[UK-CONTEST] CQWW SSB 10m SO Unassisted : G3ZQH
Chris G3SJJ
g3sjj at btinternet.com
Wed Oct 31 05:39:51 EDT 2012
Clive, I agree modelling antennas and terrain would be interesting but in real life the important issues are finance and visual impact. Dave and I
know we are very lucky to have a large half acre plot each but even so there are limitations. Certainly an 80ft Versatower each would be fantastic but
our Tennamasts represent good value for money and at least allow us to have a beam which many people can't achieve. Choice of antenna is then limited
to what the mast will carry and also cost. I originally chose the A4S since it has a separate 10m reflector and less traps than the A3S making it
slightly more efficient. I think I paid around £450 but now it is around £750 which would make it restrictive.
Over the years I have gained a good insight into antenna performance and the surrounding terrain and I guess software modelling would confirm that,
but I doubt very much if doing it first could or would have changed the eventual outcome.
One thing we have done is to try and reduce system loss. I found changing from a 90m run of RG213 to Westflex 103 made a noticeable difference. Dave's
run is about half that length but he also noticed an improvement. With all the various connectors going in and out of the WX0B SixPak relay box at the
base of the mast plus another 18m of RG213 up to the beam I still reckon I have about 3dB loss on 10m and 12m so my next major expenditure will be
some good Ecoflex or similar. In total I would probably need a 500m drum. Maybe one day!!
Chris G3SJJ
On 31/10/2012 00:04, Clive GM3POI wrote:
> Dave I am afraid Contesting is even more demanding than Dxing. Take for
> example trying to work a ZL on 20m today either SP or LP the required wave
> angle is 3 degrees. Your antenna at about 14m high has a gain of about
> -1dbi at 3 degrees, over flat ground.
> It may be the case that you can work one but the basic figures do
> not make it easy. Every potential Dxer or Contester should examine the facts
> about their location and optimise antennas to suite it. My suggestion to
> anyone thinking of spending any money on a station, is first of all spend
> money on Software, and model any considered antenna and its terrain BEFORE
> buying anything. See how any antenna interacts with others and get a feel
> for how it will perform before doing anything for real.
> I would not consider putting up any antenna without first spending a
> lot of time checking the likely results beforehand.
> 73 Clive GM3POI
>
> -----Original Message-----
> From: UK-Contest [mailto:uk-contest-bounces at contesting.com] On Behalf Of
> G3ZQH
> Sent: 30 October 2012 19:48
> To: uk-contest at contesting.com
> Subject: Re: [UK-CONTEST] CQWW SSB 10m SO Unassisted : G3ZQH
>
> Sorry about the bad format of the antenna data- it looked fine when I sent
> it! Tried to reformat it below, but not sure if this will be successful...
>
>
>
> I worked lots of E EU of the back of my hexbeam when beaming towards US so
> maybe that is an advantage! When I check F/B on receive with the hexbeam it
> is about 4-5 S points on 10m using my FT1000MP. I was thinking about
> contesting not just DXing, where you might need some higher angle radiation
> as well as low angle. Nevertheless very interesting comparison with Mike
> G3SED’s 2el. No chance of 75 ft here, but could risk another few metres on
> the Tennamast stub mast to get the hexbeam up to about 50-55ft. Point taken
> about the narrow lobes on the 5-el- perhaps this is where the SteppIR
> reversible mode comes into its own. Not used one- but this seems quite a
> neat trick.
>
>
>
> 73 Dave G3ZQH
>
>
>
>
>
> Ø The lower noise floor on the 4 ele Yagi is due to it's better F/B,
>
> Ø narrower forward lobe but mainly due to the lack of side nulls on the
>
> Ø Hexbeam.
>
>
>
> Ø Clive is right, If you hear Mike SED on the higher bands then you may
>
> Ø know he uses an optibeam, but with only 2 elements on 10M (actually 2
>
> Ø elements on all 5 bands) but its up at 75ft. Mike is only 9 miles away
>
> Ø and we are always comparing with stations at the other end. On 10M Mike
>
> Ø is neck and neck with my 5 ele @45ft on 90% of the stations.
>
> Ø Unfortunately planning restrictions, a 21ft wide garden, and overhanging
>
> Ø tree branches limit what I can do here so the 5 ele is the biggest
>
> Ø antenna I can get up for 10M for my everyday DXing, the problem when
>
> Ø using that in a contest is the narrow forward lobe, deep side nulls and
>
> Ø 25dB F/B. When beaming to the West Eastern Eu can be barely readable but
>
> Ø swinging the beam round they can be 9+. Great for point and shoot, not
>
> Ø so good for multiplier hunting. I have a dipole at 90deg on the sub Rx
>
> Ø which helped in CQWW but I need to dig out my 10M 5/8 vert which is
>
> Ø corroding in the grass somewhere, that is a more effective mult finder.
>
>
>
> Ø Darren G0TSM
>
>
>
> On 30/10/2012 13:39, Clive GM3POI wrote:
>> Forget about minor differences in alleged gain of the different antennas,
> and think in terms on Wave angle required at the wanted frequency. For
> example 10m is roughly half the angle of that required at 20m typically
> often below 5 degrees. This is the only real DX performance to worry about,
> fractions of a db are meaningless. Far better to have a 2el 10m yagi at 70ft
> than a 6el at 30ft and you can make a 2el 10m yagi for next to nothing.
>> 73 Clive GM3POI
>>
>> -----Original Message-----
>> From: UK-Contest [mailto:uk-contest-bounces at contesting.com
> <http://lists.contesting.com/mailman/listinfo/uk-contest> ] On Behalf Of
> G3ZQH
>> Sent: 30 October 2012 07:52
>> To: uk-contest at contesting.com
> <http://lists.contesting.com/mailman/listinfo/uk-contest>
>> Subject: Re: [UK-CONTEST] CQWW SSB 10m SO Unassisted : G3ZQH
>>
>> Thanks for info on hexbeam vs Yagi. Interesting that the noise level was
> lower with the Yagi- possibly as a result of the higher angle lobe that
> appears on the hexbeam at around 50’ height.
>> I have pasted in a table I put together a couple of years ago when I was
> looking for best value for a 5-band directional antenna. It is interesting
> to see that with these inevitably compromised antennas there is generally
> fairly poor performance on 10m particularly F/B ratio. The SteppIR in 2- or
> 3-el format is actually worse than the hexbeam on 10m F/B!
>>
>> SteppIR 3 el SteppIR 2 el Optibeam 10-5
> G3TXQ hex Spiderbeam
>> Max. Element length (m) 10.97 10.97 7,70
> 6.6 10
>> Boomlength (m) 4.9 1.44 3.75
> 6.6 10
>> Turning Radius (m) 6 5.61 4.3
> 3.3 5
>> Weight (kg) 19 13.6 14
> 10 11.5
>> Windload (sq ft) 6.1 4.0 3,2
> 6.0 3.8
>> Gain dBd 20 4.9 4.2 4.2
> 3.2 4.5
>> Gain dBd 17 5.5 4.2 4.4
> 3.2 3.2
>> Gain dBd 15 5.7 4.1 4.2
> 3.5 4.7
>> Gain dBd 12 6.2 4.0 4.4
> 3.0 3.0
>> Gain dBd 10 6.3 3.8 4.8
> 3.6 4.9
>> F-to-B dB 20 21 18 22
> 22 15
>> F-to-B dB 17 20 19 17
> 19 20
>> F-to-B dB 15 27 13.7 15
> 16 20
>> F-to-B dB 12 21 13 15
> 13 10
>> F-to-B dB 10 11 9.3 20
> 16 18
>> Price £ 1500 1100 1000
> 500 450
>
>
>
>
>
>
>
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