Hello,
First of all I start to document it while the build is ongoing so there will be lot of update (fine tuning) and modification.
This is the first version aka prototype. It is only for developmnet I plan to build one for into backpack, one into my campercar, etcetera.
It looks now:
I have been started with microcontroller part. My build based on a chinese clone of arduino pro mini. It is employ an LCD without backlight.
Next part is an SI5351 module also from china. There is two problem with my work: loud reflection of I2C communication in the speaker. Another proble is, some HF injection because the oscillator signal goes thrugh a simple wire. The possible improvement what I plan is to change the simple wire to coax cable and shorten the I2C cables and employ ferrite on it to reduce the noise.
The quick and dirty solution to drive the relays is an ULN2003 🙂
The RF comming through a 30MHz lowpass filter. I have designed one here with following details and measured good performance:
All are minicircuits ADE1 mixers, installed on a small PCB with impedance adapter:
Next one is broadband amplifier. I created small PCBs for it, the plan created in KICAD (http://kicad-pcb.org/). All component is smd 0603. I used toner transfer method for creation. I’m not 100% aware of the licensing so plans are not published here now.
The 45MHz filter is a simple two pole chrystal now, how it shows o the upper photo. I plan to check the performance of the original (http://www.phonestack.com/farhan/ubitx/ubitx.html) and final commercial version (http://www.hfsignals.com/index.php/ubitx-circuit-description/) in the future. Characteristic of filter is the following
Next is again a ADE1 mixer, and broadband amp again.
12MHz crystal filter is the following. It is an ugly weekender style installation. Design is the original, but the transformer created on a binoculer ferrite. 6 turn bifibrillar. The outcome is self explain nice.
Next is the mixer again and the AF amplifier. There is the next peroblem because the IC is hot. I can imagine some oscillation is in the background because if I change the potentiometer to maximum then lot of distorsion. Middle level is ok. 😦 Need improvement also. Another portion is I have forgotten the CW-in so need to redesign.
Next step is the amplifier part and improvements.
Will be updated soon.
Thanks for reading!
73 DX HA7MAC
ha7mac 