is bigger really better

Status
Not open for further replies.

dintdinger

Member
Joined
Feb 14, 2010
Messages
15
Location
houston
my question is: will height overcome all?

if you go high enough can you pick up a clear transmission period.(assuming u have good coax and a good scanner) the broadcasting towers are 15 miles away and im at 40 ft(my mast) now and the transmmisions are choppy.(better than when at 20 ft, but choppy)
 

rdale

Completely Banned for the Greater Good
Feed Provider
Joined
Feb 3, 2001
Messages
11,380
Location
Lansing, MI
Will it overcome everything? No. There's no distance you can go that would let you hear Dallas Fire. Will higher help? Sure.
 

JStemann

Member
Premium Subscriber
Joined
May 17, 2004
Messages
494
Location
SE Indiana
What freq's are you trying to listen to?

I would think you should be able to here vhf and uhf (400 mhz) just fine at that distance. I could see having trouble with 800mhz systems. I'm only talking about dispatch or repeated systems, the car side of the conversation will most likely be a problem at that distance.

jeff.
 

dintdinger

Member
Joined
Feb 14, 2010
Messages
15
Location
houston
800 mhz. trunked. im trying to pick up with a pro 106 and can pick up conv signals at the 160 mhz no prob.
to me its weird cause i can pic up 800 trunked with a rubber antenna inside the house on a different system, but not with a 40 ft antenna on this new p25 digital trunked system.
 

jackj

Member
Joined
Jul 19, 2007
Messages
1,548
Location
NW Ohio
Yes, no, maybe. There are too many variables to give an unqualified answer to your question. The frequency band, distance to the transmitter, surrounding terrain at both ends, obstructions at both ends, antennas, feed line; all effect range. Sorry.
 

JStemann

Member
Premium Subscriber
Joined
May 17, 2004
Messages
494
Location
SE Indiana
At 800mhz a lot of cables get real lossy. LMR400 will lose around 4db per 100ft while rg58 or rg6 will lose 9-11 db or more per 100'.
So, depending on your cable you could be losing more than half your signal just getting inside. Now, the antenna, you could go to a 800 mhz specific antenna or even a directional 800 antenna.

One other "possibility" I don't think this is too likely but I'll throw it out there for you to consider. If you have a cell tower(normally nextel) nearby, you could be overloading the front end of your scanner. if this is the case it would definitely get worse with a better (outside) antenna and cabling.

jeff.
 

dintdinger

Member
Joined
Feb 14, 2010
Messages
15
Location
houston
what does that mean? overloading the frontend of my scanner. and yes i do have alot of obstructions. im thinking about going op another 20 feet though.
i get real poor signal strength on my phone and my aircard connect on my computer shows real low bars as well.. does this relate in any way?
 

prcguy

Member
Joined
Jun 30, 2006
Messages
9,860
Location
So Cal - Richardson, TX - Tewksbury, MA
There is a formula for height vs feedline loss vs range and for suburban areas the key was around 8dB feedline loss puts you at the point where further height will then become detrimental.

With better feedline you can go higher before reaching the 8dB point and with RG-58 you'll eat up your loss budget faster and at a much lower height.

If you live on top of a mountain the particular formula would not be appropriate, otherwise height is really important.
prcguy
 

dintdinger

Member
Joined
Feb 14, 2010
Messages
15
Location
houston
im using rg6u... im consider purchasing a tower, but i have 50 trees and am about 15 miles from the transmitting towers. a tower is expensive to buy and i just dont know if its cost effective to but a 60 ft tower unless im certain that it or a 80 to a 100 ft tower will receive 100 perfect
 

N0IU

Member
Joined
Sep 26, 2009
Messages
802
Location
Wentzville, Missouri
Radio waves at VHF and above are line of sight which means they leave the antenna in a straight line as opposed to HF waves which go up into the ionosphere and (hopefully) bounce back to earth. This is why TV and radio stations put their antennas on towers hundreds of feet tall (or taller!) so their signal will get out as far as possible to overcome the curvature of the earth as much as possible. At some point, it does not become cost effective to go higher.

http://en.wikipedia.org/wiki/Line-of-sight_propagation

As you can see from this list, some broadcast towers are over 2000' tall!
http://en.wikipedia.org/wiki/List_of_masts

Nobody can guarantee 100% perfect reception on your end, but the major cost in installing a tower is the base. There is the cost of digging a hole and filling it with rebar and several cubic yards of concrete. At that point adding another 20 - 30' of tower sections is no big deal. IOW, it does not cost twice as much to put up a 100' tower as it does a 50' tower. But also, a taller tower will most likely need to be guyed so you will need sufficient real estate to accomplish this.

The other factor that you need to consider are your local zoning ordinances. You need to make sure it is legal to put up a tower that tall. Even if you live in a remote unincorporated part of your county, you still need to check. You will also need to check how close you are from an airport. Above a certain height and depending how close you are, you may also need to get permission from the FAA.

Good luck!
 
Last edited:

JStemann

Member
Premium Subscriber
Joined
May 17, 2004
Messages
494
Location
SE Indiana
what does that mean? overloading the frontend of my scanner. and yes i do have alot of obstructions. im thinking about going op another 20 feet though.
i get real poor signal strength on my phone and my aircard connect on my computer shows real low bars as well.. does this relate in any way?
Basically, what I was suggesting. If you have a nearby source of RF that is fairly strong and is near the frequency you are trying to receive, it will "over power" the front end of the receiver to such an extent that your receiver won't be able to hear the more distant station. The reason i mentioned nextel was because they operate very close in frequency to many 800mhz trunked systems. I have heard, over the scanner, conversations between officers and dispatch not being able to hear/understand each other while "near the nextel site".

As far as the aircard and cell phone goes, I don't know about that. The Nextel is notorious because because of their proximity to the public safety band. GSM (at&t for one) can be close. Most other are using 900, 1800 or 1900 mhz. You can google all kinds of info regarding the cell bands and see if there is any relationship.

Also, talked with my dad last night, he travels through Houston every week. According to him the 800 system gets out pretty good. He's hearing it mobile from ~20 miles out.

I'm leaning towards your antenna being weak or "deaf" on 800mhz. I don't know what kind of antenna you have, I will say the Radio shack discone doesn't seem very good in the 800 band, great on others just not impressive on 800. I plan on experimenting with some other antennas I have, just to see how far away I can hear on 800, but I'm waiting for warmer weather. The rg6 isn't that bad, assuming about 60 feet for your total run, your losing about 3.5-4 db( a little over 1/2 power). You could get a little better with lmr400, not enough to warrant changing out the rg-6, though.

jeff.
 
Status
Not open for further replies.
Top