Hello,
I have also done transverter for 2M in the past as well as 2m
RX designs.
A good filter for 2m can be done with 3 coils of helix design
using aperture (window) coupling. Constuction is a 3 cell box
using 2 sided copper clad board material.
I have also found it convenient to develope for VHF/UHF using
modular construction. For BITx this would be the audio,
modulator, carrier osilarot and IF stages on one board and
encased then later stages in boxed. Connections between boxes
is with coaxial cable for RF. The whole radio becomes a box
of boxes. This appears difficult but allows good shielding
and makes stage by stage testing easier.
Good luck with 2M.
FYI: I have tested early stages of the BITx for 6M without power
amplifers. With only 1mW (.001w) the range was only a few miles
but the signals sounded good at the other end and recieve performance
is as expected. More work is to build the power amplifier chain
and enclose it.
Allison
KB1GMX [FN42hh]
toggle quoted message
Show quoted text
--- In BITX20@..., "eb7hpm" <msraya@t...> wrote:
--- In BITX20@..., Paolo Cravero as2594 <pcravero@a...>
wrote:
Hi
Great to read about your BITX developments!
I have one concern, though: will it be possibile to efficiently
filter
out unwanted harmonics +-n*10MHz at 144 MHz?
I think VHF&up transceivers use higher modulation IF or a
different
generation method.
Good... good question. ;-)
The Yaesu FT-290R have 4 passaband filters sintonized at 144MHz with
the aid of varicaps as output of mixer (it has also a ring diodes
mixer), it has a 11MHz FI, then I suposse this is not problem,
having some narrow passaband filters (four etapes minimun). The
consecuence of this is that the sintonization range will be narrow
also, but this is not a problem. I want to use only at 144.300 +-
50KHz. ;-) I do not use varicaps for sintonizing..
I make a tranverter for 28MHz to 144MHz a year ago and it also have
a 4 coil passaband filter little trickly to adjust. But no much
problem afterthat.
Howhever I not have made yet the tests. The 4 coil passaband filter
must be enclosed in a box, and the coupling must be soft. A coil
near the other coil assures soft coupling. It woks, as work for my
transverter a year ago.
Thank You for your coments.
Greetings
Manuel
EA7ARX
Just my thoughts,
Paolo IK1ZYW
--
| QRPp-I #707 + www.paolocravero.tk + I QRP #476 |
| SpamAssassin-based email antispam/antivirus solutions |
\ Italian/English-to/from-Croatian translations /
\ Skype: pcravero /
