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Author Topic: Are these CB Silver rods?  (Read 2303 times)
2E1CLS
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Posts: 23




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« on: January 07, 2013, 03:13:40 PM »

Hi, Have been looking at the multi band vertical antennas like this one on ebay http://www.ebay.co.uk/itm/SE-X80-VERTICAL-HF-RADIAL-FREE-ANTENNA-80-TO-6-METRES-/320946478404?pt=UK_Mobile_Phones_Communication_Radio_Antennas&hash=item4ab9e69d44

Is this just a CB silver rod with a 9.1 unun stuck to the bottom? It is around 18ft which is about the right size to. I use a 9.1 unun with a 10m windsock.

Carl.
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AC4RD
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Posts: 1236




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« Reply #1 on: January 07, 2013, 03:22:05 PM »

I am NOT an antenna expert ... but it's just a quarterwave for something near 20mhz ... and with no radials, and a lossy transformer to make it look like a reasonable load to the transmitter, I'm guessing you could load up a banana plant or a crutch or a mailbox or something and have about the same efficiency.  :-)
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W9GB
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Posts: 2611




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« Reply #2 on: January 07, 2013, 03:30:15 PM »

It states that the main radiaor (vertical element) is 18 foot, which is ~ 5.4 meters.
When used as a 1/4-wavelength antenna, it would be a bit LONG for 20 meters.
When used as a 1/2-wavelength antenna, it works at 11 meters (CB band).
Gotta love the repackaging of old antennas for something else!!
Quote from: M6CLS
Is this just a CB silver rod with a 9.1 unun stuck to the bottom? It is around 18ft which is about the right size to.
That's a good summary.

The mounting base / insulator / bracket is a copy of the late-1950s Hy-Gain AVQ series of Multi-band vertical, which was also used from 1965-1980 by Hy-Gain for their model 500 Penetrator vertical (Citizens Band, 27 MHz).
« Last Edit: January 07, 2013, 03:36:54 PM by W9GB » Logged
M6GOM
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Posts: 884




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« Reply #3 on: January 08, 2013, 07:05:18 AM »

Quote from: M6CLS
Is this just a CB silver rod with a 9.1 unun stuck to the bottom? It is around 18ft which is about the right size to. I use a 9.1 unun with a 10m windsock.

Carl.

Pretty much Carl. And they really suck on 80m and 40. They start being usable from 20 up. And despite the claims, you do need radials otherwise you'll get a lot of common mode on the coax.

You would find no benefit over what you already have.
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W9GB
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Posts: 2611




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« Reply #4 on: January 09, 2013, 06:05:17 AM »

Since this is an End Fed Half-Wavelength Antenna (EFHW or EFHA), take time to read these articles (SOME are QRP hardware designs, 5 watts of less)

Balun Designs, 9:1 UN-UN
52.5 feet OR 124 feet of wire -- for best 160-6 meter performance
http://www.balundesigns.com/Wire%20Length%20for%209132s.pdf
QRP
http://www.balundesigns.com/servlet/the-102/QRP-9-cln-1-Unun-1.5/Detail
2 kW
http://www.balundesigns.com/servlet/the-100/9-cln-1-9-dsh-1-unun/Detail

The End Fed Half Wave Antenna
Steve Yates - AA5TB
http://www.aa5tb.com/efha.html

G0KYA's HF End Fed Half Wave (EFHW) antenna – construction details
http://www.infotechcomms.net/downloads/EFHW_construction.pdf

End Fed Half Wave or "end-fed dipole" Antennas - Tom, W8JI
http://www.w8ji.com/end-fed_1_2_wave_matching_system_end%20feed.htm

"EFHW" - the end-fed half wave antenna (QRP)
http://pages.suddenlink.net/wa5bdu/efhw.htm

VE3GAM list of EFHW designs
http://ve3gam.webqth.com/?p=435

End-Fed Half-Wave Antennas
by Joe Everhart, N2CX
http://www.njqrp.org/n2cxantennas/halfer/index.html

A new article by Diana Eng KC2UHB in MAKE magazine describes how to build an End-Fed Half-Wavelength Antenna (EFHWA) for portable QRP usage.  It works on the 7, 10, 14 and 18 MHz bands.  Ms. Eng recently joined ARRL Public Relations department
--
'How-To: Make a multiband EFHWA for amateur ham radio'
http://blog.makezine.com/archive/2010/03/make_a_multiband_end_fed_half_wavel.html
« Last Edit: January 09, 2013, 06:23:18 AM by W9GB » Logged
K5LXP
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Posts: 4465


WWW

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« Reply #5 on: January 09, 2013, 06:49:13 AM »

Since this is an End Fed Half-Wavelength Antenna (EFHW or EFHA),

But only on one band (27MHz).  Everywhere else it's not a half wave.


Quote
A new article by Diana Eng KC2UHB in MAKE magazine describes how to build an End-Fed Half-Wavelength Antenna (EFHWA) for portable QRP usage.

She describes using a counterpoise, so the antenna is no longer an end fed but an OCF.  I don't discount the idea of using a configuration like that but one can no longer call it an EFHWA.


Mark K5LXP
Albuquerque, NM



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W9GB
Member

Posts: 2611




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« Reply #6 on: January 09, 2013, 09:44:11 AM »

Quote
But only on one band (27MHz).  Everywhere else it's not a half wave.
CORRECT.  Throwing tuners at their base don't make them 80-10 Multi-band verticals.

The original Cushcraft AR-10 is also a 1/2-wave vertical, that uses the tuning ring for matching.
They even sold a CB version, AR-11, for a short period.

The Cushcraft R-3 was the 1/2-wave AR-10 vertical,
with a motorized capacitor and 2 fixed capacitors for matching 20, 15, and 10 meters.

Add L-C traps; matching box with 1:4 and choke balun; 0.05-wave counterpoise wires --
you get the Cushcraft R-4, R-5, or R-7 Multi-band verticals --
and later the clones: Hy-Gain Patriot series (AV-620, AV-640).
===
Point being ... all these CB/10 meter verticals are "one band wonders" -- as you stated.
IF you want to make them Multi-band, it requires adding more parts and aluminum :-)
« Last Edit: January 09, 2013, 09:51:19 AM by W9GB » Logged
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