Antenna/coax gain loss.

[WSEW367]

Hello, I have installed a Comet GP-9NCA antenna on top of one of my trees. The antenna is 110' up and I used 140' of 400 cable connected directly to my radio a  Wouxon 1000plus. (50 watts)

I suspect my power loss is about 60%. How does the gain from my antenna (11.9) affect my total power broadcasted?

This combination  fit into my budget since the tree climber is a friend. I would have loved to go bigger in the cable but this was all I can afford. I have been able to pick up over 50 miles away but notice I cannot pick up one of my friends who is .5 miles away. My elevation of my antenna is approximately 70' higher than is hand held. Any suggestions on how to keep my gain yet widen the signal up close?

 

Thank you in advance. 

[WRXB215]

Maybe an antenna switch and a second antenna.

[MarkInTampa]

18 minutes ago, WSEW367 said:

Hello, I have installed a Comet GP-9NCA antenna on top of one of my trees. The antenna is 110' up and I used 140' of 400 cable connected directly to my radio a  Wouxon 1000plus. (50 watts)

I suspect my power loss is about 60%. How does the gain from my antenna (11.9) affect my total power broadcasted?

 

You are about dead on on power loss. 59% according the the calculator, but with the gain of the antenna you have an effective radiated power of almost 200 watts. Keep in mind the tool I used (https://kv5r.com/ham-radio/coax-loss-calculator/) uses dBd for antenna gain, dBd = dBi - 2.15

 

[SteveShannon]

32 minutes ago, WSEW367 said:

Hello, I have installed a Comet GP-9NCA antenna on top of one of my trees. The antenna is 110' up and I used 140' of 400 cable connected directly to my radio a  Wouxon 1000plus. (50 watts)

I suspect my power loss is about 60%. How does the gain from my antenna (11.9) affect my total power broadcasted?

This combination  fit into my budget since the tree climber is a friend. I would have loved to go bigger in the cable but this was all I can afford. I have been able to pick up over 50 miles away but notice I cannot pick up one of my friends who is .5 miles away. My elevation of my antenna is approximately 70' higher than is hand held. Any suggestions on how to keep my gain yet widen the signal up close?

 

Thank you in advance. 

That’s exactly why we work in decibels. You just add them together. 
So rounding off all to -3 db per 100 feet for lmr400, 1.40 x -3 db = -4.2 db. 
-4.2 db + 11.9 db leaves you with 7.7 db gain. I assume the 11.9 db you quoted for the antenna is dBi.
So, compared to an isentropic antenna you’re radiating a little better than four times as much power horizontally. If the antenna gain was actually expressed as dBd you add 2.15 db to it and the result is 9.85 db gain which is about eight times as much power. 

[WSEW367]

So that is pretty good, right?  LOL

Any suggestions on how to hit my friend who is 70' lower in elevation and still keep my gain? I suspect he will need to gain some height on his antenna (handheld radio antenna). Is that correct? Will he want a low gain (like a J pole) to reach up into my radio wave? Or would a high gain (he only has 5 watts) help?

Thank you for helping me out.

 

[BoxCar]

30 minutes ago, WSEW367 said:

Hello, I have installed a Comet GP-9NCA antenna on top of one of my trees. The antenna is 110' up and I used 140' of 400 cable connected directly to my radio a  Wouxon 1000plus. (50 watts)

I have been able to pick up over 50 miles away but notice I cannot pick up one of my friends who is .5 miles away. My elevation of my antenna is approximately 70' higher than is hand held. Any suggestions on how to keep my gain yet widen the signal up close?

Did you look at the radiation pattern for this antenna? Comet shows it having a very narrow lobe (around 20 degrees is my guess) so the power is directed at the horizon and not close to the ground. In order to pick up your friend a 1/2 mile away you will need to ring the antenna down or use a second, low gain antenna, I

[WSEW367]

Yikes... what does it mean to "ring the antenna down"?  Can I add a 2nd antenna to my existing coax? And if so...how do I do that?

Thank you for your help, I really appreciate it.

[BoxCar]

3 minutes ago, WSEW367 said:

Yikes... what does it mean to "ring the antenna down"?  Can I add a 2nd antenna to my existing coax? And if so...how do I do that?

Thank you for your help, I really appreciate it. I

Misspelled - should have been bring the antenna down (closer to ground level).

[SteveShannon]

Atan(70/2640) = 1.5°

The height difference should not matter. 

[Jonolvey]

16 hours ago, WSEW367 said:

Hello, I have installed a Comet GP-9NCA antenna on top of one of my trees. The antenna is 110' up and I used 140' of 400 cable connected directly to my radio a  Wouxon 1000plus. (50 watts)

I suspect my power loss is about 60%. How does the gain from my antenna (11.9) affect my total power broadcasted?

This combination  fit into my budget since the tree climber is a friend. I would have loved to go bigger in the cable but this was all I can afford. I have been able to pick up over 50 miles away but notice I cannot pick up one of my friends who is .5 miles away. My elevation of my antenna is approximately 70' higher than is hand held. Any suggestions on how to keep my gain yet widen the signal up close?

 

Thank you in advance. 

Ok , gp9 n is a 2m 70cm gmrs is about 68 cm Or so . what is your swr ??? 

Please look up 3/8s hard line cost was about $1.40 or so a foot . The difference in performance line loss and receive between helix Hardline 3/8 and LMR 400 will a amaz you

[WRYZ926]

25 minutes ago, Jonolvey said:

Ok , gp9 n is a 2m 70cm gmrs is about 68 cm Or so

There are several different versions of the Comet GP9 antenna. The GP-9NC and GP-9NCA are both for GMRS and MURS. The GP-9 and GP-9N are for amateur bands. The MURS and GMRS versions have the C and/or A in the model number.

@WSEW367 stated that he is using the GP-9NCA which would be correct for GMRS use.

Here are the numbers for coax loss using 467.600 (repeater channel)

 

[Jonolvey]

7 hours ago, Jonolvey said:

Ok , gp9 n is a 2m 70cm gmrs is about 68 cm Or so . what is your swr ??? 

Please look up 3/8s hard line cost was about $1.40 or so a foot . The difference in performance line loss and receive between helix Hardline 3/8 and LMR 400 will a amaz you

Lmr 400 is great for 100' hf or vhf not so much uhf . 

[LeoG]

2.7dB loss vs 2.33dB is a difference, not exactly substantial under 100'

 

1/2" Heliax is pretty substantial.  1.4dB/100'

[Jonolvey]

On 11/19/2024 at 11:38 PM, LeoG said:

2.7dB loss vs 2.33dB is a difference, not exactly substantial under 100'

 

1/2" Heliax is pretty substantial.  1.4dB/100'

If I remember right the velocity factor of LMR 400 is 85% and the velocity factor of 3/8 Hardline is 88% the velocity Factor has something to do with your receive as well as the transmit although 3% does not sound like a whole lot with weak signal receive it's actually more than it looks like or so I have been told

[Jonolvey]

On 11/18/2024 at 11:51 AM, tcp2525 said:

Finally, someone that knows what he's talking about. Hardline is the only way to go. Stop wasting money on LMR-400 and buy the real deal, Heliax. You'll never find LMR-400 on any of my installations. Might as well use RG-8x and generate heat.

When the day comes I know what I am talking about the world is probably going to be in trouble all I know is what friends have tried to teach me

[Jonolvey]

On 11/19/2024 at 11:38 PM, LeoG said:

2.7dB loss vs 2.33dB is a difference, not exactly substantial under 100'

 

1/2" Heliax is pretty substantial.  1.4dB/100'

And jest under $3 a foot

3/8s is under $2 a foot 

Although  hard line ends are kind of pricey 

[Lscott]

16 hours ago, Jonolvey said:

If I remember right the velocity factor of LMR 400 is 85% and the velocity factor of 3/8 Hardline is 88% the velocity Factor has something to do with your receive as well as the transmit although 3% does not sound like a whole lot with weak signal receive it's actually more than it looks like or so I have been told

Velocity factor typically unimportant unless you're using line sections for building filter stubs or phased array antenna systems. What the number specifies is how fast the signal propagates along the coax verses in free space, which at a velocity factor of 100 percent would be exactly the speed of light, so at 85 percent the signal is moving at 85 percent the speed of light.

https://picwire.com/Resources/Technical/Technical-Articles/Velocity

https://www.febo.com/reference/cable_data.html

The reason why it's important for phased array antenna systems is the length of the cable has to be calculated so the RF signal arrived at the respective antennas at the exact point in time for the radiated RF waves to add/subtract in space to give the desired signal strength in the preferred direction.

https://hamsignal.com/blog/2-element-vertical-phased-array-my-first-attempt

[LeoG]

13 minutes ago, Lscott said:

Velocity factor typically unimportant unless you're using line sections for building filter stubs or phased array antenna systems. What the number specifies is how fast the signal propagates along the coax verses in free space, which at a velocity factor of 100 percent would be exactly the speed of light, so at 85 percent the signal is moving at 85 percent the speed of light.

https://picwire.com/Resources/Technical/Technical-Articles/Velocity

https://www.febo.com/reference/cable_data.html

The reason why it's important for phased array antenna systems is the length of the cable has to be calculated so the RF signal arrived at the respective antennas at the exact point in time for the radiated RF waves to add/subtract in space to give the desired signal strength in the preferred direction.

https://hamsignal.com/blog/2-element-vertical-phased-array-my-first-attempt

Is that why duplexers have those loops?  So all the wires are the same length?  Or is that just a change direction thing?

[Lscott]

1 hour ago, LeoG said:

Is that why duplexers have those loops?  So all the wires are the same length?  Or is that just a change direction thing?

https://wd8iel.com/wp-content/uploads/2023/01/Duplexer-Cable-Length-Determination-Procedure.pdf

https://www.repeater-builder.com/antenna/w6nbc-duplexer-book/ch9.html

[WRXL702]

This Isn't Really About LMR 400 vs Heliax Coaxial Cable. The Loss Comparison Is Minimal, & Not That Relevant.

This Is More About The Installation - "A Transceiver Stick In A Tree."

My Suggestion, As You Could Do Just As Well With A Roof Mount Antenna - Loose The Additional Tree Branch & Keep The LMR 400.

[tcp2525]

On 11/21/2024 at 9:01 PM, Jonolvey said:

And jest under $3 a foot

3/8s is under $2 a foot 

Although  hard line ends are kind of pricey 

Damn, I think that I'm selling my LDF4-50a spool ends too cheaply at $1.00 a foot!

I must have been board, so I played with a crushed end of Heliax and was able to clean it up with the prep tool. Just experimenting and this piece won't be used and tost in the trash.

[tcp2525]

On 11/22/2024 at 1:17 PM, Lscott said:

Velocity factor typically unimportant unless you're using line sections for building filter stubs or phased array antenna systems. What the number specifies is how fast the signal propagates along the coax verses in free space, which at a velocity factor of 100 percent would be exactly the speed of light, so at 85 percent the signal is moving at 85 percent the speed of light.

https://picwire.com/Resources/Technical/Technical-Articles/Velocity

https://www.febo.com/reference/cable_data.html

The reason why it's important for phased array antenna systems is the length of the cable has to be calculated so the RF signal arrived at the respective antennas at the exact point in time for the radiated RF waves to add/subtract in space to give the desired signal strength in the preferred direction.

https://hamsignal.com/blog/2-element-vertical-phased-array-my-first-attempt

Very true! I used to make the harness back in the day, but I find power dividers more practical and easier to make. Here's one after being tested on the spectrum analyzer, still has the 50 ohm terminations on it.

432 MHz Power Divider totally sealed and water tight.

Modified 3/4" Copper TEE on type "M" copper pipe.

11mm Brass Tubing

 

[Lscott]

45 minutes ago, tcp2525 said:

Very true! I used to make the harness back in the day, but I find power dividers more practical and easier to make. Here's one after being tested on the spectrum analyzer, still has the 50 ohm terminations on it.

432 MHz Power Divider totally sealed and water tight.

Modified 3/4" Copper TEE on type "M" copper pipe.

11mm Brass Tubing

 

 Very nicely built!

 

[tcp2525]

1 hour ago, Jonolvey said:

Ok , gp9 n is a 2m 70cm gmrs is about 68 cm Or so . what is your swr ??? 

Please look up 3/8s hard line cost was about $1.40 or so a foot . The difference in performance line loss and receive between helix Hardline 3/8 and LMR 400 will a amaz you

Finally, someone that knows what he's talking about. Hardline is the only way to go. Stop wasting money on LMR-400 and buy the real deal, Heliax. You'll never find LMR-400 on any of my installations. Might as well use RG-8x and generate heat.