Date: Wed, 19 Dec 2018 13:57:18 +0000
From: Chris Wilson <dead.fets@gmail.com>
Message-ID: <825616835.20181219135718@gmail.com>
To: =?utf-8?Q?VIGILANT_Luis_Fern=C3=A1ndez?= <rsgb_lf_group@blacksheep.org>
In-Reply-To: <6DB8451D7F3D3947A5918808A59621EA26397DBA@servigilant.vigilant.local>
References: <10f465fa-37f0-4ac6-b53d-793f955ea011@email.android.com> <5C19FFCB.1060305@posteo.de> <16876196-3308-f722-dfca-5232150e7394@n1bug.com> <6DB8451D7F3D3947A5918808A59621EA26397DBA@servigilant.vigilant.local>
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Subject: Re: LF: Ebnaut receiver frequency stability qustion
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Hello Luis

A  link  to  which  Ebay supplier you got the correct Ublox units from
would  be great, I believe these are a bit of a mine field with fakes
and various specs abounding :) Thanks!

Wednesday, December 19, 2018, 1:42:09 PM, you 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: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] En nombre de N1BUG
> Enviado el: miércoles, 19 de diciembre de 2018 13:01
> Para: rsgb_lf_group@blacksheep.org
> 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


-- 
Best regards,
 Chris                            mailto:dead.fets@gmail.com