Message-ID: <497D9856.7080601@sighthound.demon.co.uk>
Date: Mon, 26 Jan 2009 11:02:46 +0000
From: John P-G <gm4slv@sighthound.demon.co.uk>
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References: <20090125092908.0aec06a4@lurcher>, <00d301c97f22$87d998d0$6401a8c0@asus>, <20090125194232.05798210@lurcher> <497D91B0.1756.4B9405@mike.dennison.ntlworld.com>
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Subject: Re: LF: Re: WSPR 503.5
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Mike Dennison wrote:
> GM4SLV wrote:
>  
>> There was much discussion on the WSPR forum on the merits or otherwise
>> of this approach, in the HF sphere at least.
>>
>> It might be easier if we adopted the same approach as is recommended
>> for HF use - to report the actual TX power, not ERP.
> 
> This does not follow. On the HF bands the ERP is close to RF power, 
> especially on the bands where WSPR is popular, and can therefore be 
> used a a rough approximation. That is most certainly not the case on 
> LF/MF. On 136kHz I have to run 800W RF to get 300mW ERP. Another 
> station might need just 100W RF to achieve the same power. Although 
> the ratio is smaller on 500kHz, there is still a huge discrepancy 
> between the RF needed to achieve the same ERP for different stations. 
> RF power is therefore meaningless.
> 
> Mike, G3XDV
> ==========
> 

Hello Mike, LF

This is precisely why I thought it might be instructive to report TX power!

In the above example, of an inefficient antenna and 800W vs an efficient
antenna and 100W for the same ERP, the WSPR reports will make this
plainly obvious, as similar S/N should be reported for both systems, due
to similar ERP, but the different efficiencies will be obvious from the
reported TX power - one reporting 60dBm and the other 50dBm, rather than
both reporting 23dBm ERP(using the closest available power options in WSPR)

However, I must admit I'm swayed by the general argument to stick to ERP
in WSPR on LF/MF, for the reasons given by Jim et al. and I'm
withdrawing my initial argument for using TX power.

Cheers,

John