Topband: Antennas and saltwater

Wed Dec 28 09:07:25 EST 2022

Here is my TX antenna setup for Topband (and 80m) taking advantage of the Baltic Sea water. I have the Axtorp 18 meter tall linear loaded vertical from 160 and 80 meter. My QTH is on a tiny rock in the archipelago and the antenna is located on a bridge with water beneath it. Over the years I have been using lifted bent radials and also tried the FCP. These were good performers and connected well with the brackish archipelago water. But with one flaw, they were very sensitive for difference in sea level and general humidity. 

A few years ago I was inspired by N6LF Rudy’s paper on Ground Systems over Saltwater and decided to try something similar. Rudy’s paper made me better understand the skin depth and I concluded that I could use copper rods tied up with net buoys to place them just under the surface. I started with one rod in the water plus 6 radials on ground. I tuned the antenna for resonance on 1.850 MHz then I removed the ground rod from the water, the resonant frequency was lifted by 92 kHz. I wasn’t sure how much difference the brackish water would make, but it moved the needle enough to motivate more rods in the water. 

First season I had three rods, then I added another one so now I have four. First rod made about 20 Ohm difference (compared to the six short + two 1/4 radials on ground), second rod around 10, then 5 and the last one 2,5. Not sure it is worth the effort to add a fifth rod, but the antenna works well and I stopped worrying about optimisation of TX capabilities and have recently focused on preparing and renewing my RX antenna setup. I have attached a photo, not sure it makes it way through to the list, but if not its available on the link below.

There is a bit more info on my contest blog, http://blog.se0x.info/?p=3442.

73+HNY de Björn,
SM0MDG
SE0X

> On 20 Dec 2022, at 06:37, jh-mty at sbcglobal.net wrote:
> 
> On some of my wharf visits, I would attach a lug to the base of the hamsticks with a long piece of braided copper wire soldered to it with metal washer and other weights attached to the far end, thinking that I would increase the saltwater ground coupling effect.
> That really didn't pan out and was not much improvement.  However, twice some tourists came up and began hauling on my wire, thinking that a Dungeness crab might be on the other end (LOL).
> Thinking back, I should attached a dang chicken leg to that wire end and caught me some tasty crab!! 
>    On Monday, December 19, 2022 at 09:29:42 PM PST, jh-mty at sbcglobal.net <jh-mty at sbcglobal.net> wrote:  
> 
>  I am an avid /M op, including on 160, quite active on 30M and higher WARC bands.  I lived in Monterey, CA for around 10 years and visited monthly for several more after that.  One of the greatest attractions of the beautiful Monterey area was the Monterey Commercial Pier...a long, elevated pier with buildings and fishing boat dock improvements, along with a wonderful view.  
> None of the touristy advertisements for the "Fishermen's Wharf" attractions mentioned that the elevation pattern of a "loaded" mobile hamstick vertical antenna mounted high up on a metal van hatchback lid 18 feet over 20' deep salt water with downsloping, sandy bottom leading to near-field abyssopelagic depths would produce peak gain at 18 degrees or less elevation.  The coveted "Brewster angle." As Frank, W3LPL, observed in this thread:  "Radials cover a very small fraction of the very large reflection zone (Fresnel zone) that produces low angle radiation.  A vertical over a salt marsh or within about a wavelength of salt water will produce 6 dB or more of gain at low angles compared to a vertical with poorly conducting soil in its reflection zone."
> On that wharf, I worked maybe 100 rare countries on 40, 30, 20, and WARC bands competing with landlocked, high-power stations with major beams and low-band wire arrays.  Worked VQ9 and other Indian Ocean countries on the antipode, FR7, lots of southern African stations on 30M and 20M, and even some EU on 40M phone.  Heard most continents on 160M including EU, but couldn't work many countries on top band with my  low power 100W IC-706MIIG (got some Central America, Oceana, Alaska, east coast US and Canada, etc.).
> I took some friends on the ride to the wharf hearing very little over the land, but an entire unheard world opened up when driving over the ocean on the wharf, with signal strengths building on the wharf approach and peaking as the water depth underneath increased.  I do miss that wharf and will return QRV when I visit the Peninsula.
> John W6UQZ  
>  
>     
>     
>     On Monday, December 19, 2022 at 04:18:48 PM PST, kq2m at kq2m.com <kq2m at kq2m.com> wrote:  
> 
> 
> In 1990 I was visiting Antigua (V2) for 2 weeks.  I had a Butternut HF6V 
> with 160 coil and I mounted it on a 3' piece of copper pipe in a 
> secluded part of the beach near the rocks about 2' above the waterline, 
> with about 30 short radials attached to it.
> 
> At some point in the middle of the night, I noticed that I began to hear 
> what sounded like "swishing" sounds, not loud but persistent, for a few 
> hours and then it stopped.  The swr and resonant freq. on 80 and 160 
> changed slightly but not enough to matter.  Curious, I went out just at 
> dawn and noticed that the radials were all in a clump and riding on the 
> water like the tentacles of a Man 'O war.
> 
> During the night the tide came up about 3'vertically and the bottom of 
> the vertical was immersed in the water along with the radials which were 
> then washed into a mess.  That apparently was the "swishing" sound I had 
> heard.  LOL!  The performance was excellent the sounds were cool, the 
> only time that I have ever heard them.
> 
> The salt water effect was so remarkable that I could hear a 3W station 
> round the clock on 15M for several days - but he couldn't hear me except 
> in the daytime.  The EU stations were absurdly loud on 80 cw and I heard 
> several levels of Russian stations that I never heard before or since 
> from W1.
> 
> I had a similar experience with a 14AVT vertical stuck in the oil sands 
> of Aruba in January 1986 when I was the first to activate P4.  The 
> vertical was not as good and it was planted 100' back from the water, 
> but the water table was high and water was in the beach sand only 1' 
> down and the copper pipe was stuck into that (there was also oil just 
> underneath the surface in the water - I'm not sure if that helped or 
> not.)
> 
> Even though it was the bottom of the sunspot cycle, the LP JA signals on 
> 40 at Sunset were INCREDIBLE!,  often S9 - S9 + 20 and the pileup of 
> JA's literally drowned out the pileup of Europeans for about an hour.  
> LOL!
> 
> 73
> 
> Bob, KQ2M
> 
> 
> On 2022-12-19 17:18, W7TMT - Patrick wrote:
>> I run an 80' high vertical on 160M from my sailboat in the saltwater
>> of Puget Sound/Salish Sea near Seattle. After experimenting with a
>> number of different saltwater connections I've simplified it to a
>> single piece of 1/2" dia. copper pipe 10' long and tapped in the
>> middle. I hang it horizontally over the side just below the water
>> surface. Works great.
>> 
>> I recently ran across a post by SE0X running  an 160/80M vertical on a
>> floating dock who uses two lengths of suspended pipe. His RBN testing
>> suggested that adding a second one made a difference. Details here:
>> http://blog.se0x.info/?p=3442#more-3442
>> 
>> 73
>> Patrick, W7TMT
>> 
>> -----Original Message-----
>> From: Topband <topband-bounces+w7tmt=outlook.com at contesting.com> On
>> Behalf Of GEORGE WALLNER
>> Sent: Monday, December 19, 2022 14:19
>> To: Radio KH6O <radio.kh6o at gmail.com>; topband at contesting.com
>> Subject: Re: Topband: Antennas and saltwater
>> 
>> If the antenna stands in the salt-water or if you have a short, low
>> impedance connection to the water, you don't need radials.
>> During the VK9WWI DXpedition to Willis Islets, we installed a vertical
>> on a sand spit that was covered by water most of the time. We had 12
>> radials of various lengths a couple of feet above the water. The
>> antenna was fed via an antenna coupler (tuner) mounted on its base.
>> Every night during high tide the waves knocked down and washed the
>> radials into a tangled mess. For the first three days we restored the
>> radials every morning. But we never noticed any difference between
>> when the radials were up or when they were in a heap at the base of
>> the antenna. After three days we got rid of the radials. The antenna
>> had a heavy metal base which was always in contact with the water.
>> Ever since then, on various DXpeditions (TX3A, VK9GMW, PT0S, etc.), we
>> always put the antennas into the water (or the very edge of it where
>> we drive into the sand a grounding stake) and never bothered with
>> radials.
>> 
>> Years ago I had a vertical at C6AGU standing in the water. During one
>> night a storm knocked it down. I reinstalled it up the beach about 75
>> feet from the high tide line. I added 16 radials about 3 feet above
>> the sand, I was told that my 160 m signal was down 10 dB. I put the
>> antenna back in the water and had a good signal again. Whether the
>> difference was really 10 dB, I don't know. But it was substantial.
>> (That was before RBN.) 73, George, AA7JV/C6AGU
>> 
>> On Mon, 19 Dec 2022 09:23:54 -0800 Radio KH6O  wrote:
>>>> Ideal is if you can run some RG58 out to the beach and plunk it next
>>>> to thewater.  Also use 4 radials there.Enjoy.Ed  N1UR
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