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SvenG · 06-12-2013, 23:09

One of the reasons why ICOM tells you to connect the ICOM directly to the battery instead of through a breaker has to do with the crystal oven:

Quote:

NOTE:
Disconnect the battery from the IC-M802 main unit, or charge the battery during anchor, otherwise the battery may be exhausted.

The IC-M802 has a high-stability oven-heater type crystal oscillator, and when connected to the DC power socket directly, it keeps its temperature to at the specified level even if the transceiver power has turned OFF

That's from the ICOM manual.

What I'm wondering is what current draw that oven imposes. It's nice that the radio is always warmed up and ready to go but I'm not sure that our all-solar budget is happy about the constant drain. I don't want to install a switch if the draw is miniscule, but our power budget seems to have suffered ever since the installation.

BTW, the radio with the KISS is outstanding !

-Sven

**Wotname** · 07-12-2013, 01:18

I'm sure one of the radio bods will post the correct figure but I sotta recall it is around 100 mA, maybe less.

funk-an-bord.de · 07-12-2013, 01:58

The power drain when receiving is stated in the manual as max. 3 Amp.
Short answer: 1 Amp might be the consumtion of the oven.
So you might have a 24 Ah per day.
So a switch is apropriate.
The ICOM M801 has a power switch at the black box.
The internal oven might have a temperature of 75 degees Celsius.
So you have a constant heat loss and the electrical energy to heat the oven depends on the temperature of the environment.
You can easily measure the current drain.
During a hot day you will have less current than in a cold night.
Don't try to transmit in that moment, the current of 30 Amp will blow up the Amp-Meter.
Greetings, Wilhelm

CarinaPDX · 07-12-2013, 02:03

I think the best approach is to turn off the power to the M802 after using it, then turn it on a half hour or so before transmitting for the xtal temp to stabilize. That is pretty common practice.

Greg

SimonV · 07-12-2013, 02:22

Simple Sven don't go where the temperature is less than mid 70s. I have a 60amp circuit breaker in line and just flip it open when I finish using the 802.

svBeBe · 07-12-2013, 02:45

Quote:

Originally Posted by SvenG

One of the reasons why ICOM tells you to connect the ICOM directly to the battery instead of through a breaker has to do with the crystal oven:

I do not think that ICOM tells you to connect the radio directly to the battery without a breaker in the circuit. That is wrong on many levels.

Bill

funk-an-bord.de · 07-12-2013, 04:23

Quote:

Originally Posted by CarinaPDX

... then turn it on a half hour or so before transmitting for the xtal temp to stabilize. That is pretty common practice.
Greg

Half an hour is useful when you have an HAM radio without a temperature regulated oven for the crystal oscillator. Then the entire transceiver has to warm up.
The goal of the oven is to get the cristal in a shorter time to the optimal operating temperature. That is reached in some minutes.
If the temperature is not reached, the receiving station will get your voice with a pitch - a frequency shift.
HAM radios without a Oven Controlled Crystal Oscillator (OCXO) have an extra knob to compensate the frequency shift.
Greetings Wilhelm

SoonerSailor · 07-12-2013, 06:23

The radio draws less than 200 mA to keep the xtal warm. The oven is intended to keep the crystal at a constant temperature well above the varying ambient for a more predictable and constant resonant frequency. The oven assembly is small, so requires little power to heat.

steve77 · 07-12-2013, 07:20

Quote:

Originally Posted by svBeBe

I do not think that ICOM tells you to connect the radio directly to the battery without a breaker in the circuit. That is wrong on many levels.

Bill

The power cable supplied with the M802 has an in-line fuse holder installed in the positive lead. ICOM does recommend you connect directly to the battery, and this fuse is the protective device for the circuit.

btrayfors · 07-12-2013, 07:53

As usual, lotsa good and lotsa bad info here.

1. All SSB transceivers should be connected directly to the house batteries, not thru the switch panel (mostly to ensure good clean power to the radio and avoid RFI as much as possible). HOWEVER, you MUST have a suitable fuse or breaker in the line, and you must use appropriate-sized battery cable. The cable supplied with the 802 DOES NOT qualify. For runs up to 20' one-way, use AWG6 cable. Use AWG4 cable for longer runs. Terminate these cables near the main radio box, cut the supplied power wires short, leaving a foot or two extra, and connect to the larger cables.

2. The only CPDs (circuit protection devices) which qualify under ABYC guidelines for direct connection to the house batteries are ANL or MRBF fuses, or one of the new Blue Sea Systems breakers with more than 5,000 amps interrupt capacity.

3. You must fuse BOTH the positive and the negative cables, preferably very close to the house batteries.

4. If 5AH per day draw for the xtal oven is too much for your boat, then by all means cut off all power to the 802, using the breaker or fuse as appropriate. I generally install a small battery switch like the Blue Sea Systems #6006 directly in the positive AWG6 cable, located near the radio. This is in addition to the ANL or MRBF fuses located near the batteries, and makes it convenient to cut all power to the radio.

5. While the comment re: ham radios certainly applies to the older tubed transmitters, modern all-transistor ham radios generally don't need much if any warmup these days. Any of the 10 ham radios in my shack and workshop will come up right on frequency right away....and they stay there.

6. Crystal oven warmup time is generally about 60 seconds or so after turn-on from a cold start. This "always-on feature" Icom has built into the 802 is a questionable one, like many other design decisions on this radio.

Someday when time and energy permits I'll start two new threads: "What's right about the 802" and "What's wrong about the 802". Guess which will be longer?

Bill
WA6CCA

steve77 · 07-12-2013, 08:01

Btrayfors- I have heard other people recommend fusing both sides of the power supply, but have never understood the reason for it. Would you mind explaining your reasoning for fusing the negative wire of a DC circuit?

Thanks!

btrayfors · 07-12-2013, 08:07

Quote:

Originally Posted by steve77

Btrayfors- I have heard other people recommend fusing both sides of the power supply, but have never understood the reason for it. Would you mind explaining your reasoning for fusing the negative wire of a DC circuit?

Thanks!

Sure. It's a safety precaution. On most boats, a dropped ground could result in an unwanted draw -- sometimes a very large one like engine starting -- thru the radio and it's ground wire. Clearly, this is not desirable :-)

Many new SSB radios these days -- both ham and marine -- come with fuses in both the positive and the negative power wires. That's fine insofar as it goes, but the in-line fuses are not rated for direct connection to a large battery bank (the house bank), nor is the wire size adequate for most marine applications, where house battery voltage may be low and where little or no voltage drop is desired. That's the main reason for using larger battery cable directly to the house batteries, along with the reduced RFI potential of such connections.

Bill
WA6CCA

highseas · 07-12-2013, 08:24

Bill,would you say the Icom M710 needs same modifications?

steve77 · 07-12-2013, 08:28

Apologies to the OP, not meaning to hijack this thread. Btrayfors, by "dropped ground", do you mean an inadvertent connection of the ground wire to DC positive? I'm just not familiar with the terminology.

Back to the original topic, I won't be on the boat until after Jan 1, so I can't measure the current of the Icom when powered down. I also am curious as the current draw, so I will measure it when I get aboard.

If no one else has posted the result by then, I'll let everyone know what I find.

Steve