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Originally Posted by SEMTTP
N8CHB,
I use a Larsen 7 element yagi at 35 feet with LMR 400 coax with "N" connectors. I can only get about 1-2 s units on the detroit simulcast. If I am in the truck I can not get it at all. SO, it is more than just drilling holes and mounting the antenna. Remember that more are just scanning and whether or not it is perminatly mounted should not matter one way or the other, although all of mine will be perminatly mounted here real soon.
I'll just echo what Rob said a couple of post ago, there definatly is an issue somewhere and Rob is proablay correct that it is in the scanners. However, from reports that I am getting the sub systems and the regular MPSCS are the same.
But the more I think about it Rob is correct, there is something going on that is not allowing the scanners to follow it correctly. If you do monitor Detroit with perfect copy, consider yourself lucky because you are in a great spot, but move around and you probably wont get any copy
If you ask me I think somebody knows something about the subsystems and just does not want to let the cat out of the bag.
Eric
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Eric my friend yes there is something different but it not a secret,
Things have changed and scanner folks can no longer be appliance operators. One needs to read and understand more
about wave propagation. Each band on the radio spectrum requires different radio and antenna designs to copy.
Then folks might stop comparing one system to an other and know why heavily dense areas are different than others.
Signals above 800MHz act much like a spot light or a lighthouse. They give out a foot print of radio energy in a fine pattern.
They are adjusted horizontally and vertically. Many of the Detroit arrays are tilted down a few degrees.
A great deal of the signal is absorbed, blocked, bounces off solid things and is scattered in unpredicted directions.
If you have lived in the area for a long time this problem was very apparent when channel 50 first went on the air.
Receiving UHF TV has the same characteristics except they radiate a million watts of power at 750 to 1000 feet with
full pattern in all directions using one antenna and in most cases you still need a Yagi to clearly receive the main signal
or you will get multiple ghost images. This is the reason for rapid fluctuations in signal strength seen on a scanner
that receives higher frequencys. A big problem to over come on digital systems that is the radios can not tell
multiple signals of equal strength from true signals.
Many are under the assumption that they don't have any problems receiving other stand alone sites. Well guess what
they are not even aware that in most cases they are missing 1/3 of the transmission because no matter where they
are located one side of the site is directed away from them to serve it's defined area. Real good antennas and preamp
are just one thing needed to overcome this.
A ship out at sea never sees the lighthouse until the light energy is turned his way and if it were tilted down 1 or 2 degrees
he might not see it at all plus the view from the crows nest would be no help. (higher antennas don't always help)
This is clearly why cell phone will not work in airplanes. It's not that they can't it because the ground station antennas don't direct RF up into the air.
I have installed and repaired communications system for many years and am not always very good at explaining how they work
as well as some others can so hopefully some of the things I have said will encourage folks to read some articles that
are written much and better explained than I can. I strongly suggest people read some of them because the hobby has changed.
A word about hand held scanners and portable radios. Most are sold to folks with identity problems with a need to
impress others much like the morons that take laptop computers on airplanes to show how insecure they are.
I apologize if I have offended anyone.
73,
Roger
Any new developments with Detroit's system?
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