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Old 16-01-2015, 07:01   #31
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Re: SSB Current Draw - Both Transmit and Receive

No offense taken. I actually deleted the post you quote minutes after posting having read the rest of the thread (which of course I should have done before posting. My bad.).

I'm a typical cruiser-with-a-ham-license, not a died in the wool ham much less radio engineer so my focus does tend to be on what works--for me. Troubling to think that distortion from low voltage or varying voltage or whatever other shortcomings my equipment suffers from could be causing interference elsewhere in the spectrum and elsewhere in the world. I remember a few years back in Georgetown Pactor users would be asked not to transmit during the morning VHF net. I'm not hearing anything on this issue this season. I think most folks are using the Internet (or sat for the better-financed) for routine comms these days anywhere there's decent cellphone or wifi coverage. Come to think of it, I haven't used the Pactor since I tested it before heading out of my homeport in the fall. I used it (successfully) every day when underway while sailing around the world '06 to '09.

Speaking of Pactor, my point was that the operator can usually decrease the RF power during a connection to reduce power consumption and interference. I've never tried to use this feature, but I think Airmail can and will reduce power automatically if the radio is under computer control.

The voltage drop chart in the West catalog (by Ancor, I gather) indicates 10 gauge wire for a short run (say 10 feet round trip) and 8 gauge for up to 25 feet for a 3% voltage drop at 30 amps. Obviously no harm in bigger wires from a physical point of view, but weight, cost and wastefulness are important to some cruisers. And we all need to understand and be reminded that the power wire should be rated for the peaks of consumption, not the average consumption, to minimize voltage drop and attendant performance and interference issues.

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Old 16-01-2015, 07:59   #32
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Location: UK and Central America
Boat: Tucker CA41 Steel 40 foot Ketch
Posts: 218
Re: SSB Current Draw - Both Transmit and Receive

I can confirm that the iCOM 802 draws about 2 amps just being switched on

And to the OP with a steel boat BE AWARE that the 802 set is powered UP even when the switch on the head set is off.

The ground wire sends RF and 12V dc to the grounding point so I have had to fit a double throw, double pole switch to stop this and also a grounding isolation bridge as I also have a steel boat and do not want stray 12 volts flowing around.

There is no hint of this in the manual and it took me 8 years to find this out. I am pretty sure this has resulted/contributed to me having to replace steel plates before their time

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Old 16-01-2015, 08:37   #33
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Re: SSB Current Draw - Both Transmit and Receive

Originally Posted by ka4wja View Post
Sorry to resurrect a 7 month old thread....but, I have some additional info...

Working with a ham radio manufacturer who is looking into improving their transceiver's transmit IMD, he mentioned that it seems the M-802 used a fair amount more power than typical "100-watt" ham rigs did, and asked me if I had the current draw figures (which I did for the most part, but I went ahead and did a new round of tests..)

Here are the Icom M-802 current draw figures (normal production run tolerances might be reflected in other M-802's having minor variations on different bands/freqs, but overall these should be very close for all M-802's...)

The stand-by and receive current draw...
Under stand-by, radio turned off, the TCXO draws about 100-110ma (~0.1amps), and on receive w/ audio, in all modes, it draws about 2.1 amps....all at 13.7vdc

My M-802 is run off a large (1125 A/H) battery bank, charged via a large solar array....and early this morning the battery voltage was 13.7vdc....a short run of 2ga wire powers the radio, with typ. max voltage drop of about me about 13.3-13.4vdc at the radio this morning, at the max current draw of 29.4 amps...

So, here are the overall current draws of the radio on the various bands (subtract 2.1 amps, the current draw in receive, for transmitter-only current draw), at approx. 140-150 watts output...

The zero-signal, mic-keyed but no modulation, current draw was 5.4 to 5.5 amps on all bands, 160m - 10m...

Band ```` SSB-whistle````` FSK Carrier (PACTOR-I)
160m````` 25.6amps`````` 25.6amps
80m ``````28.7 ````````` 28.7
40m ``````25.6`````````` 25.6
20m ``````28.7``````````28.8
17m```````24.7 `````````24.6
15m```````29.3 ``````````29.4
12m ``````24.4```````````24.3
10m ``````24.6``````````` 24.5

PACTOR-II is an approx. 50% duty-cycle mode, so "average" current draw in PACTOR-II would be about half of the FSK PACTOR-I figures....and PACTOR-III's duty-cycle varies from ~ 30% to ~65% (depending on speed), so your "average" current draw in P3, will be 30% - 65% of the FSK PACTOR-I figures...

(FYI, the M-802 is spec'd at 30 amps, max current draw @ 13.6vdc....and all of these figures are about typical for a 150-watt marine HF transceiver....and yes, that is more than your typical "100-watt" HF ham rig...)

All measurements were done near the radio, with a fairly new Klein clamp-on meter (which has proven to be within 0.1 amps of other meters I have tested it against), at ambient temp of about 70*F....with battery voltage of 13.7vdc, and voltage at radio of approx. 13.3-13.4vdc under full current draw of ~ 29amps...

So, when people tell 'ya that you need to figure on 30 amps of current draw from a Marine SSB radio, they are correct....judge and size your wiring run accordingly...

I hope this helps...

Fair winds to all....

John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110
Nice to a good objective response. Thanks.

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