[TrunkCom] Outside Antennas - A Rambling Epistle

Wed, 1 Jan 2003 13:06:33 -0500

The 70 Centimeter Ham antennae might work for trunking in the 400 -425
band.  Then again alot of people do NOT listen to that portion since the
trunking in the area of the spectrum ii usually Business Band L.T.R..

Then again, from what I undestand, by logging onto
http://www.trunkedradio.net, one of the municipalities from this area
actually uses a bbusiness band LTR for their Snow Plows.  
On Mon, 30 Dec 2002 09:45:09 EST [email protected] writes:
> 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://ww
w.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, 
> [email protected] 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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Wesolych Swiat, Bozego Narodzenia, I Sczclwego Nowego Roku - 
Polish for Mery Christmas and a Happy New Year!!!!

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