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Old 06-08-2012, 01:02 AM   #1
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Hi Folks,
I have a ICOM 710 SSB...I just got an antenna tuner SEA 1216c I plan to connect it to the 710. As I understand it, this (and all ) tuners connects to a long wire - can be the back stay, etc., to the back of the insulated connector on the SEA 1216c. I was planning to run a coax cable from backstay to the antenna tuner..so far so good? Should I NOT connect the ground shield to the R59 connector?

If I decided to get a 23 foot whip antenna, do these come with a ground/shield connection plus the "hot" wire with the coax? I 'm confused about using an antenna without a ground, like in a dipole type antenna, since these tuners have no connection to the antanne ground/shieled. Speaking of the hot connection, should I just solder on a ring type connector?

Thanks in advance,
John
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Old 06-08-2012, 01:59 AM   #2
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Put one insulator on the top of your antenna as long as the backstay isn't bonded. If it is use two insulators. The antenna can't go to ground and to air simultaneously. Connect the tuner to the antenna with a piece of 10 ga. wire. The antenna starts as the signal leaves the tuner. Ground the tuner to the keel with 4" copper strip and you should be good to go.

Jim
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Old 06-08-2012, 11:20 AM   #3
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Okay Jim I got it...
Thanks John
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Old 06-09-2012, 11:13 PM   #4
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I'm looking for 1612C SEA (Datamarine) HF Antenna Tunner - Installation and Maintenance Manual. Not the 2 page data sheet...any ideas?

John
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Old 06-09-2012, 11:13 PM   #5
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I did try here but no luck...
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Old 06-16-2012, 06:45 PM   #6
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So sorry we didn't have anyone who could help you here. One of our previous mods, Richard, aka MMNETSEA was excellent with these sorts of radio-related questions. Sadly, he passed away last fall. We really miss his knowledgeable input here.

I'm ever hopeful that one of our members with a strong background in radios will come up with help for all. So far, no such member ;(

Fair winds,
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Old 06-16-2012, 10:24 PM   #7
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Quote:
Originally Posted by JohnPNorth View Post
I'm looking for 1612C SEA (Datamarine) HF Antenna Tunner - Installation and Maintenance Manual. Not the 2 page data sheet...any ideas?

John
Here's a list of dealers, maybe one of them can photocopy it for you:

SEA COM Corp. Dealer Selection

Rob
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Old 06-17-2012, 04:12 AM   #8
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John

my suggestion is to get an antenna book and read that, rather than rely on some (biased) mfr info. After all, they are in it for the $'s.

To put 5 lbs of poop into a nutshell or blivet, here are some basic points to consider:

Antenna tuners only match a given nominal output impedance to the antenna. Your IC 710 or similar has a typical 52 ohm output requirement, so into a 52 ohm pure resistor ( non-inductive) it can pour in (via a 52 coax ) all the signal with no reflected power. ( i.e. 1:1 SWR ) That resistor is your antenna and I'll come back to that later.

Chances are your antenna is not 52 ohm resistive, which would be the ideal case. It could show a reactive or a capacitive resistance to your TX, from perhaps under 10 ohms to 90 or more ohms. So, the tuner will ( well, most at least ) match into that load but at the cost of LOSSES, due to heat generated. Worse are the losses you don't see, viz. RF getting absorbed by boat conductors like wiring, other metals, pulpits and so on.

Typically, owners are happy with tuners because their set sees a 1:1 SWR, so many mfrs even use built-in tuners as it sells sets.

Now read carefully: the catch is that to be effective, the tuning needs to occur right AT the antenna. The output of the tuner cannot go into a shielded coax cable, rather, IT IS THE ANTENNA that comes out of the tuner. So, if this runs along cabling or lifelines etc. they will absorb and mess with the signal. ( lights dim up and down, stereo speaks by itself etc. )

Many owners instal their $500 auto-tuners closer to the antenna, say a backstay, but it's still mounted below deck which is a no-no for EFFICIEWNCY. ( efficiency is the non-polish spelling ) What happens is your 710 sees a good 1:1 SWR but in real life 98% of your signal never leaves the boat. ( my tuner is mounted on the rear radar arch with the output run directly into the insulated backstay)

One cannot stress enough that it's the quality of the antenna set-up that makes for a good on-air signal. A low-power signal that is able to RADIATE WELL is worth more than tuners and high power.

A 54" tall mobile mount vertical antenna ( for motor vehicles ) mounted on the railings gave me good results over many thousands of miles distance from Linnupesa. The trick lies in the antenna but more importantly how it is grounded right at the feedpoint.

Consider this: for an antenna to work it needs to power or work into a balanced configuration in two dimensions. One puts radiation lobes into the sky, the opposite dimension (ground ) acts as a reflector, to enable the signal to LEAVE the antenna. A bad installation can give you a good SWR but still have almost zero output. This is especially evident with a waterlogged or bad coax running to a VHF whip at the mast-head. You could still get GOOD swr with even an open circuit or a short across the end. The signal gets attenuated as it runs along and just heats the coax... none ever gets out, or back to the SWR bridge. The operator scratches his butt and wonders why, the SWR is great, but still no cigar. WTF? This is where the story of the "Fallacy of the tuner" ends.

Back to the antenna, which can be considered a dipole, even as a vertical or near-vertical antenna like a tuned back-stay. So, the upper half radiates into the aether, the lower part forms the counterpoise, aka known as a ground-plane or radials. ( google it)

At the feed-point ( or tuner output ) the RF current is heaviest, it flows. At the antenna tip it's voltage that oscillates up and down, rather than current, That EMF field is what you want to get into space, at as LOW a radiation angle as possible for best effect.
Depending on how high above "electrical ground" your antenna sits, will affect its impedance etc, from a few or even fractions of an ohm to over 100's in some cases. This height also affects the radiation angle. It's worthwhile to do a little experimenting here.

It is important to note the signal needs to LEAVE the antenna by radiation, it has to bounce off into space. A poorly designed antenna can have a great bandwidth with good SWR but still not work well. A good one will generally have a sharp tuning effect and much more limited resonant bandwidth.

Typically you will gain most improvement by having several radials cut to the antenna resonant frequency attached at the antenna grounding point. The "no-ground needed" antennas are a marketing gimmick. There's no such animal. Instead, they rely on the coax shield ground as a counterpoise or radial, but it has bad side effects. Best effect is from a number of shorter radials, as the name implies, radiating from the base of your antenna. One company bundles a bunch of these, cut for both marine and ham frequencies, into a plastic tube that you can snake below decks. The direction and bends are not that material, the RF knows where to go as long as it's in a general direction. The mfrs. claim good results and their theory holds. Dynaplates as grounds are far more expensive and probably less bang for the buck.

Copper braid and strips, all can make good conductors for RF which is really a SURFACE following thing... so go for the area. Weight against weight, very finely stranded wire is much more effective than solid. Aluminum is also good and light.

Spending time to make an effective ground below your radiating element is key. Use railings, lifelines, the aluminum toe rails if your boat has them. Connect them all up and they can make a very good ground. Do some cut and try, re-site the antenna or consider a side stay fed partway up. The feedpoint impedance changes dramatically along your "typical dipole" or vertical antenna, so it is possible to find a "sweeter spot".

Another option is the use of a 4:1 balun at the end of the feedline. You could convert a 52 ohm coax line into the low 12 or so ohm impedance of a short loaded vertical antenna. At the same time you'd effectively isolate RF running back down the line to your transmitter. I had great results with a front fender loaded whip used with such a balun on my VW in the bone dry Namib desert, one of the worst possible antenna grounds imaginable. Conversely, the salt water below your boat is an excellent ground, so you could just throw a bare conductor ground over the side in a pinch. Try it.

So how again did we get from antennas to the fellatio of the tuners and sweeter spots?

BTW: to cut resonant radials for each band you can use:

length in feet=240 divided by frequency in Mhz.

e.g. for the 20m ham band at 14.150 Mhz I get 16.96 feet. Don't sweat the exact inch and remember that on the low bands you may not have enough real estate on the boat, but the capacitive coupling to the water via the boat will help a lot. In fact, any conductor will help, especially close to the feed point.

The best of good luck and success getting on the air.

Ivo on sv Linnupesa and oinker station KI6S
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Old 06-17-2012, 07:21 AM   #9
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Oh, thanks so much, guys, for bringing more info to this topic!
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Old 06-18-2012, 02:47 PM   #10
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... as I am just at the beginning of the planning to install a SSB RX/TX, your info on the antenna-setup is sooo valuable! Especially your infos on the antenna ground.
Many Thanks!

Uwe
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Old 06-18-2012, 03:14 PM   #11
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Quote:
Originally Posted by linnupesa View Post

Typically you will gain most improvement by having several radials cut to the antenna resonant frequency attached at the antenna grounding point. The "no-ground needed" antennas are a marketing gimmick. There's no such animal. Instead, they rely on the coax shield ground as a counterpoise or radial, but it has bad side effects. Best effect is from a number of shorter radials, as the name implies, radiating from the base of your antenna. One company bundles a bunch of these, cut for both marine and ham frequencies, into a plastic tube that you can snake below decks. The direction and bends are not that material, the RF knows where to go as long as it's in a general direction. The mfrs. claim good results and their theory holds. Dynaplates as grounds are far more expensive and probably less bang for the buck.
http://www.sea-tech.com/KISS.pdf

73,

Rob (formerly VK3XVK)
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Old 06-18-2012, 07:30 PM   #12
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Thank you Uwe and Rob and of course BeBopaloopski too for her kind words.

Just to get John and perhaps others that looked at Roberts link about the KISS ground system a little less corn-fused:

The KISS shows a total length of 9'10". A 1/4 wavelength radial for 14 MHz is around 16' and twice that for 7 MHz. Clearly some shortening was needed and I suspect the designers used some coiling of the wires to reduce their length.

All that's important is that the radials RESONATE similarly to the upright "radiator" portion of the antenna. This can be achieved in various ways by adding coils/capacitors etc or by "spiral winding" the wire.

What the KISS mfr does not point out is that having several KISSES attached would improve the effect, but at $139 each that would argue against it being a cheaper system. You could make dozens of wire radials at a fraction of the cost of a single KISS and achieve an even better result.

You would:

1. Enlarge the size of the ground plane and achieve a lower radiation angle and more uniform lobe distribution.

2. Divide the heavy RF current amongst several radials, so coupling into boat wiring would be reduced because of the reduced field strength of each individual one.

3. There likely would be less reactance and hence a better resistive component to the system leading to better efficiency.

Practice has shown that something like 120+ radials would be ideal, but that only 3 or 4 opposed ones are already quite effective. Also, making these radials much longer than the vertical antenna itself does not buy you much imore in gain. Ideally, the two portions should electrically mirror each other, so avoid a big disparity in length.

On a saltwater boat it is quite sufficient to have distributed and shorter radials, as they will capacitively couple into the salt water via the hull. The larger number of radials (or connected metal for that matter) aids in this coupling effect.

The heavy RF current flow close the antenna base (remember?) is distributed over a wider area and so it forms fewer "hot spots" that might interfere with other electronics. Also, it is better to have more shorter radials than a single but longer one. Even if the radials are not "tuned" to any band, they will still help to achieve a ground plane effect.

Reading the KISS leaflet it claims "lifelines, engines....through-hulls and other metal is the most common cause of RF interference".

Yes and no. Or is their wire special in any way? Of course not. But yes, electrical equipment like alternators on engines can create RF-noise, as will poorly bonded life-lines or corroded joints. But that holds true for all electronics, as in the saw about 95% of electronic faults being due to poor connections!

Similarly, running your radials AWAY from critical electronic wiring will aid in reducing interference, both on TX and RX.

Ciau fer now and 73 to the hamster

Ivo s/v Linnupesa KI6S

( I like the KISS idea but I think they plagiarized my call sign )
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