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  #1 (permalink)  
Old 02-08-2018, 1:26 AM
westcoaster's Avatar
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Default Max High power adjust?

Kenwood TK-7180H. I Bought this radio used so these settings were in here when I got it....

Test Mode

I see in the service manual settings, the Max high power adjustment is supposed to be 53 watts.

This radio is pumping out 80 watts and drawing some 12 amps....
Depending what tab is selected, it can be slightly lower. All above 60W but below 80W

How to proceed?
Just ease the slider on down some to reduce the power?
Or just forget about it because the radio doesn't typically transmit at that power?
Run it into a shop for a proper alignment?

What other settings are impacted by the transmit power settings?
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Old 02-08-2018, 1:39 PM
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I suspect there are some issues with your test setup. While I don't doubt you are seeing 80 watts out of a TK-7180, I'd be really surprised if it was actually doing that at 12 amps.

What is your test gear and how is it configured?
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Old 02-08-2018, 5:45 PM
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12 Amps too high or too low?
The Fluke 75 is only rated as a 10 amp ammeter so it is entirely possible the meter simply can't go any higher.

Bird 43 with 100w 0-500Mhz slug into 50 ohm dummy load ~ 12" patch into antenna on the back of the radio.

Fluke 75 digital multimeter on ammeter setting on + power lead into radio.

DuraComm LP-14N (11 amp continuous) power supply.
With a 50 watt transmit, on my favorite channel the power supply would dip down to 13.26v and draw in the ball park of 8.2A to 9.5A depending on radio and frequency.


I have no reason to believe the bird is wildly inaccurate. Precise, perhaps not.
Wildly inaccurate, no. Multiple radio's provided results that are within the acceptable range of transmit power.

On the TK-7180H, with the above setup I select my favorite channel, grab the microphone and transmit at high power (50 watts) into the bird and dummy load and draw about 9.5 amps through the fluke 75.

I check the tuning data for high transmit power and it is about the same with very small variables across the 6? test points.

It's when I check the max high transmit power and acknowledge the warning that I am seeing the bird meter jump up to 80 watts. The various tabs in this alignment section provide significantly different results, some down in the ball park of 60-70 watts (with a corresponding drop in amperage drawn)

Just using the radio doesn't transmit at 80 watts, it's when I check the tuning data for max high transmit power (in the service manual the spec calls for 53 watts) that is pumping out at 80 watts.
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Old 02-08-2018, 9:57 PM
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This was done with no multimeter as ammeter in the circuit.
multimeter connected as voltmeter.

Radio on no transmit: 13.81V



test:
Rx:162.21
Tx:162.21
Data:77
96 watts
Voltage dips to 12.88V

Low:
Rx:136.05
Tx:136.1
Data:78
84 watts
12.97V

Low'
Rx:145.55
Tx:145.6
Data:80
82 watts
13.03V

Center
Rx:155.05
Tx:155.1
Data:77
95 watts
12.91V

High'
Rx:164.55
Tx:164.6
Data:78
97 watts
12.89V

High
Rx:173.95
Tx:173.9
Data:83
78 watts
12.99V

I'm looking for a comparison to the data numbers on other radio's if possible. If my numbers are wildly out that could explain what I'm seeing. If they are similar then I have something else going on.

My power supply probably isn't up to the task however, I can't imaging it creating a 40 watt difference for what it should be vs. what it is...

Trying to learn,
Thanks.
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Old 02-08-2018, 10:23 PM
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I don't know that rig. Couple of observations:
The power supply is putting out more than the 11A it is rated for, presumably, which is why it is "crumping" and the voltage dropping. That would confirm the radio is indeed pulling the extra amps. How many amps inut can be expected isn't for sure, but a 50% loss between power in and rf out is not out of scale.

If the radio is spec'd for 53 watts out, and a previous eager owner tweaked it to 80ish? It could be fine that way. The transistors and other parts just might be rated for that much power. The heat sinking might be adequate. And you might be able to legally use it. (There are power restrictions of all kinds, I'm not guessing what might affect you.)

But then again, for every 10C that you raise the operating temperature of solid state devices, you cut their life IN HALF. So if the radio seems fine at 80W, but that makes the finals run 20C or 30C hotter? Yeah, that could cut their life to 1/4 or 1/8 of design life, and that becomes more of a concern for an older radio.

I'd check ratings, check operating temperatures, see if it really seemed safe to operate at a 60% overlaid and if not, find a service manual and reset the power level. But then that's just me--I like to be kind to the servants, as long as they stay loyal and faithful.(G)
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Old 02-08-2018, 10:36 PM
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I'm not eager (don't want) to run it at this wattage.
I want to drop it back down to spec but want to ensure I'm not throwing something else out of whack in the process.


edit:
I'm not even sure what the "Max High Transmit Power" is even all about as it doesn't appear to have an impact on what the radio transmits at.

The channels I key up on are putting out 50 watts

Last edited by westcoaster; 02-08-2018 at 10:42 PM..
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Old 02-08-2018, 11:36 PM
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If it puts out normal Power when you're not into test mode you're fine. If you are going to the max power tab that's where you calibrate for absolute maximum power. If you Jack the slider up you can smoke the PA if not careful. If you can get ahold of the service manual for that radio, it will give you the procedure to calibrate your low, high and MAX power across the band. An NX800 H will do the same thing on UHF. Nominal output power maximum is 45 Watts but if I go into the max power Tab and slide it way up I can get 65 -70 Watts out of it but the life expectancy becomes extremely doubtful. When you're in the max power tab, you can move the slider down to reduce your max power to 50 Watts but it's also going to affect your high power calibration and it's going to drop accordingly. I wouldn't make any large changes without following the alignment procedure for power output.
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Old 02-09-2018, 12:26 AM
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Correct, it puts out normal power (50W) when not in test mode and draws 9.6A (less than the 13A the service manual calls for)

If I'm fine, then I won't worry about it and leave well enough alone.

I don't see in the service manual where there is more to the alignment procedure for power output than simply ensuring it's drawing less than 13A.
If there is more than that to the procedure just say "there is more" I have another radio that's producing less than advertised power output and want it up to advertised spec. If it needs to be aligned by a shop then so be it...
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