Eric -
Thanks for the comments on duplexers. When I started this in January,
I remember reading some comments about some duplexers getting "out-of-
tune" from bouncing around (mainly in shipping) and that's what got
me thinking about simplex repeaters and, now, about cross-band
repeaters. Is subjecting the duplexer to vibration and shocks in a
truck on a rough road really something about which to worry?
One of the comments I received when I proposed using simplex
repeaters was that, if a fixed-repeater went off the air because of
power failures, it would be possible (with the permission of the
repeater owner/trustee) to tune the simplex repeater to the fixed-
repeater frequencies as a temporary measure until the fixed-repeater
could be returned to service. What do you think of that?
Paul W2ARK
On May 8, 2006, at 8:20 PM, Eric Lemmon wrote:
> Paul,
>
> When you push for a wide-spaced portable repeater pair on 2m,
> suggest a
> separation of at least 3 MHz. The reason is that you can buy
> "compact base
> station" duplexers that are specified for 3.0 MHz spacing, but the
> performance rapidly deteriorates as the spacing is reduced below
> that point.
> I bought a Celwave 5085-1 duplexer that was factory tuned to a
> 2.655 MHz
> split, and it works okay with a 10 watt R1225 repeater, but it took
> some
> tweaking. The entire repeater fits into a rugged fiberglass case
> that is
> less than a cubic foot in volume. I hope to complete the final
> version
> shortly.
>
> It will be a challenge to create a 3 MHz pair in only 4 MHz of
> spectrum, but
> it can be done. Let's not forget that the purpose is to support
> *temporary*
> communications of an emergency nature. While it would be nice to
> have a
> pair permanently set aside for this purpose, I'll bet that a true
> emergency
> will trump any other claim to existing frequencies. If the PL
> encode and
> decode tones are intelligently selected, any interference to
> established
> repeaters should be minimal to nonexistent. If the portable
> repeater is
> positioned in the area where radio comm is needed, low power works
> wonders!
>
> 73, Eric Lemmon WB6FLY
>
>
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