[UK-CONTEST] Antenna for SSB field day

[Andy Cowley]

> Message: 4
> Date: Fri, 13 Aug 2010 14:07:51 +0100
> From: Andy Summers <g4kno.mail at gmail.com>
> Subject: Re: [UK-CONTEST] Antenna for SSB field day
> To: uk-contest at contesting.com
> Message-ID: <4C6543A7.2000506 at gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
>   Hi Rob,
> 
> It sounds like the precedent has already been set to allow a fan dipole,
> or whatever you want to call multiple elements on a single feedline. So
> I'd go ahead with that unless you're specifically told not to by the
> contest committee.
> 
> I'm all for trying not to be too descriptive with the rules, but what I
> do object to is successive committees giving inconsistent replies to
> questions about the rules.
> 
> Presumably, the idea of the restricted section is to allow entrants to
> be competitive with a minimum of hardware (and money). So I would
> imagine the phrase 'single element' is used in the parasitic or driven
> array sense. Would you say that your fan dipole is a 4-element array?
> No, you wouldn't!
> 
> Chris asked why you would want to use a fan dipole. I can't imagine a
> cheaper, simpler antenna. No ATU required! It also allows instant QSY.
> 
> You can get gain of course from a single element, as others have
> mentioned, but you can only optimise this for one band, and the
> feedpoint impedance is now nowhere near 50R. If you try to common lots
> of these higher gain doublets (or loops) it doesn't work, because the
> method relies on power matching to select the appropriate element.
> 
> The 'one antenna only' rule must be trying to stop you from having
> separate optimised antennas for each band. Personally, I don't see this
> as a big problem anyway because of the single element and only two
> supports restrictions. But does this rule have to be adhered to over the
> entire contest? If so, then adding wire on in the evening to improve LF
> performance is against the rules.
> 
> What about adopting the 21/28MHz antenna rules...
> 
> "Restricted - a maximum of 100 watts output and only one antenna per
> band, which must be a single element with a maximum height of 15m"
> 
> But maintain the two supports rule?
> 
> I think this would make it easier to get a simple station on, and at the
> same time possibly result in better signals and more Q's (especially
> 10/15m).
> 
> 73,
> Andy, G4KNO.
> 
> 
> 
> On 13/08/10 01:37, Rob Hall M0RBY wrote:
>> There are only so many variations on a theme! If a fan or common feedpoint
>> dipole is classed as a single element or just a simple doublet of a length
>> left up to the station concerned and any non-amplifying AMU introduced then
>> I might understand the "rules" but they are a tad ambiguous and I have had a
>> few differences of opinion!
>>
>> Again, I will use the proviso that this is my first ever contest and I
>> really, really don't know.
>>
>> 73, Rob
>>
> 
> 
> 
> ------------------------------
> 
> Message: 5
> Date: Fri, 13 Aug 2010 14:16:04 +0100
> From: Chris G3SJJ <g3sjj at btinternet.com>
> Subject: Re: [UK-CONTEST] Antenna for SSB field day
> Cc: uk-contest at contesting.com
> Message-ID: <4C654594.1050402 at btinternet.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
>   Some interesting thoughts Ian but I don't think it is the rules that are broken. Most of us understand the concept of the rules for Restricted
> section antennas and can work within that so
> I just wonder if it is the concept of impedance matching that some find confusing, and therefore want to opt for something easier to understand?
> 
> Chris G3SJJ
> 


And the next development from the fan-dipole is of course the
log periodic. I'd be interested to see how the rules distinguish
between them. With great difficulty I suspect, as they are
essentially the same thing.

I would prefer to see a single wire element (i.e. no fan dipoles)
but allow three supports so that the centre of a doublet could
have the ATU supported at the feed point. Currently the rules
forbid this so ladder-line must be used or one end just pulled
out as far as possible, without a raised support.

73

Andy, M1EBV


andy.cowley at uwe.ac.uk