Atlas Si5351 Interconnect



The Interconnections to the Atlas RX110 whihc also function as the connection points for the TX110 are staright forward and are minimally invasive. The output of the VFO is connection to a metal post on an auxilairy circuit board behind the VFO ( a Brown wire). The power to the VFO comes off of that same board via another post and this time an orange wire. Simply unsolder the two wires, tape the ends and move them out of the way. Restoring the original VFO is a matter of connecting the two wores back to their respective locations. This same connection post for the VFO passes through the circuit board and is accessible from the top of the circuit board. On the top side access we will connect a 10 nF cap and to the other end the center conductor of a short length of RG-174/U coax. There is a metal bolt connecting the circuit board to the common metal chassis in cose proximity to the connection post. Intall a ground lug on that bolt and connect the coax shield to that ground lug. The other end of the small coax is connected to a RCA jack on the back side of the case. The LO from CLK0 signal is routed to this RCA jack and "Bob's Your Uncle".

[ For those who wonder the "Bob's Your Uncle" is an English phrase that deals with nepotism in the British government during the Colonial period specifically to Robert Balfour. It seems that his many relatives ended up with plum government positions or fast forward to the current time in the USA where we can say "Don's Your Uncle" (or Dad, Father-in Law or some other family connection ).]

For the BFO signal from the Si5351 we will simply remove (by unsoldering) the BFO crystal. Uisng a piece of Gorilla Tape --affix that crystal to the underside of the Atlas chassis -- this way if you want to restore the original BFO it is close at hand. Find the Base connection to Q313 and connect a 10nF cap to that base. On the other end connect a short length of coax to that point and the shield can be soldered to one of the ground traces on the circuit board. Route the other end of the RG-174/U to the second RCA jack which has been installed on the back panel and this then connects to CLK 2.

Thus the interconnections are minimally invasive and the restortaion to the original circuit is straight forward. A construction tip would be to look at the coax rounting to the back panel and prepare the coax ahead of time as to correct length and tinned leads etc. This will greatly facilitate the install.