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Skip like CB?



Hey there! Been a GMRS user for about 6 months, and finally got a 50 Watt Midland MXT500. While in the truck I'm pushing 45 watts on the low end and 47 at the high. I'm impressed with it. I talked further today than I could with the repeater in the area, simplexing around an entire forested hill! 15 miles was nothing! Anyhow... 

As you can tell by the title of the post, I'm wondering if GMRS skips like CB does... and if it does, to what extent? A 4 watt CB can skips for miles and miles, what can a 50 watt GMRS do, if anything? How far? How often? The conditions it requires? What are the chances I'll get further out than the "desired" range?

I'm not looking to be muddock. Just wondering becuase I very commonly simplex with people on 16/575 and 20/675 as I even have stickers on the back of the truck designating the channel I listen on, and would love to know who else can hear me.



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No, UHF (GMRS frequencies) do not 'skip' like HF (CB frequencies) does.

What you can experience occasionally is tropospheric ducting where a warm air mass gets in overtop a code air mass and creates a tunnel for VHF and UHF frequencies to travel in far beyond normal line of site.  This is NOT a common occurence however and shouldn't be relied upon for consistent communications the way it is with HF communications.  HF 'skip' is caused by the RF reflecting off the Ionosphere and back down to the ground where it's then reflected back up again, over and over until the path loss of the signal becomes too great for a receiver to hear it.  

With ducting, the greatest path distance that can exist only extend slightly past the area covered by the air mass inversion since frequencies above 50 Mhz typically do NOT reflect off either the ground or the ionosphere. 

VHF and UHF frequencies also do not have any 'ground wave' propagation like the lower HF and VHF frequencies do.  Ground wave is a phenomenon where the RF wave 'hugs' the ground and carries long distances  past normal line of site (past the curvature of the earth) by staying on the ground.  This only works below 5 Mhz or so in frequency.

There are several web sites and books including the ARRL Amateur Radio Handbook that discuss the propagation of different RF frequencies at length and might be a good source for a better and more detailed explanation than a half away guy posting at 4 in the morning while half awake.


Edited by WRKC935
50 Mhz not 5Mhz
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No, the higher frequencies of gmrs don't "skip" like the lower frequencies of cb do.

That said, some areas see occasional ducting (affects vhf more than UHF, where gmrs resides) that see signals going a bit further than expected.

APRS.mennolink.org is a good one to get an idea what ducting conditions are like at a given time.

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5 hours ago, bd348 said:

(Monitoring two channels?)

Yeah? I keep roughly 4 radios in my truck. 1 MXT500 (50W I use for repeaters or long distance simplex), 1 CB handheld to com with truckers, 1 UV5G for Handheld GMRS use (it dual monitors 16 and 20), and a UV5R I keep in the bottom of the truck for emergency use in case I have no signal on my phone (I have it programmed to every REACT/SAR Repeater and frequency in Ohio, KY, and WV)

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