Well my service has some new officers in the kingdom now and the ideals of having base stations and other communication items is now being heard.
A proposal made by myself and some others in having a base radio (well mobile with power supply) at the station is now being looked at.
The ideal is to have one upstairs and one downstairs. The one upstairs would be in the lounge/MCI area so it could be used daily for station alerts and communications. The one downstairs would be used for answering pages and for staging operations in case of MCI as well as command post operations.
So we instantly knew that a mobile with dual head configurations would be out of the question. So of course we would need two mobile radios as the chance of using different freqs on the radios is possible.
We looked at using a combiner but due to the different freqs we would be using the cost would be to expensive so we opt to use two base station antennas on the roof of the station.
Now the length of the staiton is about a 1/2 a block long and about 1/4 a block wide. We plan on only using 50 watt radios with about a 5 to 7 dB gain antenna mounted on a 3 ft. tri-pod on the roof. (The building is high enough and we do not have access to any towers or if they want to buy a tower.)
Now we thought that if we mounted the antennas at the end of the building opposite each other we should be good for interference reasons. However, we still want to look at measures to not cause interference with each other radios.
So has anyone ever ran into this set-up befire and what sort of isolation can be used to help not cause interference to each other?
Base station antenna seperation
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Base station antenna seperation
" ah the fatman made a funny!" - Stewie from the family guy.
I went to the doctor and all he did was just suck blood. Never go to Dr Acula - M. Hedberg
I went to the doctor and all he did was just suck blood. Never go to Dr Acula - M. Hedberg
Re: Base station antenna seperation
Not to be a smartass, but...
Concrete cinder block or lego? City block or country block? NYC block, Miami block, or Omaha Nebraska block?n9upc wrote: Now the length of the staiton is about a 1/2 a block long and about 1/4 a block wide.
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N4DES
- was KS4VT
- Posts: 1234
- Joined: Thu Dec 25, 2003 7:59 am
- What radios do you own?: APX,XTS2500,XTL2500,XTL1500
Well first off you didn't mention the frequency used and the seperation between the TX & RX frequencies. This is pretty important in determining what kind of desense you may experience.
The other item it why run the radios at 50 watts? If you turn the power down (or use a varilator system to further decrease the power) you will lessen the chance of interfering with yourself. This would be the first item that I would look at as it's the easiest to do.
The other item it why run the radios at 50 watts? If you turn the power down (or use a varilator system to further decrease the power) you will lessen the chance of interfering with yourself. This would be the first item that I would look at as it's the easiest to do.
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MSS-Dave
- Posts: 770
- Joined: Mon Jun 30, 2003 6:02 pm
- What radios do you own?: Harris XL200M. XPR7550E, NX300
I agree with Mark. High power on control stations will really make things difficult. In general, vertical seperation is the best thing you could do in any case. If your control stations talk through a single site repeater system (or you could use a single receive site in a voted system), you are best to use yagis and as low power as you can to give full quieting into the receiver. If you need to have omni directional coverage from both radios, my suggestion would be to mount omni antennas end to end on a standoff from the tripod. You get MUCH better isolation in a little vertical seperation than lots of horizontal. The big issue here is what band are you on? You indicated 5 to 7 dB gain antennas, at VHF these would be 15-20 feet or so. At 800 you can get that much gain in about 8 feet or so.
Dave
Dave
Well...Ex /\/\SS.
My two bits worth:
Dave is right. Horizontal separation is not very effective, so how can this problem be solved with the least cost?
I think that a remote control could be fitted to the existing control station at little cost.
Motorola used to make a "Gutless wonder" which was an extension of the Mike, and speaker lines, which required a multi conductor cable. The distance limitation is 50' or so.
A DC remote is another possiblity. This uses a single twisted pair.
The distance limitation is 22 miles or so.
Tone remote costs more, but is more versitale, and can be used with leased lines where there is not a "copper path". Over kill in your application.
There are many manufacturere of this equipment, however beware of "Gai Tronics" I have had very much grief with after sale support, and do not reccomend them.
Dave is right. Horizontal separation is not very effective, so how can this problem be solved with the least cost?
I think that a remote control could be fitted to the existing control station at little cost.
Motorola used to make a "Gutless wonder" which was an extension of the Mike, and speaker lines, which required a multi conductor cable. The distance limitation is 50' or so.
A DC remote is another possiblity. This uses a single twisted pair.
The distance limitation is 22 miles or so.
Tone remote costs more, but is more versitale, and can be used with leased lines where there is not a "copper path". Over kill in your application.
There are many manufacturere of this equipment, however beware of "Gai Tronics" I have had very much grief with after sale support, and do not reccomend them.
Aloha, Bernie
We are using the VHF freq range and the reason we will be running 50 watts is due to the heavy mix we have for simplex and repeated channels.
We are lucky to have a receive site for our main repeater not even 3 blocks away so using low power on the repeater inputs would be set-up. However we do run into the snag of our simplex freqs.
Being in the center of the county it is not hard for us to need to go to one of four different simplex channels for an MCI or major incident. The county is pretty strong on the fact that county repeater channels should only be used for unit to dispatch comms. All other comms should either be done on mutial aid channels (simplex) or ground channels. In addition if we need more range then what simplex will give then we (as a service) should either invest money into our own system. Now since we do not have the money for our own repeater a base set-up and continued simplex use is the way to go for now.
The county does not give us to hard of a time if only we are out on a call or just someone else is. HOWEVER, if another agency is out there then only unit to dispatch or unit to unit for direction to simplex freq should only be taking palce.
IN doing some drawings and layouts it looks like we may do the upstairs radio antenna on a three foot tri-pod, and the bay radio antenna on a 10 ft tri-pod which will have the antenna on top of a 5 ft mast in the tri-pod. The antenna will be apart by about 30 to 40 ft and at some different heights.
As for the ideal of the remotes it will not work as we want to have the ability to lets say have the upstairs radio on the repeated channel to communicate with dispatch, while the bay radio is on the simplex ground channel. Two independant radios which can talk on two different channels at the same time.
Another option was to maybe have the one radio low power repeater freqs only and the other one repeater and simplex. The only problem that the admin sees with that is even thought it has an alpha-display they remember channel 1 is dispatch, 4 is county mutial aid, etc... Some would not look at the display and turn it three clicks and assume they were on channel four. OF COURSE this is a training issue which we are delaing with all the time.
The main thing is to have two independant stations with same radio set-up for use.
We are lucky to have a receive site for our main repeater not even 3 blocks away so using low power on the repeater inputs would be set-up. However we do run into the snag of our simplex freqs.
Being in the center of the county it is not hard for us to need to go to one of four different simplex channels for an MCI or major incident. The county is pretty strong on the fact that county repeater channels should only be used for unit to dispatch comms. All other comms should either be done on mutial aid channels (simplex) or ground channels. In addition if we need more range then what simplex will give then we (as a service) should either invest money into our own system. Now since we do not have the money for our own repeater a base set-up and continued simplex use is the way to go for now.
The county does not give us to hard of a time if only we are out on a call or just someone else is. HOWEVER, if another agency is out there then only unit to dispatch or unit to unit for direction to simplex freq should only be taking palce.
IN doing some drawings and layouts it looks like we may do the upstairs radio antenna on a three foot tri-pod, and the bay radio antenna on a 10 ft tri-pod which will have the antenna on top of a 5 ft mast in the tri-pod. The antenna will be apart by about 30 to 40 ft and at some different heights.
As for the ideal of the remotes it will not work as we want to have the ability to lets say have the upstairs radio on the repeated channel to communicate with dispatch, while the bay radio is on the simplex ground channel. Two independant radios which can talk on two different channels at the same time.
Another option was to maybe have the one radio low power repeater freqs only and the other one repeater and simplex. The only problem that the admin sees with that is even thought it has an alpha-display they remember channel 1 is dispatch, 4 is county mutial aid, etc... Some would not look at the display and turn it three clicks and assume they were on channel four. OF COURSE this is a training issue which we are delaing with all the time.
The main thing is to have two independant stations with same radio set-up for use.
" ah the fatman made a funny!" - Stewie from the family guy.
I went to the doctor and all he did was just suck blood. Never go to Dr Acula - M. Hedberg
I went to the doctor and all he did was just suck blood. Never go to Dr Acula - M. Hedberg