ldgelectronics wrote: > Hi all, > > I've been working on this problem for a while and have not come up > with any good solutions. So I'm hoping to find someone that has "been > there, done that" with some suggestions. > > The issue is that I want to add a same-band remote base to an > existing repeater. The main problem is that the remote base is a > transceiver and I can't find a way to provide proper isolation > to/from the repeater. > > Here are the frequencies, but it looks like it really doesn't matter > all that much. The repeater transmits on 443.300, receives on > 443.800.
Did you mean something else? That's a 500 kc split.... > We're using a typical UHF pass-reject duplexer with about 70 > db of isolation between those two freqs. The remote base will > transmit on 444.225 and receive on 449.225. > > I can put two antennas on the tower, but my horizontal space will be > less than 20 feet. > Did you mean vertical? That should be plenty of vertical spacing. > >From the pile of spare parts, I have a multitude of UHF band pass and > notch filters. I would also not be opposed to adding something like a > pass-notch duplexer if there is a way to configure it to work. > > >From my testing, it seems that the real issue is that the remote base > is a transceiver and there is pretty much no way to add anything > except notch filtering. Adding band pass cans will filter either the > tx or the rx, but not in any combination (that I can find) to do both. > > If the remote base had a separate tx and rx, then a band pass can > with a notch can (on the repeater freqs) on each side would probably > work fine. > > Anyone have a good solution? Nothing beats antenna separation for a cheap way out, vertical is best for vertically polarized antennas. I have a repeater on 443.925 TX and 448.925 RX I have a remote base on 443.950 RX and 443.950 TX. There is 100 feet of vertical separation, the repeater is a Micor with the AFC disabled. Link is Radius M120 at 4 watts, no desense either way..... (that's 25 kc of spacing!!!) The repeater is running a preamp, and no it is not deaf.... Kevin Custer
