vertical antennas

<< < (4/22) > >>

ve6pg:
..ok john...i had a cushcraft r-7 yrs ago..it had some kind of matching box near the base...40-10, but it sucked...had to guy it with poly rope as well...i was very disappointed with it...as i understand, you werk nights, or operate in the wee hours on the morning...i'm likely going on a 3-11pm shift (eastern time) in the next month....what time/where do you operate mostly?..

..tim..

..sk..

K1JJ:
Verticals are cool antennas to look at. Must be the old AM broadcash influence in us... ;)

Yes, as we all know, the ground plane, whether it be in the form of a car, ground radials or elevated radials is the key to vertical performance.  I suppose we could say that otherwise, a vertical is a vertical is a vertical. The difference being the loss in traps or of a severely shortened vertical. Though, W2FMT? showed us that shorties on 40M with big capacitance hats did quite well for efficiency.

Many of the guys (including the previous posts) report outstanding results on 40M and higher with verticals.  160M and 75M DXing works well too. Though, the anomaly appears to be when using a vertical for "local" AM work on 75M. Out to maybe ~300 miles, in general, I've never seen a vertical stronger than a dipole. This 300 mile range on 75M is of utmost importance to AMers, at least on the east coast. The high angle radiation can be down as much as 20db compared to a dipole.

Farther away, W9AD has proven how well verticals work on 75M using his phased array of Hygain? towers.

What I'd really like to see is someone try a 4-square of verticals, even 1/8 wave whips, on the higher bands, put out in a clear field away from everything. There are a few phasing boxes available (Comtech and DX Engr?) that are plug and play. The ability to see f-b, forward gain and directional changes with those low angles when using a good ground plane would be quite versatile. I still think a high Yagi would be hard to beat, but a 4-square could be installed with much less cost and effort, depending on the ground system used.

I agree that the Earth soil plays an important part into how elaborate the radial system needs to be. The elevated radial debate has been interesting over the years.

Chris, AJ1G, was talking in another thread about yesterday driving his car mobile out on Stonington Point, CT (next to the ocean) and using 5 watts  20M CW to work Europeans easily. It wud be an interesting experiment to see the difference when he drove inland 10 miles and tried the same thing.

T

k4kyv:
What is the alleged magic about the 43' vertical on 160? ???  I hear a lot of people, even those with plenty of space to erect something taller, report that's what they are using. Some operate with a good radial system and some without.  Obviously, performance will be much improved with the good ground system, but so would increasing the height to at least 1/8λ, approximately  65'.  Even with top loading and a good radial system, as the vertical length is decreased below 1/8λ, radiation efficiency drops off rapidly.

43' on 160 would be equivalent to 10'9" on 40m, barely more than an 8' mobile whip.

KX5JT:
"i'm likely going on a 3-11pm shift (eastern time) in the next month....what time/where do you operate mostly?."

Tim, It isn't easy finding AM activity during dark hours in Summer.   75m (no antenna on 160) noise floor is 20 to 30 over S9 where most AM signals are... (except maybe Don KYV or Brandon IIA) into my location.  Makes it difficult copy.  On 40 I do play on 7290 and call CQ a lot to no avail between midnight and dawn.  Sometimes on 7.160 but there are a lot of VK's and ZL's around there on sideband, so I often don't bother firing up AM.  

The way my job works is I get 3 nights off in a row so I am occasionally up in the early afternoons, but not too often.  When I am I could be anywhere between 40 and 6 meters on the usual AM frequencies for each band.  

The best success I've had running AM in the early mornings (dark hours) during static season is with scheds.  Paul VJB and I hooked up one morning, that was fun.  

"What is the alleged magic about the 43' vertical on 160? "

From http://www.hamradio.me/antennas/answer-to-everything-43-feet-antenna.html

The peak radiation angles and relative antenna gain for each bands are:

    ~ 5 dBi @ 57° for 10 meters – impressive, but high angle
    ~ 4 dbi @ 37° for 15 meters
    ~ 1 dBi @ 16° for 20 meters – nice low angle
    ~ 0 dBi @ 25° for 40 meters
    ~ -2 dBi @ 29° for 80 meters – this is quite functional
    ~ -8 dBi @ 23° for 160 meters – lossy, but it does work

Several things are apparent:

    The antenna has “better than nothing at all” performance on 160 meters and is certainly interesting for this difficult band.....................

I think the stats there and that last statement says it all.  It will load up and put out a signal on 160 but it is certainly a compromise there.   Don, the fact that you actually hear people using them proves it does do this, but pretty poorly.  My elevated ground plane (26 ft radiator) actually loads on 80 m and puts out a signal a bit poorer than my low inv vee.  If I had no 80 m antenna, I could use it and make contacts.  Maybe come winter, It will do better for real long distances, but I doubt it.  I'll do A/B comparisons then.

K1JJ:
Interesting stats, John - tnx for posting them!

What stands out is the "gain" on 10-15M is in the higher angles. 20M is perfect at 16 degrees however. Ever hear someone say, "Boy, I sure would like to fly a 400' high balloon wire as a vertical on 75M."   Your stats are a good example showing how the pattern gets moved into the higher angles just like a 160M Zepp acts on 20M... the desirable ½ wave pattern goes to heck.

The optimum angle on 20M for east coast to Europe is around 15-20  degrees take-off or so. On 15M it's about 10 degrees and on 10M about 5-7 degrees. This all varies with sunspots and conditions, of course, but studies have shown on average, a Yagi stack designed for these angles works well overall.

So, there is a reason to use a 1/4 wave or 1/2 wave long vertical on the band of interest. That's when the angle is lowest  - and also the IR efficiency is higher compared to a shortie version.

Another thang to consider is, "Can my location SUPPORT" a low angle of take-off?"   If you do the geometry, to support a 15 degree vector angle coming off an antenna, it takes quite a distance on the lower bands. On the higher bands, it still means the area around the antenna must be clear of major obstructions like houses, power lines, etc to be optimum. If the lobe needs to go thru a close-by house, the plumbing, wiring, etc may make it down many db compared to the higher angle lobes that clear the house.

The word, "optimum" is the key. Installations will still work, but not as well when radiation has to propagate thru structures to cover the lower angles. RFI is another symptom of low angles in neighborhoods.

Also, especially for horizontal DXing antennas, can the location’s EARTH soil support the lowest angles 1000’s of feet away?  Radials will not help these very low angles when they attempt to reflect off the ground and reinforce the main lobe.

Verticals are very demanding systems and jealously guard their territory. The best installation is to mount them out in a clear field with nothing for a mile around. But few of us can pull this off.  Here, I not only have tower obstructions, but my Earth soil is rocky and poor. High horizontals are all I can work with… sigh.  I would love to try a 4-square  or even 8-square on  40M and 10M, but the results on the other bands was poor.

The exception was a 3-vertical phased system I built for 160M using about 15,000’ of radials. That vertical system took out a dipole at 190’ into Europe by 10db. Verticals indeed work well on 160M if they have big radial fields to work with. Plus the optimum angle on 160M for Europe is MUCH higher, like maybe 25-30 degree or higher.  BUT, the wavelength distance is longer, so we still need a minimum of obstructions to clear even a 30 degree takeoff angle.

No free lunches or everyone would be doing it already…  ;D

T

Navigation

[0] Message Index

[#] Next page

[*] Previous page