SSB transceiver

[Auzzee]

I have an Icom IC-718 linked to an SG-230 Smartuner and then to an insulated backstay aerial. I have detected a separate twin flex power style cable labelled 'HAM ADAPTER', which comes from the tuner, but which is not attached anywhere else.

Perhaps it is something to do with lunch...........

Can anyone shed any light on this seemingly superfluous cable?

[haiqu]

It's not mentioned in the manual, so looks like it's an add-on. Probably have to open the box and see where it connects to tell you its function, sorry.

[gts1544]

Would it have anything to do with connecting a HAM radio to the same antenna through the tuner?

[haiqu]

One could guess so, it's a resonable assumption. But the description of the wire doesn't support that theory at all.

[JeanneP]

This is a very uneducated guess, but I'll give it a go.

We used to have a SEA XXX (? #) SSB, but it received and transmitted only on the upper sideband, so we couldn't hear a lot of the HAM transmissions. Stevens Engineering sent us a HAM modification which was, essentially, a wire soldered somewhere in the rig to enable lower sideband signals. We did it ourselves on the boat, but that was more than 20 years ago and the SSB was fried when we were hit by lightning in Malaysia in '98, so no way of checking.

Can you check with ICOM?

[JohnT]

Auzzee,

In the past some HAM radios did not supply a brief voltage pulse to force the tuner to "tune up" before transmission. A number of HAMs did mods to the tuner and ran a separate set of wire to a box next to the rig. What you did was set the frequency on the radio and then push the button which forced the tuner to tune up on the dialed in frequency.

Your 718 should automatically tune the SG-230 but you need to check that this is actually happening by using a SWR meter. Otherwise, you could burn out the finals on your 718. I have never used a SG coupler/tuner with an Icom rig so do not know of any mods that may be needed to get the two working happily together.

John

[Auzzee]

Thanks all. JohnT, I think you are right on the money. As near as I can determine, the 'ham adapter' has been used to supply current. The 718 has an inbuilt SWR which appears to be doing what it is supposed to do' ie. It pulses to the high end of the scale momentarily before settling on about 1- 1.5, which I understand is close to excellent. It does this in all bands except for RTTY, where it runs off the scale as soon as the mike is keyed and it does not return to the low end of the scale while still in TX.

I have called the Icom dealer in Guaymas. I have been told he is very good. He charges 100 pesos to make a service call (That's about $7.50) and that comes off the bill if I use him to make the repair.

I'll let everyone know the outcome.

[JohnT]

Auzzee, be carefully! What you are describing is the radio actually not matching to the antenna. All the modern Icom radios have a built-in "failure" circuit. If the radio sensors a SWR that is too high, it automatically cuts the wattage output to protect the finals. The so called internal SWR meter is not too good. The only proper way to check if it is matching is to use an external SWR meter between the radio and the tuner.

Do yourself a favour and do a Google search using Icom and matching circuit and SG-230 and see what comes up. Quite a few radios do not match with the SG tuners and need small modifications or circuits to assist them to do a proper match.

John

[Auzzee]

Thanks John, will do.
Cheers.

[linnupesa]

After all these erudite replies here's a dumb one to ponder as well:

Lacking coax an adventurous ham may have spliced in this "get-by twin feeder". This really old-style stuff came in around 92 ohms and and would result in a still quite acceptable SWR below 2:1

This "ham adapter" could just be clipped to the 52ohm SO-239 socket of the ham rig. I'd suggest you do that and just RX (listen) on the ham set, your other ear listening for crackles and your nose crinkled to detect smoke signals. If you get good audio or band noise you'd be in business. The marine SSB set might have been used to set the tuner to a frequency close to the ham one. Do check for any DC voltages on the twin lead first and stop if there is any.

Another possibility is that it is a ground cable to the ham set, to let it use the counterpoise/ground of the tuner set-up. Been there, done that too.

Ivo / KI6S on s/v Linnupesa

[Sailor_Hutch]

I'm not sure if you're using the original SGC cable. I don't suppose you're talking about this cable:

SGC Smartlock Remote Locking Control for SG 230 SG 237 SG 239 | eBay

Is the cable you're referencing completely separate from the main one? In the original configuration, I think there was a single coax, a black (ground wire), a red (12VDC wire), a red/white striped (smartlock wire), and a black/white striped (tuning indicator wire). The ebay cable is for the smartlock. Is it possible someone rigged up a homemade smartlock, and then removed the head?

If you're using non-original cables, all bets are off on the colors ...