21-869.fm Page 1 Wednesday, October 13, 1999 11:50 AM
Cat. No. 21-869
10M Ham/CB Base Antenna
Your RadioShack 10M Ham/CB Base
IMPORTANT SAFETY
PRECAUTIONS
Antenna provides excellent reception of
amateur radio, CB, and commercial radio
signals. The antenna can handle up to
2000 watts of transmit power.
Many do-it-yourself and professional an-
tenna installers are injured or killed each
year by electric shock. Many power wires
are within 20 to 25 feet of the ground and
could easily be touched by an assembled
antenna or cable. Touching the overhead
wires with any part of the antenna is the
same as touching the wires with your
bare hand. Contacting an electrical wire
almost always results in a very serious
shock.
Your antenna’s features include:
Electrical Half-Wave Design — pro-
vides high gain.
Note: To improve your antenna’s gain,
you can connect an optional ground
plane kit (available through your local
RadioShack store) to your antenna.
To avoid electric shock, please read and
follow these important safety precautions:
Three Easy-to-Assemble Sections —
help you quickly and easily assemble the
antenna.
• Be sure to select an antenna site
well away from all overhead wires.
Dual Tuning Rings — help you quickly
set the antenna for optimum perfor-
mance over a wide range of frequencies.
• Do not try to guess which overhead
wires carry high voltage. Check with
the power company.
Ultraviolet Inhibitor — the antenna’s
UV-protected housing is made of impact-
resistant fiberglass, making the exterior
resistant to weathering and color change.
• If you notice anything making con-
tact with the overhead wires, call the
power company to have it removed.
• Do not run the antenna’s cable over
power wires.
Strong Internal Construction — pre-
vents the antenna’s internal wires from
rattling, for maximum strength.
• Get help from a qualified profes-
sional when removing the old
antenna, especially if you have any
doubt about clearing overhead
wires.
• Never install an antenna by your-
self. Be sure to have at least two
people available for help.
• Never install an antenna on a windy
day.
© 1999 Tandy Corporation.
All Rights Reserved.
RadioShack is a registered trademark used by Tandy Corporation.
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21-869.fm Page 3 Wednesday, October 13, 1999 11:50 AM
2. Remove the cap from the top of the
top element.
PREPARATION
3. Use a tape measure to measure the
length you need to cut off of the top
element, then use a hacksaw to
carefully cut the top element.
Pre-Tuning the Antenna
Your antenna is preset to use 27.205
MHz (the middle of the CB band) for the
lowest SWR. If you are using your anten-
na with a CB radio, you do not have to
pre-tune it. See “Assembling and Mount-
ing the Antenna” on Page 3.
4. Replace the cap on the top element.
5. Set the tuning rings on the bottom
element of the antenna to their low-
est position.
Before you assemble and mount the an-
tenna, you must determine the frequen-
cy range you will be using with it. If you
are not using CB frequencies, you must
either trim the antenna’s top element to
match the range you are using or use an
antenna tuner (not supplied) to electri-
cally trim the antenna.
Note: If you trim too much off of the top
element or use the antenna for a differ-
ent frequency later, you can order a re-
placement top element from your local
RadioShack store.
If you need to pre-tune the antenna to a
frequency lower than 28 MHz, use an
antenna tuner (not supplied).
Caution: To avoid damaging the anten-
na, do not trim the antenna’s middle or
bottom elements.
Assembling and Mounting
the Antenna
If you are using your antenna with an
amateur radio and want to trim the an-
tenna’s top element to pre-tune it, follow
these steps.
Before you can use the antenna, you
must assemble and mount it then con-
nect it to your radio. You can mount the
antenna outdoors on a vertical, solid ob-
ject such as a TV antenna mast. For the
best results, mount the antenna vertical-
ly as high as possible away from trees or
other obstructions. (Higher frequencies
are noticeably affected by obstructions.)
1. Use the following chart to determine
how much you need to trim off of the
top element (if any).
Important:
• Do not mount the antenna on a
metal surface such as aluminum
siding. This greatly reduces the
antenna’s ability to receive signals.
• Before you assemble the antenna,
prepare the structure that you will
mount it to. RadioShack stores carry
standard TV masts which you can
use to mount the antenna. Make
sure the supplied U-bolts will fit
around whichever mast you choose.
For example, to pre-tune the
antenna to use a frequency of
29.328 MHz, you must cut off
enough of the top element (about 21
inches) to leave it approximately 51
inches in length.
3
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21-869.fm Page 4 Wednesday, October 13, 1999 11:50 AM
Follow these steps to assemble and mount the antenna.
1. Lay the antenna’s components on the ground in a flat, open
area.
2. Place the supplied 3 -inch lock washer (2) over the threaded end
/8
of the top element (1).
3. Insert the threaded end of the top element into the threads on the
center element (3), screw the top element into the center ele-
ment, then use a 1 -inch wrench to tighten it.
/2
4. Place the supplied 1 -inch lock washer (4) over the threaded end
/2
of the center element.
5. Insert the threaded end of the center element into the threads on
the bottom element (5), screw the center element into the bottom
element, then use a 1-inch wrench to tighten it.
6. Hold the assembled antenna vertically next to the structure
where you want to mount it, then slide the supplied U-bolts (6)
over the antenna and the structure.
7. Slide the supplied brackets (7) over the ends of the U-bolts, then
use the supplied lock washers (8) and hex nuts (9) to secure it.
Caution: To avoid damaging the bottom element, do not over-
tighten the hex nuts.
8. Connect one end of the coaxial cable (not supplied) to the con-
nector on the bottom of the bottom element. Then route the cable
to your radio and connect it to the antenna jack on the back of
the radio.
Important: Your antenna is designed to let excess moisture escape
from inside the bottom element. Do not use a silicone sealant or
caulking material around any part of your antenna to seal it. Other-
wise, the antenna might not work properly.
4
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21-869.fm Page 5 Wednesday, October 13, 1999 11:50 AM
4. Using an SWR meter, check the
SWR at the top and bottom of the
band. If the SWR is higher at the top
of the band than at the bottom, raise
both tuning rings counterclockwise
TUNING THE ANTENNA
If you are using your antenna at frequen-
cies in the range of 25 to 30 MHz, you
can tune the antenna using an standing-
wave ratio (SWR) meter (not supplied)
and the dual tuning rings on the bottom
element.
1/2
turns.
at increments of 1 to
/4
5. Repeat Step 4 until the SWR is as
low as possible at both ends of the
band.
Notes:
6. When you have set the desired
SWR, tighten the tuning rings
against each other by simulta-
neously turning the top ring down
(clockwise) and the bottom ring up
(counterclockwise) to lock them.
• If you are using your antenna at fre-
quencies below 25 MHz, you will
need an antenna tuner (not sup-
plied) to tune it.
• The antenna's coaxial cable con-
nector is the best place to check
your antenna's SWR, but you can
also check it at the radio's coax con-
nection.
After you have properly installed and
tuned your antenna, use a watt meter
(not supplied) to test the amount of pow-
er your transmitter is sending to your an-
tenna. If you have properly tuned the
antenna, the meter should show the
transmitter’s maximum output power and
the SWR meter should show very low re-
flected power.
Follow these steps to tune the antenna.
1. Follow the instructions supplied with
your SWR meter to adjust your
antenna’s SWR to the lowest possi-
ble value.
SWR values of 2.0:1 are generally
acceptable, with readings of 1.5:1 or
lower being more desirable.
2. With the antenna assembled and
mounted, slowly move the tuning
rings up as you check the SWR,
until you reach your desired fre-
quency.
3. If the center frequency is still too
low, follow the steps under “Pre-
Tuning the Antenna” on Page 3 to
1/2
shorten the top element by
inch.
Then check the SWR again. Keep
shortening the top element until you
reach the desired SWR.
5
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21-869.fm Page 6 Wednesday, October 13, 1999 11:50 AM
TROUBLESHOOTING
If you have problems mounting or tuning your antenna, here are some suggestions that
might help. If you still have trouble, contact your local RadioShack store for assistance.
PROBLEM
POSSIBLE CAUSE
SOLUTION
SWR reading is too
high or cannot be set.
Depending on the frequency you
want to use it for, the antenna
might be too long or too short.
Pre-tune the antenna (see “Pre-
Tuning the Antenna” on Page 3).
The antenna is not installed in a
good location.
Move the antenna to a different
location and try again.
The coaxial cable might be broken
or damaged.
Use another coaxial cable.
The coaxial cable might be coiled.
Uncoil the coaxial cable.
The SWR meter might be con-
nected incorrectly.
Make sure the SWR meter is con-
nected correctly to the antenna
and your radio.
The antenna or radio might not be
properly grounded.
Make sure the antenna and radio
are properly grounded.
6
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21-869.fm Page 7 Wednesday, October 13, 1999 11:50 AM
SPECIFICATIONS
Reception ....................................................... VHF and UHF (Pre-tuned for 27.205 MHz)
Half-Wave Gain ....................................................................................................... 9.9 dBi
Optimum SWR Range ............................................................................... Less than 1.5:1
Height (assembled) .............................................................................................. 17.5 feet
(5.3 m)
Maximum Diameter ........................................................................................... 1.8 inches
34 mm.)
Weight .............................................................................................................. 4 lbs 15 oz
(2.24 kg)
Specifications are typical; individual units might vary. Specifications are subject to change
and improvement without notice.
7
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21-869.fm Page 8 Wednesday, October 13, 1999 11:50 AM
Limited Ninety-Day Warranty
This product is warranted by RadioShack against manufacturing defects in material and workman-
ship under normal use for ninety (90) days from the date of purchase from RadioShack company-
owned stores and authorized RadioShack franchisees and dealers. EXCEPT AS PROVIDED
HEREIN, RadioShack MAKES NO EXPRESS WARRANTIES AND ANY IMPLIED WARRANTIES,
INCLUDING THOSE OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE,
ARE LIMITED IN DURATION TO THE DURATION OF THE WRITTEN LIMITED WARRANTIES
CONTAINED HEREIN. EXCEPT AS PROVIDED HEREIN, RadioShack SHALL HAVE NO LIABIL-
ITY OR RESPONSIBILITY TO CUSTOMER OR ANY OTHER PERSON OR ENTITY WITH RE-
SPECT TO ANY LIABILITY, LOSS OR DAMAGE CAUSED DIRECTLY OR INDIRECTLY BY USE
OR PERFORMANCE OF THE PRODUCT OR ARISING OUT OF ANY BREACH OF THIS WAR-
RANTY, INCLUDING, BUT NOT LIMITED TO, ANY DAMAGES RESULTING FROM INCONVE-
NIENCE, LOSS OF TIME, DATA, PROPERTY, REVENUE, OR PROFIT OR ANY INDIRECT,
SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, EVEN IF RadioShack HAS BEEN AD-
VISED OF THE POSSIBILITY OF SUCH DAMAGES.
Some states do not allow the limitations on how long an implied warranty lasts or the exclusion of in-
cidental or consequential damages, so the above limitations or exclusions may not apply to you.
In the event of a product defect during the warranty period, take the product and the RadioShack
sales receipt as proof of purchase date to any RadioShack store. RadioShack will, at its option, un-
less otherwise provided by law: (a) correct the defect by product repair without charge for parts and
labor; (b) replace the product with one of the same or similar design; or (c) refund the purchase
price. All replaced parts and products, and products on which a refund is made, become the prop-
erty of RadioShack. New or reconditioned parts and products may be used in the performance of
warranty service. Repaired or replaced parts and products are warranted for the remainder of the
original warranty period. You will be charged for repair or replacement of the product made after the
expiration of the warranty period.
This warranty does not cover: (a) damage or failure caused by or attributable to acts of God, abuse,
accident, misuse, improper or abnormal usage, failure to follow instructions, improper installation or
maintenance, alteration, lightning or other incidence of excess voltage or current; (b) any repairs
other than those provided by a RadioShack Authorized Service Facility; (c) consumables such as
fuses or batteries; (d) cosmetic damage; (e) transportation, shipping or insurance costs; or (f) costs
of product removal, installation, set-up service adjustment or reinstallation.
This warranty gives you specific legal rights, and you may also have other rights which vary from
state to state.
RadioShack Customer Relations, 200 Taylor Street, 6th Floor, Fort Worth, TX 76102
04/99
We Service What We Sell
RadioShack
A Division of Tandy Corporation
Fort Worth, Texas 76102
10A99
Printed in the USA
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