Linking repeaters

[lancerice]

Hi all, I have two repeater stations which are located about 30 miles apart, each repeater is 2 Gm300 vhf radios linked ogether with 2 antennas up a 60ft mast, they both work very well, but how can I lik the 2 together so if I am near one with my handheld the other handhelds closer to the other repeater can hear me and talk back, I think it is called Linked Repeater, but I am not sure how this is done.
Can any one help me please
thanks lance

[Bill_G]

You could crossband, wifi, or an internet tunnel.

[lancerice]

I would prefer to use normal gm300 vhf radios if poss, I have an idea of 2 working repeaters which would be 4 radios 2 at each repeater working as a normal repeaters, I would then use another 2 radios one at each repeater but tuned to work with each other, but I would need to connect the 3rd radio on each repeater to tx the repeater when rxing a signal from its brother radio on the other repeater, and for the rx side of the repeaters to tx both the tx side of the repeater and the 3rd radio, I am quessing this would work
thaks lance

[wavetar]

I would prefer to use normal gm300 vhf radios if poss, I have an idea of 2 working repeaters which would be 4 radios 2 at each repeater working as a normal repeaters, I would then use another 2 radios one at each repeater but tuned to work with each other, but I would need to connect the 3rd radio on each repeater to tx the repeater when rxing a signal from its brother radio on the other repeater, and for the rx side of the repeaters to tx both the tx side of the repeater and the 3rd radio, I am quessing this would work
thaks lance

Yes, your concept is correct. We installed a similar setup a number of years ago to link two GR1225 repeater sites, using VHF CDM750 radios for the link. COR from the local GR1225's keyed the link radios, and COR from the link radios keyed the remote repeater.
However, 30 miles is a long way to go with only 60-foot masts to work with, depending on the terrain in between. High gain Yagi antennas will give you the best chance, if the mast can accommodate them.

[Bill_G]

Are the two repeaters on different freqs, but in locations they can hear each other well?

[lancerice]

both repeaters are on the same freq so you can use the same channel at both sites

[Bill_G]

Then you will definitely need a third radio pair to act as a simplex link between sites. Just be aware that any overlap zone between the two sites will be clobbered and unusable. Post the lat and long of the two sites, and I'll post a predicted coverage plot. I'll need ant elevation, gain, xmit pwr, and rcvr sense too.

[CircleBat]

just put the repeater output on the same tone and the input with 2 different tones so that you don't get the overlap

CircleBat

[lancerice]

Site 1, 51.526475, 0.539017, Ant Height 40ft, not sure of gain the antennas are 1/4 wave
site 2, 51.200215, 0.386925, Ant HEight 60ft, not sure of gain the antennas are 1/4 wave
Thanks Lance

[Bill_G]

I'll have interference maps for you this evening based on the following assumptions -

25w xmit pwr to ant
-116db rcvr sense
0db gain

[Bill_G]

Site 1, 51.526475, 0.539017, Ant Height 40ft, not sure of gain the antennas are 1/4 wave
site 2, 51.200215, 0.386925, Ant HEight 60ft, not sure of gain the antennas are 1/4 wave
Thanks Lance

Lance - Please verify the coordinates for site 1. I show it on the shore with a land elevation of 1 meter.

[lancerice]

site 1 is on an island of which most is below sea level, canvey island, essex, UK

[Bill_G]

As promised - an interference map of your proposed linked repeaters. If you can achieve the link, you may actually have a poor man's simulcast by accident of the terrain. There are two very neat puddles bisected by the range of hills. I apologize for the color choices, but they make excellent contrast. Green in the north site coverage, and hot pink is the south site coverage. A mobile in those areas should have exclusive use of just the one repeater with little interference from the other. The black areas are where they are within 5db of each other, and are sure to cause beating in the mobile receiver. This is an optimistic map. This is the least worst it can be based on the assumptions I gave earlier.

Cheers.