Batboard

I know that all radios are different and must be tuned differently. But roughly for a 5W UHF (R or S split doesn't matter), what is the nominal power range (measured at a service monitor or wattmeter)? I'm assuming the nominal range is about 4.8W. I had almost all of my portables except for one tuned recently, and I measured the output of all 7 Tx Points and they each average about ~4.8W.

However, for the radio I did not have sent to the shop, when I measured the 7 Tx Points it has a measured power out of nearly 5.8W. I'm just wondering whats accepted as a nominal range for power tuning.

What voltage are you testing at? Are you using a regulated power supply set to the proper voltage as indicated in the test procedures? or are you using a battery?

Testing using a battery can give you significantly different readings based on state of charge.

When I was portable boy, back when MX300's and MT500's were current production, I balanced xmit power with current drain leaning towards min current rather than max power. On a high power portable (4-5W) if I could get within a watt of rated power at rated current, I sent it out. I rarely saw more than rated power at rated current.

RFguy wrote:What voltage are you testing at? Are you using a regulated power supply set to the proper voltage as indicated in the test procedures? or are you using a battery?

Testing using a battery can give you significantly different readings based on state of charge.

Regulated supply at 7.8V (these are portables).

Shouldn't batteries be avoided for tuning in almost all cases?

The cable also makes a difference. To get rated power on out XTS5000s I use a short 12 in or so cable. If I use a normal 6ft test cable I loose a watt or so.

I had a Ham officer complaining about the loss on his gutter mount with low loss claimed cable. It was no surprise that the Teflon rg 174 style cable lost 3/4 th of the power at UHF.

He said but it says low loss on the package!

GlennD wrote:The cable also makes a difference. To get rated power on out XTS5000s I use a short 12 in or so cable.

I have a short 1ft LMR400 pigtail connected between the radio and test set.

gatekeep wrote:

RFguy wrote:What voltage are you testing at? Are you using a regulated power supply set to the proper voltage as indicated in the test procedures? or are you using a battery?

Testing using a battery can give you significantly different readings based on state of charge.

Regulated supply at 7.8V (these are portables).

Shouldn't batteries be avoided for tuning in almost all cases?

Portables should be tested at 7.50 Volts at the radio. A proper dummy battery or adapter is needed.

Yes, a battery should NOT be used for transmitter tests.

The other issue that sticks it's nose into any measurement is just how good is the measuring divice used to get the RF output power? When was the last time it was calibrated?

When your in the 5 watt range, it doesn't take much of an error to move the measured power up or down. The cable being used and the connector at the radio all come into play here. The difference of 4.5 watts and 5.0 watts is not that much difference on the range the radio will have. Think your getting too picky on this power point. The current the radio pulls is much more important.

Jim

Jim202 wrote:The other issue that sticks it's nose into any measurement is just how good is the measuring divice used to get the RF output power? When was the last time it was calibrated?

Even if perfectly calibrated, what is the uncertainty on the measurement? If you have a power meter rated to +/- 0.1dB accuracy, that is still 0.2 watts of uncertainty - and 0.1dB is lab grade gear.