lunedì 16 luglio 2018

MITSUBISHI RDxxHHF Silicon MOSFET Power Transistor, a useful gift for Hams

This is a not really new component but not so often used in homebrew schematics on the web.
I discovered it surfing the really intyeresting pages of Jeff WA7MLH with a lot of suggestion and ideas for the true homemaker.
In a pic I saw a different component, the RD06HHF and in another a couple of RD16HHF
Inspection on Mitsubishi website gave me a really interesting datasheet and after  some inspection I stated to make a try with this interesting power device. I also made several web serach and found interesting works of some homebrewers in different world parts:
the YO4HHP's blog describe mounting of a QRP power amplifier using a couple of these Mosfet;
the M1KTA's blog describes his experience in doing a QRP PA also;
VK5FE also describe his PA for QRP on a dual band version;
IN3OTD make some good tests on different amplfier and one is the amplfier sold by QRP project site, called QRP-PA-2008,
 and several QRP MAS project published on the website of homebrewers pages show several users of these MOSFET and so is possible to get idea and practical application of this really interesting device.

But the more important for me was a G QRP SPRAT article I got on theSpring 2018 issue of the newsletter by  Andy G0FTD, the title is " Iron Fist- a 5 W CW Tx from top band  to ten metres". The article describes the experiences and test that Andy did about the "low power" version (RD06HHF) version  of the Mosfet and possibility to do a 5W tx with just TWO stage.
Andy was also so kind to give me more answers via email and on the web there is possibility to download the article for interested people.

So decided to get some sample of the Mosfet and so it from a Ham in Greece: SV1AFN, in order to do some test for my own.
I did a simple two stages transmitter, with first stage  using a simple 2N3904 xtal oscillator and the RD16HHF as a PA.

 As Andy G0FTD wrote in his article:
The input impedance is about 200 ohms for this device (not an issue), output is typically 12 ohms. This suits our 50 ohm world, since a simple broadband 1:4 un-un wound on an FT50-43 is all that is required to couple into your chosen 50 ohm LPF circuit. I think I managed to get about 17-20 bifilar wound turns on my toroid, which will provide ample inductance to work down to 0.5Mhz and up to 50Mhz. Whatever you do, just fit as many on as you can within the 340 degrees or so or the toroid, using about 22 SWG wire

So the impedance is easy to adapt in input and output.
Decided also to test it during the QRP MAS test of last spring and so the test was really not just for power but for a continous use and verify the ability to not heath too much.

Really we can use the device at high power supply also, and power can vary, but mainly the CW use without heath sink let long QSO/Chat without any excess of heath.
Power is really over 5 W (on some band up to 8 W) and this makes the similarity with a tube TX, just two stages and a really QRP level TX, NICE and interesting!

The following schematics are given from several QRP MAS edition and show how several Hams used this very interesting and affordable device (authors are pointed inside or under the drawings)

(by DC0DA)

(by DL1ARH)

(by DL7UWE)

(by DL8WIG)

The last schematic is what I did for the QRP MAS of 2018 using infor from previous sources

 (by I5SKK)

I think that this is a great device for QRP (and not QRP also) in Ham Bands for homebrewer and that is worth to make some tests and use for Ham that like to do by theirselves the rig they use.

Last but not least a good a good seller is SRD-KITS shop. This Eu shop sells really Mitsubishi devices and not chinese replica that are found on ebay, cheaper but not so reliable. The Power Fest page of this shop summarize the characteristics and the prices are really honest and found on the webshop page.

Wish you enjoy this devise and do a lot of QRP contact using it on your homemade TX.

Best 72!

martedì 27 marzo 2018

REGEN RECEIVER: some notes by prof. Arnie Coro CO2KK and something more from Kostas SV3ORA

  (pic from: 


The following Regen Receiver notes by a well known expert Ham, Arnie Coro CO2KK.

The notes are freely reprinted from a Regen receiver Yaooh Group (Regenrx) :
and from the Arnie onoline newletter: Radio Havana Cuba DX Unlimited:

Dear amigos:
After years of experimenting with vacuum tubes receivers here are some
of my findings...

6AK5 / 6ZHE1P/5654 my all time choice for Pentode or grounded grid RF
amplifier stage up to the 50 MHz band

Same tube works nicely as crystal oscillator for the front end section
of my Regenerodyne receivers... Frequency range up to 12 MHz or so
direct oscillation and up to 50 MHz using third overtone crystals.

Same tube works as a very simple front end mixer... You feed the RF to
the grid from the RF amplifier stage and then feed the local oscillator
frequency either to the screen grid, or to the cathode... Output of the
mixer goes via a low impedance link to the grid tank circuit of the
regenerative detector that works as a variable frequency IF... The
detector that I like best is the Hartley with screen grid voltage
regeneration control.... that provides silk smooth regeneration while
working with plate voltages not higher than 50 volts. I typically run
them at 36 to 48 volts using well regulated DC... The detector feeds my
universal audio tail end for SWL and AM band Dxing, using a 6AU6 and a
6AQ5 running from the 120 volts bus of the power supply....

Your regenerodyne will outperform even the best regenerative receiver ,
by using the following layout


Dual tuned top coupled bandpass input filter to grid of 6AK5... plate of
6AK5 feed mixer grid via a small capacitor... You can control RF gain
easily using the classic cathode potentiometer properly bypassed....

6AK5 mixer .... plate at 120 volts, screen at 50 volts... signal into
grid, local oscillator injection to the cathode...  Output untuned , via
a RF choke that is coupled with small capacitor to the grid circuit of
the 6AK5 regenerative detector using the classic Hartley circuit with
screen grid voltage ( regulated ) regeneration control....

Feed audio to the tail end module, 6AU6 followed by 6AK5 with 120 volts
to the plates....

You can also use a 6AK5 as the first audio to end up with a radio that
requires just two tube types... I have yet to test the 6AK5 as an audio
output stage, possibly using two in pararell... Reason for this test ?
The availability of hundreds of 6AK5's 5654's from the IF amplifier
chains of microwave radio relay sites now dismantled....

You will need a dual gang variable capacitor for the front end filter

You will need two good quality air spaced variable capacitors, one for
the main tuning and the other for bandspread, but if you are as lucky as
I was then a BC221 or CHA4-M heterodyne frequency meters variable
capacitors and superb mechanical dial mechanism will make your receiver
an outstanding performer, and also very good looking cosmetically

The tuning controls are

1. Bandpass input filter tuning

2. RF gain control

3. Main tuning dial and bandspread

4. Audio level control

Later you can replace the audio module for a more sophisticated version
that includes two audio filters, one for CW peaking at around 700 Hertz
and a bandpass filter 300 to 3000 Hertz for voice or digital..

NO rare parts, many obtained from recycling but please follow my advice
and check them before soldering in place to avoid headaches during start
up !!!

Metal work for the Regenerodyne follows the ZL1JJ New Zealand
regenerative construction practice regarding shielding and by passing...

73 and DX

Arnie Coro CO2KK

Here is now our technical topics section of the show, coming up at the request of several listeners that are experimenting with home built short wave receivers, one of the more than 90 ways that you and I enjoy this wonderful hobby....
My personal preference for regenerative radios comes from the fascinating fact of their outstanding performance when well
built and the extreme simplicity of the circuit. A single vacuum tube or a field effect transistor, a battery power supply and a few parts when properly assembled into a regenerative receiver circuit will provide amazing results

Nowadays one has the option to home brew a classic vacuum tubes regenerative, one built using bipolar transistors , or a radio built
using field effect transistors.

Of the mentioned three options I am an all time regenerative vacuum tubes receiver enthusiast... As a matter fact, after testing many different solid state regenerative sets, my thumbs up signal goes to the more sophisticated and complexvacuum tubes designs, especially the non plus ultra of them all , the ZL2JJ design , that I have modified to use more modern vacuum tubes types than the 1930's and 40's types used by the original set.

Regenerative receivers do require a very solid mechanical construction if you really want to achieve top notch performance.

Time spent assembling a very rugged chassis, proper placement of the components and careful assembly of the electronic circuits are the difference between a mediocre set and one that shows really high performance. This is how the Zl2JJ receiver was designed and built ….

More modern designs using the cascode circuit that were experimented by Dutch radio amateurs and later published by the British Radio
Communications magazine, when properly built achieve amazing sensitivity and razor sharp selectivity. Cuban radio amateur CO3BN , Bernardo from Artemisa province of western Cuba recently reported to me that his home brew cascode receiver performance was simply amazing… providing both excellent selectivity and frequency stability as well as a very easy going bandspread tuning .

It is important to keep the power supply of the regenerative radios built on a separate chassis, and connect it to the radio using a well shielded multi conductors cable. Some builders prefer to run the radios using a 6 or 12 volts accumulator for the filaments and a set of series connected batteries for the B plus line. But this may prove to be really expensive, especially when time comes to replace the high voltage battery.

My classic simplified regenerative vacuum tubes radio is fed by a solid state power supply that provides 6.3 volts regulated direct voltage for the filaments and between 50 to 75 volts also regulated for the high voltage.

In a recent e-mail that I received from listener Norbert from Genoa, Italy, he asked why he could not find a single factory made vacuum
tubes regenerative receiver , after searching several radio hobby magazines.

Well amigo Norbert, regenerative receiver circuits, built using vacuum tubes or solid state devices , do not lend themselves to mass
production. Each radio is a one of its kind, according to what practical experience building them shows quite clearly.

But that is precisely what makes regenerative detectors so fascinating... Even the simplest on single active device radio, be it a vacuum tube or a solid state component, does require some experimenting before the best possible results can be achieved, and that amigo Luigi is where the fun of it comes out!!!

I do have three or four very well designed and proven in practice regenerative receivers that cover from the very low frequency bands up to around thirty megaHertz, and they are all available by just sending an e-mail to


But we have more to show and point out. 
The friend Kostas SV3ORA has a very well done webspace for homebrewers.
In the main the experiment of Kostas lead him to a very simple but effective solid state Regen RX that's able to amaze the homebrewer.
The direct link leads to a very interesting page to read and study and after this we have just to do it and test.

The Kostas headlines are as follow:

"....a reflexed regenerative receiver that is simplicity itself, yet capable of remarkably good performance, better than anything I have built so far. The highly sensitive, single signal capable, all-bands receiver, can be easily built in one afternoon, and it is capable of receiving any frequency on HF (1-30MHz) by just replacing the crystal for that frequency. No other components need replacing or rescaling apart from the crystal itself..."
Kostas spent quite a lot of time in searching the right manner to have this receiver functioning properly and now you can find a very simple and minimal but effective Receiver, able to be a portable one, aside a QRP TX that is possible to get from the Kostas pages ore everywhere.
I want to underline the mind of Kostas to obtain good performance with simple circuits, not commercial at all, but well designed and tested by a true Ham, that loves Radio and Electronics and show with results his love.


We hope this first post will be useful as a source  of possible ideas and plans.
Please give us suggestions  and  feedback, they will be welcome.
Best 73 and wish you amusing homebrewing.

mercoledì 14 marzo 2018

The Beginning

In questo blog parleremo soltanto di autocostruzione in campo radioamatoriale, o Ham Radio se preferite.
Principalmente di tipo analogico, per il Radioamatore normale, per chi non è esperto e non deve per forza essere un ingegnere o tecnico specializzato, quello non ha bisogno di noi. Noi scegliamo ed auspichiamo un buon livello di Radioamatore, senza necessariamente una laurea, ma con una vera e pura passione che lo porti a cercare di imparare in ogni occasione e da chiunque.

Non di kit, ma di costruzione, di mettersi alla prova, magari anche sbagliando, ma per avere la soddisfazione di poter sapere che "l'abbiamo fatto da noi stessi"

Noi vogliamo parlare di Autocostruzione per chiunque.

Here we will speak about "Just Home Made Radio Amateurs" (or Ham Radio if you prefer).
Main analog, for the medium Ham, for the beginner too, not just for top technician or engineer, but not just basic: we  choose a good level of Ham Radio without any graduation, but with a lot of true and pure Ham Spirit and desire to learn from everywhere and in any place.
No kit, just construcion, the challenge in doing by ourselves, with errors too, with the final satisfaction of a done with our hands equipment to use and enjoy.
We want to speak about HomeBrewing for everybody !