Pocket FM

Everything technical about radio can be discussed here, whether it's transmitting or receiving. Guides, charts, diagrams, etc. are all welcome.
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piratefm
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Pocket FM

Post by piratefm » Wed Dec 13, 2017 10:38 am

Just came across this neat little thing.

http://www.pocket-fm.com

More vids on YouTube


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FM King
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Re: Pocket FM

Post by FM King » Wed Dec 13, 2017 6:17 pm

A new little bargain at just 2,700 euros.

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Analyser
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Re: Pocket FM

Post by Analyser » Wed Dec 13, 2017 9:47 pm

A noble idea perhaps, if any Syrians wanted such a thing.

....and I think the Germans have forgotten the fact that it's illegal to broadcast without a licence.

Albert H
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Re: Pocket FM

Post by Albert H » Thu Dec 14, 2017 1:12 am

MiCT started out as a group of wannabe anarchists in Berlin in the 80s. They bought a load of my old 10 Watt board through a guy called Dave who went over there and showed them how to assemble and align them.

They've been supplying little FM broadcast set-ups for years. The latest "Pocket FM" is a simple design, using an at-frequency oscillator, steered by a PLL. This is amplified by an MMIC up to a couple of hundred milliwatts, and then a Mitsubishi 30 Watt FET takes care of the RF output. Their antenna is a slightly weird ¼-wave groundplane job, using that fat radiating element to widen its bandwidth. (The idiot in the video didn't know that the log rods he assembled and inserted were groundplanes). The transmitter box includes a Chinese USB player, a satellite receiver, a GPS receiver to provide an accurate clock, and a couple of Raspberry Pi computers to handle all the housekeeping. It's actually quite a sophisticated package.

They also provide a DC power conditioner which can be fed from almost anything and develops the correct supply voltage for all the electronics. I've seen them run from car batteries, lantern batteries, windmills, water wheels, solar panels and even a little wood-burning steam generator!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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Analyser
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Re: Pocket FM

Post by Analyser » Thu Dec 14, 2017 7:47 am

I did also notice during the set-up videos that the guy on the roof seemed to have RG213/ WF103 coax, but by the time he went downstairs and plugged it in to the rig it had reduced to something along the lines of RG58/ RG223 and was plugged in using a BNC connector.

I also happened to notice that the power output display only registered about 10W and seemed to go up and down with the mod. Looking at the website, the power output is supposed to be 25W.

Albert H
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Re: Pocket FM

Post by Albert H » Sat Dec 16, 2017 1:35 am

I've heard one of these on the air and it had a weird whistling artefact when they played memory sticks! The power output is 25 Watts over most of the band, but falls off a bit at either end, apparently. I haven't bench-tested one of these - it could be interesting!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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radionortheast
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Re: Pocket FM

Post by radionortheast » Mon Jul 02, 2018 7:31 pm

was wondering what that aerial was, I don't think it will widen the bandwidth that much, i've experimented with ground plane antennas, pretty much my favourite type of aerial. It looks like the width of that aerial is not more than 5 cms, it will lower the swr on frequencies its not tuned too, the swr will go from 2.5 to 2, it still won't be tuned unforunately.

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yellowbeard
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Re: Pocket FM

Post by yellowbeard » Mon Jul 02, 2018 8:24 pm

http://www.sirioantenna.com/index.php?m ... egdn82urp5

The SWR curve in the product manual looks legit, probably... :tup

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radionortheast
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Re: Pocket FM

Post by radionortheast » Thu Jul 05, 2018 9:56 am

yellowbeard wrote:
Mon Jul 02, 2018 8:24 pm
http://www.sirioantenna.com/index.php?m ... egdn82urp5

The SWR curve in the product manual looks legit, probably... :tup
so dc ground makes me wonder if it isn’t a folded dipole, it actually might just be possible to cover the fm band, my ground plane was tuned to 107, I was alble to make the radials longer to 73 cms and also the radiator 67 cms, by using a sort of gamma match I was alble to pull the performance up again on a high frequency. only 0.5w reflected on 89 from my 3w and 0.1 on 107, this without exstending the width of the radiator.

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