AmateurRadio.com

Do we need those inline fuses between our radio and power supply, most if not all radios come with them but are they always needed? There was a time when I thought the more fusing the better and safer, but does it add to the safety or is it just redundant fusing? First off let me begin with, this is my own opinion and I do follow it whether you choose to or not it is absolutely up to you. 

I was having an issue with my Icom 7610 cycling off and then back on again while transmitting . The issue was narrowed down to resistance within the cable from the power supply to the radio. I first replaced the poor terminal connections on my Astron power supply. The issue returned again it was then further determined that the guilty party was the inline fuse/fuse holder connection. I cut out both inline power cable fuses...OMG, you say?
Well, not really if (the big if) you have a power supply with very good built-in protection meaning over-voltage protection (crowbar), over-current protection (fold-back current protection), over-temperature shutdown and an internal AC fuse I believe you are good to go without inline DC fusing between power supply and your rig. Again in the background I hear "OMG, you did what"

I do hear some saying "Wait what if there is an issue in my supply line from the power supply to the rig" This is true BUT keep the power cable as short as possible and if you have worries about overheating cables, moving parts or rodents then you have bigger issues than un-fused power cables. Having said that if something between the power supply to the radio power cable causes a sudden increase in current or voltage the power supply protection will quickly look after that. 

 Some who have a large rig such as the Icom 7610 or other manufacturers could be saying "there is no way this rig will be used as a mobile by the average ham but it has fused leads". My answer to that is the big 5 (Icom, Kenwood, Yaesu, Flex and Elecraft)  have no idea what power supply you are going to use. Also, some may opt to use a deep cycle battery at home on a trickle charge or whatever. 

After everything I have said about fuses I am not against them and as a matter of fact I have a Rigrunner fused rail and use it and I am thankful for it. I connect my external ATU, noise cancelling unit and SWR meter (for the light) to it. 

Now if you have no issue with your supplied power to your radio and things are not acting up like they were with me then by all means keep the fused line but for me, some radical thinking cured the problem and some power supply understanding allows me to sleep at night knowing the radio is in good power supply hands.

 This past weekend I was rolling along in the CWop open CW contest when all of a sudden when I sent CW my Icom 7610 shut down and then cycled back on all on its own. My output power was 100 watts and each time I transmitted the rig would cycle off and back on again. I had already been contesting for about 3 hours and all was good and now this!

With the contest completed and still hearing CW rings in my ear, it was now time to turn my attention back to the 7610 power cycling issue. I subscribe to Groups.io which is an email group and one of my email groups is called Icom 7610 you guessed it, it's all about the Icom 7610. I read the threads regarding power cycling and the Anderson power pole. The consensus seemed to be the connection point of these connectors can develop a poor connection. The fix some used was like I did to connect and reconnect a few times. While others removed that style of connector altogether. 

On the Icom touch screen, you can bring up a menu called meters. One of the meters is the Vd. This meter reads the real-time internal voltage of the 7610. On the scale, there is a red section and if the voltage gets to this point the radio will shut down. Once the sufficient voltage is supplied again the radio will cycle on again. Thus the issue I was having. When I was transmitting I was drawing much more current then bring in a poor connection (resistance) thus drawing more current. When you draw more current your voltage goes down and if it goes below what the Icom 7610 wants the radio shuts down. As soon as it shuts down more than enough voltage is available as very little current is being used and the radio cycles back on again. 

On the Anderson power pole site, they do have a bulletin as to why a connection issue may exist. Some causes they mentioned were a poor crimp connection if you decided to solder the connection a poor solder job and if the solder flowed down onto the connection tabs this could be an issue as well. I have to be honest I have been using Anderson power poles for a long time and I have never had an issue. 

I wanted to see if the Anderson power poles have in my case become an issue. My test was set up as follows. I wanted to have a steady constant load on the Icom 7610 and what better way than to transmit an FT8 tune signal, I choose to use 100 watts. I would connect the radio as it was during the contest and then send an FT8 carrier at 100 watts. Record the voltage drop on the Icom Vd meter. Then remove the Anderson power poles from the Rig runner. One is the power cord from the radio, the other from the power supply to the Rig runner. Run the same test and record the results. finally, remove the Anderson power poles from the cable from the Icom and connect it directly to the Astron SS-30-M power supply which has screw terminals. Then record the results. 

Before I began I checked the terminal voltage on the Astron power supply and it was 13.8 volts DC. Also during the tests, the power supply voltage stayed at 13.8 volts DC. Below are the results from the tests. 

Just a word about the Vd meter before we begin. I determined that the Vd meter scale is 0.24 volts per hatch mark. Therefore the minimum voltage red trip line on the Vd meter scale is the 6th hatch mark from left to right (11.44 volts) with the first hatch mark counted as zero. 

The first test was with the radio connected to the Rig runner via the Aderson power pole and the power supply connected to the Rig runner via the Anderson power pole. The results below when FT8 test tune at 100 watts was Vd voltage dropped to two hatch marks above the trip red line. 

For the second test, I removed the Rig runner and connected the two Anderson power poles one to the other. The FT8 100-watt test tune gave the same results,  two hatch marks from the trip red line. 

Finally, I removed the Anderson power pole from the radio power cord and stripped the ends and attached it directly to the Astron power supply via its screw connectors. The FT8 100 watts test resulted in a surprising result of 5 hatch marks above the red trip line.