[UK-CONTEST] Vertical versus Inverted V - IOTA Findings
MM0BQI at blueyonder.co.uk
Thu Aug 7 15:56:00 EDT 2008
Thanks to all for your advice and comments. The advice and experiences were so varied I decided to set up a little experiment and try as many aerials as I could in the wide open spaces of the Summer Isles. This was in no way scientific but I am reporting real life findings for my particular location. All the aerials were on a headland ridge and no further than 100m from the sea on nearly three sides. The soil is thick peat and rock.
All aerials were fed with about 25m of Westflex to a six port auto antenna switch and then to the shack. I swapped the feeder cables to make sure there were no differences due to excess feeder loss. Rigs were an MP and IC7000 with similar readings on both rigs.
Full size vertical on a SpiderBeam 18m fishing pole. 66 feet of thick insulated wire loosely helically wound round the pole with the feed point a few feet off the ground.
My four tuned radials would not tune properly so I ended up with sixteen 20m radials laid on the ground.
This was the star performer and under no conditions was it bettered by the other two 80m aerials and was always a minimum of 2 S points ahead.
Inverted L, 66 feet of insulated wire on a 12 m fishing pole with the wire pointing to EU and about 4m off the ground at the end. eight 20m radials on the ground.
Good simple antenna which gave acceptable performance in all direction but two S points lower then the vertical
Low full sized dipole about 7m AGL. This was no use what so ever! I installed it looking for some NVIS benefits to work 'local' stations but it was like a dummy load and always four or five S points lower in all directions. It also did not have the desired effect of lowering EU noise and enhancing UK signals. Am I too far north to benefit from NVIS and low dipoles? Don't think I will bother with this next year!
Full size vertical on 12m SpiderBeam fishing pole. feed point about 2m AGL with two tuned quarter wave radials sloping down to about 1m AGL.
Again this outperformed the low 40m dipole by about four S points at all times.
Hustler 4BTV Ground mounted with eight 10m radials. Surprisingly only an S point or so down on the full sized vertical.
Low full sized dipole - not worth the effort!
Full sized vertical on the same pole as the 40m vertical, feedpoint 2m AGL and two tuned radials.
Horizontal dipole with feed point at 10m AGL
These two aerials performed well with each proving better signal strengths at certain times with no obvious pattern. Most of the time they were very similar with the maximum difference being about two S points on a few occasions. For performance versus ease of use I would go for the vertical everytime. The difference off the ends of the dipole were not as pronounced as I would have expected but enough to make me think about using the same antennas next year but with a rotator to gain maximum advantage.
Hustler BTV4 about three S points down at all times.
Inverted V with apex at 8m much lower than the dipole and vertical with no significant advantage
Full size 40m vertical which tuned okay with the rigs internal tuner. I am looking for an article I saw a few years back which had a loop of wire added to a 40m dipole to improve the match on 15m. I wondered if this would be true of the vertical? An okay performer.
Full size horizontal dipole at 10m was two S points up on the vertical and always the best performer
Hustler 4BTV down at least four S points on the dipole
Full size horizontal dipole at 10m always best by three S points
Hustler 4BTV worked but very much lower signals than the dipole
80m the full size vertical which can be put up by one person in under an hour is a must. Need to work on the radials again as in previous experiments elevated radials always out perfumed ground mounted ones.
40m again the full size vertical with elevated radials, cheap, quick, simple and can be multi-banded without loss of performance.
20m Either the diplole or the vertical. The vertical is easy and safe to put up, the rotational advantage of the dipole could possibly be an advantage.
15 and 10m the dipole every time.
The Hustler is a very good trapped antenna which is easy to use and gives four bands in a small package. However a fishing pole and several bits of wire will cost less than thirty pounds and outperform it significantly on all bands. Off the shelf or home brew it's your choice!
Photos are on GMDX and CDXC Yahoo groups and videos are on YouTube at http://uk.youtube.com/watch?v=nDS9ippAsaw
Jim, MM0BQI - MM0Q
----- Original Message -----
Sent: Tuesday, July 08, 2008 4:24 PM
Subject: Vertical versus Inverted V
I am making some wire antennas for IOTA this year and not sure what my best bet is for 20m. Last year I used a rotatable dipole and it worked very well but I will not be taking the big mast or rotator this time.
I can't decide whether to use a quarter wave vertical with the feedpoint at 10m and four radials or an inverted V with the apex at 10m. Would there be much difference between them? Is there a better option?
I have ploughed through the antenna books but can't find a direct comparison anywhere so would appreciate views or experiences.
I am also looking for 50m of 7 way cable suitable for my remote antenna switch, can someone please suggest a suitable source?
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