In article ,
Tom Horne wrote:

On Monday, December 30, 2013 8:59:38 PM UTC-5, Fred McKenzie wrote:
In article ,

Tom Horne wrote:



We would like to be able to use 50, 144, 220, and 440 MHz radios at any
position and we would prefer not to have to resort to diplexers and separat
e antennas on the roof if it can be avoided.

Tom-



Phil and CRN have good suggestions that directly address your needs.

Another approach for common local frequencies, is to have a single base s
tation for each frequency, with a remote control at each position.

This allows the base station to be located (in a separate equipment room?
) closer to the antenna to minimize feed line loss. All it takes is teleph
one wires to connect between the base stations and remotes. Each remote co
uld have a switch to select base stations.

Fred K4DII

Fred

I take it that would involve using only identical radios so as to be able t
o use any control head with any radio.

Tom-

That may also work with same-family radios on different bands. But
someone with more experience than I, might design a universal remote
that could be adapted to several different model radios.

One approach would be to develop a standard interface consisting of
transmit and receive audio pairs operating at line level, plus a keying
pair. To reduce the number of wire pairs, you could use split-winding
transformers to accomplish DC keying on the transmit audio pair.

Fred

On 12/30/2013 8:59 PM, Fred McKenzie wrote:
In article ,
Tom Horne wrote:

We would like to be able to use 50, 144, 220, and 440 MHz
radios at any position and we would prefer not to have to resort to diplex
ers and separate antennas on the roof if it can be avoided.

Tom-

Phil and CRN have good suggestions that directly address your needs.

Another approach for common local frequencies, is to have a single base
station for each frequency, with a remote control at each position.
This allows the base station to be located (in a separate equipment
room?) closer to the antenna to minimize feed line loss. All it takes
is telephone wires to connect between the base stations and remotes.
Each remote could have a switch to select base stations.

Fred
K4DII


Fred,

This isn't a good idea for several reasons (as have been explained to
Tom by others and myself several times via email). The main one being
lack of backup. When you have a radio remoted like this, if the radio
or control head (or even the connecting cable) fails, you are in
trouble. Often times the equipment room is not readily available,
especially if there are other radios nearby. And even if the radio is
available, you can generally only replace it with the same make (and
often model) of radio. That would be great if everyone used the same
radio. But they don't. And in an emergency, the number one
consideration is reliability. And since these radios aren't used or
tested regularly, chances of a failure going unnoticed are higher than
your home or mobile station.

When the radio is at the operating position operating off of 12VDC, you
can replace it with generally any mobile radio. And if the power supply
fails, you can replace it with almost any other power supply (as long as
current demands can be met in both cases, obviously).

In an EOC or similar situation, there are "necessities",
"recommendations" and "nice to haves". Reliability is at the top of
"necessities". IMHO, "being able to operate any radio from any
position" is at the bottom of "nice to have". Sure, it would be nice -
but would it actually be used? And what are you giving up to get it?


--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

For single frequency use without all the bells and whistles,
I use CPI tone remote units.
http://www.cpicomm.com/
Reasonably priced on eBay.


--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

I do not believe that 222 MHz is a harmonic of 2 meter or 70 cm - hence the only antenna that I am aware of that will do all would be a custom built J Pole antenna with a radiator for 220 MHz...

The J-pole would require a ground plane - as does all vertical antenna's, and it would have 0 gain...