View Full Version : 40/80 meter V-Beam plans?
08-12-2008, 01:45 PM
I would like to build a V-beam for 40/75/80 meters. If anyone has any suggestions on a fairly simple to construct V-beam that work well on 75/80 Meters as well as 40 meters I would appecitated. I have a lot about 150 ft by about 150 ft and several trees about 30 feet tall on the south and west property lines. I also have a 25 ft mast about 20 from the east property line. Not much else to work with as far as antenna supports. Anyone have any Ideas? Send email to firstname.lastname@example.org
08-12-2008, 02:51 PM
Are you confusing "V beam" with "inverted V"?
A true "V beam" has legs several wavelengths long, and there's no chance an 80m version would fit in your available space.
08-12-2008, 11:56 PM
No, I'm looking to build a wire V-Beam not an inverted V. You're right...optimized for 80 it would be too large. I'm hoping that someone has built a design that would fit on my lot and work well for 40 m and possibly get it to load up and work 80 (even at a compromise)?
I couple of years ago I was working off a V-Beam in VQ9 land (VQ9J) that was about 273 feet each leg (i think) and fed with homebrewed 600 ohm ladderline. It really worked out quite well. I was hoping to build something a bit smaller that would work 40m and IF i was able to get 75 and 80 to work that would be bonus.
It might be wishful thinking...anyone have any ideas?
08-13-2008, 07:54 AM
You could try a Vee Beam with a 90 degree included angle by putting one 150ft leg along your Western border and the other 150ft leg along the Southern border where you have the trees for support.
EZNEC shows it would provide some useful gain over a dipole along the NE/SW axis as follows:
On the higher bands the gain reduces because the 90 degree angle is too big.
On 80m the pattern becomes almost omnidirectional and is therefore a bit down on a dipole: -0.9dBd, but still very usable.
Of course you would need to feed at the SW corner using open wire line, and NE/SW might not be your preferred direction.
08-14-2008, 03:17 PM
Thanks for the reply. I was looking at that same configuration and was wondering how well it would work. North and N.E. is direction I am most interested in so this would be ok.
I am not really interested in using it for the higher bands so the fact that it wont work well there is ok too.
When you ran this on EZNEC, at what elevations did you show the feedpoint and ends mounted? What type of open line would be best? Does the wire size used for the antenna come into play at all? I have several 500 ft rolls of #12 insulated THNN solid and stranded house wire available.
I have also thought about trying to run an inverted V but thought that with only being able to get the apex of the inverted V up to 25 or 30 feet, I couldnt get the right angle for the legs before they hit the ground. How critical is the angle of the V and how high off the ground should the ends be? I know that this would not be very good for DX work but I am mostly interested in 100 to 2000 miles for local rag chewing on the low bands.
08-14-2008, 03:43 PM
I assumed you could get both wires up to 30ft, and that the feedpoint was between the legs in the South West Corner.
The size of the antenna wire is not at all critical.
Open-wire line, or 400 Ohm "window", would be fine for the feeder.
On the low frequency bands, at these sorts of heights, most of the power will be radiated at high take-off angles, but that's not a problem if you're looking for local/medium distance contacts.
An inverted V with the centre at 25ft/30ft will also get you plenty of local/medium distance contacts on 80m/40m. Don't worry too much about the included angle; it only becomes an issue if it falls below about 90 degrees, which it wont with your support heights.
I think it was Doug DeMaw who used to talk about his "special antenna". It had a "special length" - the distance between two convenient supports; and it had a "special length" of open wire feeder - the distance from the centre of the antenna to the shack:)
It's an over-simplification, but there's a deal of common sense in it. Of course you need a good ATU to go at the shack end of the feeder.
08-14-2008, 04:45 PM
I can probably get all supports at 30ft using a mast for one of them (nw corner).
Do you have access to google earth? If so, you can get a birds eye view of my lot by entering the following coordinates:
33 24' 09.69"N 110 49' 15.00"W
This will center you on the metal roof of my home. You will see the trees on west and south. The east is bordered by a brick wall and N & S. is bordered by a metal chainlink fence. My driveway is on the West NW side.
The Neighbor on the north may let me use one is his trees on the west end of his lot and South east corner. He's thinking it over. If so, that will give me some additional length if needed.
08-15-2008, 02:20 AM
While he is not looking for an inverted Vee for 40M, 3 element...
Please see other thread for my request for plans.
08-15-2008, 09:36 PM
I am working on this. 3 element, 500ft/leg, 40ft high at feed point, over an arroyo about 50 deep, 0 feet elevation at far end. 600 OHM feed line.
Relays at the feed point for switching.
Im doing this because my mentor in the late 50's had a V beam and it was magic. I said someday and that someday is here,now that I have the space.
08-15-2008, 09:43 PM
sounds great! 3 element? I'm trying to picture that as a v-beam...how does it work? I wish i had room to run 500ft. Do you have any pictures? I'd love to see it. I was just in your area too the other day. I work for Freeport McMoRan Miami and get back and forth to Tyrone and Chino mines quite often.
At my last QTH I had a vee-beam with three wires each about 270 feet long. The center wire was connected to one side of the ladder line feeder. A vacuum relay mounted at the top of the mast switched the other side of the ladder line between the other two wires to give instant change of direction. Best antenna I ever had...
08-27-2008, 05:59 PM
that sounds great! What type of vaccum relay did you use? Was it tough to set up? I'd like to try that using a design from W5GI website for the D3+ cut for 40M (103ft each leg) and fed with 450 ohm window line. I wonder how that would a model of that would look with the feed point at 35 feet and ends sloping to 6 ft from ground level and about 80 to 90 deg angle of separation between the wires? I need to buy a modeling program:-)
Jesse, It was an SPDT vacuum relay from Surplus Sales of Nebraska - nothing very special, whatever they had which was on sale at the time with a few amps / few kV rating. The relay normally connected the legs of the antenna which gave a NE/SW pattern, but switched to a NW/NE direction when the relay was energized.