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Old 29-09-2010, 14:52   #1
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Icom 802 Reception Issues

Over the past year or so, I've suspected that our Icom 802 is not receiving signals as well as other 802's in the same region. I've confirmed over the past few weeks, that we cannot hear the same signals as other 802's located in the same anchorage. For clarification- we're talking about reception only; we're told that we put out a great signal when transmitting. When receiving signals we've already gone through the drill of shutting everything down, and then turning on items individually, so we do not have equipment running that puts out noise. We've checked the antenna connection. We have a decent grounding system (we transmit fine).

Using headphones doesn't seem to help either. Too much noise on the radio, and we can't turn up the volume higher. We've tried fine tuning with the clarifyer, adjusting the RF gain, and noise blanker.

It's been suggested that a new speaker- "Clear Speech" may help significantly... but at over $200... I'd like to get additional opinions...and any ideas on anything else we should check. As a full-time cruiser and getting ready to cross the Pacific... having a decent receiving SSB/Ham is important to us.

We'd appreciate any and all suggestions as to how to remedy the reception issue.

Steve
Bahia de los Angeles
Sea of Cortez
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Old 29-09-2010, 15:33   #2
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Hola Steve!
A couple of years ago Bahia de los Angeles was getting power poles for electricity, but projects in Mexico do sometimes go awry; the previous source - and I am sure present back-up - is a local generator, which puts out an impressive amount of RF interference. So - if the generator is being used - do you have the same receiver situation away from BLA?
We have found that tuning the radio at the frequency (or a few KHz off) you want to monitor helps a great deal. And we have the Clear Speech, the variety that comes without a speaker - you provide your own and can change them out - and love it, would recommend it even if you didn't have receiver issues 'cuz it cleans up everything and sometimes makes unintelligible broadcasts intelligible.
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Old 29-09-2010, 16:08   #3
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Try plugging headphones into the jack to see if the problem persists; if it is better with the headphones, then your speaker is the problem.
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Old 29-09-2010, 18:12   #4
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G'day, Mate. Ditto on SVCambria's insights. Along with external generators, typical power line transformers can also creat reception interference despite being able to transmit successfully. Cheers.
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Old 29-09-2010, 18:26   #5
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It does sound like there is a high noise source somewhere around you (thus keeping your signal to noise ratio low). It is unlikely (but not impossible) that the radio is faulty.

While you have tried to track the source down, the fact remains that the noise source is more likely to be onboard. They can be very difficult to locate and can occur from the most unlikely source.

One very real test is to disconnect your battery (or batteries) right at the terminals and then running a temporary lead from the battery to the 802. This guarantees nothing else is powered up on board, no even a digital voltmeter (a common source of noise).

Good luck with the fault finding, it can be tiresome.
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Old 29-09-2010, 18:36   #6
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Originally Posted by Wotname View Post
It does sound like there is a high noise source somewhere around you (thus keeping your signal to noise ratio low). It is unlikely (but not impossible) that the radio is faulty.

While you have tried to track the source down, the fact remains that the noise source is more likely to be onboard. They can be very difficult to locate and can occur from the most unlikely source.

One very real test is to disconnect your battery (or batteries) right at the terminals and then running a temporary lead from the battery to the 802. This guarantees nothing else is powered up on board, no even a digital voltmeter (a common source of noise).

Good luck with the fault finding, it can be tiresome.
Very good advice.... do it!

Cheers,

Jim
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Old 30-09-2010, 10:01   #7
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Hi Wotname and Jim- our 802 is powered directly from the batteries, only running through a dedicated circuit breaker. RE: outside interference, I'm noticing the same issues even in more remote anchorages. The reason for me suspecting something on board or a radio issue is that other boats near me, in the same anchorage, at the same time, with the same radio... are not having the same noise/reception issues. It's evident on the morning and evening nets when we're all listening to the same broadcasts.

I've tried headphones, no improvement.

Sounds like I need to recheck all connections, and look at one of the 'clear speech' set-ups.

Thanks for all the input... if any other ideas come forward, please let me know.

Oh- SV Cambria- BLA now has 24-hour commercial power, even with street lights!! And 2, count-em, 2 Pemex stations in town. Kinda like being in the big city.

Steve
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Old 30-09-2010, 13:50   #8
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Hold on to your headphones and don't jump to buying a noise filtered speaker or audio filter. Before anything else, what is the background noise level in receive vs. the other boaters with whom you are comparing signals? If their noise level is lower than yours, you just identified the issue. If not, the radio is attenuating the signals which could be as simple as operator error-induced.
How does background noise level compare?
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Old 30-09-2010, 17:58   #9
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Hold on to your headphones and don't jump to buying a noise filtered speaker or audio filter. Before anything else, what is the background noise level in receive vs. the other boaters with whom you are comparing signals? If their noise level is lower than yours, you just identified the issue. If not, the radio is attenuating the signals which could be as simple as operator error-induced.
How does background noise level compare?
Illusion is correct.

I can't help you with operator error but I can repeat that tracking down on board interference can very difficult. It is not just a case of turning the obvious sources as often the source is a small electrical system tucked away somewhere out of sight (or out of mind). It may not even have an on/off switch. This is why I suggest disconnecting the batteries at their terminals to ensure EVERYTHING electrical is not operating.

In your case you will be spared the effort of running a temporary lead .

At least (and again I repeat), if you have any sort digital of battery monitoring system (even a simple digital voltmeter), disconnect it - they can put out a surprising high level of RF noise.

An old electronic adage - It is far better to remove interference at its source than to mask or filter it at the circuit it affects.
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Old 30-09-2010, 18:36   #10
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Its probably too obvious, but since none has mentioned it... You are pressing the TUNE button every time you change frequency I presume.

This can make a big difference on receive as well as transmit particularly when jumping bands. You should see at the top of display "THRU" change to "TUNE" after the ATU has done its stuff. Even if it already displays "TUNE" it won't do any harm to press it again.
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Old 01-10-2010, 17:02   #11
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HF Reception Issues????

Steve,
You've gotten some good responses here.....perhaps I could add a few thoughts and clarifications....
In addition to using my M-802 on-board for the past 6+ years, I have 35+ years of HF communications experience, maritime and ham, both at sea and on-shore.....


ALL the below assumes that you ARE doing what Richard mentions about making sure you have a decent tune for the frequency that you're attempting to listen to!!!!!

So, here goes....

1) Turn OFF the M-802's Noise Blanker.......
"Noise blankers" are designed for "impluse noise" such as ignition / spark noise from gasoline engines, and/or some powerline noise.....
BUT, in general "noise blankers" typically have a serious negative impact on receiver performance.....(most blankers significantly reduce the receiver's dynamic range, increase internal IMD products, etc....and AF-DSP blankers generally just distort received audio.....and even decent IF-DSP blankers have little positive effect, and generally distrupt an otherwise excellent receiver.....)
While a noise blanker does have some usefulness, in > 95% of the situations, they make matters worse......especially on crowded ham bands!!!!

{Of note, in the past 35+ years, out of the 100's of HF rigs I've used, I've only seen two radios with truly outstanding noise blankers which did not produce any ill-effects....in the late '70's, the Drake Tr-7 / TR-77 / TR-4310, where the noise blanker was a very well designed $200+ option.....and to a lesser extent, in the early/mid '80's, the Collins KWM-380, where it was also a ~ $200 option.....and while I never used one, I heard some of the commercial Rodhe and Swarchtz HF transceivers had decent blankers as well.....}

So, before you try to pick out some weak signals, please turn-off the noise blanker....



2) Please have a look at your M-802's receive signal meter (the "S/RF" bar graph)......
Make sure you have the M-802's "RF Gain" set to "9" (its maximum) for these tests....
When listening to the mid to upper HF bands, on a clear frequency (nobody else transmitting there, or near there), you should NOT be seeing much on the meter......

Some M-802 rough guidelines:
a) On (or near) the 14 mhz band, you should have NO (or maybe just one, on a bad day) segments showing on the meter, when listening to a clear frequency......
b) On higehr frequencies (18 mhz and up), you should have NO segments showing....
c) On lower frequencies, such as 7 mhz / 8 mhz (during the DAYTIME), you may find one segment of your "S/RF Meter" showing some distant noise (whether natural or man-made).....
d) At night, on these lower frequencies (< 10mhz), you can have quite high noise levels, so do NOT use these as a guideline.....

If, you find that your "S/RF" meter is showing as described above in a, b, and c, then you may not have any significant RF noise distrupting your reception.....
BUT, if you find that your "S/RF" meter is showing moire segments when listening to a clear frequency, you probably DO have some RF noise reducing your receive performamnce, and you'll need to track it down....(see next item)




3) Next, please understand that there is a BIG difference between "switching things off" and "disconnecting them".....
While I assume you did truly disconnect things so that there is NO power to them, rather than simply switching them off.....if you did not, please understand that many items can (and do) produce RF interference when supposedly switched-off, but are still being supplied electrical power (either from ship's batteries, or their own batteries....)

So, in addition to the advice given by the others here, please have a read of this thread on the SSCA discussion board....
SSCA Discussion Board &bull; View topic - Testing a SSB/Ham radio - poor reception

Here, you'll read of many sources of RF noise, and some thoughts on tracking it down and reducing/eliminating it!!!!

Here's just a small quote from that thread....
Quote:
3) Another fact is that the typical modern cruising boat is full of "noisy", static producing devices......while this is typically spoken of as just being the "big" and popular stuff, such as: inverters,
battery chargers,
gensets,
engine alternators,
electric fuel pumps,
computers and their power supplies,
solar panel charge controllers,
wind generators and/or their charge controllers,
battery system monitors (Links, etc.)
LED lights,
fluorescent lights,
electronic instruments,
watermakers,
automatic bilge pumps,
etc. etc. etc...

(Please take note that while marine refrigeration units are talked about interfering with HF radio reception, their primary interference is in radiating "birdies" (lots of RF carriers, mostly pulsing on/off sounding like morse code), and not radiating wideband noise / "static"......although it is a possibility that your frig is causing the problem, using the words that you posted, it's more likely to be something else.....)

The fact is that wideband noise / static can be caused by so very many things on board, your best way to track down where your static is coming from is to turn off EVERYTHING on board.....absolutely everything disconnected, with breakers switched off, NOT just "turned-off".....Hopefully you can switch off your main battery switches, and disconnect everything else from the batteries that doesn't go thru the main switches....(and also check to see if you have anything else on board that might be powered by its own source / battery.....and remove the batteries from them as well...)


4) And, another thread (which is mis-titled, but should be useful to you) has much info on HF receive issues....
SSCA Discussion Board &bull; View topic - kiss-ssb grounding system and ham rig



5) I'm VERY surprised that you find no positive effect from the use of headphones.....
Typically headphones will make a significant difference....
The best "noise filter" in the world is the human ear / brain combination.....it is truly amazing what you can train your ears/brain to listen for, and what to ignore.....
I'm not sure how much HF communications experience you have....but most experienced HF operators find a decent pair of communications headphones to be of great help.....

I'm hestitant to mention this point, as it will tend to stir debate.....but...
If you find that your "S/RF Meter" is showing little or no segments on a clear frequency, and you have no external RF noise issues, but you're still
having difficulty pulling-in some weak signals, try using decent communications headphones (NO music-listening headphones, nor noise-cancelling headphones).....and then also try turning the RF Gain DOWN, and turning the volume UP (while using these headphones) and see if that helps......
What you are after here is the best S/N (signal-to-noise ratio) that your ears and brain makes sense of.....and that may be different for you than others....
In general, for HF receiving, you should use the LEAST RF Gain possible and still be able to hear the station you want.....and this becomes much more important as the RF noise (whether natural of man-made) is greater, such as on the lower HF frequencies of < 8mhz, where much of the "cruising nets" take place.....

Please understand that while this issue, IS very important, it may not be the proximate cause of your troubles.....



6) Also, Steve, please be aware that every boat and every installation is different.....not the least of which is the antenna, and its length....as well as how huch of your antenna is inside your boat, and how/where it is run....(remember the GTO-15 wire from the AT-140 tuner running up to the backstay IS part of your antenna....)

If you are comparing exactly the same set-ups (exactly the same!), then it is a good comparison.....but if there are big differences, then there can be big variations in performance.....

Just something to keep in mind....


7) Save your $$$.....
Any external speaker, or speaker with AF-DSP noise reduction (such as the Clear Speech) will be a waste of your money, and will do nothing to reduce the noise coming out of the M-802, nor make any improvements to the M-802 at all.....


8 ) This final point may be off target, so please forgive me if I'm wrong here.....but, I wonder if there is anything at all wrong????
Or, is it just that you are new to HF operating and haven't quite yet got all the tricks / techniques figured out????
Please let us know....



I do hope this helps.....

John
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Old 03-10-2010, 17:41   #12
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Many thanks to all who have taken the time to respond and provide words of wisdom. I'll be spending time this next week chasing down any noise on-board, starting with disconnecting everything from the batteries, except the SSB. I'm kinda limited on when I can do this... usually during the morning or evening nets. We will most likely still consider the 'clear speech' speaker, only because getting equipment brought down takes a bit of logistical coordination... and the SSB is really important to us.

Thanks again for all the input.
Steve
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Old 03-10-2010, 17:46   #13
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Good luck and please let us know how it all turns out.
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Old 08-10-2010, 07:27   #14
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I will share an experience - but was in my home.

I generally use outdoor antennas, but I also have an antenna in my attic. It picks up lots of noise.

I went to the circuit breaker box and turned off one breaker after another. Turning off the breaker that provides electricity to the top floor of the house eliminated the noise.

There were two culprits -
1. The desktop computer in my daughter's room, and
2. My wife's alarm clock - rather the power supply thing one plugs into the wall for the alarm clock. This was a fancy alarm clock that shines the time onto the ceiling so you can read it laying down in bed. It also has a slot to insert an IPOD. The little switching power supply that plugs into the wall put out significant RF noise.
3. My wife's side of the bed has a lamp with a built-in dimmer switch. This was also a significant source of RF noise.

After turning those two items off, the noise level was much reduced, but not as low as when the circuit breaker turns off all electricity to the top level of the house.

Also in the attic I have a Channel Vision amplified splitter. It takes the cable TV coax and splits it into several coax lines - one for each bedroom. Since splitting a signal reduces its strength, this model has a built in amplifier to keep the output signals as strong as the input signal. I suspect this as the final source of noise, but did not bother to crawl into the attic to power it off.

Anyway, the point is that RF noise can come from many sources including a simple little switching power supply that one plugs into the wall. Turning off the device does not help - as it must be unplugged from the wall.

Also a simple dimmer switch can also be a RF noise source.

Howard
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Old 08-10-2010, 07:42   #15
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I would suggest shutting down all electric in your boat, direct connect your SSB to the battery, neutralizing the filters and settings, and use spectrum analyzer software or hardware. Then add one device at a time.

Hopefully, noise isn't coming from the dock or around you.
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