Of course with 5G bands now extending to 28 GHZ, and talk of higher
bands, Remote Radio Units would have become necessary anyway for
feedline loss reasons. Not to mention that large coax doesn't even work
at mm wave frequencies.
-Steve K8LX
On 5/17/2022 6:16 PM, Steve Maki wrote:
Actually the transition to top mounted radios had nothing to do with TX
loss, nor RX dB loss. TMA's (tower mounted amplifiers for RX) had been
around forever, and TX power is cheap at the 20-60 W levels.
It was all about PIM (passive inter-modulation) which reared it's ugly
head during the transition to 4G LTE (which requires VERY low noise
floors). The typical coaxial TX path from ground to antenna had a
zillion connectors. It rapidly became clear that maintaining a zillion
paths, each with up to 20 connectors, to the low PIM levels demanded by
LTE (and knowing that 5G was coming down the road), was going to be
impossible.
The main decision now is between RRU + RF jumpers + antenna, which has
some flexibility for maintenance (but you still get flaky connectors),
or AIR antennas which have the radio built in, but any fault in either
the radio or antenna requires an expensive replacement of the whole unit.
-Steve K8LX
On 5/17/2022 2:56 PM, Gene Smar via TowerTalk wrote:
In commercial (cellular, LMR) services, the decision of where to put
the power stage (in the equipment hut or on the top of the tower)
depends on the cost to generate enough power to compensate for dB loss
in the coax. At today's mm-wave freqs for 5G operation, e.g., Freq
Range 2 from 24-52 GHz, it would be costlier to put a PA of sufficient
power in the hut at the tower base to yield the necessary ERP at the
antenna than it would to put a smaller PA stage at the tower top and
run a fiber/copper cable assembly to it from the hut.
It's a different story at HF and even V/UHF. The coax losses are
significantly less in this freq range than at mm-wave so the advantage
(coax loss reduction) of remoting the RF components is not as great.
For us Hams it becomes a matter of personal taste - how loud do I want
to be? - vs how loud MUST I be?
On another hand, running fiber vs coax to the tower could eliminate
much of the danger from lightning strikes. The problem then becomes
(a simpler?) one of protecting the power feed(s) going to the
electronics from inside the Ham shack.
73 deGene Smar AD3F
-----Original Message-----
From: Chuck Dietz <w5prchuck@gmail.com>
To: Kelly Taylor <ve4xt@mymts.net>
Cc: Steve Maki <lists@oakcom.org>; TowerTalk@contesting.com
Sent: Tue, May 17, 2022 12:34 pm
Subject: Re: [TowerTalk] Fw: Feeding single band HF yagis 500+ ft from
the shack
I was wondering the same thing. I’m surprised that no amp company
makes an
amp to go at the tower. Maybe remote a rig and amp close to the towers?
Chuck W5PR
On Tue, May 17, 2022 at 11:23 AM Kelly Taylor <ve4xt@mymts.net> wrote:
Curious… at what point, given the cost of hardline, does one consider
running code-compliant power out to the towers, putting the RF
components
there and using either ethernet or fibre between the control heads in
the
shack and the rf components?
Just a question. Flames will be ignored.
73, kelly, ve4xt
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