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IC-M802 Compression

Radio/Satellite/Phone/E-mail

Re: IC-M802 Compression

by Mdsilvers » Mon Oct 14, 2013 10:30 am

All of this info is very helpful. I'm getting my 802 tweaked before heading to the S. Pacific. My boat is in Grenada at the present, so not very easy to take the unit out, and ship to have the Comp selectable from the front panel.

So given this, looks like the software may be the best approach. However, I have the Pactor and it sounds like I need to turn compression off to get better performance from the Pactor. Am I correct? Just want to make sure I understand the implications and 'headache' to switch between Comp ON and OFF.

Mark

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Re: IC-M802 Compression

by ka4wja » Sun Nov 03, 2013 4:43 pm

Mark,
As I don't have a PACTOR modem, I felt I should not answer your query....and I assumed that someone here would have answered you by now!!! After all it has been 3 weeks!!!

But, in the absence of any first-hand users answering you...here are my answers...


--- My first / best answer is to call and ask Gary at Dockside Radio...

--- Next, I would say it should not matter all....assuming the PACTOR modem is wired to the M-802 correctly (not thru the microphone circuit), and assuming the M-802 is operated in one of its data modes (NOT USB or LSB), but rather in the "Wide" (2.8khz) or "Middle" (2.4khz) e-mail mode such as J2B/AFSK (although you could use "narrow" for PACTOR-II, you MUST use "wide" or "middle" for PACTOR 3 and/or PACTOR 4)....
Not sure if all M-802's have a 2.4khz "middle" bandwidth in J2B....so use "Wide"!!!

--- And, finally, even if operating the M-802 in one of the voice modes (such as USB or LSB) when using your PACTOR modem, although not sure why anyone would....the facts are that PACTOR-1 is FSK, and PACTOR-II is a multi-tone DPSK (with a narrow-bandwidth), and a PACTOR-III is a multi-tone (18-carrier) DBPSK / DQPSK (in a max 2.4khz bandwidth)...
And, since there is no actual "average tone level", they're either on or off....it is doubtful that the DSP "voice compression" in the Icom M-802 would have any effect at all on these PSK (Phase Shift Keying) modes...
BUT...
But, if using the radio/PACTOR modem in this configuration, you will most likely need to adjust your PACTOR Drive Levels, after the Speech Compressor is turned on...
EDIT:
See this page for details...
http://www.sailmail.com/setting.htm


So, while someone else here may have a real-world example for you....the science behind it, says it is a non-issue!!!
So....
So, go for it...get the speech compressor turned ON!!!


BTW, 100's - 1000's of M-802 DO have the speech compressor ON....my first one came that way when I bought it from Don Melcher (HF Radio On Board) in 2004....and at that time I was considering adding a PACTOR modem, and Don was aware of this, as he was the one suggesting I buy one... :)
Just saying...the science and 100's++ users can't all be wrong...can we??? :)



Fair winds and good luck!!!

John
Last edited by ka4wja on Mon Nov 04, 2013 8:38 am, edited 6 times in total.
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Re: IC-M802 Compression

by ka4wja » Sun Nov 03, 2013 4:47 pm

FYI, I recently made some videos on-board, detailing the Icom M-802 operations....

Please have a look here at this thread for descriptions and links to the videos...
viewtopic.php?f=5&t=16779&p=79472#p79472


And, you may wish to look at my youtube page for updates and new videos as I have the time...
http://www.youtube.com/user/captainjohn49



Please enjoy....and fair winds...


John, KA4WJA
s/v Annie Laurie, WDB6927
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John, KA4WJA
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Re: IC-M802 Compression

by ejshrader » Thu Nov 21, 2013 12:30 am

Has anyone uncovered which resistor needs to be added or removed in the resistor matrix to enable "set mode B"? I'm not afraid of a little soldering but there could be many permutations to try. Does anyone have a photo of the resistor combo in an early radio that had this enabled?

Cheers, Eric
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Re: IC-M802 Compression

by svNorthStar » Sun Mar 09, 2014 8:35 am

Has anyone discovered the resistor combination for this mod yet?
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Re: IC-M802 Compression

by svNorthStar » Sun Mar 09, 2014 8:56 am

Also, would someone please confirm that turning the compression on with the cloning software accomplishes the same thing as the hardware mod? I assume the only difference is the ability to flip it on and off from the panel? Is that correct?

On my 802, which is new as of a year ago, when transmitting on the SSB the meter indicates very low output. SWR is fine with AT140 tuner, but if I basically yell into the mic I can get a couple of bars. Speaking normally gets no output indication at all. Ampmeter confirms this. However, if I go AFSK, full scale and the expected ampmeter reading. Don't have a Bird anymore to truly read output, but based on the ampmeter readings it is quite low. I assume this describes the symptoms the compression boost is supposed to fix?

Thanks,
Steve
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Re: IC-M802 Compression

by btrayfors » Sun Mar 09, 2014 12:02 pm

Steve,

Yes, the hardware mod and the software mod essentially do the same thing as far as turning the speech compression ON.

A few things:

1. In the very recent 802's I've come across and tested, I find the same thing as you. Very low average voice output as shipped. Gordon West calls this "low talk power". Same thing occurs on-the-air....very often new 802 installations suffer from "low talk power" as compared to other SSB installations operating from the same location.

2. I've turned on speech compression in a number of 802s. It does make a big difference!

3. For a while I was a bit concerned that doing this would somehow interfere with Pactor modem use, as it's general practice to turn off all compression when using digital modes. However, the results of some testing I requested, and in actual operation of Pactor modems with 802's I've come across with COMP turned on have led me to believe that turning COMP on does not interfere with Pactor use with the 802.

4. On-the-air reports, specifically requested, also have found no deterioration in the voice quality of 802s with COMP turned on.....only report is a much stronger signal.
Bill
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Re: IC-M802 Compression

by svNorthStar » Mon Mar 10, 2014 1:11 pm

Thanks for the input Bill. This morning I borrowed another mic from a cruiser anchored nearby and there was quite a boost in avg power output using the borrowed mic. You know the scientific speaking and whistling into the mic comparison. I took the mic apart on this thing and also the one from my 700PRO that took the lightning hit. They went to a little piezo type element in this mic instead of the conventional "speaker" looking element in the 700PRO mic. We are waiting on wind for a departure to the Galapagos and am running out of time to deal with this here. If you look inside it, the entire top area of the mic that you speak into is empty. There is a circuit board there, but not the element. The mic element is actually down toward the cord and looks like a watch battery. If you look close, there are 3 tiny holes drilled at about the 5:00 position holding the mic vertically that are actually for the mic element. The whole slotted face that occupies 80% of the mic face doesn't really do anything. Odd. Not sure how the new mic design bods for the future.

Anyway, waiting on an answer from a US vendor about Fedex'ing the disc/cable and maybe a new mic?

Has the hardware mod seen the light of day yet, certainly seems the best way to go??

Steve
S/V North Star
Balboa, Panama

BTW, anyone have any experience with the Panama Icom guy? Alberto. He says he has a mic at about 3X the US price?
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Re: IC-M802 Compression

by ka4wja » Tue Mar 11, 2014 9:09 am

Steve,
1) I have had very good luck with Williams Communications / Icom Service Center in Tallahassee, FL....
Icom Service Center - Florida
5046 Tennessee Capital Blvd.
Tallahassee, FL 32303
Phone: (800) 649-5783
Fax: (850) 575-

They gave me excellent and very rapid (next day) service on my Icom M-802 microphones (deteriorated mic cords)....
I would highly recommend a call to them!!!



2) As for the mics themselves...
Icom has gone from the older dynamic mics to the newer electret condenser mics, some years ago...both on their marine radios and ham radios...
(electret condenser mics are ubiquitous these days...the only reason many microphones are still the size they are is to give the human hand something easy to hold on to and allow easy PTT with an index finger!!!)

The electret mics output about 20db more audio signal, so they are not interchangeable...and I believe the in normal Icom mic wiring scheme, trying to plug an old mic into a newer radio may cause a short in the +8vdc power feed to the mic....(which may blow this circuit out???)
I believe this is one reason for the different mic plugs being used???



3) As for the M-802's speech compressor...
a) Yes, the hardware mod vs. the software, accomplish the exact same thing....(with the hardware mod allowing a "push-button" control to switch on/off, rather than needing a laptop connected to the radio to do this)

If you wish this mod done, contact Gary at Dockside Radio....
http://www.docksideradio.com/Icom%20SSB%20Radios.htm

But, to be honest, I cannot think of a reason to want to turn it off....so, if the "local Icom guy" has the CS-802 software, you could have the speech compressor turned on via software in less than 5 minutes....


b) The M-802's speech compression has no adverse effect on use of a PACTOR modem...
Aside from checking (and adjusting if necessary) the PACTOR drive levels, after you turn ON the compression, there should be no issue at all...
http://www.sailmail.com/setting.htm



4) FYI, Icom (as well as many other manufacturers) has had some problems with mic cord deterioration (bad plasticizers in the rubber cord jackets made by a vendor)....
Here is a thread dealing with that...

viewtopic.php?f=5&t=12001



Fair winds and good luck!

John
John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110

(currently lying, Sewall's Point, FL)

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Re: IC-M802 Compression

by ka4wja » Mon Mar 31, 2014 6:50 pm

With the spring outfitting season starting, and with Atlantic-Crossing season starting in the next 6 - 12 weeks, I thought some may find this information helpful...

John
John, KA4WJA
s/v Annie Laurie, WDB6927
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(currently lying, Sewall's Point, FL)

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Re: IC-M802 Compression

by ka4wja » Mon Sep 01, 2014 5:09 pm

With the fall outfitting season starting, and with Atlantic-Crossing season / US-to-Caribbean passage season both coming up, I thought some may find this information helpful...

PLEASE make sure that your M-802 is working fine on VOICE (and DSC, as well!) communications, BEFORE you head out!!
And, making sure the Speech Compression is turned On, is a simple/east/cheap way of significantly improve your M-802's performance!!


Fair winds....

John
John, KA4WJA
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Re: IC-M802 Compression

by jrp » Wed Nov 02, 2016 3:47 pm

Found on saildocs:

This document describes how to modify early Icom M802 radios for increased modulation with voice SSB transmission. Step 1 requires removal of three components in the control head and increases the mic gain, step 2 requires removal of a resistor in the main box and enables an internal speech compressor.

This modification should be done only by skilled technicians with experience with surface-mount (SMD) technology. These are tiny surface-mount components and the best way to remove them is with tweezers and a miniature temperature-controlled soldering iron. Extreme care must be used to not damage any other circuits or PCB traces. A good light and a magnifying glass is also required. If the proper equipment is not available, or if you are unsure of any of these instructions, do not proceed. These instructions are carefully written but may contain errors, they may not be clear, and radios can change. These modifications are made entirely at your own risk.

Step 1: Disconnect power. Open the control head (8 screws), do not disconnect ribbon cable to rear of case. Lay the control head face-down with knobs towards you, that is "bottom", side away from you is "top". Below the ribbon cable (located near top edge just left of center) is a metal shield (shallow box). Centered above the metal box, just left of a white plastic "clip", are two tiny resistors that are oriented vertically, and three that are oriented horizontally. The right-most of the two vertical resistors is R8229, our target: remove it.
Now go to the upper-right corner, and find the small round can (capacitor) closest to the screw in the extreme upper-right. Immediately left of that is a tiny black rectangle with 3 connections, that is Q8280 and our second target: remove it. And just below and to the right is another resistor, R8288 and our third target: remove that also.

Step two requires opening the main box (8 screws total). Orient the box with the printed circuit board (PCB) towards you (call this "down"), antenna connector away (call this "up"). Near the center towards the front is a metal about 2 inches x 4 inches, that is a "daughter PCB". Lift it off the main board, rocking it very gently and being careful of the metal grounding tabs. Under that daughter board is a black rectangular component with a million connections (the microprocessor), and above (towards the rear) and to the right of the microprocessor is a double row of 14 resistors per row, separated by a row of 14 small holes. Just to the right of the row of 14 holes is a single resistor. For reference, this lone resistor is just left and above the upper-left corner of the larger white connector that the daughter board was plugged into. Our target is R3403, which the right-most of the upper row of 14 resistors just described. Remove this. This allows the internal speech compressor to be enabled, see below.

Double-check, replace the daughter board, re-assemble and test. The increase in DC amps indicated by a "Link" battery monitor (or equiv) is the best guide to power output. Whistling next to the mic should generate 75-100 watts, about 8-14 amps increase.

To change the speech compressor setting, power off the radio, press and hold "F" and MODE keys, and power on. Rotate the left "group" (GRP) knob to select "COMP", and set it "on" or "off" with the right "CH" knob. (Make sure it is off for email use). When using the speech compressor monitor power output and avoid over-modulation.

--jec 6/2004
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Re: IC-M802 Compression

by ka4wja » Fri Nov 18, 2016 3:25 pm

jrp,
I find the recommendation to increase the "mic gain" to be extremely worrisome!!
(actually, it is one of the worst things that anyone can do to any radio needing to produce clean linear RF signals, such as SSB Voice!)

Simply turning on the DSP-based Speech Compression is fine....and this alone increases the M-802's "talk-power" significantly, without adversely effecting the transmit spectral purity, nor significantly increasing ancillary background noise pick-up by the microphone...
And, whether you choose to do this via software or a hardware fix, it should be the same...

But, not only is there no reason to increase the M-802's mic gain, doing so will effect both the transmit spectral purity and reduce intelligibility of your signal!!!
I highly advise against doing this!!
It will not improve your system, but actually the opposite! (and, at the same time end-up causing interference to both other mariners, as well as possibly other HF users!!

PLEAEE do NOT try to increase the M-802's mic gain!!!
(Turning On the Speech Compressor is okay, but NOT increasing the mic gain!)

One good note here is that some that would attempt this, might screw-up their radio trying to remove surface-mount devices...but, just save yourself the heartache, just turn on the DSP-based Speech Compressor, and you'll be fine!!



BTW, sorry about the long absence....it seems that the SSCA IT team finally got the system here working okay, so I can now log in!!
(fyi, this is why I've not been around here in a long while...heck, I even had to give up my SSCA membership, because I could no longer log-in to the SSCA site, read meeting minutes, etc....but, to be honest they've got a ways to go to get me back...)


Fair winds..

John
John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110

(currently lying, Sewall's Point, FL)

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