[UK-CONTEST] What antenna for AFS?

Mon Jan 2 16:50:58 EST 2006

OK, presume there was a high angle lobe off it then? A complicated way 
to get NVIS!

Strange about the ON4UN-fed Delta Loop 'cos it is supposed to be for low 
angle. Maybe the surrounding ground and objects were giving it some high 
angle.

Reference the noise, I wonder if you are close to Super Grid power 
lines. Here, just listening to SU9HP on 160 I have an s7 n/l which goes 
up to s9+ when it rains. Drops to around s5 on 80m and not noticeable on 
the higher bands, although I can detect a slight increase in noise when 
I point the beam that way.

Chris G3SJJ

col wrote:

>I vaguely remember a couple of years ago Clive GM3POI did an analysis of 
>AFS test propagation from GM and suggested that we would need a 3 el Yagi @ 
>180' to be competitive from up here!
>
>We thought the wire reflector did help, but that is subjective. I have 
>looked at wire yagis but don't think we can get them up high enough to make 
>them worth the effort. I do like the look of the 80m Moxon Cebik describes, 
>might be worth a try if you have a small garden.
>
>One of the best all round antennas we have used from GM6NX on 80m was a 
>full size quad loop fed 1/3 wavelength up one side, Chapter 10-6 ON4UN 
>Lowband DXing
>
>I think Geoff has got it right with an inverted L, easy to make with a fishing 
>pole for vert section and feed with a 2:1 unun, couple of elevated radials. 
>Works every time, takes minutes to put up.
>
>Talking of wideband noise, I wish I could cure my s9+++ constant noise at 
>this QTH from 1.8-30 MHz, noise dies down a bit above 21 MHz to s5. Have tried 
>to locate but to no avail, it's not in my house or immediate neihgbours. Turned 
>all electricity off to test.
>
>It has a spike every 50-100 khz wideband, I suspect it's a switched mode power 
>supply. The noise never dissapears, vhf frequencies clear.
>
>Is it worth asking Ofcom to have a look as it does interfere with AM 
>reception?
>
>Regards Colin
>
>
>----- Original Message ----- 
>From: "G3SJJ" <g3sjj at btinternet.com>
>To: "col" <col at v21mail.co.uk>
>Cc: <uk-contest at contesting.com>
>Sent: Monday, January 02, 2006 6:24 PM
>Subject: Re: [UK-CONTEST] What antenna for AFS?
>
>
>  
>
>>Be interesting to know if you actually noticed the 0.1dB gain!!  Seriously 
>>though, might be worth trying to calculate what take off angle is required 
>>to put maximum signal into say Berkshire from a location in central 
>>Scotland and then designing the 2 el array spacing for that.
>>
>>What I find interesting about that article, which John LZQ sent me a 
>>couple of years ago, is that for "good" ground my antenna at 55ft is very 
>>close to the optimum height for max NVIS gain, and for "very good" ground 
>>it is a few feet too high. I would class the heavy clay soil around here 
>>as "Good to Very Good." My AFS/80m Cums results over the last few years 
>>appear to verify this.
>>
>>We came to the conclusion that a parasitic reflector would not have any 
>>major effect, although I am tempted to try a 140ft wire apex about 15ft, 
>>sloping to about 5ft to mimic the slope characteristic of the driven 
>>element.
>>
>>Interestingly I notice on 160m that the dipole (which is the 80m dipole 
>>with 60ft extensions on each leg, jumper dissed for 80m) always performs 
>>similar to dipoles 15 to 20 higher at other locations. Again I have put 
>>this down to local ground conductivity and that it is uninterrupted for 
>>many wave lengths.
>>
>>Chris G3SJJ
>>
>>
>>col wrote:
>>
>>    
>>
>>>Hi Stewart HNY
>>>
>>>have a look at w4rnl's site lots of info on NVIS antennas for 80m
>>>http://www.cebik.com/wire/cb.html
>>>
>>>John mm0ccc and I used the 2 el wire yagi firing straight up approach at 
>>>gm6nx
>>>
>>>Colin GM0RLZ
>>>----- Original Message ----- 
>>>From: "Cooper, Stewart" <coopers at odl.co.uk>
>>>To: <uk-contest at contesting.com>
>>>Sent: Monday, January 02, 2006 3:31 PM
>>>Subject: [UK-CONTEST] What antenna for AFS?
>>>
>>>
>>>
>>>      
>>>
>>>>HNY contesters! AFS is only a few days away, and I wondered what antenna 
>>>>would be best? I have a vertical and a delta loop. Perhaps I ought to put 
>>>>up a dipole? Last year my crappy old dipole seemed to perform the best as 
>>>>I recall.
>>>>
>>>>Stewart
>>>>GM4AFF
>>>>
>>>>P.S. Perhaps the dipole ought to be in Oxfordshire, but that's another 
>>>>matter.
>>>>
>>>>
>>>>
>>>>----------------------------------------------------------------
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>>>>Offshore Design Ltd
>>>>
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