Re: Raspberry Pi as WSPR transmitter up to 250Mhz


Ronny Julian <k4rjjradio@...>
 

Stephen you might take a page out of the 4 States QRP group book and make everything part of the board for a 30 or 40  meter version.  Seen this?

Look forward to what you come up with.
Ronny
K4RJJ



On Thu, Mar 21, 2013 at 4:51 AM, Stephen <squirrox@...> wrote:
 

Guys,

I'll be meeting up with Guido tomorrow for a couple of days to discuss, among other things, production of a "kit o parts" for a set of Low Pass Filters which can be switched from the Pi plus a small on board Power Amplifier.

You need a Low Pass Filter on the output of the Pi to stop it transmitting the harmonics of the programmed output frequency. The Pi puts out a square wave rich in harmonics. To find out more about this topic see here :-

http://electronics.stackexchange.com/questions/32310/what-exactly-are-harmonics-and-how-do-they-appear

For a discussion about how to make one you can do no better than here :-

http://www.interalia.plus.com/q_tech2.htm

Toroids and capacitors can be bought from a fellow ham here :-

http://www.kitsandparts.com

If Guido and I decide to do some kits for a multi band LPF and PA board we will let you know

Hope this helps,

73s Steve G0XAR



--- In Raspberry_Pi_4-Ham_RADIO@..., Ray Wells wrote:
>
> LPF = Low Pass Filter. It's purpose is to allow the wanted frequency
> pass to the antenna but attenuate all harmonics and other unwanted
> rubbish in the spectrum above the wanted frequency.
>
>
>
> Ray vk2tv
>
> On 21/03/13 12:25, Ronny Julian wrote:
> >
> > As one that wants to try this copying the mail, whats and LPF?
> >
> > On Wed, Mar 20, 2013 at 11:18 AM, Guido > > threeme3@...>> wrote:
> >
> > There is now a modified version of Dan's, WsprryPi that should be
> > capable transmitting WSPR on HF and VHF bands, just with a LPF and
> > antenna connected to GPIO4.
> >
> > For experimentation, my code and binary can be found here:
> > https://github.com/threeme3/WsprryPi
> >
> > 73, Guido
> > PE1NNZ
> >
> > On Sun, Mar 17, 2013 at 8:11 PM, Daniel Ankers > > md1clv@...>> wrote:
> >
> >
> > > you will see that it is possible to use the Pi as an FM Tx
> > without any
> > > additional components other than a piece of wire for an aerial.
> > >
> > There is also https://github.com/DanAnkers/WsprryPi which uses
> > the same
> > technique (or to be more accurate, reuses the code!) to
> > produce WSPR on LF
> > with only a low pass filter and an antenna.
> >
> > Regards,
> > Dan MD1CLV
> >
> >
> >
>


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