I was tuning a few VHF GP330's (EMEA equivalent of HT750, and 5-tone) with the latest Professional series global tuner (R02.18.00 IIRC).
The readme (help) states the following of the PA BIAS tuning:
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1. Ensure that the radio’s antenna output is terminated in a 50-Ohm load. This is to prevent self-destruction of the PA.
2. Under Tx Align, select PA Bias, select High Power.
3. Measure/read the dc current drawn by the radio (specifications will vary from radio to radio). Call this X. This value should typically range from 70-100mA or 0.07-0.1A. If it is higher than 0.1A, refer to the section "How to Screen for Special PCICs".
4. Press Toggle Voltage to enable the PA control voltage edit box/spin control.
5. Increase the Voltage softpot value and measure/read the current from the meter. Call the new value Y.
6. Increase Y until Y - X is within the range given for PA current in table below.
7. Press Toggle Voltage again to disable the PA control voltage edit box/spin control.
8. Press Toggle Bias 1 in order to enable the PA Bias softpot.
9. Increase the softpot value to obtain Z until Z - Y is within the range for Bias Current as indicated in the table below.
10. Press Toggle Bias 1 again to disable the PA Bias softpot.
11. Program the Bias softpot into the radio’s codeplug by pressing Program.
12. Exit the PA Bias High Power function.
13. Under Tx Align, select PA Bias, Low Power.
14. Repeat steps 3-11.
15. Exit the PA Bias Low Power function.
However, after I checked a dozen radios, all had the softpot value of 47 in the low power PA bias. Aligning it according to instructions will set it to anywhere between 50-70. Changing this from the tuned to default (47) did not affect any tuning values with a quick checkup.
These radios do not use low power.
Is there a flaw in the help-file, or are just all the radios tuned wrongly from the factory?
Furthermore the table "PA Bias default value for professional portable radios" lists N/A for as the low power value for: VHF, LB, 700, 800 and 900 MHz where as for all other than VHF, the instructions say that low power tuning is not required.
Example: "800 MHz and 900 MHz do not require low power PA Bias tuning."
I'm a bit in the woods here, any help appreciated