11 Dec
2013
11 Dec
'13
3:20 p.m.
Subject:
Re: [44net] Raspberry Pi - FM transmitter
From:
David Ranch <amprgw(a)trinnet.net>
Date:
12/11/2013 04:49 AM
To:
AMPRNet working group <44net(a)hamradio.ucsd.edu>
Hello Tom,
One of my elmers tried setting something similar up for WSPR but even with adding the
various filters, the harmonics on the higher frequencies were very significant and went
well out of the HAM bands!
Well, the article says that the harmonics must be 43dB
down to meet FCC regulations, or maybe 40dB
when reading the complicated if-then-else-if sentences in those paragraphs (why not use a
table?).
That is quite harsh, for a 10mW transmitter. 1uW is not a lot of power. A homeplug
device probably transmits
a lot more than that.
Rob
12 Dec
12 Dec
8:50 p.m.
New subject: Raspberry Pi - FM transmitter
Hello Rob,
That is quite harsh, for a 10mW transmitter. 1uW is
not a lot of
power. A homeplug device probably transmits
a lot more than that.
Yeah.. I hear what you're saying but I was really surprised when he even
disconnected the antenna, I could still hear his HF signal through I
think it was the 7th odd harmonic 360 ft away! He's recently been
thinking that part of the problem was that ribbon cable connecting the
Rpi to the filter board but he hasn't tested out that theory yet.
None the less, a Rpi makes a pretty amazing WSPR beacon for cheap!
--David
KI6ZHD
4222
days inactive
4224
days old
1 comments
2 participants
participants (2)
-
David Ranch -
Rob Janssen