08/03/2019 16:36

Regen in a BC221


In the group of friends with whom I share my radio-experiences and knowledge, there has been a recent stir in the pot with Regenerative receivers.

Mr. RegenMan threw the stone in the lake insisting on making a receiver with only 12 V on the plates. On the web there are many examples. I made mine and he made his version, but inside a recovered old BC221 Frequency Meter.







The schematic is rather self explaining, other that Mr. RegenMan used a 12AU7 pre-RF/Detector + 12BH7 audio section. The adopted tubes are not 'space charge' type, but rather meant to be used with 100 ... 200 Volts on the plates. We wanted to see how they perform at much lover voltages.

The optimization has lead to a device that can drive a normal High-Impedance headset without need of further amplification, even though the audio level would actually need some help ...

The operating point at the RF preamplifier is set by the 'rf set' potentiometer. One should find the proper setting noticing the noise raising, but not too much. The preamplifier has a chocke at the grid, and feeds the main tuning tank: this configuration, if the amplification is too much, would generate self oscillations and mixing cross products with the incoming signals.

Mr RegenMan uses only a 4 mt whip on his window, and by the whole setup we can easily carry out radio-traffic down to 3.8 MHz, being our preferential frequency around 5 Mhz though ...

Along the audio path, a parallel resonant circuit has been added, exploiting a 220/6 V transformer as inductance, to narrow a bit the very wide frequency response typical of these receivers: the Radiotelegraphy reception is better.

On some evenings, the overall performance of this receiver has comparable (if not better) reception quality of a modern 'rice box'. Again: the key of success is the lack of the Automatic Gain Control and a very minimal number of active stages, resulting in a high signal-to-noise ratio.

I can confirm the performances as I made a similar receiver, with 12 V on the plates, but with different tubes, i.e. pentodes instead of triodes on the RF path: EF805S at the preamplifier and the detector, and an ECC802 double triode on the audio section, special version of the 12AU7 (... first to come in my hand when digging in the boxes ...). My prototype is still a bit far from being properly optimized, and as I prefer loudspeaker listening, I added an external audio amp.

On these nights we use our respective '12V B+ regeneratives' to make some good QSOs ... on the Shortwaves.

Radioman, Aug. 2019

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02/22/2019 16:16

Regenerative Receiver


What about a '1-V-2' regenerative receiver ? '1-V-2', according to the long time tradition, means: 1 Tube RF preamplifier, a regenerative detector ('V', for Valve), and 2 Tubes in the audio chain.

In the prototype below, the RF amplifier is an EF805S, the detector is an ECC81/12AU7, with both sections in parallel (I hate to have unused tubes in a device ...), and the audio amplifier section is made by a triode-pentode, ECL84/6DX8.

Single band, from 3.5 to 4.0 MHz, the RF amplifier uses a tuned circuit, separately from the main tuning. The detector and the front end coils are not mutually shielded, but the RF tube is: it was necessary, otherwise any tuning variation in the RF section around the frequency tuned by the detector, makes the tuning setpoint of this whole thing unstable.

Soon it has been discovered that feeding a preamplified signal to a regen detector might be an overkill often, especially if long antennas are used. The receiver as it is allows to listen easily on 80..90% of the stations on the 80 mt band, by using only 5 ft piece of wire as antenna.

The detector is fed by a VR90 gas voltage stabilizer and the regeneration is set by tapping this voltage with a potentiometer. With 470 kOhm as bias resistor on the 12AU7 grid, from 1 to 2 Volts are sufficient (!) to enter the oscillation and therefore to copy CW and SSB. The greater this resitor, the greater the anode supply voltage to enter the regeneration. And less distorted tends to be the SSB reception.

Overall, the same sensitivity, stability and excellent signal to noise ratio have been possibile by this radio receiver, as compared to those achieved with 'Polyphemus'. The only substantial difference is regarding the dial resettability, which in this case is moderate, being this essentially the consequence of a regenerative detector, which is a free running analog oscillator and therefore the stability entirely depends on the mechanical rigidity of the all assembly.

In any case, it is again very pleasant and satisfying to tune in radio stations on the Shortwaves, by simple means.




Radioman, Feb. 2019

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11/09/2018 21:41


The time to make some further improvements to the Hartley transmitter has come. I wanted a more stable tone when the wind blows. It's Fall at the time of writing this post ... so having a warm tube on the desk, to make some good QSO with my friends, is just perfect on this part of the year.

The antenna link made by rigid Copper wire has been replaced by two turns of coaxial cable, wound right upon the main coil. The braid is left open on one side, and grounded on the other. The central conductor is the usual link to the antenna.

It's important with a Hartley having a center tapped coil, to place the link right in this position: the ground connection of the tap brings the electric potential of the turns, here, the minimum, therefore making also minimum any stray capacitive coupling to anything around. 

By placing the antenna link here, plus electrostatically shielding it, by the grounded coax cable braid, the tone quality is now much better and the frequency sensitivity to a windy weather, reduced.

And here, the result: the transmitter, loaded into the antenna, normally waving in the air ...

Radioman, Nov. 2018


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07/31/2018 21:31

Ham Radio ... where are you going ?


Below, a very quick promenade along the 'ham radio' way in the years. From the 'I need to get on the air at all costs', of the beginnings, to the 'world is mine by just one mouse-click'.

I haven't to tell you what I consider as true Radio ... and it's pretty obvious it's not that interesting playing with a PC for controlling a 'rice box'. I did this for living enough hours each day (i.e. sitting and using a PC), and I already have someone else shouting on my back 'run to reach the goal!!!'.

Anyway, the short collection of pictures illustrate a variant among many, on the direction of the humankind.

I don't feel ashamed at all in saying ... let's stop and revert a bit our way. We are loosing too much fun ... believe me.



Radioman, July 2018

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01/27/2018 23:23

Why 'Full Spectrum' ?


By 'Full Spectrum' is meant a kind of radio-activity managed throughout the HF, using very low power, improvised radios & antennas, on any or on a casual frequency.

If the web is surfed looking, for example, for 'shortwaves beacon', one can find a lot of sites on this topic. Many are experimenting with very low (and sometimes even not low at all) powers, in the range of tens or hundreds of milliwatts, by running beacons on almost any frequency on the Shortwaves.

A cathegory of these experimenters rely on those portions allocated to Short Range Device applications, industrial heating, medical applications, so to reduce the impact on the spectrum and therefore reducing possible disturbancies to some other radio stations.

This kind of activity is a new frontier. By suitable programs it is possible to filter the output from a receiver so that morse code sent by a few milliwatts can be perfectly decoded across the oceans. If the power is very low, the signal would not be noticed by a professional user of a given frequency, so everything would not be harmful. It is a frontier in the sense it is being experimented and investigated the real limit of the informaiton delivery by the ionosphere, with ultra-small power.

On top of this activity, a few more points should be added. Operating on non-conventional frequencies has always been a source of attraction by many. By the same many that, at a certain point, became licenced radio amateurs.

The bands today are often overcrowded and the users are just limiting themselves to push the buttons or to play with the menus of devices looking more domestic appliances than radios.

By operating improvised 'wireless sets', like, for example, a couple of transistors, crystal controlled, as TX, and further two or three transitor as Direct Conversion RX, with a power in the range of a few hundreds of milliwatt, anywhere in the HF away from the crowd, from the QRM and the infinitely boring guys using domestic appliances, is fun ! 

The fun is increased if these operations are run during outdoor trips, and agreed with the correspondent operating in the same conditions on a distant place, hundreds of miles away. Each time from a different location and on different frequencies. Low power, with the trusty piece of wire hanging between trees or hidden in a wooden roof.

Electronic components dealers offer plenty of crystals on frequencies in the good part of the Shortwaves, from 2 Mhz up to 12 MHz, where the limit of the experiments is only the imagination. These frequencies are often 'standard', so if more experimenters of this kind will be active, there would be chances to meet on the air other radio-fellows and establish contacts.

If receivers capable of demodulating a phone signal, typically AM, are needed, a NE602 mixer + a MC1350 IF amplifier would make a reasonable device, if the homemade way is preferred. Many 'world receivers' today available on Ebay, can be purchased by a few tens of $ and have more than sufficient performance to run a reliable radio-traffic.

Schematics with 3, 2 or even 1 solid state component transmitters can be found anywhere on the Web. The components are cheap, ready to get and perfect for cut-and-try optimizations, in which they might fail in search for the best performance. No worry, they are cheap and therefore the game will still run with no dramatic financial impact.

Sadly the Shortwaves Spectrum is day after day emptier. On the other side, those empty spaces might be used, occasionally, for unconventional radio experiments for very low profile radio traffic.

It can be often noted, besides, that on the same Forums where beacons-hunters and beacons-runners exchange their info ... there is apparently no discretion, and often people tell the time, frequency and power they will run with on a certain experiment. And they sign the posts by nicknames, but sometimes even not personal names (or ham calls !).

I have always thought that this is the prelude of a revolution regarding the HF Spectrum use, having its main origin in the frustration coming from the mess currently found on the 'official' bands. It is certainly generated by the curiosity of experimenting new things, and by the courage of operating out of band.

If this practice is not abused and managed with care (i.e. listening a lot, before sending a signal on a frequency, and, again, at extremely low power levels), for sure it will bring a breath of fresh air in the world of the radio enthusiasts!


Radioman, Jan 2018

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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



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.


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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