I would recommend not using a 12.5 kHz spacing freq in this case of a
control receiever, a receiver that is only 12.5 kHz away from your
regular repeater input.
With typical good FM analog receivers these would both have overlapping
passbands and an input signal on the repeater input would interfer with
the control input. With som many using IC type DTMF decoders any
interference, just over lapping distorted voice would hender the decoder
decoding.
A typical UHF duplexer would have a notch wide enough for a freq +/-25
kHz away. Know this is going to be another repeaters input, but with
some research could find is close in distance to you.
I have used control UHF freq that are 6.25 kHz spacing, but these were
in the 446 range and on separate antenna. Just had access to this. I
used this freq to give some added security.
73, ron, n9ee/r
Ron Wright, N9EE
727-376-6575
MICRO COMPUTER CONCEPTS
Owner 146.64 repeater Tampa Bay, FL
No tone, all are welcome.
On Sun, May 11, 2008 at 10:24 PM, Laryn Lohman wrote:
--- In Repeater-Builder@ yahoogroups. com
<mailto:[email protected]> , "John Transue" <[EMAIL PROTECTED]
.>
wrote:
Laryn K8TVZ,
So, if I understand, I should put a splitter after the pre-amp, and
the control frequency should be a split channel. Does this mean that I
use half way between two channels?
Right, one of the 12.5 kc. in-between channels would be less likely to
have something on them.
Another question, who makes a good splitter, and how can I know I am
getting a good splitter?
Well, I've seen 50 ohm splitters quite often at hamfests. I don't
have a good brand name to point you to. I am, however, using a 75 ohm
TV splitter. Purists will hate this, but especially, if you are after
a preamp, I don't see this as a big deal. It works just fine here
with no measured loss in repeater receiver sensitivity through the
system. Use quality coax and fittings. I've found that RG142 works
reasonably well with the TV splitters since it has a solid center
conductor.
If you are not using a preamp, then you really need to do things
right, using a proper splitter, and still you may lose some sensitivity.
Some of you are saying, where's the quality in that splitter scheme?
Well, experimentally I've found it works well here, so after initial
measurements showed me that things were still the same, I'll tend to
stay with what works, but ready to ditch the whole thing if needed and
go another route. Sometimes <quality> takes the form of performance,
not looks or perfection. If system sensitivity had suffered it
wouldn't be there for more than 15 minutes.
Laryn K8TVZ
<mailto:[email protected]>
