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Author Topic: Pirate Radio  (Read 18525 times)

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Taors

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Re: Pirate Radio
« Reply #15 on: December 08, 2008, 03:54:23 PM »

Will it piss off your neighbors?  If not, it's probably reasonable.

Like the couch, right?
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kalmia

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Re: Pirate Radio
« Reply #16 on: December 08, 2008, 06:49:24 PM »

Will it piss off your neighbors?  If not, it's probably reasonable.

Piss them off by the sight of it?  I seriously doubt this.  I meant is it reasonable to think that I can get a clear 5 mile radius with another 20 feet.

I was planning to couple together 3 - 10 foot 1-1/4" steel conduit pipes as an antenna.  It should have guy wires if this tall.  It will be on a roof that is about 20 feet or so above the ground.

I'll send you an email too Ian.

KDus

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Re: Pirate Radio
« Reply #17 on: December 22, 2008, 03:08:04 PM »

The steel pipes may cause problems with your ground plane depending on what kind of antenna you use.
I've used a rotator/ beam on top of pipes, but a 1/4 wave dipole and 1/4 wave ground plane had to be on a wood pole.
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kalmia

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Re: Pirate Radio
« Reply #18 on: December 24, 2008, 08:53:48 AM »

The steel pipes may cause problems with your ground plane depending on what kind of antenna you use.
I've used a rotator/ beam on top of pipes, but a 1/4 wave dipole and 1/4 wave ground plane had to be on a wood pole.

Should I use wood, fiberglass or plastic for the upper portion?  I currently just have it cable tied to a PVC vent pipe.


This is the cheepy that came with it.  I am looking at upgrading to something more durable.I'm sure this weather is giving it a beating.  But I haven't been back on the roof in a bit since it has been so icy. 








I've seen some durable ones that look good on eBay, listed at under $100 with shipping.

Here are some:


http://cgi.ebay.com/FM-Broadcast-Transmitter-Antenna-88-108Mhz-up-to-300w_W0QQitemZ180308905485QQihZ008QQcategoryZ296QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

==============



http://cgi.ebay.com/FM-Stereo-Broadcast-Antenna-1-4-wave-Tunable-300-Watt_W0QQitemZ280266606960QQihZ018QQcategoryZ4675QQssPageNameZWD1VQQrdZ1QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

==============





http://www.hllye.cn/html/fm_transmitter_1_46.html?currency=USD&products_id=46





Do any of you have any thoughts on choosing 1/4 wave over 1/2 wave or 5/8 wave?

kalmia

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Re: Pirate Radio
« Reply #19 on: December 24, 2008, 08:55:13 AM »

NOTE to Ian:

Direct your callers that discuss doing this to this thread, unless you know of a better thread.

KDus

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Re: Pirate Radio
« Reply #20 on: January 01, 2009, 04:26:20 PM »

5/8 wave has the most inherent gain, and is close enough to 50 ohms. Look at the terrain. If you want most of your signal to go straight out in all directions, go with 5/8. The trade off is size. A 1/4 dipole will fit in a tree or behind a chimney.
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RFBurns

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Re: Pirate Radio
« Reply #21 on: September 04, 2010, 10:35:47 PM »

The 5/8 wave antenna is your best option, especially if your tx power is below 5w.

Now if you really want to throw a big flame...then assemble a multi-bay antenna system comprised of 3 or more folded dipole elements, spaced 1/4 wave apart, and 1/4 wave from the tower. To properly phase the arrays, use 1/2 wave length chunks of coax for each bay using T fittings. To have beam tilt to drop the outer edge of the signal back down to the horizon, decrease the lengths of the coax feeds from the T fittings by about an inch or two compared to the very top array. The shorter the lower feed coaxes, the more beam tilt you will get. Usually this is not necessary, but in some terrains there may be hills between the antenna and a section of the town, which your signal will just fly right over that sunken portion of area on the other side of the hill. Beam tilt will compensate and bring the signal back down to the horizon instead of it all just shooting up past the atmosphere and into space.


RFB
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