[TowerTalk] Rotator loops

[Joe Subich, W4TV]

> Interesting.. Do they use a more flexible chunk of feedline 
> at the top? 

Generally not.  The feedline tends to be a high quality foam 
.405" cable for the 2 GHz band.  The transmitter (2W) was in 
the rack below with power amplifier (ca. 10W) mounted at the 
top.  The loss provided sufficient attenuation to prevent the 
power amplifier from being overdriven. 

On the 7 GHz and 13 GHz bands the feedline was actually IF 
with upconverter/power amplifier at the top.  IF feedlines 
were typically foam RG-6 style cables since they were easier 
to accommodate in the 1.25" nycoil. 

73, 

   ... Joe, W4TV 
 


> -----Original Message-----
> From: jimlux [mailto:jimlux at earthlink.net] 
> Sent: Saturday, February 27, 2010 10:37 AM
> To: Joe Subich, W4TV
> Cc: 'Tower and HF antenna construction topics.'; n4zr at contesting.com
> Subject: Re: [TowerTalk] Rotator loops
> 
> 
> Joe Subich, W4TV wrote:
> 
> > 
> > Having designed and built those trucks for a few years, there
> > are two issues here: 
> > 
> > 1) mast height is accommodated by the many turns of the "nycoil" 
> >    which stretches like a slinky as the mast is raised.  By the 
> >    way, the length of feedline is almost double the mast height.
> > 
> > 2) the antenna rotation is accommodated by a single loop.  The 
> >    "nycoil" is attached at the top of the mast for support.  The 
> >     mast does not rotate - only the antenna rotates.
> > 
> > 73,
> > 
> 
> 
> Interesting.. Do they use a more flexible chunk of feedline 
> at the top? 
> (I suppose, further, that the actual microwave up and 
> downconverter is 
> probably up at the antenna, so loss in the cable is less of a worry)