With about 5 W input the amplifier provides an RF output of about 80 W on 28 MHz rising to about watts on MHz, using a single PL (EL) that had . EL/6KG6. High Performance Beam Power. Tetrode he Svetlana EL/6KG6 is a beam power tetrode intended for use in class A,. AB or B audio amplifiers. EL Substitutes. No information available. EL Ratings. No information available. EL Application Data. No information available. EL Data sheet.
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The regular visiting of ham flea markets is a money-saving way to obtain parts for a home-brew linear amplifier meeting the requirements of the Telecom authorities. This topic, in Dutch, was originally written about in order to fill some gaps in the Dutch literature on this subject. Inexperienced hams, in the Netherlands as well as well as in Great Britain, have successfully built this W PA-project, more or less duplicating the e519 d design published here.
My preceding designs were mostly intended to pep up 10 W home-brew sets. I therefore based th e amplifier described here on a grounded grid amplifier, using cheap and still easily obtainable valves. Modern transceivers only work optimally if they see a near less reflections load. Datasheeet was the basic circuit, however for safety reasons I do not advocate this design for inexperienced home brewers!
This is taken care of in this circuit. The transceiver is loaded correctly without variable input tuning. After band changing, only two capacitors need to be tuned. The PA has at least an output of Watts on all bands, except 10m and 12 m, where output is down to about Watts. In this circuit sweep-valves are being used. Hams not having much experience with valves may learn much from this project.
One day they may want to build an amplifier with dataasheet “real” daatsheet valve. For them, more in formation has been included. I leave it to the pro’s to argue about which specific valves should be used in this project; when properly adjusted, every amplifier will behave linearly. Satasheet cooled sufficiently, these sweep-valves are nearly impossible to destroy. They especially can withstand high voltages datashret peak currents. They will even function well with anode voltages far in excess of Volts, but in order to protect you from extra problems not to mention the wrath of neighbours and Telecom authoritiesI am advising you to apply only with — Volts.
The valves may be mounted vertically or horizontally, the choice giving more freedom of layout. While the claimed W could be extracted from three or even two valves, practical reasons dictate a set of four in parallel. One should reckon with satasheet diameters differing with different brands: Anyhow, the valve sockets should be spaced at least dataseet cm centre to centre for heat-dissipation reasons.
EL519 Datasheet PDF
Valves unused for a long time and even new one’s, should be first warmed up by having only the filaments on, with the correct voltage, for half an hour. After that, the other electrodes can be connected with the valve drawing its idling standing current, without drive for 30 minutes.
The internal heating activates a chemical diffusion process, which raises the emission level and also helps restoring good vacuum, thereby diminishing xatasheet number of possible “flash overs”. Only I wonder whether it is a penthode or a beam deflection tube.
The tube is thicker and often is the envelope made of thicker glass, but there is quite a difference in the mutual production. Note for example in the photos on the anode and the small plates above the anode. According to some users the tube is “stronger” than an EL, but there are also negative messages. So I think the datqsheet sound comes from users who apparently obtained the better product.
FRINEAR RF Amplifier with 4 x PL(EL)
SV2GNC’s amplifier, the external anode supply is not shown. To avoid flashover in a new or a long time unused tube, it is prudent to prepare “reactivate” it for his task.
There are various opinions and solutions how to do it, but with a PL it can be relatively simple. A DC of Then supply a “high voltage” of 12 – 15 V and set the voltage to a current of mA.
Usually I will not reactivate longer than 30 minutes. Soon you will find out at which voltage a good tube drawn mA, so you have an indication if another tube is better or not. The static input impedance of the cathode in a grounded grid circuit can be calculated if the valve characteristics relating to the specific circuit are known.
The dynamic input impedance during working conditions is often higher. Furthermore it varies during a SSB transmission because the driver the transceiver is delivering power varying between say 0. The input- and output impedance of the amplifier are constantly varying and the driver sees a constantly varying load.
If the internal controlling system ALC cannot handle this, a distorted signal will be generated in the transceiver. The input impedance of the PL’s in the circuit chosen by me was not known. With an experimental test rig, I have tried to obtain some relevant data.
In most cases a tuned circuit between driver and final stage is recommended. By way of flywheel-action this tuned input-circuit will, to a degree, level out the quite variable input impedance, thereby preserving a reasonable match and thus linearity and output of the driving transceiver. The tuned input circuit also shortens the HF return path between anode and cathode by preventing this HF current to follow the longer path via the transceiver.
As modern transceivers have more than sufficient power, the “flattening” of the input impedance may also be obtained by extra loading swamping the input-circuit with a resistance or suitable wide band combination, in which excess driving power can be absorbed. This also helps in lowering the HF return-path impedance. In our case, matching is done with a 4: Nearly all transceivers can deliver about W with such an SWR without an antenna tuner.
Eventual use a pF trimmer for minimising the input SWR in the 10 m band. Adjustment of the input- and output-circuits must be done with full carrier power key down for maximum output power and minimum input SWR.
A 5 cm piece of 1 cm diameter will do, longer is OK.
With enamelled wire of 14—19 SWG, 9 close bifilar turns are made on a 9. This is a safe method as the ferrite is quite fragile. The two outer wire ends will go, via capacitors, respectively to earth and, with a piece of coax cable, to the input relay. This right picture alternative simpler resistor input circuit has ek519 higher SWR on 10—40 m and reduced output on 10 m, however this should not be a problem with a modern transmitter with a built-in antenna tuner.
When using valves in parallel, we have to consider the individual differences. With datashret bias, individual-resting currents will differ.
Even if the idle currents are made equal, the HF-amplification factors datahseet not. In datashet bare-bones circuit, an individual adjustment was considered, but left in favour of a simpler system, based upon DC-feedback during excitation.
The resistors will also partly determine input-impedance. However, the SWR will be higher on some bands, causing a transceiver without built-in antenna tuner to resolutely settle back. The older, valves transceivers wi th pi output tuning do not have this problem.
Collective and individual bias. Bias per tube with variable transistor “zener diodes”. The value of the collective bias is dataaheet with a string of 3—10 diodes in series. Short circuit one of more for a standing current of about 20—25 mA per valve, i. When using this simple bias circuit, it is advised not to wait too long with datasheer after pushing the PTT button, in order to let the valves draw standing current for only a short moment.
The reason for this prudence is the possibility that the individual currents deviates so much, that one or two will draw much more current and dissipate excessively. In this way, the valves will only conduct when the PTT is activated.
As a rule, the individual products of standing current and anode voltage should stay below the maximum dissipation of 35 W per valve. Eventually use the individual bias system with a string of diodes in series with each cathode.
Filaments and capacitor in series connected to mains. In our circuit, the four filaments may be fed in series; with a capacitor of 5. The string may be connected directly to the VAC mains.
If the chassis of the PA is grounded through the mains cable this method is acc eptable, with the added benefit of a gradually heating up soft start of the filaments, i. Because the cathodes are not at HF earth level, the filaments are by-passed to earth with capacitors. The right figure is an example for the calculation of the capacitor in series with 0.
In this circuit all grids are at earth potential.
At each valve socket, all six grid-pins must connected to each other and be grounded via one point to a common spot chassis, print-board copper side with short connections of thick wire or ribbon strip low inductance. The grids are negatively biased with respect to the cathode through the forward voltage drop of the string of diodes, which positively biases the cathodes with respect to earth.
In triode circuits, contrary to tetrode or penthode circuits, the bias voltage required for a given anode current greatly depend on the anode voltage: The anode connection is at the top of the PL Top clips are difficult to obtain, but transistor-cooling clips are a good alternative.
These may have to be bent a little for a good fit. They are made of blackened copper. The contact area should be scraped bright as well as the area where the connecting lead is to be soldered.
The cooling clip keeps the temperature of the top within reasonable limits at high dissipation.
With a good design and neat mechanical layout, there is no need for the usual parasite killers in the anode leads to stop parasitic oscillations. About plate chokes, varying stories circulate. However, least problems arise with one-layer chokes. Because of the dissipation and closeness of the power valves, a heat-resistant coil former is a must: A sturdy ceramic wire-wound resistor, with its resistance wire removed, will make a good former.
A diameter of about 2 cm and a length of 10 cm is satisfactory. Closely wind the former with one layer of 25—28 SWG enamelled wires over a length of 5—10 cm. In most cases its inductance is sufficient, even at a lowest frequency of 3.