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Author Topic: Operating HF mobile from the beach  (Read 5891 times)
HS0ZIB
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Posts: 418




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« on: July 07, 2014, 06:34:10 PM »

I am lucky to live 5 minutes from beaches bordering the eastern edge of the Indian Ocean.

For HF mobile DXing, I drive down to the beach and park up within metres of the sea, (my qrz.com page has one photo of me actually parked in the sea...)

Using my screwdriver antenna and 100 watts, I can make good DX contacts worldwide, especially at greyline local dusk.

But is there anything that I can do to improve my reception?

I don't want to boost my tx power, (I am at the legal limit now and a stronger signal would enable DX stations to hear me better but not vice-versa)

I am thinking along the lines of using a 'Clearvoice' audio speaker/DSP to reduce the noise/QRN on the received signal.

For those of you with experience of operating from right next to the sea, would it help if I laid out some radials on the beach?  I could fabricate some radials bonded to my vehicle that could be quickly laid out after I park up.

Any other suggestions for mobile HF operation by the water's edge?

Thanks

Simon
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KD0SFY
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Posts: 297




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« Reply #1 on: July 07, 2014, 06:53:34 PM »

I am lucky to live 5 minutes from beaches bordering the eastern edge of the Indian Ocean.

For HF mobile DXing, I drive down to the beach and park up within metres of the sea, (my qrz.com page has one photo of me actually parked in the sea...)

Using my screwdriver antenna and 100 watts, I can make good DX contacts worldwide, especially at greyline local dusk.

But is there anything that I can do to improve my reception?

I don't want to boost my tx power, (I am at the legal limit now and a stronger signal would enable DX stations to hear me better but not vice-versa)

I am thinking along the lines of using a 'Clearvoice' audio speaker/DSP to reduce the noise/QRN on the received signal.

For those of you with experience of operating from right next to the sea, would it help if I laid out some radials on the beach?  I could fabricate some radials bonded to my vehicle that could be quickly laid out after I park up.

Any other suggestions for mobile HF operation by the water's edge?

Thanks

Simon

Well, radials shouldn't hurt.  But as long as you are using a screwdriver instead of a full sized antenna, you probably won't see dramatic improvements.  If you can find an RF preselector (ideally a motorized one or a manual one) you will probably see more improvements on your receive than can be gained thru DSP speakers
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K5LXP
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« Reply #2 on: July 07, 2014, 08:18:31 PM »


Serious beach operating:

http://www.k2kw.com/verticals/verticalinfo.htm


Mark K5LXP
Albuquerque, NM
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K0BG
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« Reply #3 on: July 08, 2014, 03:10:09 PM »

Well, if the vertical is attached to the vehicle (mobile antenna), it would take a whole lot of radials before you would notice any difference. A vertical installation like Mark alluded to, is a different story.
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K1DA
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Posts: 500




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« Reply #4 on: July 17, 2014, 08:23:57 AM »

Try a ground rod far driven  enough in to hit damp sand.  Simple to do and it may improve things.  If you can contact salt water, which is a far better conductor than soil,  radials are not going to be much of an improvement.
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NH7L
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« Reply #5 on: August 02, 2014, 09:50:57 PM »

Two things that seemed to improve shoreline parked mobile HF operation when I lived in Hawaii:

1. Parking as close as possible to the saltwater ... ideally, within 1/4 wavelength.

2. Parking on saltwater-saturated ground, which typically meant a parking lot (car park in UK/down under English) on man-made fill rather than a rocky shoreline.

Given surf action, etc, getting a vehicle that close to the sea may sound improbable, but it can be done ... look for a parking spot along a reef-protected shore, or in a harbor or marina, on a bridge, breakwater, pier or dock, etc. The good news is that you get more DX. The bad news is that you get more antenna maintenance problems from corrosion.
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K2FOX
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Posts: 109




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« Reply #6 on: August 07, 2014, 07:26:22 PM »

 I go fishing on the beach in OC New Jersey and while I'm out there I operate the HF bands (when the fish aren't biting). I use a variety of Hamsticks mounted to a stake pocket mount, which is grounded to the truck frame. I have a roll of wire that has a 6oz surf weight on one end, and one of those large copper alligator clips on the other. I throw that weight out into the water and clip the other end to the truck frame. It definitely makes a difference in lowering my receiver noise. I've never checked it with another operator as far as disconnecting it to see if there is a difference in my signal, but I'll take the quieter receiver any day.

Have fun and 73's,

Jay
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N5UD
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Posts: 800




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« Reply #7 on: August 08, 2014, 07:26:52 AM »

Simon, occasionally I do operate from the beach. I park on sand as near as I can near the water. Need to be that 1/4 wave distance from the salt water. Signals definitely come up. Some times significantly. I use a Clearspeech speaker for noise reduction. Usually just the first level of noise reduction. I also use an external speaker with more bass.

The wire in the water I have heard of, but never actually tried it.

73 Tony N5UD /M
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VK3YE
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Posts: 12




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« Reply #8 on: August 09, 2014, 10:55:31 PM »

Simon - not sure if it would improve reception but I'd be inclined to replace your antenna with a full sized quarter wave.  A wire up a 5m fishing pole will be suitable.

If there's housing along the beach it might be worth searching for a quieter spot with least noise.  Another possibility is a separate receive antenna, eg a magnetic loop.
Interference from local noise sources can be nulled out.

As a fellow beach dweller I do a lot of HF pedestrian mobile from near the water.  My preferred antenna is a backpack supported 5m vertical with a centre loading coil for 7 MHz.
This setup works on 7 - 50 MHz.  Especially on 14 MHz and below signals increase when there is good coupling between the ground connection and the water.  This can either
be a metal bar parallel to and over the water (eg a railing on a pier) or some metal in contact with the water.  Both seem to give similar results but so I can be walking I typically
have an aluminium ring around my ankle and walk through ankle to knee deep water when transmitting. 

More info and videos at: http://home.alphalink.com.au/~parkerp/gateway/pedmob.htm

73, Peter VK3YE
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HS0ZIB
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Posts: 418




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« Reply #9 on: August 10, 2014, 04:11:37 AM »

Peter, thanks for your reply. My preferred beach location is just a few minutes from my home QTH and is in a national park with no power lines.  As I leave the main road and proceed into the park, the power line RFI drops dramatically.

There is a location where the local fishermen beach their small boats and I can drive up to within metres of the sea water (no big waves unless it's stormy weather).
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ZENKI
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Posts: 934




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« Reply #10 on: August 21, 2014, 07:31:49 AM »

A 1ft square copper plate attached to a ground wire connected to the vehicle. The copper plate has to float on the waters surface and make contact with the  seawater.
Seawater has a skin depth, and there is very little point in putting anything in seawater that is deeper than 1 or 2 inches.   That would like burying your antenna below  a copper plate.

You have to be 1 wavelength or less from seawater to obtain maximum benefit from the fresnel brewster angle enhancement. Antenna efficiency  by using a full size whip always helps.

Every time that I have operated from near the seawater hearing was never a problem. I was wondering  why you receiving situation is handicapped that you deem it necessary to  take measures to improve reception?  It is getting hard to find a good seaside parking spot these days since waterfront is prime real estate everywhere in the world. The amount of interference can be staggering when you have small shops and apartments nearby The best location I have found was  in big shipping ports especially when there is no ships berthed. You right at the edge of the water and there is never buildings on these wharfs. The result is that you get less QRM on RX unlike the popular city beaches with lights and powerlines and many other noise sources.


I  had a chance to visit Ko-Chang Island  and had a "shortwave receiver with me. The amount of pirates on the  HF bands was amazing. The 40 meter band  was total mess. I dont know why YB stations dont stick to the ham  band plans. I could not hear any CW because of all the SSB chatter in the CW sub bands. Very disturbing what I was hearing  from Indonesia. Someone told me that these were hams and not pirates which made it even worst because the behavior was so bad.

You cant beat a saltwater location thats for sure especially with vertical antennas

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VK3YE
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Posts: 12




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« Reply #11 on: September 17, 2014, 05:52:06 AM »

A 1ft square copper plate attached to a ground wire connected to the vehicle. The copper plate has to float on the waters surface and make contact with the  seawater.
Seawater has a skin depth, and there is very little point in putting anything in seawater that is deeper than 1 or 2 inches.   That would like burying your antenna below  a copper plate.

You have to be 1 wavelength or less from seawater to obtain maximum benefit from the fresnel brewster angle enhancement. Antenna efficiency  by using a full size whip always helps.

Some good points.  Agree about being near seawater, though when using a vertical antenna a good ground may be more important.  Hence my tendency to wade in salt water when pedestrian mobile at the beach.

I'm not so convinced about the 1 to 2 inches depth being that critical.  I've done numerous tests (mainly on 40m) when in ankle to knee deep water.  There has never been a difference when in ankle deep water (ground contact ring 1 - 2 inches below the surface of the water) and knee deep (contact ring in a foot of water). The tuning position of my antenna coupler doesn't change either. But there's a huge immediate difference when I'm out on the sand with signals dropping by 3 or 4 S points (and often into the noise) even when the antenna coupler is readjusted.
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K0BG
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« Reply #12 on: September 17, 2014, 12:54:19 PM »

In reality, near field conductivity has nothing to do with far field signal strength. Yet, most people will argue otherwise. The main reason sea side operation is rewarding, is mainly because there are no buildings, trees, and other structures close by. Clear field of view in other words.

Lastly, dropping an attached copper plate into the sea water from the frame of your vehicle may make the operator warm and fuzzy, but is doesn't accomplish a single thing.
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