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Old 09-10-2011, 12:44   #16
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Re: SSB - Transmission Problems with Lower MHz

Don't guess. When you go back to the boat, carry a good power/swr meter with you (like the Daiwa CN101L) and put it in line full time.

EVERYONE should have one permanently installed in an HF system.

With such a meter, you'll know instantaneously and continuously:

1. how much power you're putting out; and
2. how well your antenna system (coax, tuner, transmission line, antenna, RF ground) is working.

A small investment ($99 online or at HRO) which will continue to pay big dividends throughout your SSB experience.

There really is no good substitute (the built-in LEDs on some radios may be useful, but can't compare).

Bill
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Old 10-10-2011, 07:59   #17
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Re: SSB - total wire antenna length

1. Bill is right - by any means check via an swr-power meter... even with bad VSWR you will at least see if any power goes out - I would try on LOW power setting first! (hoping that on this Icom 802 low power will trigger the tuner?

2. 12.4m or about 40 ft of total antenna wire until the automatic tuner is indeed about 1/4 wavelength on 6Mhz but:
- I have experienced problems to tune 40m band (7 Mhz) on a 9.6m vertical with radials (home QTH) using a CG3000 atu....and other users of the CG3000 have mentioned the same issue when tuning a 1/4 wave wire....which sounds very odd since a 1/4 wave vertical should be about the easiest to tune
- you report about 5m/16 ft of GTO15 from the lower backstay isolator until the ATU - is that spaced well away with standoffs from the remainder of the backstay and from other (grounded) metal hardware like pulpit..? I have seen too many boats with the GTO15 or even coax just taped/strapped around the remainder of the backstay
- how much of that 16ft is underdecks? => preferably the atu is located just below the through-deck gland and close to the backstay as mentioned before

3. If there are no issues with the Icom 802 cuttting back power (known issues) and all tuner, coax and antenna connections are OK, then a 12.5m radial (wire) along the deck and connected to the atu ground lug, in a temparary setup, will help tuning (even if Mr. ka4wja doesn't think so) if there is a real tuning issue due to ground issues and/or problematic antenna wire length.

BTW as a temporary easy solution you might make an inverted-V wire dipole that you hoist into the mast with a spare halyard tying of both ends stern and aft (simple isolators even nylon rope would do)(but fix it a far away from backstay and forestay as possible - I guess on your 11m long boat your mast will be at least 13m high).
Of course you would need a coax feed length = mast height + length needed to get to your SSB, connect it durectly to the antenna out without the atu. Starting length: 300/frequency in Mhz/2 x 0.96 gives about 11.07 metres per dipole leg. Hoist it when on a stable sailing tack or at anchor, take it away when done- it should take you only 5 minutes to set it up. Do check swr when making it (60 min. max).
This should give you a good alround antenna albeit monoband but not really suited for real long range communication given its rather high takeoff angle.
Good luck!

Jan
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Old 10-10-2011, 09:56   #18
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Re: SSB - total wire antenna length

Quote:
Originally Posted by Goudurix View Post
I would try on LOW power setting first! (hoping that on this Icom 802 low power will trigger the tuner?
The Icom tuner's do not tune on normal SSB output. They only tune when you push the tune button or the mic button (if enabled in set mode). This causes a 10 watt cw signal output to the tuner during tuning of which less than 1/2 watt goes to the swr detectors, tuning elements and antenna. A downfall of these tuner's IMO. I have seen tuner's work fine during tuning but then see high swr at the radio when operating full power SSB due to problems in the antenna system that just don't show up during tuning.

Eric
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Old 11-10-2011, 06:12   #19
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Re: SSB - Transmission Problems with Lower MHz

Thanks everyone for all the tips and info to sort out.. We just got the wifi going again picked up the full messages, the plan is to start sorting all the questions out and then respond... Sorry for the delay - we are working through the info/list supplied.. The unit is about 8 yrs old - but I need to locate the serial number on the radio - the head unit doesn't have anything in the serial number slot so will need to extract the main box from it protected location..... Not sure about the clipping thing but sounds like a real possibilty, I will start eliminating the suggestions...
Most appriciated,
Jim
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Old 11-10-2011, 06:20   #20
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Re: SSB - Transmission Problems with Lower MHz

Jim,
You're welcome and Good luck....
Quote:
Originally Posted by bluemoon365 View Post
The unit is about 8 yrs old - Not sure about the clipping thing but sounds like a real possibilty, I will start eliminating the suggestions...
An 8-yr old M-802 was made well before the "fix" was discovered, so it's now VERY likely that this (the clipping problem) is most of your problem....

Getting your radio modified in Gib is the real hurdle, and/or having the time to send it off for repair/modification....
It's a rather simple fix, but not one that should be attempted by laypersons....


John
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Old 11-10-2011, 11:47   #21
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Re: SSB - Transmission Problems with Lower MHz

Even if you have the clipping problem, you would still see the power indicator bars on the display when talking into the mic. The clipping only occurs on voice peaks so the power bars would be fluctuating from full to none.

Eric
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Old 11-10-2011, 13:10   #22
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Re: SSB - Transmission Problems with Lower MHz

Does anyone have any thoughts/ideas on using a split backstay for an SSB antenna?
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Old 13-10-2011, 17:15   #23
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Re: SSB - Transmission Problems with Lower MHz

If you could get 90* on the two stays, I would guess it would work like an inverted Vee, and work really good. Nice 50 ohm feed point at the top of the vee, and if cut for a single band, would not need a tuner for that band.
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