SWR and TX power output questions.

[WRCC711]

I have a question or two for people who are way more knowledgeable than me about GMRS base radio set ups. I have a Midland MXT 400 40w GMRS radio paired with a Pyramid ps15k.5 power supply hooked up to a Retevis GMRS base antenna 7.2 dbi uhf repeater antenna mounted on a telescopic 30ft flag pole (because of terrain) , that's my base station set up. I've measured my SWR on lower channels 1-5 at 1.1 the upper channels including repeater channels are measuring 1.81 . Is that an acceptable range for SWR readings? Second question my radio is supposed to have a maximum tx of 40w my meter was showing a maximum of 38 to 37w on the high side.  My radio is a few years old so not new. Is that an acceptable reading? I am using a surecom gam3gear SWR meeter.  

[SteveShannon]

Yes, that’s an acceptable SWR range.

Yes, that’s an acceptable power output. 

[Socalgmrs]

7 minutes ago, WRCC711 said:

I have a question or two for people who are way more knowledgeable than me about GMRS base radio set ups. I have a Midland MXT 400 40w GMRS radio paired with a Pyramid ps15k.5 power supply hooked up to a Retevis GMRS base antenna 7.2 dbi uhf repeater antenna mounted on a telescopic 30ft flag pole (because of terrain) , that's my base station set up. I've measured my SWR on lower channels 1-5 at 1.1 the upper channels including repeater channels are measuring 1.81 . Is that an acceptable range for SWR readings? Second question my radio is supposed to have a maximum tx of 40w my meter was showing a maximum of 38 to 37w on the high side.  My radio is a few years old so not new. Is that an acceptable reading? I am using a surecom gam3gear SWR meeter.  

Swr below 2 is fine.  Sorry to here about the midland but yes on most radios the actuall wattage is less buy 10% or more then advertised 

[WRCC711]

27 minutes ago, Socalgmrs said:

Swr below 2 is fine.  Sorry to here about the midland but yes on most radios the actuall wattage is less buy 10% or more then advertised 

Thanks for answering my questions. I've been wondering if im getting out when I do a radio check . Yeah I would like to upgrade from the Midland. 

[nokones]

2-3 watts is nothing to worry about. How did you check your RF power output? With a meter in-line with an Antenna connected or a Power Terminator connected? If you're using a Power Terminator make sure it measures out at 50 ohms for an accurate reading. Having an antenna connected is not the most accurate method because of the reflected power.

[WRCC711]

2 hours ago, nokones said:

2-3 watts is nothing to worry about. How did you check your RF power output? With a meter in-line with an Antenna connected or a Power Terminator connected? If you're using a Power Terminator make sure it measures out at 50 ohms for an accurate reading. Having an antenna connected is not the most accurate method because of the reflected power.

I did use a meter with a 50 ohm termination load on the end. I wanted to make sure all my readings were OK on my setup.  I wasn't too sure my signal was getting out. Thanks for replying, the missing wattage did have me woried a bit. 

[WRYZ926]

As others have said, getting 37-38 watts out with a 40 watt radio is perfectly fine. A 50 watt radio only putting out 35 watts would be enough to contact the manufacturer and ask questions.

I also would not worry much about having an SWR of 1.8. You will be fine as long as the SWR is 2.0 or below.

[WSEZ864]

3 hours ago, WRYZ926 said:

As others have said, getting 37-38 watts out with a 40 watt radio is perfectly fine. A 50 watt radio only putting out 35 watts would be enough to contact the manufacturer and ask questions.

I also would not worry much about having an SWR of 1.8. You will be fine as long as the SWR is 2.0 or below.

Agreed.

One thing to take notice of is that most GMRS radio marketing statements specify power as "up to x watts", or "as much as x watts" and do not actually state your 40 watt radio will deliver 40 watts.

[Davichko5650]

1 hour ago, WSEZ864 said:

"up to x watts", or "as much as x watts" 

Made me think of the old Mad Magazine quote, "remember that the phrase 'up to' also includes the number zero."

[SteveShannon]

Another thing to consider is the voltage input to the radio. Most mobile radios are rated with an input voltage of 13.8 vDC and the output RF power frequently varies with the voltage. Boost your voltage by a half volt (observing the tolerances listed in the manual) and you might see 41 watts. 
But a variation of one or two watts at that general power will not make a bit of difference in your ability to communicate. 

[WRYZ926]

2 hours ago, WSEZ864 said:

Agreed.

One thing to take notice of is that most GMRS radio marketing statements specify power as "up to x watts", or "as much as x watts" and do not actually state your 40 watt radio will deliver 40 watts.

This goes for amateur radios too. 

 

1 hour ago, SteveShannon said:

Another thing to consider is the voltage input to the radio. Most mobile radios are rated with an input voltage of 13.8 vDC and the output RF power frequently varies with the voltage. Boost your voltage by a half volt (observing the tolerances listed in the manual) and you might see 41 watts. 

This is very true. You will definitely see a different output power when running on a 12V battery versus a 13.8V power supply or when running the radio in a vehicle.. The voltage on newer vehicles can go up to 15.1 volts when charging the battery and are around 14.1 to 14.3 volts under normal driving conditions.

[WSHH887]

Hmm. I worked with power conditioners for control equipment. That was AC. I wonder if they have these for DC. 

[SteveShannon]

14 minutes ago, WSHH887 said:

Hmm. I worked with power conditioners for control equipment. That was AC. I wonder if they have these for DC. 

Look at the Samlex or Astron product lines. There are very tightly regulated and filtered DC power supplies.