[TrunkCom] Outside Antennas - A Rambling Epistle

[W5HLMNEWS@aol.com]

As way of background, I live in Harris County, Texas and have been monitoring 
various agencies here for over 20 years.  I've also been a ham radio for over 
ten years (W5HLM), and am active on the UHF/VHF bands.  To answer your 
question, I'd like to share some of my experiences with various antennas over 
the years.  Please keep in mind that this information is based strictly on 
empirical observations, and reflects what worked best in my particular 
situation.  Your mileage (and opinion) may vary.

First, I've yet to find a single antenna that would do everything I needed 
for just scanning, much less scanning and ham use.  The closest thing I've 
found is the Radio Shack discone.  As I recall, the RS discone has a power 
limitation of something like 25 watts, so it's not an ideal antenna for 
transmitting with the full power available to most mobile rigs.  There are 
numerous discone antennas on the market, but the Radio Shack antenna is the 
only one I've experimented with.  Some other brands also employ a vertical 
whip on top to increase effectiveness on the lower bands.  

I've found discone antennas to be reasonably good monitoring antennas, but 
their main drawback is that they have no gain.  Also, they tend to work 
better on some parts of the spectrum than others.  On a positive note, they 
seem to work relatively well for aviation monitoring.  On the downside, they 
are less than ideal for monitoring 800 MHz systems--especially weak signals.  


Through experience, I finally came to the realization that I was never going 
to get a single antenna to do everything I needed, so I sought alternative 
solutions using multiple antennas.  

I used to live in a home in the suburbs, and had a house with a huge attic.  
I had six UHF/VHF antennas up there, and this arrangement worked very well.  
Now, I live in an apartment (third floor) and my antenna options are much 
more limited, so I've had to come up with more creative solutions.

For amateur use, I've found a good dual-band mag-mount on a metal surface is 
pretty effective.  I have a gun safe in the closet of my study, and have a 
Larsen dual-bander on a mag-mount on top of the safe.  This gives me 
reasonable range--comparable to what you'd get in a mobile.  And if you are 
having trouble finding a metal surface to mount the antenna, an old ham trick 
is to set it stick it to a pizza pan in the attic.  A hot water heater also 
works very well as a mag-mount base.

I've found 800 MHz scanning to be the biggest challenge.  I live a 
considerable distance from the main county trunked system transmitter, and 
have a very difficult time receiving the signal consistently.  I think I've 
tried almost every antenna/amplifier solution known to man!  What seems to 
work best are highly directional, high-gain commercial antennas.  Two that 
I've had good luck with are Yagi (beam) antennas tuned for the mid-800 MHz 
band and "corner" antennas designed for commercial cellular use.  Both pop up 
on eBay from time to time.  The main drawback to these antennas is that 
unless the signals you are attempting to monitor at lower frequencies are 
pretty strong, they are fairly ineffective outside of the 800 MHz band.  They 
are pretty much a one-trick pony, but for distant 800 MHz systems, they can 
be highly effective.

The other problem with 800 MHz signals is that the coax and connectors 
designed for use on lower frequencies tend to attenuate the signal 
significantly.  This is especially true when using cheap coax.  Also, PL-259 
connectors can impact the signal adversely, since they are not recommended 
for use above around 500 MHz.   As a matter of fact, any modest gains 
achieved though a good antenna are quickly negated with a long run of s
ubstandard coax or multiple connectors.  What has worked well for me is a 
good grade of commercial cable TV coax.  Yes, I know it's 75 ohm as opposed 
to the 50 ohm impedance of the radio.  But as long as you don't attempt to 
transmit on it, it seems to work well.  Since finding a BNC connector to fit 
this type of coax may be a challenge, I just leave the original "F" connector 
on the coax and use an "F" to BNC adapter (available at Radio Shack).  Both 
types of connectors work in the 800 MHz range with no significant signal 
degradation.

Another trick I've used for 800 MHz, especially where I have limited outdoor 
options, is a mag-mount cell phone antenna.  These antennas usually have 
about 3 dB of gain, which is less than ideal, but is often enough to do the 
job.  Also, because you don't have a long run of coax to contend with, 
coax-induced loss is kept to a minimum.

If you are limited to mounting a single antenna outdoors, you will need to 
assess which is band or requirement is most important to you, and use that as 
your primary outdoor antenna.  If you consider the amateur band to be most 
important, then you may wish to mount a dual-band base antenna outdoors, and 
use a discone and Yagi in the attic for the scanner.  Unfortunately, this 
will require that you swap antennas, depending on the band you are 
monitoring.  And this will be dictated by the strength of the signals on the 
various bands.  

If you are most interested in scanning UHF/VHF, then you may wish to mount a 
discone outdoors and use an amateur mag-mount antenna indoors.  However, if 
you use an antenna for transmitting indoors, remember to observe RF safety 
rules and make sure no one comes in contact with the antenna while 
transmitting.  Also, don't discount the usefulness of dedicated 800 MHz 
antennas.  I simply sat a corner antenna on the shelf of my closet and it 
provides good coverage of the 800 MHz system that I wouldn't normally be able 
to monitor.

As you are evaluating your monitoring options, consider using one scanner for 
trunked monitoring and one for conventional UHF/VHF systems.  This makes the 
antenna decisions less of a hassle, and you can apply the right antenna 
solution to each scanner.  Since a typical UHF/VHF scanner is now relatively 
inexpensive, this multiple scanner approach is now in financial reach of the 
average hobbyist.  Also, this arrangement allows you to monitor multiple 
agencies more effectively during a significant event or emergency.

Finally, don't be afraid to experiment.  Some of the best solutions I've 
found were the result of trying things out of the ordinary.  Have fun, and 
share your solutions with your friends on the message boards!

For more information, and to read some of the articles I've written for 
Monitoring Times, please visit my web site at: <A HREF="http://home.houston.rr.com/w5hlm/">
http://home.houston.rr.com/w5hlm/</A>

For more monitoring tips and trips, refer to the article at this URL: <A HREF="http://home.houston.rr.com/w5hlm/mt1.html">
http://home.houston.rr.com/w5hlm/mt1.html</A>

Another great source of information is the fantastic Strong Signals web page. 
 The antenna evaluations can be found at:
<A HREF="http://www.strongsignals.net/access/content/antenna.html">http://www.strongsignals.net/access/content/antenna.html</A>


Regards,

Haskell Moore, W5HLM

In a message dated 12/29/2002 6:49:21 PM Central Standard Time, 
at649@tcnet.org writes:

> Hi everyone.  I am finally going to be putting up and outside antenna in
> the near future.  Although it will mainly be for ham use, I have always
> wanted something that will do well on 800 MHz for scanning distant trunked
> systems, and systems that I am just on the fringes of.  The ham bands that
> I will be using this for is 2-meters and 440, but I figure that if I am
> going to do something I had might as well look into what will help also
> with scanner use as well.  Any help would be good, and thanks and happy
> new year.



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