55 dB should be adequate isolation for a repeater,
unless you are running a high gain pre-amp and/or high
power.
These duplexers are better in most ways than the BP/BR
type because they provide better isolation at most
frequencies further removed from the TX/RX. A small
spur on your TX that is 30 MHz away from the TX
frequency will be greatly attenuated. Likewise, a high
power commercial UHF paging TX will have lots of
attenuation, due to the true BP nature of the device.
The additional dB or so of loss should not be
noticeable.
These duplexers are especially sought on very crowded
sites, if yours is not crowded, you might be better
off with a BP/BR type. Someone would probably trade
you for one of the other types.
Joe
--- n0pwz <[EMAIL PROTECTED]> wrote:
>
>
> I am the proud(?) new owner of what a believe to be
> a T1507
> duplexer. I believe it is a bandpass only duplexer.
> I use, and am
> familiar with, the T1504's which are Bp-Br
> duplexers. If the
> duplexer in question is actually a T1507 it would
> seem to have
> inferior receiver isolation of 55 dB vs 80 dB in the
> T1504.
>
> Whether this is actually difference that is
> significant, is a
> question I've been puzzling over for a bit. Is 55 dB
> of isolation
> enough for most repeaters? I also noticed a
> difference of 1.3 vs.
> 2.0 dB insertion loss between the two, but I suspect
> I can
> compensate for this with a better antenna.
>
> I note that some folks have been using these
> bandpass only duplexers
> in their repeaters with some success, so there is no
> doubt on my
> part that it can be used with a repeater. I would
> like to get some
> input from the folks on the list as to the benefits
> (or disbenefits)
> of this type of duplexer compared to a Bp-Br
> duplexer such as the
> T1504. Also, is one better off with a T1504 or a
> T1507 at a location
> where there is another 450 mhz repeater?
>
> Thanks very much in advance!
>
> Mark
>
>
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