Re: [Elecraft] RE: Low Antenna on Mountain Top
AC7AC wrote: a decent comparison with a horizontal 1/2 wave radiator can only be made with a vertical 1/2 wave radiator The Par EF-20/40 ***IS*** a vertical 1/2 wave. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] RE: Low Antenna on Mountain Top
The Par EF-20/40 ***IS*** a vertical 1/2 wave. 73, Bill W4ZV -- Then it should be a good basis for comparison, at least on 20 meters. Even the PAR EF-20/40 may not be comparable on 40 since it's physically only a 1/4 wave long on 40 meters. Being electrically 1/2 wave long and physically 1/2 wave long are two different things in terms of impedances and efficiency. Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] RE: Low Antenna on Mountain Top
Hello, I have plenty of experience with antennas on mountain tops. I have tried dipoles on mountain tops with good results. I usually tie off the center of the dipole at around 15' to 20'. The mountain height does the rest. I once had a very interesting experience with the issue of HF and antenna height. We were in a large motor home operating the PA OSO Party on 20m. The band sounded poor, but as we climbed the mountain, I started to work more and more people. By the time we reached the summit , I had a pileup! As we descended, the Qs stated to drop off. At the bottom of the mountain we all were screaming to the driver to go back up!! Recently I compared a 40m dipole fed with 300 ohm ladder line up 20 feet to a ground-mounted vertical on a 100 foot cliff at Turkey Point Lighthouse, MD. The vertical beat the dipole by around two S-Units. This wasn't DX either just US contacts. I tried both on 40m and 20m. In the past, a group of us always operated the PA QSO Party at a Boy Scout Camp in PA. We usually finished near the top or won the MS Category. We used a A3S Tribander up around 20' and two dipoles. One dipole was setup at a height of 10'. This was our cloud warmer for the close in contacts. The other dipole was our (40m beam). We joked about this antenna because most ops would say, what type beam are you using? In reality it was a 260' dipole fed with 400 ohm ladder line up around 50'. So you see, you have to setup a dipole for the area you want to cover. I once meet Rich Arland, K7SZ, on top of the AT here in PA. He spent hours setting up his dipole in the trees. I showed up and tied the center of my AT Dipole off at around 15'. I then just threw the ends over some brush at a height of around 6' off the ground. Keep the ends at least 6' off the ground! Rich couldn't believe how well this setup worked and how little effort was spent to put it up. He operated on 40m with my antenna and had a pileup for most of the afternoon! Again erect the dipole for whom you want to work. We worked the close-in stuff that day. I once hiked to the summit of Mt. Washington, but that's another story...! If anyone is interested in what an AT Dipole looks like, look in Rich Arland, K7SZ's book entitled, Low Power Communication: The Art and Science of QRP. Look in chapter six. If anyone wants to view an AT Dipole, go to http://www.wa3wsj.com 72, Ed, WA3WSJ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] RE: Low Antenna on Mountain Top
WA3WSJ: Recently I compared a 40m dipole fed with 300 ohm ladder line up 20 feet to a ground-mounted vertical on a 100 foot cliff at Turkey Point Lighthouse, MD. The vertical beat the dipole by around two S-Units. Interesting. I had just the opposite experience in the recent Flight of the Bumblebees test. I was using an 88' doublet with 40' apex and 25' ends fed with 300 ohm line to an Emtech ZM-2 versus a Par End-Fed 20/40 Half Wave Vertical. The doublet was almost always better than the vertical although there were a few times when the vertical was clearly better. This was on a mountain top about 300' above average surrounding terrain. I did a lot of comparing signals on both 20m and 40m during the test. Over flat terrain, a dipole up ~1/2 wavelength has 7-8 dB gain over a vertical at typical 30 degree takeoff angles. On a mountain top, the TOA goes down because the effective height is raised. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RE: Low Antenna on Mountain Top
In re the comments on Marconi antenna and ground effects, Isn't the Par end-fed a vertically polrized Hertz antenna, not a Marconi? Leigh / WA5ZNU On Fri, 12 Aug 2005 9:29 am, Bill Tippett wrote: Interesting. I had just the opposite experience in the recent Flight of the Bumblebees test. I was using an 88' doublet with 40' apex and 25' ends fed with 300 ohm line to an Emtech ZM-2 versus a Par End-Fed 20/40 Half Wave Vertical. The doublet was almost always better than the vertical although there were a few times when the vertical was clearly better ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RE: Low Antenna on Mountain Top
Ed, WA3WSJ wrote: Recently I compared a 40m dipole fed with 300 ohm ladder line up 20 feet to a ground-mounted vertical on a 100 foot cliff at Turkey Point Lighthouse, MD. The vertical beat the dipole by around two S-Units. Bill, W4ZV wrote: Interesting. I had just the opposite experience in the recent Flight of the Bumblebees test. I was using an 88' doublet with 40' apex and 25' ends fed with 300 ohm line to an Emtech ZM-2 versus a Par End-Fed 20/40 Half Wave Vertical. The doublet was almost always better than the vertical although there were a few times when the vertical was clearly better. This was on a mountain top about 300' above average surrounding terrain. I did a lot of comparing signals on both 20m and 40m during the test. - It is my understanding that the vertical pattern of a half wave vertical splits up into several narrow lobes when it is installed on top of a 'narrow' mountain top, with the dominant lobe being at the lowest TOA. Because of the nulls, the incoming signal has to be arriving at just the right angle plus and minus not very much for the vertical to be seen as better than a doublet at the same location. The doublet has the broad vertical lobe.This might explain Bill's experience. When the vertical is placed on a cliff edge, I would suspect that some null filling could take place, especially if the vertical is a ground mounted quarter wave. However I think that it would be very difficult to model such a situation with any accuracy - what is the pattern of ground currents for starters? This antenna no doubt benefits from zero obstructions and little ground loss over the cliff's edge. If propagation is via the E layer, the angles of arrival are low - about 14 degrees for a 500 mile hop and 4 degrees for a 1000 mile hop. So a 'DX' antenna is also a good antenna for short haul - if the E layer is involved. 73, Geoff GM4ESD ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] RE: Low Antenna on Mountain Top
The definition of Marconi antenna is that it is quarter wave. A half wave antenna is called a Hertz antenna in some older literature. Stuart K5KVH
