HAM Radio power hookup

While it is true that IF you have a good connection from radio to chassis and IF you have a good connection from chassis to battery it will serve as a ground that's two big ifs. Poor connections, corrosion, loose or rusted frame members over time, etc. Can decrease the effectiveness of the ground path. (Ever work on trailer lights? They use a frame ground. It can be problematic.)
Wire is cheap and you have to run one to the battery anyway for the positive side, why not two?
If you don't fuse the negative wire you can create a situation that is dangerous for your radio. Your radio's chassis is connected thru the shield on your coax to the sheet metal of the vehicle and thru the power wire to the battery. If for some reason your main negative wire from your battery to the chassis comes loose your radio is a path for a lot of current to try to flow. This could send a lot of amps trying to travel thru your coax and radio. Again, fuses are cheap, radios are not.
Also, as mentioned, using a frame ground can cause problems with audio hum, interference, etc. I've been installing high power stereos and two-way radios in vehicle for over 20 years. I always run a positive and negative direct to the battery. It's not that much extra work but makes for a much nicer installation in my opinion.

I assume I can hook to one of the posts on the right side from this relay setup?

Clay L wrote:

ShutterStuff wrote:

Clay L wrote:
If you go HERE you can download a small program that will calculate the proper wire size for your application.
I use 12.6 volts for the DC supply voltage and allow it to drop to 12.4 or 12.5 volts at the load.
If you want to use the frame as one conductor there is a box to click for that.

Clay, your link does not work. But I just ordered 8 gauge wire to run to the battery box as it was not much more than 10 gauge wire.

Thanks for letting me know. I fixed the link by putting the setup.exe file in my dropbox.
Not sure why it stopped working. It is the library at rvforum.net and has worked fine for several years.

Got the file and thanks! 8 gauge will do just fine.

ShutterStuff wrote:

Clay L wrote:
If you go HERE you can download a small program that will calculate the proper wire size for your application.
I use 12.6 volts for the DC supply voltage and allow it to drop to 12.4 or 12.5 volts at the load.
If you want to use the frame as one conductor there is a box to click for that.

Clay, your link does not work. But I just ordered 8 gauge wire to run to the battery box as it was not much more than 10 gauge wire.

Thanks for letting me know. I fixed the link by putting the setup.exe file in my dropbox.
Not sure why it stopped working. It is the library at rvforum.net and has worked fine for several years.

Clay L wrote:
If you go HERE you can download a small program that will calculate the proper wire size for your application.
I use 12.6 volts for the DC supply voltage and allow it to drop to 12.4 or 12.5 volts at the load.
If you want to use the frame as one conductor there is a box to click for that.

Clay, your link does not work. But I just ordered 8 gauge wire to run to the battery box as it was not much more than 10 gauge wire.

If you go HERE you can download a small program that will calculate the proper wire size for your application.
I use 12.6 volts for the DC supply voltage and allow it to drop to 12.4 or 12.5 volts at the load.
If you want to use the frame as one conductor there is a box to click for that.


EDIT: Fixed link

wa8yxm wrote:
On many cars, trucks and yes, even my motor home on the main fuse panel there is a quarter inch bolt, usually brass, there are often 2 of them.

This bolt (Again on many vehicles) is directly connected to the battery by heavy gauge wire.. Great place to tap in power. and no need to drill holes since it is USUALLY already inside the cockpit. (not the case on my MH).

Source: Chrysler engineering dept employee, My Teacher (Extra class class) and personal observation.

I will look for that as I think I saw something that looks like that behind the dash. But the battery solenoid setup is close by as well and that was mentioned too.

On many cars, trucks and yes, even my motor home on the main fuse panel there is a quarter inch bolt, usually brass, there are often 2 of them.

This bolt (Again on many vehicles) is directly connected to the battery by heavy gauge wire.. Great place to tap in power. and no need to drill holes since it is USUALLY already inside the cockpit. (not the case on my MH).

Source: Chrysler engineering dept employee, My Teacher (Extra class class) and personal observation.

Yes run to the battery and ground the negative wire NOT on the battery post but nearby on the frame where the other grounds go. No need to put a fuse in it. If possible do NOT connect to the positive battery post either. There is probably a good solenoid nut or master switch where you can get some distance from the potential corrosion issues of connecting directly to the post.

With rusty chassis' and poor ground connections I recommend to NOT ground a 100 watt radio to anything nearby. A low power radio is less likely to cause any RFI issues. Most high power radios we install come with long positive and negative leads.

If you are having those kinds of problems in your mobile or home station set up I suspect it is more than just the difference between a copper ground and steel ground. You most likely don't have your antenna matched and the RF is getting into everything. I've been running mobiles since 56. Never had that problem. However nothing wrong using a torroid in a positive lead, especially if it is a long run to the battery. I use torroids to and from computer keying etc. But that wasn't the question I saw posted.