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Old 5th December 2004, 08:42 PM   #1
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Default east west antenna

Can someone tell me if my 30 foot east/west antenna has the best transmitting range north/south or as I heard somewhere that it was around 20 degrees off vertical. I know this is the wrong forum for a question like this but with all the traffic here I figured it was worth a shot. Thanks in advance.
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Old 5th December 2004, 09:01 PM   #2
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Transmitting is more complex than receiving. 30' would be a resonant 1/2 wave for 20M shortwave HAM band. Are you using an antenna tuner? I think we need to analyze this further.

- What frequency are you using?
- What is your antenna height?
- What type of feedline are you using?
- Where along the antenna are you feeding it? (end, Zepp, dipole, etc.)
- What type of ground or counterpoise are you using?
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Old 5th December 2004, 09:16 PM   #3
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- What frequency are you using?
=1500 Kc
- What is your antenna height?
=20'
- What type of feedline are you using?
=single copper. no co-ax
- Where along the antenna are you feeding it? (end, Zepp, dipole, etc.)
=end
- What type of ground or counterpoise are you using?
=no ground


mmm. If it was higher, another freq and co-ax would it radiate at a different angle?
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Old 6th December 2004, 12:24 AM   #4
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at 20' in height, you'll get no radiation angle other than a near-isotropic ball, below 7MHz.

An end-fed wire is no good for AM TX unless you have one muthuh of an antenna tuner.

No ground and little space is bad. You are limited to magnetic loop antennae or cross-field antennae. Both are !$#@ to tune right, but work well.

I have made a mag-loop for 1520 Kc, so I can post something here if you're interested
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Old 6th December 2004, 12:38 AM   #5
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Gee, thanks for all the info. So... is it north/south or east/west?
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Old 6th December 2004, 12:48 AM   #6
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If you have it vertical, it's bi-directional - E/W or N/S depending on orientation. If you have it horizontal, it's omni-directional.

Here's the info:

front:
Click the image to open in full size.

side/top:
Click the image to open in full size.

Feedpoint detail:
Click the image to open in full size.

dowel mounts:
Click the image to open in full size.

Use a good quality air-variable for the tuning capacitor and use an insulated knob to tune it. At 2 watts into the antenna, 400V will appear across the cap and at 25 watts, several thousand volts will be there.

Run a bit of low-power into it, 100mW will suffice and using a radio with a signal meter, tune the cap for maximum strength. The antenna loop is tuned. Use an SWR meter for exact feedloop length tuning. The dimension shown should be a good start, but depends on surrounding objects that cause stray inductance/capacitance/reflections.

The "choke" of coax is needed, because the feedloop is balanced and you need to choke the stray RF from getting into mischief.

<<edit>>

I used 1mm dia. insulated alarm wire. you can use magnet or whatever you have on hand. There's a program, MAGLOOP31.EXE I found on Google for the calculations and it's bang-on for the main loop. It's off on the feedloop though. Rule-of-thumb is the feedloop should be 20% of the main loop diameter.
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