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Author Topic: 10 Meter Antenna  (Read 12527 times)
K0BG
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« Reply #30 on: July 19, 2010, 05:41:56 AM »

Adam, just about any antenna will work to some degree. It is to what degree that's in question. The Outbacker series as very lossy antennas, when compared to even an inexpensive screwdriver antenna. The loading coils as very small in diameter, and the wire size appears to be #20. And, it is expensive for what you get. You're better off with a handful of Hamsticks, if cost is a criteria.

Folks often choose small, short, and stubby antennas because they appear to be easy to mount. This is also the reason folks choose to use mag, clip, and bracket mounts. As long as you understand that such installs are minimal in performance, and you're willing to put up with the reduced performance, go for it!

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WX7G
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« Reply #31 on: July 19, 2010, 05:52:05 AM »

28MHz: A 9 foot stainless steel CB whip can be less efficient than a 7.5' Hamstick, based on measurements and simulation. The loss of a 9' 17-7 stainless whip RF loss referred to the base is approximately 15 ohms.

Given a 10 ohm GND loss the whip antenna radiation efficiency is about 60%. The Hamstick is about 70%. The difference is 0.7 dB.
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VA3WXM
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« Reply #32 on: July 19, 2010, 06:31:43 AM »

And would that 0.7 dB difference be perceptible by the receiving station?  I highly doubt it.
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N5XTR
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« Reply #33 on: July 22, 2010, 08:47:01 AM »

Better to have it and not need it than need it and not have it.  Ever been QRP mobile?  You'll need the best antenna you can get. 
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K0BG
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« Reply #34 on: July 22, 2010, 03:55:34 PM »

I'm sorry, Dave, but I just don't buy it.

First of all, CB whips are 102 inches long, not 108 inches. If you mount one atop a decent radial field, the input impedance at resonance, will be 36 ohms. Replace it with a copper pipe, and at resonance, the input will be 36 ohms. The only difference will be the overall length, due to the larger diameter of the copper pipe.
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WX7G
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« Reply #35 on: July 24, 2010, 06:20:52 AM »

Measured loss = 10 ohms, Stainless Steel whip, 26 MHz

Alan, you have a good idea there measuring the two whips in a clean installation. I just happen to be set up to conduct this measurement and have completed it.

Setup:
Aluminum mast, 114"
Stainless Steel CB whip 106"
64 radials, 20' long

Measured:
Aluminum base impedance 40 ohms at resonance
Stainless Steel base impedance 50 ohms at resonance
Calculated gain difference 1 dB

Modeling this with EZNEC using 4 ohms of ground loss resistance and the published resistivity and permeability of 17-7 stainless steel and aluminum the simulated results are:
Aluminum 40 ohms
Stainless 51 ohms
Gain difference 1 dB

17-7 stainless steel published electrical parameters
Resistivity: 8.3E-7 ohm-m
Relative permeability 120
« Last Edit: July 24, 2010, 07:31:19 PM by DAVE CUTHBERT » Logged
M6GAS
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« Reply #36 on: August 20, 2010, 01:25:08 PM »

a lot of input here guys and a lot of numbers.
i have found when working 10m that anything you use works well.
when stactic mobile,i use the 9ft whip because in my head,i have convinced myself that an unloaded full quarter wave should perform better than a coil loaded whip.in practice there is no noticable difference.
the 9ft foot has however, has found a niche in my static mobile set up, as it tunes well (using an mfj 941 versatuner) on 20 meters and is broadbanded enough to cover 10 and 11 meters,so,1 whip = 3 bands.it is though way too big to cruise around with it mounted on the roof of my van.for this application,my tried and trusty wilson 5000 has outlasted all others and is still my favourite mobile whip. 
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W5DXP
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« Reply #37 on: August 21, 2010, 07:26:54 AM »

It's hard to stuff a 9 foot steel whip into the trunk of a Toyota Corolla. Smiley
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73, Cecil, w5dxp.com
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KI4SDY
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« Reply #38 on: August 23, 2010, 12:25:08 AM »

No its not. You just bend it around in a circle and place it in the trunk. It actually fits quite well.  Wink
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KB2SEO
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« Reply #39 on: September 03, 2010, 12:45:43 PM »

well for what its worth to everyone: "the numbers" are taking some liberties and assumptions. so lets talk real world experiences...

The rig is a 757 GX II and the mobile is a Jeep wrangler sport, 2001. for the first 8 years, I had 2 large aluminum bars sticking out from under the back bumpers. the RX was "OK" .the antenna was a Hamstick Good SWR though. I showed an swr of 1.3:1 at 28.0and it finally got to a 2:1 around 28.750

I then used a Stainless Whip (I don't feel like arguing, the package says it was 108"-No ball or spring) SWR was a bit lower- I was able to take about 2 inches or so off and moved the usable SWR bandwidth to around the same as the ham stick. the usuable frequency -28.0-28.750 the wierd thing was the SWR was a bit higher across the same spread. like 1.4:1 to 1.9:1 I figured there are a few things going on construction wise that could be making the difference, but who in his right mind would be botherd about that SWR?

  Anyway- recently, I stopped using the bumper mount configs, I just was never thrilled about the tire spray on the antennas, the winter ice and snow in the North Ga mountains and the salt/Sand and junk on the roads just never made me very confident about the bumper mounted setup. I drilled my Jeep  and installed a ball mount on either side of the jeep about 12 inches in from the corners, just above the wheel wells. So I may have raised the bottoms of the antenna about 36 inches, the SWR on the Stainless whip Flattened out to near 1.1:1 and I can now use it all the way to the FM portion! the "Ham stix"(not Lakeview one0 Also had better loading, BUT- I can hear BETTER with the SS whip. I thought it was something i did, but same ball mount, I got 1/2 s unit better with the SS whip. the 40 meter Lakeview can be used with very low SWR from about 7.100 to about 7.230. ground effects, the window heater element on the hard top and the frames of the soft top worked against them.

bottom line though on the 10 meter bit? I believe the smooth one piece contruction MAY make a small difference on 10 meters between antennas. But for me, If I am heard , if the radio works well enough to carry on a QSO then I HAVE successfully accomplished what I set out to do-COMMUNICATE
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W5DXP
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« Reply #40 on: September 03, 2010, 02:25:03 PM »

bottom line though on the 10 meter bit?

Actually, bottom line on 10m is that a wire coat hanger will work just fine because 1/4WL on 10m is 2.5m (8 feet).
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73, Cecil, w5dxp.com
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
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