Fuse for Palomar 80

[Ike]

I have a Palomar 80, it has no info on it for the power. Any recommendations on the fuse size?


Thanks

 

[Robb]

80 watt linear would probably use/need a 10-amp fuse. It shouldn't pop - should be OK.
But that's a guess - but I'll bet I'm close...

 

[Moleculo]

That amplifier has one MRF455 transistor, which is good for about 60 watts. The amplifier is a class C amplifier meaning that for calculation purposes, it's about 60% efficient. That means that about 60% of the power consumption will be used to amplify the incoming singal, but the other 40% will be wasted as heat. To figure out how much current it draws, use Ohm's law:

60 watts / 14 volts (typical car charging voltage) / 60% efficiency = 7 amps current draw.

A 10 amp fuse is what you need.

 

[Ike]

Thanks. Its working with a 10 amp fuse.

The quality of my reception has gone down after installing it but its using some crappy coax I had laying around. This weekend I'll get it installed properly and use some good coax.

 

[Ike]

The best i could ever get the swr was about 1:1.5 now its about 1:2.5. Can't seem to get it much better than that.

This is a mobile set up, the antenna had a grounding lead that raised the swr before so I cut it off after playing with the tuning rod. Now I think I need it. I'm going to order a new one. Hopefully with better coax and a new antenna I can get the swr better. My transmit range has gotten a tiny bit better but I'm told I sound stronger. My cheap meter is showing 40 watts. Hopefully with a low swr reading I can take advantage of those 40 watts.

 

[Ike]

That amplifier has one MRF455 transistor, which is good for about 60 watts. The amplifier is a class C amplifier meaning that for calculation purposes, it's about 60% efficient. That means that about 60% of the power consumption will be used to amplify the incoming singal, but the other 40% will be wasted as heat. To figure out how much current it draws, use Ohm's law:

60 watts / 14 volts (typical car charging voltage) / 60% efficiency = 7 amps current draw.

A 10 amp fuse is what you need.

My box says it is a 2SC2290, isn't that the transistor it uses?

Thanks

 

[Moleculo]

Could be. There were/are several different variations of that amp. If it's a 2SC2290, figure 80 watts output and apply that to the same formula.

 

[Ike]

Thanks. I'm seeing 40 watts on my meter. I often see a lower watt and a peak when amp shopping.

Under what conditions would the peak wattage be seen?

Thanks

 

[Beetle]

Thanks. I'm seeing 40 watts on my meter. I often see a lower watt and a peak when amp shopping.

Under what conditions would the peak wattage be seen?

Thanks

If you're using anything but a PEP wattmeter, you won't see true PEP, and there's no such thing as "peak" RF power. A PEP wattmeter either has internal batteries or an external power supply (wall wart) for powering the additional active circuitry it needs. Some meters have the wall wart, but it's just for powering the lights. Don't believe all of the meter manufacturers' claims.