Thanks Eugene.
If you're using the pre-amp for low-signal work through the verticals,
maybe you can get away with the pre-amp(s) in the shack on the radio side of
the triplexer. If you calculate that the increase in noise would be too
great this way, and you conclude you MUST use pre-amps at the antenna, then
you'll be forced to use two more triplexers: one near the antenna to break
out each band for its respective amp, and another one at the antenna to
combine the signals again before you connect to the antenna. Seems a bit
awkward to me.
Yep that is exactly why I wanted to ask if there was such a best as a 3 band
pre amp. There are two band amps for 6m/2m and 2m/70cm but I have not yet
found all three covered in a single amp. The reason I want a masthead amp is
to improve the signal-to-noise ratio and overcome any loss at the coax. Best
I can guess at the moment is
Rig feeding HT to HT antenna
" " 6m to triplexer A #1 connection
" " 2m to triplexer A #2 connection
" " 70cm to triplexer A #3 connection
triplexer A #output coax feed line to roof to duplexer A #input
duplexer A #1 connection feeding 6m/2m preamp
duplexer A #2 connection to 70cm preamp
duplexer B #1 connection from 6m/2m amp to antenna
duplexer B #2 connection from 70cm amp to antenna
Now would the loss in all of this be to great compared to the benefit?
Would a single coax from each output on the rig be better run to the antenna
(3 lines) each going to its own preamp then take a triplexer from the three
preamps and feed the antenna. Alternatively, go for three separate antennas
for 6/2/70?
Now my brain hurts.
--
George Shaw
eMail: george.shaw@btinternet.com
eMail: george.shaw@ukf.net
Fax/Voice Mail: +44 (0) 87 0133 6126
Mobile: +44 (0) 77 4036 1163
ICQ#: 1741675
-----Original Message-----
From: EUGENE SMAR [mailto:SPELUNK.SUENO@prodigy.net]
Sent: 22 December 2001 01:19
To: george.shaw@ukf.net
Subject: Re: [TowerTalk] triplexers and mast head amps
George:
The V2000 was my other choice for triband vertical (Comet's GP15 is
what I actually purchased.) As I have only 2M equipment in operation so
far, I haven't bought a triplexer yet, but yes, you will need one to operate
all three bands simultaneously, or at least to operate without changing coax
cables if you operate one band at a time.
My choice would be a Comet CFX 514J or Diamond MX-2000D triplexer.
These models come with female UHF connectors, just like the backs of all
Xcvrs. Other models come with various combinations of male connectors
(difficult to find mating connectors for coax) or coax cable pigtails (how
do you repair them when they fail?)
Why do you want a mast-mounted pre-amp? Is it for FM repeater work?
If so, you needn't bother with such accessories; you ought to be able to
work the local and not-so-local repeaters with your vertical and normal
barefoot power. I debated about using hardline coax up to the GP-15 at 80
feet AGL, but decided the expense was too great, even at 440 MHz, to justify
the slight improvement in cable loss. Even a 6 dB loss of power at 440
shouldn't impact your repeater work too terribly. To feed the GP-15 I use
RG-213, same as my HF antennas on the same tower.
If you're using the pre-amp for low-signal work through the verticals,
maybe you can get away with the pre-amp(s) in the shack on the radio side of
the triplexer. If you calculate that the increase in noise would be too
great this way, and you conclude you MUST use pre-amps at the antenna, then
you'll be forced to use two more triplexers: one near the antenna to break
out each band for its respective amp, and another one at the antenna to
combine the signals again before you connect to the antenna. Seems a bit
awkward to me.
GL es Merry Christmas de
Gene Smar AD3F
-----Original Message-----
From: George Shaw <george.shaw@ukf.net>
To: towertalk@contesting.com <towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Friday, December 21, 2001 1:43 PM
Subject: [TowerTalk] triplexers and mast head amps
>
>O great oracle of the radio waves hear my request for this day I seek the
>knowledge of you mighty lord (gee you can tell Lord of The Rings is out at
>the cinema:)
>
>I mount a 3 band (6m/2m/70cm) Diamond V2000 atop my mast. On the back of
my
>rig are separate connectors for each HF 6m 2m & 70cm. Am I correct in
>thinking I need a triplexer at the rig end feeding three into one?
>
>Which triplexer gives best results with lowest loss?
>
>At the mast head I have a single coax connection. So what if I want to have
>a masthead amplifier? I see dual band for 2m/70cm or 6m/2m but can't find a
>three band model? How can I defeat the cable loss on all three bands?
>
>Now back to watching LoTR.
>
>73 happy Christmas.
>
>--
>George Shaw
>
>eMail: george.shaw@btinternet.com
>eMail: george.shaw@ukf.net
>Fax/Voice Mail: +44 (0) 87 0133 6126
>Mobile: +44 (0) 77 4036 1163
>ICQ#: 1741675
>
>
>
>
>
>AN Wireless Self Supporting Towers are now available! Windloading tables,
>foundation diagrams and charts, along with full details are now at the
>AN Wireless Web site: http://www.ANWireless.com
>
>-----
>FAQ on WWW: http://www.contesting.com/FAQ/towertalk
>Submissions: towertalk@contesting.com
>Administrative requests: towertalk-REQUEST@contesting.com
>Problems: owner-towertalk@contesting.com
>
AN Wireless Self Supporting Towers are now available! Windloading tables,
foundation diagrams and charts, along with full details are now at the
AN Wireless Web site: http://www.ANWireless.com
-----
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