Looking for Cheap idea for simulcasting sites. Any ideas.
We are using a JPS voter and have Tx steering but its just problematic. Looking for ideas for simulcast.
Need simulcasting ideas
Moderator: Queue Moderator
Need simulcasting ideas
Gregg White N7SQJ
Tucson, Arizona
Tucson, Arizona
Re: Need simulcasting ideas
http://www.simulcastsolutions.com/Gregg wrote:Looking for Cheap idea for simulcasting sites. Any ideas.
VERY informative site on the subject.
Casey KJ7XE
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KuhnElectronics
- NOT ALLOWED TO BUY/SELL/TRADE
- Posts: 255
- Joined: Mon Sep 06, 2004 11:27 am
- What radios do you own?: Moto, Vertex
do agree...simulcasting solutions is who we use for guidance when we set our 2 or 3 systems up in this area....
Nick Kuhn - Communications Technician/Technical Manager
AMP Electronics - Chillicothe, OH
http://www.amp-electronics.net
AMP Electronics - Chillicothe, OH
http://www.amp-electronics.net
Re: Need simulcasting ideas
Ideas may be cheap, but to make it work is going to cost some green.
In the first place to obtain anything close to what your
calling simulcasting is going to require a very stable RF
source. This can be accomplished in a number of ways.
Most of the simulcast systems today use some form of
GPS signal to keep the RF osc on frequency. It may even
use an expensive atomic time standard.
You also have to worry about the audio time delays
between the different transmitter locations. The phase
difference of the audio between the transmitters will
increase the nulling of the signal from the different
transmitters.
If you use rental phone lines for the methode to link
the different transmitter sites, expect to have to go
out and do this audio delay adjustment on a regular
bassis. The phone companies have a bad habbit of
rerouting the cable circuits when they do cable service
work and equipment maintenance.
Jim
In the first place to obtain anything close to what your
calling simulcasting is going to require a very stable RF
source. This can be accomplished in a number of ways.
Most of the simulcast systems today use some form of
GPS signal to keep the RF osc on frequency. It may even
use an expensive atomic time standard.
You also have to worry about the audio time delays
between the different transmitter locations. The phase
difference of the audio between the transmitters will
increase the nulling of the signal from the different
transmitters.
If you use rental phone lines for the methode to link
the different transmitter sites, expect to have to go
out and do this audio delay adjustment on a regular
bassis. The phone companies have a bad habbit of
rerouting the cable circuits when they do cable service
work and equipment maintenance.
Jim
Gregg wrote:Looking for Cheap idea for simulcasting sites. Any ideas.
We are using a JPS voter and have Tx steering but its just problematic. Looking for ideas for simulcast.
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firetech792
- Posts: 153
- Joined: Mon Aug 16, 2004 12:08 pm
My two bits worth:
Simulcast design is loaded with compromises:
Generally, the better the system the more expensive.
So, how about "Cheap"?
Transmitter steering has it's own problems.
One possibility is to use "Terrain Attenuation" use hills, etc to shield your site. Use split antennas, a directional for transmit.
Plan your overlap (Area of Non Capture) for areas where you have no subscribers. Do not worry about phasing, etc.
If you can obtain another transmit channel, use different transmit frequencies for each site, use scan on the subscriber units to scan for best site.
Simulcast design is loaded with compromises:
Generally, the better the system the more expensive.
So, how about "Cheap"?
Transmitter steering has it's own problems.
One possibility is to use "Terrain Attenuation" use hills, etc to shield your site. Use split antennas, a directional for transmit.
Plan your overlap (Area of Non Capture) for areas where you have no subscribers. Do not worry about phasing, etc.
If you can obtain another transmit channel, use different transmit frequencies for each site, use scan on the subscriber units to scan for best site.
Aloha, Bernie
If you want the best there is...Motorola, without question (analog or digital).
If you are looking for a less expensive alternative. Try Harris. As in the company that makes military communications and microwave. They have an excellent product to retrofit a system with simulcast.
If you run analog simulcast: T1 lines will be your downfall. You will want dedicated connectivity. Dedicated means it's private and you own it. For example: microwave, wireless T! links, or private fiber network. The issue with T1's is that the length of the path often changes dur to re-routing by the phone company. This is more of an issue on analog because the sites will need to communicate over the backbone.
If you run digital simulcast: T1's will work. This is becausein Motorola's digital simulcast the voice packets leaving the comparator are time-stamped and tell their destination transmitter when to fire. For this reason, the sites do not need to communicate constantly over the backbone. Intermittent T1 re-routing is not a problem. It still works better with dedicated backhaul, though.
If you want to use conventional voting scan, like someone described above, you can. It is basically transmitter multicast. Each TX site uses different frequencies, inlike simulcast which reuses the same at every site. Motorola offers conventional voting scan systems as a lower cost alternative to simulcast.
If you are looking for a less expensive alternative. Try Harris. As in the company that makes military communications and microwave. They have an excellent product to retrofit a system with simulcast.
If you run analog simulcast: T1 lines will be your downfall. You will want dedicated connectivity. Dedicated means it's private and you own it. For example: microwave, wireless T! links, or private fiber network. The issue with T1's is that the length of the path often changes dur to re-routing by the phone company. This is more of an issue on analog because the sites will need to communicate over the backbone.
If you run digital simulcast: T1's will work. This is becausein Motorola's digital simulcast the voice packets leaving the comparator are time-stamped and tell their destination transmitter when to fire. For this reason, the sites do not need to communicate constantly over the backbone. Intermittent T1 re-routing is not a problem. It still works better with dedicated backhaul, though.
If you want to use conventional voting scan, like someone described above, you can. It is basically transmitter multicast. Each TX site uses different frequencies, inlike simulcast which reuses the same at every site. Motorola offers conventional voting scan systems as a lower cost alternative to simulcast.