to 1991 production. There are MILLIONS of NOS). 1j24b 1Ж24Б 13 1.6 60 Lowest power 1j29b 1Ж29Б 54 8 90 AF or RF PA or front end (500mW) 1j29b-v 1Ж29Б-B 54 8 90 More durable version 1j29b-r 1Ж29Б-P 54 8 90 Most durable/reliable. Different connections 1j37b 1Ж37Б 59 4.5 60 Mixer, AVC/AGC, Detector 1p24b 1П24Б 198 25 150 AF/RF PA: 3W Class A triode, 8W Class B Pentode 1p24b-v 1П24Б-B 198 25 150 More durable version 1j42a 1Ж42A 15 1.3 Mixer 6V HT [One Seller!] Other Rod Pentodes known to have existed. (Like gold dust very sought by collectors. No-one selling them) Model Cyrillic f mA IkMax Application 1k12b 1К12Б 60 ? Small signal 1j36b 1Ж36Б 75 n/a Shell fuse1 1j30b 1Ж30Б 15 1.5 Mixer 12V HT 1p5b 1П5Б 120 <10 P.A. 1p22b 1П22Б 115 17 P.A.2 1p22b-v 1П22Б-B 115 17 P.A. 1p32b 1П32Б 210 n/a Shell fuse1 2p5b 2П5Б 198 25 P.A. Type lettering system. The Digit is 1 or 2 depending on if able to be 1.2V (Also 2.4V with a centre tap!) or 2.4V ONLY 1st Letter of Rod Pentodes Zh (Russian: Ж) – sharp-cutoff pentode (also transliterated sh or j). or P (Russian: П) – output pentode or beam tetrode. The digits then mean nothing, except larger number might be later. The 2nd letter is envelope size! A (Russian: А) – subminiature glass envelope (5 to 8 mm in diameter) with flexible leads. B (Russian: Б) – subminiature glass envelope (8 to 10.2 mm in diameter) with flexible leads. The 1j42a is less diameter than the 1j24b. The 1p24b is largest Rod pentode, but still under 10.5mm The third letter is optional. Only the letter after a dash is rating / variation i.e. -r, -v etc. Only on 1j29b and 1p24b as far as is known, for rod tubes. See https://en.wikipedia.org/wiki/Russian_tu...iver_tubes Inherently all Rod Pentodes are sharp cut-off all the 1pNNb and 2pNNb rod pentodes have two filaments and two parallel electron beams. The "1" types, parallel or series filament and "2" types might be series, not sure as none have been found!
11-12-2016, 10:29 PM
Thank you Michael.
Goodness knows where I got the 1J42B from then  I wonder how many of all these valves added together were actually made? It would seem many many millions. 10 years ago I never knew they even existed. What an opening for the experimenter and hobbyist. To date I've added an AF preamp to my Pye black box, made a one valve reaction and regen radio with auto reaction, unbelievable performance, fitted four valves to a Osram Music magnet 4, made a two valve reaction set that drives a speaker, the micro TX and other wee projects.
11-12-2016, 11:13 PM
(This post was last modified: 11-12-2016, 11:14 PM by Mike Watterson.)
Since no-one is collecting MiGs, Sputniks, etc., and there are 10,000 more than needed per collectable Russian Military Vintage Radio, they make far more sense for projects than domestic battery valves needed for restorations, for DIY projects.
The Russian military producers made same qty almost every year till 1991, the system had no relationship between actual usage/consumption and production. There are also very many Russian and Chinese mains types to build mains radios with (used in Russian Domestic and Military), like Russian equivalent to ECH81.
12-12-2016, 12:57 AM
(This post was last modified: 12-12-2016, 12:58 AM by AlanBeckett.)
(11-12-2016, 11:13 PM)Mike Watterson Wrote: he Russian military producers made same qty almost every year till 1991, the system had no relationship between actual usage/consumption and production. That's entirely normal. Production doesn't simply stop. In 1965 Baird TV in Bradford was using some 4,500 Vales a year. By 1968 it was effectively zero, but Mullard didn't stop. That's why there's a lot of them still around - they were still in the Supply Chain. Alan
12-12-2016, 08:16 AM
Yes Alan, and it was a more exaggerated example of that in the USSR, possibly because the authorities just allowed production to continue to keep those skilled in that area in employment. The regime would not be seen to be falling down on its policy of full employment, no able bodied person in that state was ALLOWED to be unemployed, (no further comments on that one, no politics etc.
 ). What I am unable to understand is that the Raytheon 6418 hearing aid valve was also being produced into the late seventies at least, in the free market economy of the western world. I have a few from 78, they were also used as computer switching devices I believe, but I can't see there being much commercial need for them by that time. But never mind, more for the tinkerers! Andy. |
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