Does Power Output Matter? (Hint: NO!)

[OffRoaderX]

When transmitting on an HT and using the HT rubber-ducky antenna, power output on GMRS or 70cm does not matter when in the range of 2 to 10 watts!

...change my mind....

[LeoG]

11.76dB 4w > 60w

[WRUE951]

On 7/10/2025 at 3:06 PM, OffRoaderX said:

When transmitting on an HT and using the HT rubber-ducky antenna, power output on GMRS or 70cm does not matter when in the range of 2 to 10 watts!

...change my mind....

I think the only thing that matters using high power on an HT is it will drain your battery 5 times faster then low power.  

[nokones]

10 hours ago, LeoG said:

11.76dB 4w > 60w

I knew that when I wrote my response, I just didn't convey it correctly. In a rush while I was waiting for my last Physical Therapy session, I counted my multiplication factor of the 4 watts as the number of dBs with my fingers rather than the total dBs. That is what I get for rushing myself and using an android device.

[WRDJ205]

At the risk of being flamed…I tried using a Baeofeng MP-31 (output of about ~2W) to reach a low watt repeater about 3/4 mi away in a heavily tree lined suburban area.  Unfortunately, I was not able to successfully hit it.  
 

I swapped to a Tidradio H3 with the stock antenna and was able to hit and communicate through the repeater.  This radio transmits at about 5W.  
 

Attached is a photo of the area I was walking. 

[LeoG]

On 7/12/2025 at 10:11 AM, nokones said:

I knew that when I wrote my response, I just didn't convey it correctly. In a rush while I was waiting for my last Physical Therapy session, I counted my multiplication factor of the 4 watts as the number of dBs with my fingers rather than the total dBs. That is what I get for rushing myself and using an android device.

That's OK, I cheated and used the internet to do the calculation.  Put in a wattage and it spits out a dBm and you subtract the dBm's and there it is.

[marcspaz]

54 minutes ago, WRDJ205 said:

At the risk of being flamed…I tried using a Baeofeng MP-31 (output of about ~2W) to reach a low watt repeater about 3/4 mi away in a heavily tree lined suburban area.  Unfortunately, I was not able to successfully hit it.  
 

I swapped to a Tidradio H3 with the stock antenna and was able to hit and communicate through the repeater.  This radio transmits at about 5W.  
 

Attached is a photo of the area I was walking. 

 

No flames... but there are so many other things that could have contributed to your results. That fact that you didn't use the exact same radio for both tests, during the same time of day from the same location (I think), are the big items that come to mind.  Slight movement can make a huge difference, too. I can stand in one spot in my driveway with my HT using 0.5w and hit a repeater 30 miles away... but if I move a few inches out of that same spot, I can't hit the same repeater with my 115w mobile and high gain antenna. 

[LeoG]

I found a spot like that 17.5 miles from my repeater.  Pretty much a foot either way and nothing.  Amazing I even found the spot.

And there's no way I should have even been able to touch my repeater with a mountain in the way.  I know it's mine from the courtesy tone I use.

[WRDJ205]

2 minutes ago, marcspaz said:

during the same time of day from the same location

I’m just providing real life results in my situation and it was the same time of day.  
 

But, yes, two different radios.  
 

I’m trying to get a better picture of what and where different variables come into play in my area.  I was able to use the MP-31 from this same street in the winter with less dense foliage.   

[AdmiralCochrane]

8 hours ago, LeoG said:

I found a spot like that 17.5 miles from my repeater.  Pretty much a foot either way and nothing.  Amazing I even found the spot.

And there's no way I should have even been able to touch my repeater with a mountain in the way.  I know it's mine from the courtesy tone I use.

Diffraction

[LeoG]

Tropospheric Ducting as another way?

[amaff]

Uh oh, Smiley just waded into the swamp 

[AdmiralCochrane]

20 hours ago, LeoG said:

Tropospheric Ducting as another way?

Possibly, but ducting is erratic, not consistent.  If he consistently works from that spot, it's NOT ducting.

[marcspaz]

That stuff happens because terrain acts like a wave guide, confines and reflects UHF signals to extend range beyond the RF LOS.  Many people here have heard the term "Knife-edge Diffraction", but there is also Terrain Ducting / Terrain Channeling aka Guided Propagation.

[LeoG]

1 hour ago, AdmiralCochrane said:

Possibly, but ducting is erratic, not consistent.  If he consistently works from that spot, it's NOT ducting.

I only did it once.  So I don't know if it'll still be in the same spot if I went there again.  I have to go back there in September...  So it's going to be a while before I know.

[LeoG]

55 minutes ago, marcspaz said:

That stuff happens because terrain acts like a wave guide, confines and reflects UHF signals to extend range beyond the RF LOS.  Many people here have heard the term "Knife-edge Diffraction", but there is also Terrain Ducting / Terrain Channeling aka Guided Propagation.

Either way I was shocked.