I'm Sorry Carlos, but the group's language is English. You may
prioritary to post in english. The mayority of others members only
understand english. Good, You must compose the message in lowercase
also, please. I can translate your question to english:
"Dear Manuel:
To conclude the construction of BITX I have a problem: to find a vfo
circuit that was stable to high frecuency. Initially the xcver was
adjusted in the 40m band only for testing purposes, but I don't have
ham radio license yet and I could not operate it. I have interest to
convert it to the 11meter band, in which i operate provisionally
until I get the license. I encounter interesting your circuit, for
that reason I ask for schematic of your VFO circuit used. I ned to
cover 27.400 to 27.900. The VFO is working from 17.4 to 17.9 or 37.4
to 37.9.
Another question is how to modify the program in order to cover this
frecuencies that show in the display. I be apreciated for you. In
principly I was thinking to build a DDS VFO, but the expense for
single band operation was not justified.
Perhaps when I have a license I face a multiband project with DDS.
Thank You and Greetings from Argentina.
73's and DX. CARLOS EDUARDO MOSCA"
I reply first shortly in English first, then in spanish.
Carlos, el lenguaje del grupo es Ingl¨¦s, por favor postea solo en
Ingles si te es posible, pues los dem¨¢s miembros del foro no te van
a entender. Tambi¨¦n es normal postear en minusculas, hacerlo en
mayusculas no est¨¢ bien visto. Respondo de forma breve a tus
preguntas:
-> The VFO is the same of BITX, I change de emiter-base and emiter-
groud capacitor to 47pF value for 31MHz operation. I change the coil
for a 1uH to resonate at 30MHz. This oscilator can work to 50MHz
aprox. I put a AM varicap(high capacity) in series with 1nF
capacitor to the oscilator coil. I put a 100K resistor from varicap
to PLL output. I put a 39pF capacitor from emiter oscilator to PLL
input.
-> You can change the frecuency of BITX to 27 MHz, only changing the
oscilator coil and the BPF filter coils and capacitors. But you must
test if the 11meters operation with modified equipement in your
country is legal. In my country this is not legal.
-> The software don't have to be modified. It works from 0 to 180MHz
unmodified, you only must to supply a apropiate VFO that got this
frecuency.
73's and good luck.
EA7ARX, ex EB7HPM/EC7ALV
This in spanish:
-> El VFO es el mismo que el del BITX, He cambiado el condensador
que va del emisor a la base y del emisor a tierra por 47pF. He
cambiado la bobina por un bote sintonizable de alrededor de 1
microhenrio para que resuene en 30MHz. Esta configuraci¨®n del
oscilador puede funcionar sin problemas hasta unos 50MHz. Puse un
varicap de AM(alta capacidad) en serie con un condensador de 1nF
conectado a la bobina osciladora del VFO. Puse una resistencia de
100K desde el varicap a la salida del PLL. Puse un condensador de
39pF del emisor del transistor oscilador a la entrada del PLL,
usando cable coaxial.
-> Puedes cambiar la frecuencia del BITX a 27 MHz, tan solo
cambiando la bobina del oscilador y las bobinas y condensadores del
filtro pasobanda de la entrada. Pero debes asegurarte que puedes
transmitir en 11 metros con equipos modificados en tu pais de forma
legal, en mi pais no es legal.
-> El software no es necesario modificarlo. Funciona desde 0 a 180
MHz sin problema, solo debes colocar un VFO apropiado que llege a
esa frecuencia.
73's y buena suerte.
EA7ARX, ex EB7HPM/EC7ALV
