Re: shorter URL -- RF-man & Spoddy's Forum

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Date Posted: Fri 24 Nov 2006; 3:46pm
Author: Spoddy
Subject: Re: shorter URL
In reply to: hehe 's message, "shorter URL" on Wed 22 Nov 2006; 2:37pm

Thanks!

The maximum legal ERP from 8/12/06 on 87.5-108 will be 50 nanowatts, which is -43dBm, 70dB less than PMR446. Going by my 446 calculations on my technical page this suggests a level of -88dBm at 10m but don't forget the 13dB aperture advantage at 98MHz bringing it up to -75dBm (S9+18dB). The usual freespace loss formula agrees.

At 100m (10x the distance) it's 100x (-20dB) less, a maximum of -95dBm, just under S9, not brilliant for the bandwidth and the low-noise requirements for clean stereo decoding.

However, sticking one on a pole above your roof could still provide some scope for DXing of a sort, to a decent receiver in the local area, even if in mono. The figures suggest that -115dBm could be achieved at 1km, which is still a handful of dB above the noise. Worth playing with, if you can actually get one that puts out the full legal power.

Don't expect DXing from hilltops though, those iffy results at 1km are already with the advantage of line of sight, and that really is the limit.

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Re: shorter URL -- info, Tue 12 Dec 2006; 10:36am