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
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
Hi Ron, I have played and fooled around with verticals for many years and as my friend K3RA, Rol Anders says... "A vertical radiates poorly in all directions!!" LOL! At present I do have a vertical dipole... Gap Challenger Vertical and it does perform acceptably! But, I also have a dipole up about 35 feet up. I think it was the HyGain 14AVQ or the 18AVQ up on the house roof with radials/guide wires for all bands and had it all grounded to a 1/2 pipe that ran down along outside of the water well for 200 feet. Now maybe that setup was not suppose to work but it worked like gang busters. At sundown when the bands started going out the beams lost it but I stayed right in there with the DX! That was many years ago when I lived in Tenn. at the Sequachie Valley. Our Parsonage was up on a hill and I was in the clear. That was in the mid 60s. I have tried some unique grounding devices through the years and they worked out pretty good. Mercy, I even tried the old Gotham vertical from Miami Beach... The 23 foot vertical I was using a Gonset G66B Receiver and a Elmac AF 67 Transmitter in Cedartown, Georgia. I was not sure I was getting RF to the vertical so I put the transmitter in Key Down and went outside and touched the vertical with the palm of my hand It took weeks for the burn to heal on my hand. I was a novice then and knew very little. My radio teacher who was preparing me for the General class license took pity on me and built me a 75/40 dipole with one coax. I had the 40 running east and west and the 75 running north and south. Come to think of it It must have been a NVIS antenna!! I had a Gap Eagle Vertical back in 1993 and it performed well with the ground plane it uses. Had it up a few feet above the roof. I have some information I want to share about NVIS antennas but will leave that for another email. Paul Paul Gates K1 #0231 KX1 #1186 XG1 [EMAIL PROTECTED] - Original Message - From: "Ron D'Eau Claire" <[EMAIL PROTECTED]> To: Sent: Friday, August 12, 2005 12:44 PM Subject: RE: [Elecraft] RE: Low Antenna on Mountain Top Bill, W4ZV wrote: 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. --- When people say "vertical", they usually mean a 1/4 wavelength (or less) radiator. Such verticals are HUGELY dependent upon the ground return for their efficiency. There's been an on-going argument about that since Marconi hisself was tinkering with them, but that standard for comparison is that a 1/4 wave radiator should have something on the order of 50 to 100 0.2 wave radials if it's going to be comparable of a 1/2 wave radiator. That's not to say an vertical is always inefficient, but that one can't really assess how efficient it is when using other ground systems and locations. The only exception to that is a vertical over salt water, as in at sea on a ship. Short of such a massive ground system, a decent comparison with a horizontal 1/2 wave radiator can only be made with a vertical 1/2 wave radiator (or at least with radiators of the same physical length if both are less than 1/2 wave). Even then there will be huge differences based on the propagation involved, although on HF it's far less than VHF and above. On HF, reflection/refraction of the wave in the ionosphere pretty well rotates and mixes the polarization. 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 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
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
Bill, W4ZV wrote: 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. --- When people say "vertical", they usually mean a 1/4 wavelength (or less) radiator. Such verticals are HUGELY dependent upon the ground return for their efficiency. There's been an on-going argument about that since Marconi hisself was tinkering with them, but that standard for comparison is that a 1/4 wave radiator should have something on the order of 50 to 100 0.2 wave radials if it's going to be comparable of a 1/2 wave radiator. That's not to say an vertical is always inefficient, but that one can't really assess how efficient it is when using other ground systems and locations. The only exception to that is a vertical over salt water, as in at sea on a ship. Short of such a massive ground system, a decent comparison with a horizontal 1/2 wave radiator can only be made with a vertical 1/2 wave radiator (or at least with radiators of the same physical length if both are less than 1/2 wave). Even then there will be huge differences based on the propagation involved, although on HF it's far less than VHF and above. On HF, reflection/refraction of the wave in the ionosphere pretty well rotates and mixes the polarization. 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
