[TowerTalk] Fw: Feeding single band HF yagis 500+ ft from the shack

[Steve Maki]

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 at gmail.com>
> To: Kelly Taylor <ve4xt at mymts.net>
> Cc: Steve Maki <lists at oakcom.org>; TowerTalk at 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 at 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