07/02/2017 13:16

Another Old Picture

 


I have nothing against modern radio-stuff, apart that it doesn't appeal neither interest me. A matter of choices.

It would be too long for me and perhaps too boring for you to explain my view.

I limit myself publishing another illustration from the old days, recently discovered on the Web (thanks to whom that has published it).

Stylized. Essential.

Neverhteless deeply evocative and explanatory about what I mean by 'Radio' and what I see in it.


Radioman, July 2017


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05/21/2017 17:40

3579 kHz

 

A few months ago I was listening on the 80 mt band in search for a free tiny piece of spectrum, available for a QSO on radiotelegraphy.

The 3.579 kHz frequency is one of the preferred by Radio homebrewers because it corresponds to a common television crystal. Common means: plenty, cheap, easy to use ... And also, as a consequence, it allows easily to many to find on the air other fellows experimenting with the Radio, on that frequency.

Hoping to find a radio-fellow, that night, to share my same interest on home-making simple radios, I sent my 'CQ ...'. A gentleman from a 1000 km away, replied. And immediately after a digital signal also appeared, making the whole radio contact quite hard. But we managed to make it.

That OM told me, along that QSO, he has been often around 3.579 to resist against 'the aggressive behaviour of the digital guys', as he stated.

Along with that, I'm forced to recall that also the frequencies commonly allocated to QRP traffic are often disturbed or occupied by QRO stations, so disrupting the peace of those tiny spectrum portions, where more than anywhere else ... Radio homebrewers gather to test their creatures and/or to talk about Radio, on CW.

That OM ... I found him on many other evenings, insisting to defend the 3.579 kHz channel.

Well done Mate. You are an example to all that claim the right to have a few kHz where enjoying their radios, and that often are unable due to the poor conduct of the majority.

As a matter of fact he defended the right to operate with very minimal and low performance devices.


Radioman, May 2017


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05/21/2017 17:01

Comparisons

 

On a noisy evening, while listening to a CW Service station on HF, I made these videos.

An EK07/D2 with AGC and set bandwidth 4.0 kHz


Polyphemus 2.0 ...

 

... and again the EK07/D2 without AGC (same bandwidth as above):

>

 

Interesting. Polyphemus does not have any filter: nor in 'IF' circuit (impossible because the Intermediate Frequency is variable between 1.7 up to 3.5 MHz), nor the Audio stage. Even though, its audio response is a bit narrow due to the frequency cut of the loudspeaker.

Its overall performance looks really good (perhaps better in this particular case ...) on a noisy day as compared to an old, but professional and still well performing receiver.


Radioman, May 2017

 

 


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04/08/2017 12:21

Polyphemus 2.0


After some funny time with the first edition of a mixed regenerative/conversion receiver, where a poor ECH83 did the Local Oscillator, the RF Amplifier and the Mixer functions together, all these tasks have now been split among separate stages.

Now a '6AK5' UHF pentode is the RF amplifier, in a Tuned Plate - Tuned Grid configuration; an ECH83/6DS8 still works as Mixer + Local Oscillator (Pierce configuration, at the triode section); a '9002' triode now is the regenerative Detector and last an ECL84/6DX8 as the usual pre+final audio Amplifier.

After some rummage in my junk-box, a nice Yaesu FT-something transceiver Preselector was detected: perfect for a broadband tuneable front-end Amplifier, that allows to tune from about 3.0 up to 30.0 MHz. The Local Oscillator is rock bound on 5 bands, and there is provision for an external Oscillator also. The regenerative Detector section is tuneable from 1.7 up to 3.5 Mhz.

 

 

In comparison to the first edition of this receiver, the RF Preamplifier allows a more comfortable listening and the audio level is now much stronger. It has been observed, besides, that the same signals are now receiveable as what could be received with the former prototype: before, the ECH83 was amplifying a bit the incoming signal, while now there is a separate stage for this function. In the former prototype, then, the audio throttle was most of the time at full steam.

RF Amplifier, Mixer & Local Oscillator are all run at 90VDC, provided by a 'VR90' gas tube stabilizer (the big ceramic resistor on its side becomes pretty hot, as it manages the voltage drop from about 320 VDC from the supply). The audio Amplifier is run at 320 VDC.

The use of the BC221 variable capacitor resulted in a very smooth tuning and practically linear. Some 35 kc/s per turn are a very comfortable way of zero-beating any station!

 

 

The preselector has not yet being optimized, but the unhearting of a 18 MHz crystal in a remote region of my depot, allowed also to listen to many stations on 21 MHz band. At higher frequencies, the L.O. needs some help by additional tuning circuit, to raise the L.O. injection level at more than 10 V peak. Up to 14 Mhz band, the peformance of this receiver resulted more than satisfying and such that it allows to make also DX traffic when needed.

Still, the 'Tuning Eye' tube, configured as audio 'VU Meter', is helpful for tuning purposes. Fluctuations of the green light depends on the Volume regulation, and for peaking the RF Preselector it is just needed to reach the greatest closure of the 'green wings', driven by the background HF noise ...

The interesting thing of the Regenerodyne concept is that you have all the controls brought to the front panel and there is no need to align any fixed-frequency circuit inside, like MF transformers or whatever. Besides, the sensitivity is equal to at least a decent modern transceiver.

I have also been given an electronic audio Filter and a strong selectivity can be added if traffic is to be handled in one of the usually crowded Amateur Radio bands. If Full Spectrum operation is preferred ... Polyphoemus 2.0 is more than an excellent performer.

What else do you need ?


Radioman, April 2017


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02/18/2017 17:44

Being a Radio Amateur


I have a friend, an Antique Wireless 'Addict'. He lives very far from me, unfortunately. He is a friend, among other things, because we feel the same feelings in front of the same things.

We belong to quite different eras but we speak the same language even if our mother tongue is not the same.

Today I've received a present from him. A small leaflet that looks as below:



He knows I had been impressed by a picture found on the Web, showing a complete radio station of the beginnings. I asked him to provide me with a higher definition picture so I could see better the constructional details.

Amazingly he gave me the original publication from where the picture was taken, dated 1933!

Inside, the description of the Receiver:

 


... and that of the Transmitter:

 

 

... and a view of the complete station, with some additional stuff:


 

I feel deeply grateful to him for this precious gift. For the historical value of the leaflet, and for its validity in the present.

We Radio Enthusiasts often forget that our Radio-Forefathers had to be ingenious and that their purpose was to establish a communication along distance. Nothing was left to chance and everything was optimized and cheap.

My impression is that we tend to loose ourselves in front of those sophisticated (nevertheless extremely effective) modern radios, that we get lost and we forget the beauty of a radio contact made by minimal means. I seem to observe that modern radios add unnecessarily complicated stuff between an operator, that might be willingful to enjoy radio contacts, and the ionosphere.

That leaflet is entitled 'How to Become a Radio Amateur'. Right. There is a process to achieve the radio contact. But I'm convinced that it is more a matter of 'Being' than that of 'Becoming' a Radio Amateur.

At the beginning there was, perhaps, a rush among people of different ages to get and to do what was needed or required to enter the new marvellous world of Radio. So the focus was on 'Becoming'. 

Today I notice some dissatisfaction, some restlessness throughout the Radio Amateurs community (and not only in this) and it is clear the return of our attention to those old days. Collection of Vintage equipment and documents seems to increase daily.

Perhaps in modern Society it is that we all need to come back to the Essence of certain things (if not all ...). Essence is what IS and nothing less or different could be.

Exactly.

Like the Radio Station depicted in the leaflet.

When I deal with other Radio Amateur fellows I constantly support the idea that those tecnical concepts could be reproduced by modern components with the exact same schematics, and still allow you to deeply enjoying to send and receive your signals at great distances.

Despite the focus of that leaflet is on 'Becoming' a Radio Amateur, it is clear that the process can start if one 'IS' first a Radio Amateur! To enjoy the Radio, then, you only need very few things, ... like those described above. Nothing more.


Radioman, Feb. 2017


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02/14/2017 22:36

77

 

When we gather on the Shortwaves for some traffic, usually we run some odd radio-stuff. MOPAs, Hartleys, crystal driven Electron-Coupled Oscillators, regenerative receivers ...

'Odd' is to us, of course, the way we look at our radios taking the point of view of the politically correct radio amateurs world. They are all but 'odd'! We are proud of our clumsy rusty irons and nests of pieces gathered from many sources, that, put together, allow us to run over many miles in fractions of seconds.

We feel, sometimes, as the guardians of a tradition that otherwise would be deleted by the obsessive (and yet not totally understood by many) innovations. A tradition in radio communications which, when lived our way, still brings a lot of fun and teachings. Despite the dust and the rust.

So, we begun to replace the common '73' at the end of a QSO on radiotelegraphy, which means 'goodbye', by something a bit more distinctive: the '77'.

The number '7' has considered a symbol of perfection in ancient times. By saying '77' we only wish to express and stress more strongly our passion for real, simple (sometimes 'ancient') radios,  as two '7' are sent together.

'72' has been taken, some years ago, as the distinctive 'goodbye' among those going with low power. So, why not coining a distinctive greeting among those going with ultra-simple radios, most of the time made following old concepts, but yet disclosing a tremendous potential for communicating on the Shortwaves, and for having a real radio-fun ?

By sending '77' we refresh to each other the concept that we are, after all, simple guys in the real life. And that very little is needed to smile bit. So little like a small inductor, a variable capacitor, a key, a piece of wire for antenna and ... perhaps ... a valve.



Radioman, Feb. 2017


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12/29/2016 23:37

A Virtue out of Necessity

 

I assume that becoming a Radio Amateur is not the consequence of a decision, but it is rather a long process, which origin has lost at a certain point in time. A process that ended to a pretty unresistable desire to play with some Radio stuff.

I assume, despite the various National regulations, that becoming a Radio Amateur is not understood as belonging a Radio call, officially assigned by some Institutions.

A Radio Amateur is ANYONE interested in the Radio communications, performed in whatever manner he finds interesting for himslelf. A Radio Amateur, perhaps, is also someone that plays with Radio stuff for his personal interest and curiosity, but in general I consider as Radio Amateur anyone who is fascinated by the appeal of sending information to far places and receiving them through the 'aether'.

Most of those guys named 'Radio Amateur' developed that interest at young ages and being 'young' comes pretty often along with being without reasonable quantity of money to buy Radios or pieces to make one.

I belong to such cathegory of guys and I spent the most beautiful hours of my youth trying to assemble (almost casually) various electronic components in the hope, one day ... , to send over the air my own signal.

Later, some tens of years later, I made the transmitter that at the time appeared to me the most simple for the purpose: the Hartley. At the age of 12 I made a half 6SN7 triode to oscillate and to generate such a quantity of harmonics I could totally blank the TV. But no radio contact.

Today I operate, at last, what decades ago appeared to me a winning solution to make my dreams true, because essential, cheapest, sure fire. Below in the picture, my Hull-Hartley, along with its power supply.

 

 

One Triode oscillator. Only one tube. And a bunch of watts.

During the last 3 months since its construction, more than 100, reliable, radio contacts have done, over distances of up about 1000 miles.

Today, realizing that my naive, candid, childhood ideas, about the simplest radio by which I would have become a 'true' Radio Amateur, are solid, working and technically correct, unavoidably lead me to say what William of Occum said:

'Frustra fit per plura quod fieri potest per pauciora' (it is vain to do with more, when less will do).

At the time I had to make a virtue out of necessity: I was not successful though (too much inexperience ...).

Downstream to what I'm achieving now (successfully) following my childhood ideas, could it be today that we, Radio Amateurs, all should make virtue our necessity ?

That is ... do we really need to play, just a bit, with Radios, so many 'obsucre' digital stuff about which the very great majority of us only have a pale clue on how it works, and that we could never neither make by ourselves nor probably repair ?

 

Radioman, Dec 2016


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08/20/2016 20:33

Command Set

 

After 70 year since the WWII it is still possible to find Command Sets airborne transmitters in pretty good shape. I am particularly proud of the one below as that was donated to me by a friend.

I could not resist and the same power supply I am currently using for the recently built Hull Hartley transmitter ('BIG H'), is just fine also for the Command Set. 600V on the PA plates, 265 on the PA screen grids and 200 V, electronically stabilized, for the oscillator.

When the dial calibration was checked against the internal crystal, and against an outer frequency meter ... I found the scale perfectly calibrated! The power is in the range of 50 W output.

The loud sound from the inner relays ... is music to my ears.

This transmitter is now being cleaned thoroughly and will be used, I would say, quite daily, on Full Spectrum, for staying in touch with my friends on the short waves.




 

Radioman, Aug 2016


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07/24/2016 16:24

Hartley on Air - 2


The first operation hours have been full of teachings on the 'Hartley' configuration transmitter. The proper feedback tap on the coil and the proper position of the antenna link are essential for a very good tone.

The FEEDBACK TAP determines the portion of the alternated voltage fed back to the oscillating tube. The greater this voltage, the higher the drive level. Beyond a certain drive level there is no power output increase, and lot of power starts to be dissipated on the triode control grid. At low feedback voltages, the oscillations start randomnly and are very much influenced by the coupling level to the antenna.

The ANTENNA LINK should take the most possible power from the tuned coil, but with the lowest deleterious influence on the frequency stability and the tone quality. A link coil should work only with the magnetic field component generated by the primary coil. Any stray capacitance between the main coil and the link deteriorates the oscillator behaviour. They can't be eliminated but can be reduced at a minimum if the link is shaped and positioned so that to stay the most possible close and confined in the vicinity of that portion of the main coil having the lowest voltage towards ground. The feedback tap is that region and so the link shall be placed in its correspondence.

Any change in the operating frequency, for the same given antenna, determines a variation of the load impedance that the oscillator sees through the link coil. The current that flows in the link (the 'secondary'), by the working principle of any electrical transformer, develop a magnetic flux with opposite sign of that developed by the main coil (the 'primary'). Therefore, the load, through the antenna link, tends to chocke the oscillations in the main resonating tank. If the load match is not correct, either the transferred power would be very little, or the oscillations do not start. So, for any ample frequency change, according to the antenna impedance variation law, both the feedback tap and the antenna link should be moved, and in general the number of turns in the link coil should also be changed.




In the picture it is shown where the tap and the link are located, for a reasonable performance between 3 and 4.5 MHz with the antenna in use and without any need of modifications.

The big chocke at bottom left of the picture is the initial plate chocke that has been chosen to decouple the oscillator from the power supply. It turned out it has too many turns and made the oscillator being unstable on a wider frequency range than what is currently. For relatively high coupling levels to the antenna, the main resonating tank looses its 'driving' effectiveness and the circuit becomes a 'TNT' oscillator, where the main resonating tank becomes the plate chocke + plate bypass capacitor to grodund. The 'spurious' oscillating frequency is a few kc/s and at the receiver a crowd of intermodulation products appear around the resonating frequency of the main tank, at intervals equal to the spurious  generated frequency. It has been exclued and a much smaller, less critical, chocke is now used instead.

Now, this transmitter allows to make ordinary radio contacts through all its operating range (1.7 - 4.5 MHz), with a clean tone, even though very slightly and still influenced by the antenna wires oscillations in the wind ... T9 reports were achieved on 300 miles QRB radio contacts around 3.8 MHz, in the typical summer statics noise. The power is well beyond 5 W, on all the operating range, so plenty enough. In total, there are 10 components including the triode, and they appear enough to manage CW traffic reliably and with acceptable quality on average paths.

It is a real pleasure ...


Radioman, July 2016


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07/15/2016 08:40

Hartley on Air

 

Here what the connections look like for the first tests. The first tests were successful: power output was from 5W to 8W at plate voltages ranging from 250V and 400V, on frequencies around 3.55 Mhz. I was heard 200 miles away. The tone was very clean, but the frequency was unstable due to the antenna wires oscillations in the wind: there was a thunderstorm outside at that time.

Lessons learned.

1) The antenna link is too close to the main coil. So, the capacitive coupling makes the set sensitive to antenna oscillations. If the linke were a bit more apart, then the magnetic coupling would have been the one transferring energy to the radiating system, and not the capacitive one.

2) It seems that a thick copper tube as main coil is not that needed. The only reason to have it is to have relatively high efficiency for the production of oscillations. This would result in a relatively high current circulating between the coil and the main capacitor. In this way it is possible to couple the RF power to the antenna by use mainly of the magnetic field, and so by convenient use of a link, which can be, in turn, installed a bit apart from the main coil. High 'Q' in the resonating circuit, then, means that a loose coupling can be afforded so to reduce the influences on the frequency stability due to unpredictable load variations, like an antenna oscillating in the wind, and transferred mainly by the capacitve portion of the coupling.

3) The oscillations initiation is critical along frequency. For higher tuning capacitor values, the oscillations are hard to start. So, the feedback tap (see the wire within the coil) should be moved towards the plate connected end of the coil. This topic, though, is to be investigated deeper on next days ...

 

 

As said, the tone quality was very good. No chirp and no AC noise. The first Hartley was built some 30 years ago, when I was a teen. That experience was a blast to me. I was even able to apply AM modulation on the feedback tap at the main coil, by use of a carbon mike and a voltage elevator transformer, without using any audio amplification.

Now, after 30 years, I'm apparently returning on my footsteps due to some nostalgia. A kind of ... even though, today, I am bitten by the curiosity and by the desire of understanding deeply the whole mechanism by which it is possible to have such a 'ridicolous' circuit working properly as a decent CW transmitter. For staying in touch on the Shortwaves.

 

Radioman, July 2016


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