On Sun, Jul 10, 2016 at 1:20 PM, Michael Sapp <wa3tts@verizon.net> wrote:
>
> Although a diplexer or triplex may have .4 to .7 dB insertion loss, it would
> seem you could easily make that up with a single higher grade cable (LMR600,
> etc.). Another advantage is the diplexer or triplexer provides additional
> filtering. A triplexer is a low pass, band pass, high pass filter arrangement
> and you get the additional filtering benefits on both receive and transmit
> for each triplexer port. When you use a triplexer or diplexer on each end of
> a single cable, the filtering performance is approximately "dB additive" See
> below...
>
> https://www.dropbox.com/s/8owsumh7yxa2zzs/2tripxr.jpg?dl=0
>
> Reference: 2016 ARRL Handbook, Supplemental CDROM, CH13, VHF and UHF Beacons
> WA3TTS
Nice.
Once caveat with a diplexer. I have a Comet CF-4160J (all SO-239,
2m/70 cm) to connect some old AEA IsoPoles to a single run of LMR400
to the radio room at N5UWY. These antennas never really worked that
well and I ended up installing an Arrow 2m/70cm ground plane which
works FB. After several years of doing nothing, this past spring I
finally started the process of taking the IsoPoles down. Got all the
vines off the wall so I could get to the hardware. Opened the
Tupperware-style container I'd tacked up under the eaves to protect
the diplexer and noted that one of the PL259s was loose. Not good.
Climbed up another rung to get a good looks at what was going on and
noted that ...
I'd reversed the connections.
Moral of the story with diplexers: CONNECT THE RIGHT ANTENNA TO THE
RIGHT PORT. :-D
Reversed the connections, tightened them, all works great. I have no
idea what happened. I must have been in a rush when I put them up the
first time (I do remember that there was a gap in time from when I
physically mounted the antennas and when I ran the coax). Must have
been long enough that I'd forgotten what had been checked and what
hadn't. Or maybe weather got in the way.
In any case, stupid or no, do make sure the antennas are connected
they way you think they are. Free advice and worth every penny.
--
Peter Laws | N5UWY | plaws plaws net | Travel by Train!
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|
