SSB arial connection to backstay

D

dweeze

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www.buckscoop.com.au
Hi- can anyone tell me whether when making the final connection of the SSB wire to the backstay, whether its only the core that is in contact with the backstay or whether the core and the sheath need to be in contact.

The cable I am using is 10mm (RG whatever its called). The unit itself is an Icom M600 with a tuner box between the arial and the unit. The antenna is obviously an insulated backstay.

Thanks
 
If you are going from the auto tuner to the back stay you dont need co-ax cable. I think from memory I used 600volt 10mm plastic coated wire. You need to keep it at least 50mm from s/s fittings on its way between backstay and tuner, including the uninsulated part of the backstay
 
Wrong wire. It should not have a outer. Just a single conductor and a high voltage insulation.

One way around it is manufacturing your own out of the "fat" coax by removing the outer, and then shrink sleeving the lot. Use the hot melt glue on the inside type sleeving or it all goes saggy after a while.. You can not leave the white/clear inner in view if the sun. It breaks up.
 
We've got what looks like fairly heavy duty plastic coated wire, don't know the spec though because we didn't fit it. To keep the wire away from the uninsulated stay it is run through water hose and then the wire is simply clamped to the insulated stay.
 
Ok. I may be confusing the sheath with insulation. the cable was sold to me by a marine elec in Brighton. From memory his instructions were to just make contact with the core of the wire - which I have done.

So ...... can anyone troubleshoot the most obvious reasons why I wouldnt be getting any signal on the SSB. I get the usual static noise across all channels but not actual transmissions. Any simple checks I can run - tests etc?

Thanks
 
Sounds like you haven't got good connection. The wire core of the aerial lead should be tightly clamped to the insulated part of the backstay.

But if you have a good connection there are a few more checks.

If you have an auto aerial tuner you may need to transmit an am carrier (on low power) to get the tuner to adjust to the freq and the aerial. Having a good tune on the aerial sometimes helps reception.

Otherwise, are you listening to freqs used in the UK. If they are US or asian freqs less than 16MHz you won't get much during the day.

Finally you may be surprised how little HF is used compared with VHF. Not the constant radio checks or fishing chatter we get here on VHF.
 
The antenna starts from the ATU terminal. Hence the wire from the ATU to the backstay is also part of the antenna. If you have a coax then you can strip out the inner and insulation and then insulate the whole again but this sounds far too much work.

There should be no problem with just connecting the inner at both ends or for that matter, connect the inner and outer together at both ends.

An end fed antenna which is what you have carries most of the current at the feed end. Therefore the lower the resistance you can get in the cable from the ATU to the backstay, the better. Keep the resistance of the feed wire as low as possible. That meens as many strands as possible since rf only travels down the outer layer of a solid piece of copper.

Therefore: keep the ATU as close to the feed point as possible with the shortest legth of wire beteen the two. Connect the inner and the screen together at both ends of the cable and then use it as a single conductor.

As a test of the antenna tuning, the simplest way is to measure the VSWR. You need a VSWR meter connected between the radio and the ATU.
 
Be warned however, that just because the ATU has tuned out the reflections, doesn't mean the antenna is radiating effectively.
 
Re: More Questions than answers

I think you need to be certain about the wire from the ATU to the antenna. It must be a single conductor and not have an outer conducting tube around it.

Is the ATU an automatic or manual machine

What terminal on the ATU is the antenna wire connected

How is the radio connected to the ATU.

Is anything other than the antenna and radio connected to the ATU


Try putting a random length of wire directly into the ant socket of the radio, string the wire around the boat as high as possible and see if you can receive anything.

That should keep you busy for a while.
 
Re: More Questions than answers

Agreed, just because the ATU tunes to give a low VSWR, it doesn't meen the system is radiating efficently. In a former life as a design engineer, we once made an antenna as a joke. It met the sales spec completely. They'd missed out anything about radiation efficiency so we just put a 50 ohm resistor is a box with a whip mounted on it. The whip was just for show and the only thing connceted to the connector was the 50 ohm resistor. It met the spec perfectly and was the best broadband match you've ever seen but every radio connected was strangely deaf.

Seriously, if it does tune AND you are getting strong received signals, you should be OK.

At HF, 2 or 3 meters of coax with the inner & outer shorted AT BOTH ENDS will make no difference. Just short 1 end and you may have a problem.
 
Re: More Questions than answers

To make the connection to the backstay first solder the wire to a piece of copper foil. (Cut off a piece from the grounding copper ribbon about 25mm long.). Then wrap this piece of copper with the wire attached around the backstay and secure with hose clips. You should get a much better contact this way.
 
"So ...... can anyone troubleshoot the most obvious reasons why I wouldnt be getting any signal on the SSB. I get the usual static noise across all channels but not actual transmissions. Any simple checks I can run - tests etc?"

Did you have any luck this evening with reception. One of the easiest ways to check reception is to use WWV time clocks. http://tf.nist.gov/stations/wwv.html

As for the wire, it is the voltage insulation that is critical for a safe installation. Coax outside insulation is not good enough especially around the stern of a yacht where it can get damaged. So do not connect the outer. However, you should not have any metal parallel to the conductor. So using Coax is definitely wrong for the base of the aerial.

Have you checked the Coax from the ATU to the radio for shorts and opens. It should have no shorts between the inner and outer. Test it only when disconnected at both ends.

You seem to be complaining about reception anyway. Was the unit demonstrated working when you bought it. I only assume you bought it recently? Also I have not touched one of the M600s for quite a few years. Concentrate on just the receive before you go transmitting. Especially since you should listen on a freq before blasting over it.
 
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