Date: Tue, 13 Dec 2011 07:07:13 -0500
Reply-To: Derek Drew <derekdrew@DEREKMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Derek Drew <derekdrew@DEREKMAIL.COM>
Subject: Integrated AM/FM and Stealth CB (alarm) Antenna -- Anybody?
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This email is a query for someone knowledgeable about radio and CB
antennas to speak up.
I've been parking for 30 years on the streets of Manhattan, and have
had little trouble. But its still nice to have the assurance of the
beepers going off if the bad guys come. In general, if they see
anything inside the van, they break in, but if they don't see
anything they don't, possibly because the van is too weird looking
and the owner's reaction to its being entered too unpredictable for
comfort. By contrast, I used to find people sleeping in my 72 bus all
the time in NYC in wintertime, but they never hurt anything aside
from the lingering after-smell of that type of person.
I have a car alarm that transmits on a CB frequency (27Mhz) to alert
my beepers if somebody enters the vehicle while I am away from it.
When I have to park too far from the apartment or be very high in a
tall office building, I turn a switch that ups the power of the 27Mhz
alarm signal from 4 watts to 50 watts, and this allows me to depend
on the signal penetrating basements and reach 6 long city blocks
instead of 2.
I am having to mess with my antenna now and am wondering if anybody
had worked out how to get a quality setup for the antenna to transmit
on the CB bands as well as general AM/FM use. I could install a
dedicated CB antenna, but I'd prefer to use the factory OEM AM/FM
antenna for this purpose, or if I install a 2nd dedicated CB antenna
instead, I'd like it to be stealthy and not hurtful to the eye. (Most
CB antennas hurt my eye, or hurt themselves whacking trees above
while driving on parkways.)
Normally, trying to use the stock antenna for both CB and AM/FM use
is possible, but the CB functionality is greatly degraded because
such antennas are the wrong length, and AM/FM antennas are generally
a joke for CB use for many other reasons... as I understand it the
lack of a ground plane, lack of proper resonant frequencies, no coil
load, etc.
Accordingly, what I'd like to hear from a radio-head is what CB
antenna might be suitable to be used with Vanagon with the goal of
it being at least better than trying to use a stock OEM antenna, but
not look too much different from a standard AM/FM antenna (stealth).
If the antenna looks too much like a CB antenna, the bad guys might
break it off proactively, or worse, assume that there is a CB inside
the vehicle that they could steal, and it could be an inducement for
them to break in.
For all I know, a radio-knowledgeable person would say to just string
something inside the fiberglass, or make a non-standard flat antenna,
or some non-traditional design.
For my implementation, I'll either re-use the ancient Autopage
transmitter I have been using, which transmits at 27.195, or I will
implement a more modern solution, such as the DIRECTED ELECTRONICS
795T or 795W CAR ALARM 3 CHANNEL VIBRATING PAGER (example:
http://www.amazon.com/DEI-795W-3-CHANNEL-VIBRATING-RECEIVER/dp/B00076WWTY/ref=sr_1_1?ie=UTF8&qid=1323776835&sr=8-1
or
http://www.ebay.com/itm/330653062442?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
)
I provide these links in case anybody else decides that they want to
be paged if somebody enters their vehicle without their knowledge and
they want a hint as to how to go about it. The device is simply
plugged into whatever alarm system is currently in the vehicle, or
even connected to door-pin operation, so it can operate along side of
any other alarm system functionality. Be advised that some modern car
alarms have the ability to transmit an alert to the remote control
as well (which would be almost a duplicate functionality) and
manufactures claim up to a mile reception of such a device. However,
i still want the old functionality to co-exist with the new one,
provided I eventually implement the new one, for added
assurance. For the record, other systems one can employ for added
assurance include Google maps / GPS transmitters (you can look Google
Maps to see where your rig is), Canadian model extended range car
alarms, and so-called "telematic" alarms that operate through the
Internet, effectively providing infinite range.
Last time I tried to come up with a dual/CB AM FM antenna that could
transmit 50 watts on CB, the only solution I could find was to send
an OEM antenna out to Sti-Co, a company that specializes in making
stealth antennas. For $175 (in 1992) they modified my stock Vanagon
antenna so that the SWR at my transmit frequency of 27.195 was nearly
1:1. They did this by putting something on the antenna lead line,
but not otherwise altering the antenna. I notice that they are still
alive and well, with a web site and catalog at
http://www.sti-co.com/wp-content/uploads/2011/03/Stico-Cat-2010-revised-wo-ST-PD-veh.pdf,
apparently primarily directed toward law enforcement. In any case,
one option I see there is to NB-HF-DS antenna, which can handle 150
watts, and which I cannot help imagine would be much more efficient
than trying to force a Vanagon antenna do the job.
I'd like feedback from people knowledgeable about radio on this
issue. The argument that was made to me in 1992 was that it was fine
to use a Vanagon antenna to transmit CB efficiently because the
antenna only had to be tuned to operate at exactly 27.195 instead of
having it try to operate on the entire CB band range. In other words,
the argument was that by having an extremely narrow band antenna, one
could get away with using a vastly worse CB antenna and get the same
result as a quality CB antenna. Does this sound right?
I notice that the CB antenna I just named is 36 inches tall, which as
I understand it is a compatible length for use with CBs. The best
length for FM antennas is something like 29 to 33 inches, and I
notice that my OEM antenna here extends 31 inches. So, I think that
whatever solution is arrived at, it would be best if the antenna were
36 inches tall instead of 31, and that the operator would normally
use the antenna at 31 inches, but extend it out to 36 inches when
leaving the car and using the alarm functionality.
Does this sound reasonable?
Any ideas about how to go about this?
_______________________________________________
Derek Drew
Washington DC / New York
derekdrew@derekmail.com
Email is best normally but...
PHONE: 202-966-7907 (Call the number at left normally)
(alt/cell for diligent calling only): 703-408-1532
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