Maximizing Your Rig's Output Power
As you may or may not know, I enjoy operating from remote locations while using my Yaesu FT-897D as seen in the insert photo above.
Under those conditions, I power the FT-897D with the internal batteries that reside in the battery tray located at the bottom of the transceiver.
Now there are times that I operate my portable station, and this would be with the FT-897D, that I am within reach of my mobile, and therefore can take advantage of powering the FT-897D with the 75Ah DC power-pack that is located in the cargo bay of my mobile as seen in the insert photo above.
Now this power-pack is multi-purposed and one of the things it is used for is to power my APRS weather station VE6AB-8, as seen in the photo as well.
When I am operating my APRS weather station, the remote sensors ( anemometer and wind-direction sensors) are mag-mounted to the roof of my mobile.
This 75Ah DC power-pack is also utilized for other purposes, and one of its capabilities is the fact that it can be used to jumpstart a vehicle through the use of the 4 gauge accessory jumper cables made up for that purpose, that may be connected to the power-pack through the Anderson SB®175 powerpole connector located on the side of the power-pack.
Now its a rare day that this jump-start option gets used, and recently I realized that I could take advantage of this power outlet for another purpose.
The purpose that I had in mind, is to power my FT-897D when I am operating the transceiver with it sitting on the tail-gate, or from the top of the cargo-bay cover, or a nearby location.
Now this is where it gets tricky, well maybe not, and as you know or may not know, powering your rig is about more than just providing 12 VDC or there-abouts, but also about current flow, and the size and length of cables you choose should be based on the amperage required by your transceiver to provide maximum watts out.
The point is that the length of power-cables you use to power your portable HF rig capable of outputting 100 watts, need the proper gauge cables to make this happen, as you don't want to starve the rig by using too small a gauge of cable (wire) for this purpose.
In the above photo, the fused cable assembly on the extreme right is the original power-cable provided by Yaesu that came with the FT-897D, although I modified it with powerpoles installed at either end of the cable for convenience.
Now I can connect the FT-897D through the use of this stock cable directly to the various power sources available to me, that include my 30 caliber power-pack (as seen elsewhere), or the power-pack mounted in the cargo-bay of my mobile, both of which are equipped with powerpole options for that purpose..
Either way, the FT-897D may still be limiting the output power going to the antenna due to the voltage/current being compromised by the size of the wiring.
Recently while operating my FT-897D with it located on the rear deck of my mobile, and connected to the power pack in the cargo bay, I was aware that the drop in voltage as indicated on the display of the FT-897D was due to the very long 14 gauge (20') powerpole equipped extension cable that I was using to power the transceiver, this cable normally used as an extension cable for my solar panels.
I realized that I needed to make up a dedicated high-current-flow accessory power cable, and I decided to take advantage of the SB®175 powerpole connector residing on the power-pack that is connected with 4 gauge cables to the batteries located in the battery box.
The FT-897D operating at 100 watts out draws 20 amps at key-down, and once I did the math based on the fact I wished to use 12' power cables, 8 gauge cables were required.
Cables of that size and length would deliver the maximum amperage required by the transceiver, with a minimal drop in voltage, allowing the FT897D to output the full 100 watts the rig is rated for.
With the use of a SB®175 powerpole connector, the required 12' length of 8 gauge two-conductor power cable with protective housing, and 75 amp powerpoles, I made up the power-cable pictured here.
The reason I terminated the cable assembly at the output end with powerpoles rated for 75 amps, is that it gives me the option to power other devices requiring higher amperage rated cables.
For powering my FT-897D and other devices that have power cables terminated with your typical 30 amp sized powerpoles, I have various adapter cables made up that allow for plug and play options, depending on how I wish to set things up.
As you notice, one of the accessory adapters is a pair of fuse-holders that are terminated at both ends with powerpoles.
This allows me to insert fuseholders with the proper sized fuses, wherever they may be required, depending on how I have assembled the various cables shown here, and other cables that reside in my go-box.
Its critical that you have fuses protecting your devices at all times, and of the required rating as specified by the manufacturer of the transceiver or device being powered.
With stock power cables, the fuseholders are in place, but once you modify or make up new power cables, make sure and install fuse holders as required.
So with the FT-897D connected to the 75Ah DC power-pack using this high-current-flow power cable, and when I key the mic attached to the FT-897D, I know there is maximum smoke happening at the antenna.
Click on the photo for a closer look.....
Operating the the FT-897D as described above.....