RE: Low Antenna on Mountain Top
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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: [hidden email] 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: RE: Low Antenna on Mountain Top
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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: [hidden email] 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: RE: Low Antenna on Mountain Top
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In reply to this post by Bill W4ZV
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: [hidden email] 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: RE: Low Antenna on Mountain Top
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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: RE: Low Antenna on Mountain Top
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In reply to this post by Bill W4ZV
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: [hidden email] 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: RE: Low Antenna on Mountain Top
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In reply to this post by Ron D'Eau Claire-2
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!! <g> 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 [hidden email] ----- Original Message ----- From: "Ron D'Eau Claire" <[hidden email]> To: <[hidden email]> 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: [hidden email] 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: [hidden email] 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 |
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In reply to this post by Bill W4ZV
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: [hidden email] 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: RE: Low Antenna on Mountain Top
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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: [hidden email] 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 |
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In reply to this post by Bill W4ZV
when it come to RP3 on the main board instead of using the green hookup
wire, is it ok to use cut leads? they are easier to work with _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Dave wrote:
when it come to RP3 on the main board instead of using the green hookup wire, is it ok to use cut leads? they are easier to work with Dave: Yes that is fine to use. I usually use the hook up wire and install them one at a time before removing the insulation. I just remove a 1/4" of insulation and make a 90 degree bend and solder it in then trim it to the 1/2 length and pull the insulation off with my thumb and finger and then do the next one until all 8 are done. This is an easy way to do it and you still have something to hold on to if you don't cut the wires into eight small pieces. There is nothing sacred about the length either. You just need enough to get it soldered to the RF Board. 73 Jim Younce K4ZM K2 SN: 18 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by David Morley W8IXY
I routinely use cut off component leads on the thermistor board - simply
because they are laying there in the bench. If you stick them into a black foam block, you can get 3 or 4 aligned at one time before soldering (it is just faster that way. Another hint is to cut the 8 leads at an angle (so one end is full length and the others are progressively shorter) and it is easier to insert the leads into the holes. 73, Don W3FPR > -----Original Message----- > > when it come to RP3 on the main board instead of using the green hookup > wire, is it ok to use cut leads? they are easier to work with > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.338 / Virus Database: 267.10.8/71 - Release Date: 8/12/2005 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by David Morley W8IXY
it works for me. so far I am in the process of soldering the billion or so
caps in the main board and going on my 3rd tube of solder :) all of the preliminary test are good I have issues with my DVM measuring to 1M ohm. but when the first assembly of the unit all resistance checks perfect _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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On Aug 15, 2005, at 2:36 AM, David Morley W8IXY wrote: > it works for me. so far I am in the process of soldering the > billion or so > caps in the main board and going on my 3rd tube of solder :) Tube of solder? What kind of solder are you using? I guess I've never looked at anything but rolls. A one pound roll usually lasts me five or ten years... - Jack Brindle, W6FB ------------------------------------------------------------------------ --------------------- _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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How about a roll of 1 lb. solder lasting 40 years?
If you do not use much solder on joints, it will last that long thru a dozen kits and projects. Stuart K5KVH _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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