SSB Question ICOM 706

[jfkal]

Just installed an ICOM 706 with Tuner AT-180 on my boat using a 7m straight wire antenna. Grounded the whole lot to my (boats) cast iron keel.
Unfortunatlely I am getting no more than 30 watts output and even with the tuner only bad SWR ratios to the point where the tuner just gives up trying. Only around 24 MHz do I get decent output and a good SWR ratio. Then however all my LEDS and incandescent Indicator lights at my DC distribution panel light up like a christmas tree.
What on earth or heaven for that matter did I possibly screw up here?
I am a HAM Radio novice but with good electrical and electronics knowledge. /forums/images/graemlins/confused.gif

 

[Ships_Cat]

Two things come immediately to mind:

The AT-180 will not tune a random length antenna. It will only match SWR's up to around circa 3:1 ie will only match minor mismatches.

With lights lighting up, etc it would also seem that you are getting some rf feedback which could be for a number of reasons. However, it is probably pointless worrying about or trying to address that until you replace the tuner with one able to match into random length antennas (as the AT-130 and AT-140 do, for example) or, alternatively, only use a matched antenna ie one cut to length as a vertical for one band only (to which you would be limited), or else trapped for the bands that you wish to use.

Sorry to be the bearer of bad news regarding the tuner.

John

 

[William_H]

I don't know the tuner you speak of,my experience is with light aircraft HF SSB where 27 ft was considered ideal length for a long wire antenna. I find it difficult to understand the point of ICOM making a tuner which won't tune a wire. I presume you have checked all your connections and that you have as short a lead as possible from the tuner to the feedthrough insulator not that it matters so much on a F/G boat. amke sure the antenna is clear of other rigging wires. The earthing from the tuner to the keel may be critical and needs to be short.
I would suggest you try on a shorter wire and or a longer wire as tuners tend to find it tricky when the wire length is near resonance. I would suggest if all else fails that you try a home made tuner to prove a point.
Do you have an inductor about 30 turns about 50mm in diameter which you can attach a tap along this goes in series with the antenna and you need a large variable capacitor across the coax where it connects to the coil. This will enable you to tune frequencies below about 7mhz. Above that you need to fit a 47pf capacitor in series with the antenna to electrically shorten it to enable the coil to make it resonate. The variable capacitor will enable the resonant impedance to be matched to 50 ohms so is adjusted to get min SWR while maintaining reso0nance with the variable tapped inductor. There are plenty of good ham books explaining tuners. The point is if you can tune varrious frequencies with a home made manual tuner then your auto tuner is obviously faulty or unsuitable. If it is unsuitable you could tru the 47 Pf high voltage caopacitor in series with the antenna or fit an inductor in series with the antenna to see if the tuner can then cope. Lastly there is a lot to be said for a helical wound antenna on a F/G fishing rod pole mounted on the pushpit. It does mean you have an antenna if the mast goes over the side. just a few thoughts, olewill

 

[Ships_Cat]

I find it difficult to understand the point of ICOM making a tuner which won't tune a wire

It is an amateur service tuner meant for matching solid state transceivers into matched antennas but allowing some small frequency mobility away from the antenna's resonant point and subsequent small mismatch.

There is no way possible around the problem using that tuner unless a matched antenna is used (ie resonant or nearly so for single frequency only use, or multibanded with, for example, traps). So it is the problem without any doubt whatsoever and any playing around trying to get it to work on a random wire is guaranteed to be fruitless.

John

 

[Benbow]

Ships_cat is absolutely correct. There is no point in doing anything else until you have an ATU capable of matching your aerial. The AT-180 will not do this. Also, as I am sure you are aware, you risk damage to your set if you transmit with such a high SWR, use only very low power to test a new setup.

If it seems strange that this pair don't work together for your purposes, remember that the IC-706 is not a marine SSB, it is a ham set and it is virtually unheard of for hams to use random wires.

 

[jfkal]

hanks. am off shopping for an AT-130 but only after I have strangled the chap who sold me the AT-180 . /forums/images/graemlins/crazy.gif

 

[gi7kmc]

[ QUOTE ]
If it seems strange that this pair don't work together for your purposes, remember that the IC-706 is not a marine SSB, it is a ham set and it is virtually unheard of for hams to use random wires.

[/ QUOTE ]

I would disagree with this statement. Hams who have limited space quite often use "random wires". (at least that is what I am using at home) At the moment I am just using a manual ATU but most automatic ATUs will match random wires. (Check the specs first, the manufacturer normally recommends a minimum length for each ATU)

Jonathan

 

[Benbow]

I would be interested to know why you chose this set for a boat. Is it modified to transmit on marine frequencies?


Just looked at Icom's site. They recommend the AH-4 tuner for this set.

 

[jerryat]

Hi jafkl!

Sorry to hear aout the problem. I've had a 706 installed on my boat for several years now and had superb performance. I do not agree that the grounding to the keel needs to be a short as possible since, if you are using 75mm wide copper tape (as you should be) this itself forms part of the counterpoise especially if it is run in contact with the hull.
However, having spoken to a couple of the authors of SSB installation books in person and several 'ham' experts, I was strongly advised to make the insulated section of my backstay at least 11 metres long. This, I was told, would offer the best 'average' (my words) length for my ATU to work with. Unfortunately I'm away from home at the moment and can't check the Icom ATU model, but I almost always have a max of 1:1.5 SWR acccoding to the read out on the set itself.

Like some of the others, I 'm puzzled as to why your 180 won't tune a reasonably long wire antenna, though I am not familiar with this model, and it may be worth your checking with Icom before performing homicide on your seller! From other posts, it does seem there's something special/odd about this 'ATU' and I agree with ships_cat that those he suggests would be better, assuming your 180 is not faulty.

Do double check your connections, particularly that at the antenna, as the SWR you appear to be experiencing, is exceptionally bad. On a slightly brighter note, providing you do not try to transmit repeatedly, the in-built protection circuits in the 706 will prevent damage to it.

Final thoughts. When you say you've 'grounded the whole lot to the keel', do you mean both the ATU and the set separately? Do not woory about your panels lights imitating a Christmas tree, mine (and lots of my friend's) also do to varying extents. For example, on my boat, it is sometimes enough to bleep the burglar alarm sirens as I speak!! Never caused any problems though, nor caused any discernable damage. I did have the reason explaned to me many moons ago, but can't remember what it was - age again I suppose!!

Let us know what the solution when you find it.

Cheers Jerry

 

[Benbow]

[ QUOTE ]
Like some of the others, I 'm puzzled as to why your 180 won't tune a reasonably long wire antenna

[/ QUOTE ]

It just won't! Look at the specs on the icom site. Icom themselves do not recommend it for that purpose.

While assassination may be excessive, a stern word is well justified.

 

[Ships_Cat]

From other posts, it does seem there's something special/odd about this 'ATU'

There is nothing special or odd about it at all. Tuners are very commonly made to cope only with small mismatches.

For example, in the amateur service they allow operation across a band with an antenna whose SWR will rise as the frequency of operation moves away from the antenna's resonant frequency. If that minor matching did not occur the final rf amplifier protection circuitry in the transmitter would turn the transmitted power down (typically as the SWR approaches and exceeds 2:1). For such use it is unusual to have to cope with a more than an around 3:1 mismatch and so that is about all the tuners are made to handle. Consequently they will not match any random antenna over a range of frequencies (or even at one frequency unless it is close to the antenna's resonance).

As Benbow says, the AT-180 is one of those tuners and that is all there is to it.

John

 

[colin_jones]

I have run the 706 for general listening, weather fax and RTTY and amateur radio traffic for about six years. Initially I had huge problems with VSWR and low output. There was also much switching on of lights and the fridge (still is) when I transmit on certain bands.

After a great deal of frustration, I bit the financial bullet and added a SG230 Smart Tuner which will resonate any antenna length from about 6 ft to 600ft and covers 1.6 - 30MHZ. At £300 it was an expensive solution, but one I am glad that I made. I do not need to compromise the integrity of a backstay and can tune a long wire, no matter how I sling it up. Some configurations ( generally hoisting to the mainmast as an inverted V) are better than others, but they all work. A mini G5RV was also good.

The only other addition was a Dynaplate which separated the 706 earth from all the others. It seems to have worked, but quite how well is difficult to quantify.

Just persevere. It is a great little rig.

G4HHU

 

[trouville]

Just go hear http://www.mfjenterprises.com/index.php
There not the best nor least expensive but they do work
. ive been tunning my back stay for years, sometimes i put up a diapole slung between for and back stay which works best or haul up a vertical diapole useing the toping lift that works very well indeed and cut to frequency

For the back stay or any bit of wire my mfj tunner tunes it to 1:1 or very very near i note the settings so by now i can change from 40 to 80 and back and tune as fast as an ATU almost. as i go up or down the band i just fine tune

 

[Strathglass]

I have a MJF tuner, it was not too expensive and it will tune most things.

The 180 tuner is intended to fine tune resonant aerials and is not suitable for a backstay piece of wire. Would probably work on a half size 5RV as has been previously posted.

Iain (gm3ynd)

 

[Roberto]

just curious, where did you put your manual tuner ?

did you put the radio in the aft cabin ?
or did you keep the tuner at the chart table ? what happens with all that part of active antenna running aft inside the boat?

r, (m0ita)

 

[trouville]

I havent screwed my radio to anything so mostly i have it in the aft cabin then if im at anchor for some days or in port, i may hoist my diapole and let the coax in through the hatch doors.
If im sailing or cant be botherd but want the meteo and perhaps a schedual with someone i put the tunner on a shelf just about a foot or two behind the radio which i have on the chest top between the berths then i connect the tunner to the backstay fitting and earth via the rudder equipment
The connection from the tuners about a foot long and the coax from the tuner to the rigs about three foot long so i can move it about if i want

In a cold damp winter either move it to the main cabin, or use a small old ts 140s which i connect to the tuner with a 5 foot log coax and the antenna tuner is conected to the side stay via the fitting the rigs on the saloon table and tuner in the book shelf.
Sadly its getting boreing 99% of the traffic are people changing call unendingly

just looked at the new mfj range and for just $99 theres a 200w exelent manual tuner or $299 for an atu that will tune anything!!!!

 

[Strathglass]

The tuner is at the aft end of the chart table.
But the chart table is partially under the cockpit so there is effectively a live RF wire running under the deck for about 1.5 meters. There is no other boat wiring near this part of the aerial. The wire itself is the inner core from a very heavy coax cable including the insulation (ptfe) it is about 12mm dia. Where it passes from the ATU to the feed through insulator it is passed through two concentric plastic pipes, one 15mm dia and one 40mm dia.

Cheers

Iain

 

[trouville]

what rig are you useing?

 

[Roberto]

thanks Iain and trouville,

I have been on a few boats with different tuners but they were all automatic, I personally have an Ic718 and so far used it only with dipoles, a manual tuner seems an interestnig alternative..

cheers r

 

[PaulJ]

I would second Colin's vote for the SG230. So far I have only been experimenting with it but I have tried a variety of antennas, including several different "random wires" and it seems to tune just about anything. The SWR is always 1.5:1 or less.... usually 1.2 or 1.3. It seems to be a great bit of kit and well worth the investment.

Paul