[UK-CONTEST] Power Limitations

[Robert Chipperfield]

Hi Paul (and others!),

My concern - as I've mentioned before - is that ERP section limits 
incentivise adding TX power rather than antenna gain. Of course this 
doesn't apply to receive, so in that case let me present my 
(potentially) winning strategy for 6m UKACs if we changed to ERP limits:

Let's assume the "restricted" (AR) section was set at an EIRP of 500w. 
That corresponds roughly to 100w at the TX (remembering the current 
power rules for the restricted category /are/ at the transmitter, not 
the antenna, 3dB of coax and connector loss, and a 5-ele beam having 
gain 10dBi (source: YU7EF EF0605).

In that case, my new station will be 600w out of an amp to a Halo (~2dBi 
gain? Can't find a reference on that, tweak TX power accordingly...), 
giving an EIRP of ~500w (remembering we now do take coax loss into 
account, and the license limit of 400w applies at the antenna) on 
transmit, and the old 5-ele beam on receive.

My transmit performance is now identical to the current 100w section, 
and so is my receive. But I do better, because my transmit power is 
equal to its current maximum but in all directions simultaneously! How 
cool is that! I can spin the beam 360 degrees within about 2 seconds 
(armstrong rotation), which is probably quick enough to cover all 
geographies of interest within the time it takes someone to say their 
callsign, so I probably won't miss too many callers.

Why is this a bad thing? Because now, rather than me consuming 3kHz of 
spectrum in a relatively narrow beam, I do so in all directions, all the 
time. Great for keeping my channel clear, but in my opinion not so great 
ethically.

We're already seeing very significant congestion during UKACs on the 
more popular bands - encouraging setups such as the one above surely 
isn't what we want to be doing?

I don't think the above is too much of a contrived example - it uses 
reasonable kit that most stations have available (except, perhaps, a 
600w linear, but they're not so rare), and reasonable numbers. If UKAC 
AR become a 500w EIRP limit, I'm not sure why you wouldn't do it.

Unless, of course, you kept the limit on single antenna working in AR. 
At which point, I think, Bob would still be upset! :-)

73,
Rob, M0VFC

On 29/01/2012 21:21, Paul Selwood wrote:
> Currently not having much time for amateur radio it is interesting to review
> loads of emails on this reflector covering one subject in the space of a few
> minutes, especially this one on changing the sections in VHF contests in
> general or just UKAC to relate to ERP rather than purely Power. I leave the
> point of measurement  vague on purpose as there had been discussion as to
> where the power is measured at the antenna or at the transmitter output. I
> stress that I believe that Bob (G8HGN) is only referring contests for VHF
> and above.
>
> Bob  (G8HGN) has stated his case well with 100W to dipole and 100W to a
> large beam giving wildly different ERP being fired into the ether. His point
> is that the sections in a contest should be set up around ERP, and not
> merely the transmitter power. It is up to the legislating authority to
> decide the sections and limits. They can also come up with guideline figures
> for antenna gain thus leaving the vagaries of manufactures' specifications
> out of it. Site cannot be taken into account either. Some contest groups do
> rather well operating from non-elevated sites.
>
> Ray (G3HRH) raises some valid points regarding measurement gain of antennas,
> this also applies to the measurement accuracy of RF Power. Even with the
> Bird 43 attached to the end of feeder from a "Typical"  yagi will only  a
> +/-10%   measurement uncertainty at best if  you are lucky.
>
> In these days when the catch phrase is a "level playing field" let's ask the
> CC to consider this one. They did in the case of the M5 rule that has
> supposed to have levelled the field regarding geographical location. Now
> let's go for it in the case of power fired into the ether e.g. ERP.
>
> Paul
> G3YDY
>
>
>
>
>
>
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