Re: LF: Ebnaut receiver frequency stability qustion

[N1BUG <paul@n1bug.com>]

Hi Stefan,

Thanks for showing us your TX converter circuit. That is a bit more
complicated than I was expecting which goes to illustrate my point
about why diagrams are so important. I thought you meant to use a
simple DBM mixer with a LO. I see I was wrong about that.

I can build this. But how do we connect the Ublox LO? Remove the
74HC4060 and connect the Ublox to the 74HC4052 CLK pins through a
capacitor?

Do the capacitors in the circuit need to be any special type? It
seems some of them might need to be quite stable?

This could be a very interesting solution for me, because I am also
looking for some good way to TX DFCW for QSOs.

73,
Paul



On 12/19/18 7:53 AM, DK7FC wrote:
> Hi Paul,
> 
> Am 19.12.2018 13:00, schrieb N1BUG:
>> Hi Stefan, Luis, LF,
>>
>> Yes, yes! Please grab some paper and start drawing those circuit
>> diagrams! ;-)
>>    
> No problem. I've drawn the circuit years ago. But the design (based on a 
> G4JNT design) is a bit more complex. But there you don't need image 
> rejection filters, which is an advantage. Image in the attachment.
> This is what i use for LF transmissions. The xtal is GPS locked by 
> another circuit that is not shown in this schematic. But instead one can 
> use the NEO GPS modules. Not only EbNaut, the converter is good for 
> WSPR, QRSS, DFCW, OP32, JT9 and so on.
> 
>> What kind of mixer?
>>    
> For the RX i'm using an SBL-3 DBM. But a SA612AN will work too ( i use 
> that one for the MF converter). There, you will need narrow band filters.
> 
>> Can filters help? Band pass filter on antenna input to mixer? LPF on
>> LO to mixer?
>>    
> Yes, a band filter in front of the mixer and then an image rejection 
> filter on the AF side. Thus it is better to use an LO frequency of 125 
> or 120 kHz rather than 135 kHz because filtering will be easier then.
>> Probably more questions but since I am not an engineer and have
>> never seen a diagram of this, I don't know what else to ask.
>>
>> Can the same LO and mixer be used for a tx up-converter?
>>    
> I'm using the same LO for the RX and then TX converter.
> 
> 73, Stefan