Line of sight

[WRYZ926]

4 hours ago, WSFF627 said:

I can have a conversation on my repeater at 30 miles from some locations with a 4 watt Motorola portable. Standing in that same spot, a 5 watt, $15 Baofeng sometimes works, sometimes does not. I can also move 10 feet and it will no longer work. 

This is very true. I can talk on the local 2m repeater that is 22.5 miles away from inside my house with my Icom IC-T10 and my Wouxun KG-Q10H. But that is not happening with my Baofeng GT-5R or Explorer QRZ1 (TYT UV-88). 

And UHF is going to be different than VHF. I can't get into the 70cm repeater at all with any of my HT's from my house. I've tried many locations in my yard to include standing on the roof. I can however get into the GMRS repeater with my Wouxun KG-935G and KG-Q10H in certain spots in my yard.

All three repeaters are at the same location with the 2m and 70cm antennas at 900 feet and the GMRS antennas at 400 feet.

[WRYZ926]

10 minutes ago, WRUE951 said:

Steve Shannon put it in perspective..  The ISS is a mere 250 miles above earth, not thousands that many may think..  Still,  250 miles is quite a distance for a 5W HT to reach..   I'm sure there are other factors transmitting into space but i can tell you with certainty, i have never been able to talk 250 miles with a UHF HT on earth.   The best i have done is roughly 80 miles hitting the El Paso repeater from Palmdale.  A line of site shot with that repeater sitting on a 4500' mountain top.    Has anyone really talked 250 miles on earth on UHF with a 4-5 watt HT?   If so you are the King.  

Just wait a little bit. I'm sure Negative Nancy/Nana NoNo will tell us how he talks 200 + miles on an HT.

[dosw]

On 3/29/2025 at 9:06 AM, WSGH675 said:

I been told that a gmrs handheld can reach line of sight to a repeater ok but there has to be a limit how many miles a gmrs handheld can reach a repeater. I know Hawaii is a long ways away but there is nothing but ocean between West Coast and Hawaii but there has to be a range how far a handheld gmrs radio can reach to a repeater 

Line of Sight, explained

You have to account for the fact we live on a spheroid.

[dosw]

On 3/29/2025 at 10:13 AM, SteveShannon said:

People successfully talk to the International Space Station using a five watt handheld on 70 cm. That’s a couple hundred miles. 
 

240m at best, when it passes directly overhead at 17,000 miles per hour. With a decent antenna I start hearing it about 1100 miles away, a little above center frequency, and stop hearing it about 1000 miles away at a slightly lower than center frequency, due to the Doppler shift associated with its speed. It's pretty amazing, really. And it fades in and back out again not because of the miles but because of the curvature of the earth.

 

Mariners have used line of sight formulas for centuries, of course. RF line of sight formulas are only slightly different from visual. 

[WSFF627]

28 minutes ago, WRYZ926 said:

This is very true. I can talk on the local 2m repeater that is 22.5 miles away from inside my house with my Icom IC-T10 and my Wouxun KG-Q10H. But that is not happening with my Baofeng GT-5R or Explorer QRZ1 (TYT UV-88). 

And UHF is going to be different than VHF. I can't get into the 70cm repeater at all with any of my HT's from my house. I've tried many locations in my yard to include standing on the roof. I can however get into the GMRS repeater with my Wouxun KG-935G and KG-Q10H in certain spots in my yard.

All three repeaters are at the same location with the 2m and 70cm antennas at 900 feet and the GMRS antennas at 400 feet.

Nice!! That's quite a lot of feedline. Doesn't surprise me. All probably using the same type of feedline. 2M VHF doesn't loose nearly as much in the line as 70cm UHF. GMRS (UHF not far from 70cm, as I'm sure you know quite well) with 500 +/- less feedline. Any pre amp will also play a part on the RX side.

For the sake of argument lets assume the tower is using Heliax LDF6-50 1-1/4 inch feedline. Feedline loss only, in addition to any combiner or duplexer, etc. loss. Rough numbers only.

VHF at 900 feet is about 2.89 dB loss (125w TX,48% power loss)

UHF at 900 feet is about 5.27 dB loss (125w TX, 70% power loss)

GMRS UHF at 400 feet is 2.44 dB loss (50w TX, 43% power loss)

[WRYZ926]

The 2m/70cm antennas are connected with 1 1/4" hardline and the GMRS antennas are connected with 7/8" hardline.

We just upgraded our 2m repeater with a Motorola Quantar 125 and it is set for 60 watts out after the duplexer. We are using an older Motorola 70cm repeater and I'm not sure what the power output is on that. We are using a Bridgecom GMRS repeater with an external duplexer and the power out after the duplexer is at 35 watts. 

Going with 1 1/4" hardline would improve things a small amount for the GMRS repeater but the 7/8" hardline was already ran on the tower so we did not have to install new coax. 

It would be nice to swap out that Bridgecom with a UHF Motorola Quantar 125 so that we could get a full 50 watts out after the duplexer. But getting another repeater is not in the budget this year.

[SteveShannon]

4 minutes ago, WRYZ926 said:

It would be nice to swap out that Bridgecom with a UHF Motorola Quantar 125 so that we could get a full 50 watts out after the duplexer. But getting another repeater is not in the budget this year.

I’m not sure how you would ever get a full 50 watts out of the duplexer while remaining within GMRS regulations.  Regulations mandate a max of 50 watts out of the transmitter and there are always insertion losses through a duplexer.

[WRYZ926]

2 minutes ago, SteveShannon said:

I’m not sure how you would ever get a full 50 watts out of the duplexer while remaining within GMRS regulations.  Regulations mandate a max of 50 watts out of the transmitter and there are always insertion losses through a duplexer.

This is true.

I'm not saying it is right but other GMRS repeater owners in my area are using the UHF Motorola 125 for their GMRS repeaters and have the power levels set for 45 to 50 watts out after the duplexer. And that setup works well and they have not had anyone complain to our FCC overlords.

[SteveShannon]

1 minute ago, WRYZ926 said:

This is true.

I'm not saying it is right but other GMRS repeater owners in my area are using the UHF Motorola 125 for their GMRS repeaters and have the power levels set for 45 to 50 watts out after the duplexer. 

Given that people are reticent to report such things and the FCC’s dismal record at enforcement, nothing will probably ever happen about that, but honestly, their range probably is no better than that of your repeater.

[WRYZ926]

3 minutes ago, SteveShannon said:

Given that people are reticent to report such things and the FCC’s dismal record at enforcement, nothing will probably ever happen about that, but honestly, their range probably is no better than that of your repeater.

I know of one repeater that does have a better range of around 50-55 miles using a Quantar 125. We could benefit from going with 1 1/4" hardline versus the 7/8" hardline but again that is not in the budget for this year. We get 30-35 mile radius of coverage with our current GMRS setup. The funny thing is our 70cm repeater has the exact same range and the exact same dead spots.

[WSFF627]

Sorry for being short,, only got a sec... Bridgecom not bad, set tx at legal 50w out of the rpt. A good TXRX 4 can 350 watt duplexer, 0.6dB insertion loss will offer the best post duplexer wattage. Obvioulsy dont forget loss is a two way street.. Advanced Receiver makes nice pre amps.  I run them on all my projects.

[GrouserPad]

2 hours ago, nokones said:

Why? Do you live in Crater Lake or the Grand Canyon, or are you using a POS Pandaland antenna and cable with poor VSWRs?

It’s called Appalachia. Trees so thick and hollers so deep mixed with rolling hills. Can’t see the neighbors house that’s 400 yards away.  Kg1000+ 1.3/1.5 on the vizswarzometer 

[WRYZ926]

2 minutes ago, WSFF627 said:

Sorry for being short,, only got a sec... Bridgecom not bad, set tx at legal 50w out of the rpt. A good TXRX 4 can 350 watt duplexer, 0.6dB insertion loss will offer the best post duplexer wattage. Obvioulsy dont forget loss is a two way street.. Advanced Receiver makes nice pre amps.  I run them on all my projects.

Even with the repeater itself set to full 50 watts out, there will still be a loss of power output from the duplexer. There is no getting around that.

[WSFF627]

1 minute ago, WRYZ926 said:

Even with the repeater itself set to full 50 watts out, there will still be a loss of power output from the duplexer. There is no getting around that.

Thats correct. TXRX duplexers have the lowest loss of any duplexer I have seen. 0.6dB, some loss, yes, you should see 50w in and 41-43w out of the duplexer. A lot less loss on the RX path, which in my opinion is more important than TX power.

[WRUE951]

3 minutes ago, WSFF627 said:

Thats correct. TXRX duplexers have the lowest loss of any duplexer I have seen. 0.6dB, some loss, yes, you should see 50w in and 41-43w out of the duplexer. A lot less loss on the RX path, which in my opinion is more important than TX power.

the lowest loss i have seen in even some of the really really high end expensive UHF Duplexers is 1.2dB..  Put up your fishing pole, going be a hard bite tp find .6dB.    

[nokones]

6 hours ago, WRUE951 said:

Steve Shannon put it in perspective..  The ISS is a mere 250 miles above earth, not thousands that many may think..  Still,  250 miles is quite a distance for a 5W HT to reach..   I'm sure there are other factors transmitting into space but i can tell you with certainty, i have never been able to talk 250 miles with a UHF HT on earth.   The best i have done is roughly 80 miles hitting the El Paso repeater from Palmdale.  A line of site shot with that repeater sitting on a 4500' mountain top.    Has anyone really talked 250 miles on earth on UHF with a 4-5 watt HT?   If so you are the King.  

Is it possible, I think so, with an UHF (400 (Megs and higher) given certain circumstances. 

If there were two mountain tops 250 miles peak to peak apart, taking in the curvature of the earth between the two mountain tops, I wonder how high do the two mountain tops have to be to get above the earth curvature for a visual line of site between the two mountain tops. Also, the two mountain tops would have to be in a radio quiet zone for the frequency used to prevent any co-channel interference.

I'm not sure if an omni antenna or a portable would make the haul, but it may be possible with a Yagi or a Parabolic antenna.

[WSEZ864]

12 minutes ago, nokones said:

Is it possible, I think so, with an UHF (400 (Megs 300 mHz and higher) given certain circumstances. 

If there were two mountain tops 250 miles peak to peak apart, taking in the curvature of the earth between the two mountain tops, I wonder how high do the two mountain tops have to be to get above the earth curvature for a visual line of site between the two mountain tops. Also, the two mountain tops would have to be in a radio quiet zone for the frequency used to prevent any co-channel interference.

I'm not sure if an omni antenna or a portable would make the haul, but it may be possible with a Yagi or a Parabolic antenna.

Just did a quick fixit for you. UHF actually starts at 300 mHz.

[WRUE951]

21 minutes ago, WSEZ864 said:

Just did a quick fixit for you. UHF actually starts at 300 mHz.

all the way up to 3 Ghz   

[nokones]

1 hour ago, WSEZ864 said:

Just did a quick fixit for you. UHF actually starts at 300 mHz.

I know that and I hate typing on an android devices. Thanks for fixing my fat-fingered typing error.

[WSFF627]

4 hours ago, WRUE951 said:

the lowest loss i have seen in even some of the really really high end expensive UHF Duplexers is 1.2dB..  Put up your fishing pole, going be a hard bite tp find .6dB.    

Just tuned one today. Confirmed at 0.6dB insertion loss on the service monitor.

https://www.bridgecomsystems.com/products/4-cavity-txrx-350w-uhf-duplexer?currency=USD&variant=41431623172261&utm_source=google&utm_medium=cpc&utm_campaign=Google Shopping&stkn=d6eaad281b8a&utm_source=Google_Ads&utm_medium=Duplexers_Shopping&utm_campaign=Duplexers_Shopping_Campaign&tw_source=google&tw_adid=664925858611&tw_campaign=20342176746&gad_source=1&gclid=Cj0KCQiAlbW-BhCMARIsADnwasqZg1QSmh5e4yADfPU4xLrwHKAbWB9BFk2ZIo6jHxDCf44DJQ4fp-AaAj7BEALw_wcB

[WRUE951]

15 hours ago, WSFF627 said:

Just tuned one today. Confirmed at 0.6dB insertion loss on the service monitor.

https://www.bridgecomsystems.com/products/4-cavity-txrx-350w-uhf-duplexer?currency=USD&variant=41431623172261&utm_source=google&utm_medium=cpc&utm_campaign=Google Shopping&stkn=d6eaad281b8a&utm_source=Google_Ads&utm_medium=Duplexers_Shopping&utm_campaign=Duplexers_Shopping_Campaign&tw_source=google&tw_adid=664925858611&tw_campaign=20342176746&gad_source=1&gclid=Cj0KCQiAlbW-BhCMARIsADnwasqZg1QSmh5e4yADfPU4xLrwHKAbWB9BFk2ZIo6jHxDCf44DJQ4fp-AaAj7BEALw_wcB

Actually not a bad price... But damn it, i need another 3D Printer. 

[Lscott]

People buy these cheap Chinese notch-duplexers to use for home brew repeaters. This is the data sheet I found for one and some real world test data.

 

SGQ-450D-N.pdf Chinese Mobile Duplexer Measurements.pdf