This is an older thread but timely for me.
I am moving my 2 meter machine from my home at 6,400 feet in the mountains to Heap's Peak. Heap's Peak is DIRTY. I am told that the only way to get a decent system is split antennas and a duplexer. 3 cavities on RX and 3 cavities on TX. Because of 74kW FM transmitter next to my tower the TX antenna would be up top and the RX antenna would be below. I don't know the spacing that is required but both antennas are DB224e's.
Respectfully, could you tell me what is so difficult in this? I must be missing something. As far as a balanced system turn the TX power down?
Heap's is gonna be a sonna-mo-beach but besides covering all of So. Calif. on the metropolitan side it covers all of the desert as well. Advice on this particular site are welcomed. I plan on using a WaCom WP-642 BpBr. I currently have the repeater on a Sinclair Res-Lok but the cable harness doesn't use a T at the end. Besides, I think the 8" cavities will be better suited on such a noisy site. I am one mile away listening to another repeater and my 5 watt HT can barely be heard. I don't want that! I'll stay here and give up 1/2 of the desert if I have to.
Can you tell me what I need to do to make split antennas and a duplexer work? I also have a two cavity Chip Angle with a 17dB preamp. Does it go in front of the duplexer or behind? It's 1MHz window would put a cleaner signal into the duplexers.
@Steve, I haven't heard you on HF in awhile.
Bob - AF6D
147.705 ( - ) 167.9
Everything's possible but getting a repeater to function well using split antennas instead of a duplexer is pretty hard and takes experience and experimentation.
It almost always creates an "unbalanced" system, since one antenna will be higher than the other. To get enough spacing on 2m to make this work, one antenna would normally be about 100 feet higher than the other. If that's the TX antenna, the repeater will get out a lot farther than it can hear; if it's the RX antenna on top, it will hear better than it gets out.
One way this can work pretty well is "split site," where the separation is quite far (can be a mile or more) and the RX signal is linked back to the TX site via a higher frequency ham band link, or via telephone, or via the internet. That almost always results in an "unbalanced" system, but at least it works, and you don't run into desensitization and noise issues.
A duplexer's a lot easier and only requires one antenna and one transmission line. When one considers how much good antennas and coax cost, that savings could be invested in a duplexer to have a better system for not much more money -- in some cases, maybe even less money.