[cma-l] AM V's FM

[Two Lochs Radio]

>
> If you need to generate 800W of RF for an EMRP of 70W I'd say you need to
> improve your antenna system efficiency :-)
>

As you know, easier said than done for a small station David! With a typical 
wavelength of 200-300 metres, an efficient omnidirectional radiator can be a 
mighty big thing. A traditional quarter-wave vertical mast is not something 
you can just pop on a roof pole like an FM dipole! Loading coils can shorten 
it, but nonetheless efficiency rapidly falls off as you make the antenna 
more compact.

A more surprising figure is Ian's implied 28% electrical efficiency for the 
AM transmitter - Nautel's J1000 offers 60%-70% efficiency (ie ~1300W 
consumption for 800W modulated output). The Nautel TX costs around £10k, but 
it would save around £1,800 electricity a year in Ian's example, so would 
probably pay back the extra cost in a little over 2 years.

Alex

----- Original Message ----- 
From: "Info" <info at transmittersrus.com>
To: <cma-l at commedia.org.uk>
Sent: Monday, December 14, 2015 4:03 PM
Subject: [cma-l] AM V's FM


> Ian,
>
> If you need to generate 800W of RF for an EMRP of 70W I'd say you need to
> improve your antenna system efficiency :-)
>
> David
> Transmitters 'R' Us
>
> _______________