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VHF Remote Radio Questions

K

Kitchen Man

Jan 1, 1970
0
Howdy all,

I want to move a base station of a mobile radio system to a remote
location where I hope to get better coverage, but I want to keep the
mic and channel control in the present location. I have access to
either an RS-232 or a DS0 line, whichever I wish to use, and the line
length is less than 10 miles. The frequencies are currently allocated
and on the air, so there are no problems with the bureaucracy. I have
been researching VHF modems, but am unclear about design applications.
Our present transmitter is operating at 50W. I was hoping for a
little insight about how to go about setting up this system, and
possibly some recommendations about what equipment offers the best
option for implementing this type of a setup. I need to implement a
selectable two-channel system. Thanks for your time and suggestions.
 
F

Fred Abse

Jan 1, 1970
0
I want to move a base station of a mobile radio system to a remote
location where I hope to get better coverage, but I want to keep the
mic and channel control in the present location. I have access to
either an RS-232 or a DS0 line, whichever I wish to use, and the line
length is less than 10 miles. The frequencies are currently allocated
and on the air, so there are no problems with the bureaucracy.

I think you'll find that the base station location is specified on the
license. I don't think there's a jurisdiction in the world that will let
you relocate without proper authorization. It's all part of frequency
use planning. They might well want a frequency change for the new location.


I have
been researching VHF modems, but am unclear about design applications.
Our present transmitter is operating at 50W. I was hoping for a
little insight about how to go about setting up this system, and
possibly some recommendations about what equipment offers the best
option for implementing this type of a setup. I need to implement a
selectable two-channel system. Thanks for your time and suggestions.

You need a leased voice frequency line, a proper controller at the office
end, and proper remote interface equipment at the base station end.
Alternatively, you might use a UHF or microwave link. This all needs
approved equipment and is pretty damn' expensive.

If you need to ask these questions, it suggests to me that you don't know
enough about what you're trying to do to be competent, or legally
authorized.

Consult a properly licensed engineer with the proper knowledge and test
equipment.
 
K

Kitchen Man

Jan 1, 1970
0
I think you'll find that the base station location is specified on the
license. I don't think there's a jurisdiction in the world that will let
you relocate without proper authorization. It's all part of frequency
use planning. They might well want a frequency change for the new location.

Thanks for your concern, but I believe I mentioned that any
bureaucratic hurdles should not be a problem.
I have

You need a leased voice frequency line, a proper controller at the office
end, and proper remote interface equipment at the base station end.
Alternatively, you might use a UHF or microwave link. This all needs
approved equipment and is pretty damn' expensive.

As I mentioned, I can use either a DS0 or an RS-232 line, both of
which exist and are available for the project. Microwave and UHF are
out, as there is no line of sight. This is why I did not mention
those alternatives. "Proper" equipment is the reason I made the post;
I was hoping someone with specific knowledge could point me to same.
If you need to ask these questions, it suggests to me that you don't know
enough about what you're trying to do to be competent, or legally
authorized.

Your answers suggest to me that you would rather preach than offer
assistance. Have you never met an engineer who needed help with a
technical task? The fact that I need to ask these questions only
points out a lack of specific familiarity with specific equipment.
Consult a properly licensed engineer with the proper knowledge and test
equipment.

All's well. I believe that I have dreamed up a solution while camping
out this weekend. Kind of how a properly licensed engineer might
solve a problem - throw out feelers for suggestions, then ponder the
problem while relaxing a bit on holiday. The fending off of
unconstructive criticisms is all part of the day's work, I suppose.

Thanks anyway. Oh, and I do have a bit of TE lying about. No
worries, mate.
 
D

Don Bowey

Jan 1, 1970
0
Thanks for your concern, but I believe I mentioned that any
bureaucratic hurdles should not be a problem.


As I mentioned, I can use either a DS0 or an RS-232 line, both of
which exist and are available for the project. Microwave and UHF are
out, as there is no line of sight. This is why I did not mention
those alternatives. "Proper" equipment is the reason I made the post;
I was hoping someone with specific knowledge could point me to same.


Your answers suggest to me that you would rather preach than offer
assistance. Have you never met an engineer who needed help with a
technical task? The fact that I need to ask these questions only
points out a lack of specific familiarity with specific equipment.


All's well. I believe that I have dreamed up a solution while camping
out this weekend. Kind of how a properly licensed engineer might
solve a problem - throw out feelers for suggestions, then ponder the
problem while relaxing a bit on holiday. The fending off of
unconstructive criticisms is all part of the day's work, I suppose.

Thanks anyway. Oh, and I do have a bit of TE lying about. No
worries, mate.

I may be able to help, but I need you to define what you call a DS0. DS0 is
only a 64kbit/s capability or capacity. Are you trying to say you have a
channel in a digital facility available to you? If so, what type of channel
unit does it have? What are the characteristics of the voice frequency
interfaces to the TX and RX and how is the TX currently keyed?

Don
 
K

Kitchen Man

Jan 1, 1970
0
I may be able to help, but I need you to define what you call a DS0. DS0 is
only a 64kbit/s capability or capacity. Are you trying to say you have a
channel in a digital facility available to you? If so, what type of channel
unit does it have? What are the characteristics of the voice frequency
interfaces to the TX and RX and how is the TX currently keyed?

You and I are defining DS0 in the same way. I don't know the
specifics of the particular line, I've only been told that it's
availible for use if I can use it. As I mentioned in another
newsgroup, this is a low-priority project, almost a spare-time
activity. I will investigate the characteristics of the line in the
next few days. Thanks for your questions. Some further info:

The radio is a Kenwood TK-720. Today we mulled the possibility of
breaking the line at the KMC-18 DTMF mic input, and multiplexing voice
and a PTT tone onto our transmission line up to the relocated base.
The drawback is that we won't be able to change channels, but we can
live with that. We only use two, and we have interesting plans for
remote access to the other channel (mwahahahaha!). I've also been
looking at some turn-key solutions from online companies, but that
would require budget begging, and it would be neat if we can do this
as an in-house, shoe-string project.

(Just for clarity, I've started the process for asking for a change on
the license, although we won't be done with this for some time. Also,
I have a class 2 FCC license, so I'm allowed to play with the XMTR ;-)

I'll post again after I've had a chance to investigate our Cisco
network that supplies the now-empty DS0 line to the top of the hill.
Thanks again for your input.
 
D

Don Bowey

Jan 1, 1970
0
You and I are defining DS0 in the same way. I don't know the
specifics of the particular line, I've only been told that it's
availible for use if I can use it. As I mentioned in another
newsgroup, this is a low-priority project, almost a spare-time
activity. I will investigate the characteristics of the line in the
next few days. Thanks for your questions. Some further info:

The radio is a Kenwood TK-720. Today we mulled the possibility of
breaking the line at the KMC-18 DTMF mic input, and multiplexing voice
and a PTT tone onto our transmission line up to the relocated base.
The drawback is that we won't be able to change channels, but we can
live with that. We only use two, and we have interesting plans for
remote access to the other channel (mwahahahaha!). I've also been
looking at some turn-key solutions from online companies, but that
would require budget begging, and it would be neat if we can do this
as an in-house, shoe-string project.

(Just for clarity, I've started the process for asking for a change on
the license, although we won't be done with this for some time. Also,
I have a class 2 FCC license, so I'm allowed to play with the XMTR ;-)

I'll post again after I've had a chance to investigate our Cisco
network that supplies the now-empty DS0 line to the top of the hill.
Thanks again for your input.

If you get a choice of channel unit types, consider an E&M 4-wire unit.
This will provide total isolation between the transmit and receive paths for
both the audio and the DC signaling voltages (TX transmit and RX squelch if
you have that capability. You will need to work up a design to coordinate
the radio voice interface impedances and levels, and DC signaling with the
channel unit requirements.

By the way, the FCC eliminated the 1st and 2nd class licenses. We all hold
the General Class commercial license now.

Since you have dtmf capability, you could use that to switch the channel
freq.

Good luck

Don
 
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