Trouble-shooting SSB Tx problem

[sneuman]

I have an ICOM M700pro and am not getting through on the transmit side. Distant end (Cruiseheimers and Do-Dah nets) say they can hear something and, with difficulty, usually my call sign or boat name, but have reported bad signal due possibly to low voltage. Voltage to unit is good, but I do notice that when I key the mike, it takes several seconds for the draw to go up to about 8 amps. Could this be the problem? If so, what would be causing that?

[sneuman]

bump.

[ka4wja]

sneuman,
They are any number of things that could be causing this problem...not the least of which is radiowave propagation variables (remember that if your signal is being compared to others in your anchorage, within the last couple minutes, and yours is significantly weaker, then these are legit reports and your concern is warranted....but, if your signal is being compared to others that are quite aways away, and/or at different times, these would be subjective reports and as such need to be considered in that vein...)


But, some good news is in the wording you used here...."Voltage to unit is good, but I do notice that when I key the mike, it takes several seconds for the draw to go up to about 8 amps", as this implies that you have some sort of current and voltage measuring device which is not typical of a properly wired SSB radio, as this should be wired directly to the main battery bank and NOT thru a distribution panel / breaker panel, etc....so, you may in fact be getting significant voltage drop by the time the "12vdc power" actually gets TO the radio's rear panel / transmitter's PA, even if your panel meters show "good voltage"....

Also, the M-700Pro should draw about 2 amps on receive, about 5 amps on transmit when you are NOT talking at all, and between 8-15 amps on "average" on SSB Voice transmit (about 28 to 30 amps on "peak", or a solid whistle, but unlikely that you'll have a meter that would be able to react to voice peaks and you'd probably only be able to see that almost 30 amps on a solid whistle)...
So, when you say "it takes several seconds for the draw to go up to about 8 amps", you need to be more specific as to what you mean, how you are measuring this, and are you using normal speech / voice when measuring this, etc.?



The more info, the more details you give....the better we can help!!!
So, please give us more!!!

Originally Posted by sneuman

I have an ICOM M700pro and am not getting through on the transmit side. Distant end (Cruiseheimers and Do-Dah nets) say they can hear something and, with difficulty, usually my call sign or boat name, but have reported bad signal due possibly to low voltage. Voltage to unit is good, but I do notice that when I key the mike, it takes several seconds for the draw to go up to about 8 amps. Could this be the problem? If so, what would be causing that?

But, 'til then....

--- Yes, it could be a "12vdc power issue" (see above)...

--- It could also be your AT-130 tuner is not "tuning" / faulty...

--- And/or it could be that the tuner control wire from the M-700Pro to the AT-130 is faulty and/or come disconnected / corroded...

--- It could be a loose/corroded microphone cable/connector...

--- It could be a loose/dirty/corroded GTO-15 connection (usually at the GTO-15 to backstay connection)...

--- It could be loose/dirty/corroded RF Ground / Antenna Ground connection...

--- It could be loose/dirty/corroded coaxial cable connections/connectors....or bad coax...

--- It could also be an internal M700pro issue/problem (but less likely)...

--- As I wrote right up top....there are many possibly causes...but, without more info, all of the above are speculation....
(but, the good news here is both what you wrote about being able to see the current draw AND my > 40 years of HF comms experience....combine to make the speculations pretty solid!!




PLEASE give us more info, and we can be of MUCH more help!!
Not the least of which is, "was your M-700Pro working well in the past?? and when was this???"


And, read this thread here....
Re: SSB Great Receive Poor Transmit
(you'll notice that the original poster never returned back to say whether any/all of the advice/recommendations given solved his problem....but the advice/recommendations apply to most HF marine installations, so read this thread and you'll learn a LOT!)


You can also read the pertinent sections of the "sticky" right at the top of the Marine Electronics page here on Cruiser's Forum....
http://www.cruisersforum.com/forums/...tc-133496.html
Where you'll find a LOT of links to info on both proper installation, use, and troubleshooting of Marine SSB...


Also, please have a look at these Youtube videos (when you have good internet connectivity)....as they will explain a LOT...
"Marine HF Communications"
https://www.youtube.com/playlist?lis...ZDo_Jk3NB_Bt1y






Fair winds...

John

[Paul Elliott]

Originally Posted by ka4wja

But, some good news is in the wording you used here...."Voltage to unit is good, but I do notice that when I key the mike, it takes several seconds for the draw to go up to about 8 amps", as this implies that you have some sort of current and voltage measuring device which is not typical of a properly wired SSB radio, as this should be wired directly to the main battery bank and NOT thru a distribution panel / breaker panel, etc....so, you may in fact be getting significant voltage drop by the time the "12vdc power" actually gets TO the radio's rear panel / transmitter's PA, even if your panel meters show "good voltage"....

This may be an issue, and the "direct to the battery" recommendation is a good one, but it is certainly possible to wire the radio through a properly-sized distribution panel, current shunt, etc. This is exactly how it is done on my boat, with heavy wiring and a large battery bank, and it works very well indeed.

At the very least, I would measure the Voltage at the radio when transmitting and see what you have. If there is any hint of Voltage sag then you might have a problem. You might also try temporarily wiring the radio power leads directly to the battery with heavy leads, such as auto jumper cables. See if that fixes or changes the problem.

[transmitterdan]

Just a reminder that SSB radios don't put out hardly any power (nor draw significant current) until you actually say something into the microphone. Just keying the microphone does not cause any RF output. Talking is what causes the RF output to increase. This is unlike VHF radios where they draw maximum power as soon as you key the microphone. This "feature" of SSB is why a lot of ninny's whistle into the microphone so they can drive the radio to maximum power and current draw.

So you have to monitor the voltage at the input to the radio whilst talking. If you see more than about 0.5V variation when talking then the wire is too small or it is too long or both.

[ka4wja]

snueman,
The most important pieces of info that everyone should always provide when asking for help with radios/electronics is:
--- Did it ever work properly/perfectly??
--- Did you, yourself, personally witness this and have written notes to refer back to??
--- When was this "proper/perfect" operation??
--- List everything that might have changed since then...even tell us where the boat was then, versus where it is now!!

(and, please tell us WHERE you are at now that you are having these issues....and WHERE these other boats are at, that are not having these issues!!)





Paul, just for clarification...
While it is certainly possible to wire a SSB radio thru a 500-amp shunt, which would typically have 2/0 (or larger) wiring etc. to a main switch, and then onto a large buss bar, and it will be good for reducing voltage drops, this isn't typical...

Also, getting the radio's dc power wiring directly to the batteries allows the batteries to reduce/eliminate any RF / RFI flowing on/in the DC power wiring...on both transmit and receive....and transmit RFI can cause transmit distortions, as well as the radio's swr sensing circuitry to erroneously "fold-back" the radio's transmit power (to very low power)...thereby causing "weak transmit signals"....
(but, when tested on a dummy load, all is fine...with full power...)

The usual problem with running a Marine SSB radio (or any hi-current device) thru a distribution panel / breaker panel, is that very few of these panels are designed to handle individual hi-current devices....yes, the panels may be designed to handle 100 amps, but this is distributed power, not concentrated in one or two devices, and if attempting to do this will typically have significant voltage drops (which might not effect some devices, but can cause power output issues for radios, etc.)....but by not having the radio powered directly from the batteries, transmit RFI / RF feedback can also cause these same symptoms...

Typically single devices that require current of more than 20 amps, and/or require lower voltage drops, are powered thru individual breakers either from a buss bar or directly from the batteries (or hi-current shunt)....
Examples are: SSB Radios (30 amps peak), hi-current 12vdc refrigeration compressors (40 amps+), electric primary winches (40 - 80 amps), anchor windlasses (75 - 200 amps), hi-power inverters (80 - 200 amps), etc...

Paul, your boat's distribution panel may not have these limitations, but most do....and in addition to being on-board Tayana 37's, my brother owned/cruised on one for > 10 years (and I helped him do plenty of work on it!), and unless sneuman,the original poster here, has a new/custom 12vdc dist panel, then their Tayana 37's is not up to the task of having the SSB radio powered thru it.....(oh, to be clear, these installations might "work", just not very well...)






Dan, is correct that NO measureable RF power is transmitted by an SSB radio until someone is speaking into the microphone (or whistling)....but, the fact is that all real marine SSB radios have their transmit PA's biased very heavily into a clean, linear mode...and as such they DO draw a significant/measureable current from their 12vdc power source, when the microphone PTT button is pushed and nobody is speaking...
This is typically about 5.5 amps (5 to 6 amps)....
(on receive the typical current draw is ~ 2 amps)
So, it CAN be measured...

And, on typical non-processed SSB Voice comms /normal human speech, the current draw readings will be a rather wide range depending on the DC current metering's movement / damping....this could be as low as 7 - 8 amps, or as high as 14 - 15 amps....
(and these readings would typically be 50% higher if someone was transmitting processed SSB Voice)
Which is why I always recommend testing the transmit PA and antenna tuning using CW (morse code) carrier, or FSK carrier, if the vessel does not have a peak-reading RF Power / SWR meter!!!
(but, some older SSB radios do not a provision for this....and/or many marine SSB radio installs do not allow for easy triggering of a CW or FSK carrier....which is why we have so many folks "whistling"!!)

FYI, the Icom M-802 (and other modern Icom Marine SSB's), will transmit a full FSK carrier when in FSK Mode (RTTY Mode), and the microphone's PTT button is pressed...




I hope these clarifications are helpful....

fair winds..

John

[Paul Elliott]

Originally Posted by ka4wja

Paul, just for clarification...

Hey, I *said* the direct battery connection was a good idea! I am also saying that this may have nothing to do with the OP's problem.

In any case, I agree with everything you have said here.

[colemj]

It is possible to have the radio directly wired to the batteries through a shunt used by a system monitor or ammeter. This allows current to be determined without going through the panel.

Mark

[sneuman]

Thanks all. The radio is an eBay purchase so I don't know how well it operated in the past. I am simply looking at my battery meter when to to get an idea of the draw. I just made the direct battery connection and will do a radio check with the afternoon net.

I am in the Bahamas (grand bahama, for the moment), btw. There was a working SSB radio on the boat when I bought it 8 years ago, but I sold that knowing that it would be several years before I needed a new one. I left the grounding infrastructure and the tuner in place and have hooked it all back into the newer unit.

[transmitterdan]

Are you sure the tuner is compatible and properly connected to your radio? What is the tuner model?

[colemj]

Originally Posted by sneuman

Thanks all. The radio is an eBay purchase so I don't know how well it operated in the past. I am simply looking at my battery meter when to to get an idea of the draw. I just made the direct battery connection and will do a radio check with the afternoon net.

I am in the Bahamas (grand bahama, for the moment), btw. There was a working SSB radio on the boat when I bought it 8 years ago, but I sold that knowing that it would be several years before I needed a new one. I left the grounding infrastructure and the tuner in place and have hooked it all back into the newer unit.

If you connect the negative to the load side of you battery meter shunt, you can still monitor the current draw while having a direct connection.

I am assuming the battery side of the shunt is directly and solely connected to the battery, of course.

Mark

[sneuman]

I tried the direct connection and it doesn't seem to have helped. I have an AT-120, I believe (have to double-check), but the radio also has an automatic tuner, so I should (or could) bypass the tuner entirely.

I also checked the connection at the backstay and it seems fine.

[ka4wja]

sneuman,
With this additional info, and some thought, I may have jumped too quickly on the current draw / DC power being an issue....(although this is still a possibility, if the boat previously had a Marine SSB radio installed, and we assume it worked at some point....this isn't as highly probable as earlier)



EDIT:
With your further info, from 2 minutes ago, I see that my words in the above paragraph are well timed!!!




So, onto some further good news / recommendations...

1) Most of the basic troubleshooting YOU can do yourself, without any specialty tools/meters, etc....

Make sure you read the earlier referenced thread, where there is a LOT of good info/advice!!
Re: SSB Great Receive Poor Transmit



2) I'm at the dock in S. FL, about 100 miles from Freeport, and we could easily arrange an on-air sked / test....(but, I'm dealing with family medical issues / surgery, this week....so, not sure exactly when..)



3) If you are seeing some DC power draw on transmit, this is GOOD....
But, it would be really nice if you could tell us approx. how RF power the M-700Pro is outputting...both when you are speaking and when whistling...

Use the M-700Pro's RF output meter along the bottom edge of the display...
It has 8 segments, and on a whistle you should be getting 7 - 8 illuminated, and on normal voice (with the mic about 1" away from your mouth) you should see 3 - 5 segments illuminated....
If you are seeing these (or close to them), then the radio is almost certainly transmitting fine, AND the tuner is most probably also tuning properly...

You did not mention WHO on ebay you bought the radio from / what was their feedback rating / reputable / etc...
So, we have no way of knowing if your radio was in working condition, but let's assume that it is, as you have been heard on-the-air to some extent, and you have seen some DC current draw upon transmit...
But, we don't know how much power you are outputting (nor if the tuner is working)



4) Not knowing what tuner you have, makes it difficult to give specifics here....but...
But, I suspect an Icom AT-130...

EDIT:
Our posts passed each other!!
I see you have an AT-120....
FYI, this is a VERY OLD tuner....haven't been made in > 20 years!!!


So, I'm starting to suspect the tuner / tuner control wiring / etc...


Also, FYI....
The M-700Pro does NOT have a built-in autotuner!!!!
Do you not have the manual??? It can be downloaded from Icom, for free....



If this is the case, you can try just listening with your ears near the AT-130, first select a different channel/band (such as 12mhz) and then press the M-700Pro's "TUNE" button....and see if you hear any "clicking" sound from the tuner...
Also, look at the M-700Pro's display to see if "Tune" blinks....and if "Tune" stays illuminated...

Originally Posted by sneuman

Thanks all. The radio is an eBay purchase so I don't know how well it operated in the past. I am simply looking at my battery meter when to to get an idea of the draw. I just made the direct battery connection and will do a radio check with the afternoon net.

I am in the Bahamas (grand bahama, for the moment), btw. There was a working SSB radio on the boat when I bought it 8 years ago, but I sold that knowing that it would be several years before I needed a new one. I left the grounding infrastructure and the tuner in place and have hooked it all back into the newer unit.

There is a LOT more to all of this, but without any further info from you, I'd just be taking wild guesses....(and wasting everyone's time)




Please read my earlier posting above, as well as the referenced thread, watch the videos (when you can)....and provide a lot more info....and we can be of a LOT more help!!


Fair winds..

John

[colemj]

Originally Posted by sneuman

but the radio also has an automatic tuner, so I should (or could) bypass the tuner entirely.

Are you sure about that? I don't think that is true.

If you think the coupler is questionable, you could make a dipole and test a single band. Choose the band you know you have problems with and that others have worked you on (you mentioned that earlier, but my tablet does not let me see that as I'm writing).

Mark

[colemj]

Originally Posted by ka4wja

4) Not knowing what tuner you have, makes it difficult to give specifics here....but...
But, I suspect an Icom AT-130...



If this is the case, you can try just listening with your ears near the AT-130, first select a different channel/band (such as 12mhz) and then press the M-700Pro's "TUNE" button....and see if you hear any "clicking" sound from the tuner...

The AT130 has a large memory. If bands have been used before, you will not hear the relays when tune is pressed. To do this test, pick an unusual band.

Mark