100 Watt UHF Search

[WRVG593]

On 4/4/2023 at 9:52 AM, tweiss3 said:

I think you are over thinking how to get to your designated simplex. Look into a pair yagi antennas pointed at each other to use just for the hard to reach family. You will also hear the other much better as well.

Look at the numbers:

Your 25W into an assumed 6db gain omni antenna = 99W EIRP

Take the same antenna, boost the power to 100W and you get 398W radiated, but in all directions, and no improved receive from your intended family member.

Take your same 25W radio into a 10.2db gain yagi = 261W EIRP, with better ears and less likely to cause interference to anyone else. There will also be more benefit if you don't have 6db gain on your current antenna. This is taking zero line losses into account.

 

Edit, if you get one of the Yagis that has 12.2db gain, you end up with 414W EIRP with your existing 25W radio.

Well also the numbers you're running aren't accurate. I'm power testing and getting 5-8 watts. 

[WRVG593]

On 4/4/2023 at 7:52 PM, KAF6045 said:

Better check the zoning regulations for your area. For my area, antennas are limited to 35ft height (I suspect based on 60s-70s horizontally polarized log-periodic TV antennas) -- EXCEPT for LICENSED AMATEUR who are permitted 70ft height.

My area allows for 50 feet of height. I'm good.

[gortex2]

Unless I missed it you never specified your antenna cable type. If your loosing that much power from your radio your using the wrong feedline. 

[SteveShannon]

3 hours ago, WRVG593 said:

Well also the numbers you're running aren't accurate. I'm power testing and getting 5-8 watts. 

How and where are you power testing? What does it say at the back of the radio and at the other end of the feedline?  What are you using for feedline?

[WRVG593]

4 hours ago, Sshannon said:

How and where are you power testing? What does it say at the back of the radio and at the other end of the feedline?  What are you using for feedline?

I'm testing using a power meter. I use my cheap Chinese one and I've used my friends actually good power meter and the my read pretty much the same on SWR, Power, Fwd, Reflected, etc. My feed line (I could be wrong as I bought it probably over a year ago) is RG8X if I'm not mistaken. I've tested it in my mobile and from 50 watts(MXT500), it seemed to only lose about a watt or so. 

So I'm not worried too much about cable loss. And by back of the radio I assume you mean power? The advertised power is 25 Watts, but this thing has been beaten into the ground and only puts out about 7 watts. 

[KAF6045]

1 hour ago, WRVG593 said:

I'm testing using a power meter. I use my cheap Chinese one and I've used my friends actually good power meter and the my read pretty much the same on SWR, Power, Fwd, Reflected, etc. My feed line (I could be wrong as I bought it probably over a year ago) is RG8X if I'm not mistaken. I've tested it in my mobile and from 50 watts(MXT500), it seemed to only lose about a watt or so. 

Are you testing power AT THE ANTENNA, or just off the back of the transmitter?

How long is that coax?

https://kv5r.com/ham-radio/coax-loss-calculator/

50 feet of Belden RG-8X, with a 50W transmitter, at 465MHz, with an antenna SWR of 1.25:1, LOSES 63% of your power (50W transmitter -> 18.7W at antenna)

Replacing the Belden with LMR-240 (an RG-8X equivalent) only loses 47% (26.7W at antenna).

Belden 9913 (low-loss RG-8) nets 29% loss (35.6W at antenna); LMR-400 (RG-8 equivalent) 27% loss (36.3W at antenna)

Don't even consider RG-8X for 100ft cable runs at UHF. You would need an antenna with 9dB of gain to counter the coax loss.

 

[SteveShannon]

27 minutes ago, KAF6045 said:

Are you testing power AT THE ANTENNA, or just off the back of the transmitter?

How long is that coax?

https://kv5r.com/ham-radio/coax-loss-calculator/

50 feet of Belden RG-8X, with a 50W transmitter, at 465MHz, with an antenna SWR of 1.25:1, LOSES 63% of your power (50W transmitter -> 18.7W at antenna)

Replacing the Belden with LMR-240 (an RG-8X equivalent) only loses 47% (26.7W at antenna).

Belden 9913 (low-loss RG-8) nets 29% loss (35.6W at antenna); LMR-400 (RG-8 equivalent) 27% loss (36.3W at antenna)

Don't even consider RG-8X for 100ft cable runs at UHF. You would need an antenna with 9dB of gain to counter the coax loss.

 

And that’s with Belden RG-8x, which is quality.  It’s a characteristic of the cable and proportionate to length, and it’s simply not possible that you would have a 50 foot RG-8x cable that doesn’t have much loss at GMRS frequencies. There are lots of accounts of really terrible performance from the cheap gray RG-8x or RG-8 mini from Amazon.

[ClassicCarGuy]

 

On 4/6/2023 at 10:38 AM, Sshannon said:

And that’s with Belden RG-8x, which is quality.  It’s a characteristic of the cable and proportionate to length, and it’s simply not possible that you would have a 50 foot RG-8x cable that doesn’t have much loss at GMRS frequencies. There are lots of accounts of really terrible performance from the cheap gray RG-8x or RG-8 mini from Amazon.

Right now I'm about to buy  coax cable for a base antenna with no more than 50 feet. (I might even shorten this off in the forthcoming days  to 38 feet)

Anyways I'm debating if I should get this LMR-240 cable or should I go with the 400. The one thing I'm worried about the LMR-400 its such a stiff cable which is worst than the RG8 and it might snap my J-Pole antenna connector.

Any takes?

[SteveShannon]

59 minutes ago, WRZM228 said:

 

Right now I'm about to buy  coax cable for a base antenna with no more than 50 feet. (I might even shorten this off in the forthcoming days  to 38 feet)

Anyways I'm debating if I should get this LMR-240 cable or should I go with the 400. The one thing I'm worried about the LMR-400 its such a stiff cable which is worst than the RG8 and it might snap my J-Pole antenna connector.

Any takes?

Look into getting one of the cables that has a stranded center conductor. I think most of the coax companies make them, but I’m familiar with M&P. They have an UltraFlex line of cables. 

[WRYZ926]

I'll second what @Sshannon said and go with a good cable and stranded center conductor. Look at LMR400 Ultra Flex coax cable.

[tweiss3]

DX Engineering's 400MAX cable is identical to TimesMicrowave  LMF400 Ultra Flex.