9A/YO3HJV/P

 I planned to work HF/portable from Dubrovnik when coming back from Austria but, unfortunately, the change of pandemic rules for entering the country was subbject to a last minute change thus I replanned my trip.

I ended on the Lake Balaton, in Hungary and I spent my birthday there with my wife and my daughter, on a very nice villa with a beautifull view and a balcony that was the perfect spot for my HF portable setup.

I had with me the little Xiegu G90 with some portable HF antennas from which the MP-1 was the "hero".

I managed to work in 20m band some YO stations from Bucharest, Constanta, Timisoara and Brasov and from Bulgaria and on the West side, Finland, Germany and UK.

It was nice but I am a little sad I could not reach Dubrovnik!

1-10W QRP SWR meter

Pentru ca m-am hotarat sa reiau operarea din portabil QRP am nevoie de un instrument minimalist, usor si sigur care sa imi indice acordul antenelor.

Sigur, acum totul se face cu analizoare, care mai de care mai complexe si sofisticate. Am cateva insa sunt destul de incomode daca vrei sa iti incapa totul intr-un mic rucsac.

Asa ca m-am indreptat spre puntile SWR "clasice", realizate cu toroid. 

Dupa mai multe experimente, am ajuns la solutia prezentata mai jos.

Nu am avut la indemana doua toruri asa ca am folosit un miez binocular, BN-43-2402 pe care am realizat ambele transformatoare.

Diodele pot fi de orice tip, Schottky; am avut la indemana BAT54.

Indicatia se face pe miliampermetru cu cap de scala 100uA. La 5W este cap de scala, fiind foarte sensibil. Am testat pe gama 1-30 MHz iar indicatia este potrivita pentru acordul cu precizie al antenei.

Miliampermetrele pot fi inlocuite cu doua LED-uri; preferabil verzi sau galbene, caz in care este nevoie de o baterie de 1,5V instalata conform linie punctate. Bateria poate fi lasata in circuit intrucat, in absenta semnalului de masurat, pragul de deschidere al LED-urilor nu este atins.

Daca se folosesc LED-uri, rezistentele Rs vor fi inlocuite cu unele de 10-15 Ohm.

Valorile indicate sunt pentru operare QRP, rezistentele fiind 0,25W. In cazul in care se doreste extinderea gamei la 100W, rezistentele de 47 Ohm vor fi inlocuite cu doua rezistente de 100 Ohm/0,5W, in paralel (am testat si la 100W si nu sunt probleme daca se utilizeaza serii scurte de emisie).

Atentie, la realizarea transformatorului infasurarile de 10 spire se vor bobina IN ACELASI SENS iar capetele care se conecteaza la sasiu vor fi intocmai ca in schema electrica!

Incercati sa realizati montajul cat mai simetric si cu plan de masa unitar iar rezultatele vor fi excelente!

Montajul poate fi utilizat pentru masurarea cu doua circuite AD8307 caz in care semnalul se va prelua direct de pe rezistentele de 47 Ohm.

Circuitul este reversibil; nu conteaza care este intrarea dar, in cazul in care il conectati invers, semnificatia LED-urilor se schimba si ea. 

De altfel, reversibilitatea este folositoare la testarea rapida a realizari corecte. 

Pe o sarcina de 50 Ohm, doar LED-url de FWD va lumina la aplicarea semnalului. 

Inversand montajul, tot pe sarcina artificiala, va lumina LED-ul de SWR. 

Daca efectuati acest test cu doua miliampermetre identice, veti observa mult mai usor functionarea corecta. 

In varianta mea constructiva am folosit un combo de ace indicatoare incrucisate si am introdus in schema si un potentiometru pentru a putea modifica capatul de scala in functie de puterea statiei.

Succes!

	50 Ohm resistive load
Ip. A			L	1W	2W	3W	4W	5W	6W	7W	8W	9W	10W
	Rf in la Rf in
correct	a	SWR port	0.900	6.000	9.000	15.700	23.000	32.800	47.800	55.600	63.000	78.500	95	mV
	b	PWR port	0.21	0.48	0.75	0.92	1.10	1.30	1.49	1.68	1.92	2.12	2.45	V
Ip B	RfIn la ANT
revers	a	SWR port	0.21	0.60	0.77	1.00	1.19	1.37	1.57	1.80	1.98	2.22	2.44	V
	b	PWR port	14.000	40.700	58.300	76.000	98.000	117.500	137.400	156.000	176.400	195.000	217	mV

New QRP-uBITX in the shack - III - Transmitter section mods

OK, it was the time to see how the TX section of the uBITX is...










From time to time I also tested how it fits inside the case...
The radio PCB was fixed on a larger one-side plated PCB that slides into the aluminium case.

I also checked the front panel to see if the potentiometers and other stuff are OK with the main board...






First of all, the Tx power was around 7-8 W PEP on 80 and 40 m bands, decreasing to around 2W on the higher frequencies.


First tought was to fiddle aronud with the IRF transistors... I was eager to try to change them with RD16HHF1...

So, I changed them (sorry, have no pictures about this :-( ) and also changed the T11 with one 1:2 made on a BN61-202 core (I am not sure about the size but the ferrite mix is definetly a "61" type).

I noticed that the C261 and C202 was missing.... What???  Yeap, they was missing!
So, I changed the R261/R262 with 1kOhm and put there two capacitors of 1nF.
Also set the drain current to about 250 mA for each transistor.

The results was not able to convince me... The transistors ran hot, too hot and the Tx power was about the same.

So, I reverted back to IRF510, kept the new transformer. I kept the neutralisation network as described above and put a 27 pF between the Draines of Q94 and Q95.

The Drain current was set at 150mA each.

I removed the original transistors Q90, Q911, Q912, Q92, Q93, Q96 and Q97 (2n3904) and put some female pins instead to play with other transistors.

I have a lot of BFW17 and BLW65 and by looking at the datasheets, I choose BFW17.

I masured the transistors to have identical hFE and I choose one with 120 for the Q90 and the rest of them was with hFE of 92.

I added some 33Ohm resistors (paralleled) on the R87, R88, R911, R96, R941 and R942.

After this mods, I fired up the Tx answering to some CQ's and the power-meter showed about 12-17 W PEP on all range (1.8 MHz - 29 MHz).

I still had to put it on the Spectrum analyser and do the two tone test...

You can see two RG317 wires. Those are to put the final stage to test on the Spectrum analyser with tracking generator to see what is the effect of the mods I made on the PA.

Again, testing if it fits inside...

Here you can see the new output transformer and the PARF radiator.


Also, on the Raduino board (which will have it's own story), you can see a big 0,45 Ohm/3W resistor in series with the LM7805 input.

At the RF output, a 1:1 choke balun was made from the RG317 on a 43 mix toroid and a gas discharge protection was added.

New QRP-uBITX in the shack - II - A few necessary measures

First of all, the board is "Rev 4" which means it came with discrete audio PA and "Audio pop mod".

Here is the full diagram of the uBITX main board.

We'll get back later to this diagram.

1. After unpacking, the parallel LCD was replaced with a I2C one as I want to free some hardware resources for further improvements.

I uploaded the new firmware, the one from KD8CEC. 

A quick test for the Raduino board. Everything is OK.

2. The crystal ladder filter must be grounded. A small 0.8mm hole was made and a ground wire soldered on all crystal's cases.

I used the occasion to implement the mod for the variable IF filter.

For that, I removed C217, C218, C219, C220 and C221 and replaced with 5 varactor diodes.

I found SVC236-TB-E to be suitable for this purpose as I need to have between 50-100 pF and a good stability over a large temperature range.

Here it is how it looks... You cannot see the varactor diodes here because of the 47k resistors but they are behind the line of resistors, right in the place of the removed capacitors.

Here is the diagram for the mod.

A few words about:

-The Rx and Tx are 12V from the K1 relay. I took the voltage from R48 and R38. 

-The 12V which came from the Rx/Tx relay are regulated by the two linear regulators. As we increase the voltage, the IF bandwith widens. For Rx, 0 to 8V measured at the common cathodes of D6 and D7 correspond to a variable bandwith from approx 250 Hz to 4 kHz. For Tx, a voltage around 2.9V gave a nice warm modulation of about 2.8 kHz.

I have on the panel only P1. You can use any linear regulator or even some Zenner diodes with 4k7 resistors.

The components are placed on a small universal PCB. The components are not critical.

3. Some mods are necessary also on the audio PA stage.

There are some crossover distorsions that made the audio bad. To solve them, I modified the polarisation of the final transistors. Remember I told you we will revisit the schematics of the audio PA? Good! Between D15 and D16 a resistor must be inserted. I tested various values and the best results was with  10 Ohm. The trace between the two diodes was cut and the SMD resistor was placed right between.

Here it is how IF variable bandwith sound (CW):

I also use this TRX to listen to MW broadcast:

........ more to come!

Portable HF antenna setup

Well, the winter is coming (at least when I peek to the calendar) so it's time to make the antennas for portable HF.
I am using an ICOM IC-703+ with the ICOM backpack and a vertical Racal antenna. But this is not enough for me so I planned to experiment with an End Fed antenna.
I contemplated the End Fed Half Wave antenna with a high ratio UnUn but the tests I did on my lab didn't convince me. I also find the lenght of the EFHW not suitable for what I expect from a portable setup. It's simply to lenghty to use it on various setups, mainly to keep it at the necessary height from the ground.
So, the next choice for a multiband wire antenna is also some sort of End Fed but the one that can be fed with a 9:1 UnUn, an aperiodic one.
On the internet there are several places where you cand found a suitable lenght for the wire.
As I am not interested on 160m band from portable, I choose the 13.5 m as the best for me.
I quickly made a 9:1 Unbalanced to Unbalanced broadband transformer and a 1:1 choke Balun made from a piece of RG316 teflon coax on a FT-120-43 toroid core. This consist of 4+4 turns on the ferrite core.
I prepared two pieces of RG58 coax cable. One of 10m and the second one of 5m.
I can use the choke balun to make a counterpoise from the 5 or from the 10m of coax cable. If the conditions permit, I cand put a real counterpoise directly on the 9:1 BalUn and use the entire lenght of the cable with a UHF Female-female adapter without the choke balun. Or even to use the choke balun right at the transceiver's output.
So, I believe this setup let me experiment in the field with the best setup from various ones.
I will revisit this post after the Christmas holiday.
Merry Christmas!

 I forgot, this is a small Z-Match made with polyvaricons. This is to be used with 450 Ohm ladder line and simmetrical dipoles.

Home Alone Ham...

Its a (stupid) tradition here to have at the beginning of December "Home Alone" at TV.
So, I choose not to watch to because I do have a lot to do!
I recently (re) finished my HF backpack kit and I am looking forward for my new LiFe battery to get rid of the heavy SLA one!
Basically, it's an ICOM IC-703. Yeah, the one that I trade a TS480 SAT for!
After it had some problems due to an idiot (me) who put a FT2000 to tune directly to the input of the ICOM, I managed to make it again like new! I had to change the pre-driver and the little uPC which attack the pre-driver and some SMD inductances and after just a few minutes of QSO one of the final transistors gave up but now, everything it's OK.

I even want to make a small external Z-match to be able to tune balanced antennas like G5RV but I gave a second chance to the wonderfull internal ATU and made just an external matcher for the Racal foldable vertical whip which I often use on portable HF.

No, the schematics is not on public domain because I had a hard time fine tuning it, but if anyone need to have a diagram, I will send it via e-mail. An antenna analyser is a must!
In a few words, that box change the sign of the imaginary part of the antenna impedance, make it easyer for the internal antena tuner. 

After I repair and realigned the radio, it was the perfect time to finally made the handset and the headset I dreamt a lot!
Studying the service manual, I found that I have audio output on the microphone RJ45. The only problem is that I must put a dumb 3.5 mm jack into the external speaker to mute the radio and have the audio only on the handset. But this is not a real problem, right?

About the title, well, I was home alone today!

I let you with the pictures and feel free to ask for details!

73 de Adrian, YO3HJV