ICOM 802 Power Draw When Off

[SvenG]

Originally Posted by btrayfors

Fact is, MOST if not all ham radios, marine radios, military radios, land-mobile radios, etc. do in fact have such a connection, i.e., there is a dead short between the -VE power connector and the chassis.

That didn't make any sense to me as the ICOM 803 instructions specifically state:

Undesirable ground points
• Engine block
• Ship's DC battery ground

So I went and measured and confirmed that it is indeed correct for the 802, the chassis is connected to negative.



-Sven

[fairbank56]

Originally Posted by SvenG

That didn't make any sense to me as the ICOM 803 instructions specifically state:

Undesirable ground points
• Engine block
• Ship's DC battery ground

That is in reference to the RF ground. Even though they are connected, don't rely on the engine block and/or DC battery ground as your RF ground.

Eric

[SvenG]

Originally Posted by fairbank56

That is in reference to the RF ground. Even though they are connected, don't rely on the engine block and/or DC battery ground as your RF ground.

Eric

I wish you hadn't cut the rest of what I wrote:

So I went and measured and confirmed that it is indeed correct for the 802, the chassis is connected to negative.

-Sven

[DeepFrz]

One more good reason not to connect the ground lug on the chassis to the DC Neg bus. You are just asking for ground loops in that case.

Bill, do you connect the chassis grnd. point to a ground rod? When I lived in a house and was an active ham I had a ground rod through the basement floor under the Transceiver location. When I installed my ham radio on a boat I did not use that connection.

[btrayfors]

Originally Posted by DeepFrz

One more good reason not to connect the ground lug on the chassis to the DC Neg bus. You are just asking for ground loops in that case.

Bill, do you connect the chassis grnd. point to a ground rod? When I lived in a house and was an active ham I had a ground rod through the basement floor under the Transceiver location. When I installed my ham radio on a boat I did not use that connection.

No, I don't use the ground lug on the chassis, especially not in a marine installation. It can create undesirable ground loops and, anyway, the chassis is "grounded" thru the negative power cable.

In shore installations, a good station ground is usually desirable to help bleed off static electricity coming down the coax and generally to quiet the reception.

Bill
WA6CCA

[goboatingnow]

Originally Posted by btrayfors

No, I don't use the ground lug on the chassis, especially not in a marine installation. It can create undesirable ground loops and, anyway, the chassis is "grounded" thru the negative power cable.

In shore installations, a good station ground is usually desirable to help bleed off static electricity coming down the coax and generally to quiet the reception.

Bill
WA6CCA

Maybe it's a radio thing. But cases connected to DC negative are real bad, as you can inadvertently create un intended DC return paths. ( Like two cases touching ) , Very nasty. Must measure my VHF cases.

Dave

[Wotname]

Originally Posted by btrayfors

No, I don't use the ground lug on the chassis, especially not in a marine installation. It can create undesirable ground loops and, anyway, the chassis is "grounded" thru the negative power cable......
Bill
WA6CCA

FWIW, on marine installations where there are dedicated radio racks and cabinets complete with earthing bars (and equipotential bonding etc), we usually connect the chassis ground lug to the rack / cabinet earth bar. If no earth bar is available, we leave it unconnected. Not saying this is right or wrong, just saying it is how we do it. These racks usually have their own dedicated DC supplies from the ship's main AC source and the DC -ve is either floating or else tied to the rack's ground bus

In light of Dave's "idiot engineers" comment, I did come across one installation of a DC supply in a rack where the original installers (designers??) fitted the AC/DC convertor with the +ve side as the "common" (but not tied to the ground bus) and the -ve side as the fused distribution side. This made the radio chassis "live" with -12 volts with relation to the DC "ground" in that rack.

The other racks nearby all had the convertors wired in the more manner. It took a few minutes of head scratching to work out what was going on. Once the customer was advised, he soon had us re-working that particular convertor. Strange things happen off-shore