Hi Luis,

I don't understand this yet.

I thought the cheap LEO-6M, LEO-7M and LEO-M8N can supply LO or 1
PPS but not both at the same time? So for RX don't we need two of them?

Then another one for TX?

So that is three. Doesn't it make sense then to use one LEO-M8T
which can do LO and 1 PPS at the same time? And find some way to use
it for TX also?

73,
Paul


On 12/19/18 8:42 AM, VIGILANT Luis Fernández wrote:
> Hi EbNaut
> 
> My downconverter is based on NE602 and is crude simple. No filters, no gain 
> stages. A bit deaf and birdie-rich
> but wanted to test it that way for EbNaut and check if it works. It is based 
> on K0LR article you can find here
> https://www.qsl.net/k0lr/SW-RX/sw-rx.htm
> 
> The LO based in Xtal and 74HC4060 is REPLACED by a series 10K resistor and 
> series 100nF connected to the GPS output
> So, for the LO, a cheap uBlox GPS will provide both 120 or 125KHz for the LO 
> and 1pps to discipline the soundcard
> You only need to connect the GPS to USB and use the uCenter software to 
> configure the GPS outputs and save
> this cnfiguration as default for the GPS
> 
> No worth to use the same GPS for Tx. It is so chip you sure can afford 
> another one for Tx at 2x the frequency if you
> are using a D class PA
> 
> 
> 
> -----Mensaje original-----
> De: [email protected] 
> [mailto:[email protected]] En nombre de N1BUG
> Enviado el: miércoles, 19 de diciembre de 2018 13:01
> Para: [email protected]
> Asunto: Re: LF: Ebnaut receiver frequency stability qustion
> 
> Hi Stefan, Luis, LF,
> 
> Yes, yes! Please grab some paper and start drawing those circuit diagrams! ;-)
> 
> The non-engineers have many questions...
> 
> If I understand this correctly... with the NEO-M8T then I just need one 
> module... use one time pulse pin for LO and the other one for 1 PPM to 
> discipline the sound card? Else with the NEO-6/7 or M8N I need two.
> 
> For the older modules U-blox says they use a 48 MHz NCO and that the time 
> pulse output will have less jitter if configured to a frequency which divides 
> evenly into 48 MHz. So I guess 120 kHz...
> 
> But I couldn't find any information about the oscillator frequency for the 
> M8T. Does anybody know?
> 
> What kind of mixer?
> 
> Can filters help? Band pass filter on antenna input to mixer? LPF on LO to 
> mixer?
> 
> 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?
> 
> 73,
> Paul
> 
> 
> 
> On 12/19/18 3:22 AM, DK7FC wrote:
>> Hi Luis, LF,
>>
>> I agree, this is indeed the most reasonable design. Using the same 
>> here
>> ;-) but a 125 kHz LO, locked to GPS.
>> Maybe we should provide easy converter crcuits. A compromise between 
>> high end and easy to build up, for the 'EbNaut-newcomers'?
>>
>> 73, Stefan
>>
>> Am 19.12.2018 07:39, schrieb VIGILANT Luis Fernández:
>>> Hi EbNaut
>>>
>>> I think that using expensive receivers is NOT the way to go. I'm 
>>> using a simple mixer as downconverter. The LO is 120KHz generated 
>>> from a uBlox GPS. So the 137KHz outputs as 17KHz and can be feeded to 
>>> PC soundcard. The second channel of GPS provides 1pps to discipline 
>>> the soundcard using Spectrum lab
>>>
>>> Not using filters at all and no amplifier stages. So there is room 
>>> for improvement, but it works
>>>
>>> 73 de Luis
>>> EA5DOM