6_metre_conversion_prm80
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6_metre_conversion_prm80 [2018/09/14 22:17] vk3smb |
6_metre_conversion_prm80 [2018/09/14 22:24] vk3smb [Alignment] |
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| ===== Alignment ===== | ===== Alignment ===== | ||
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| Parts of this procedure has been extracted from the Phillips PRM8010 service manual. As a minimum you will need the following test equipment: | Parts of this procedure has been extracted from the Phillips PRM8010 service manual. As a minimum you will need the following test equipment: | ||
| - | A variable signal generator. You could get away with using the local oscillator on a scanner with a 21.4Mhz IF and program it to 74.4Mhz and some attenuator pads. | + | * A variable signal generator. You could get away with using the local oscillator on a scanner with a 21.4Mhz IF and program it to 74.4Mhz and some attenuator pads. |
| - | A Dummy Load. | + | |
| - | Frequency Counter. | + | |
| A service monitor would be even better. | A service monitor would be even better. | ||
| - | + | {{ : | |
| - | Program a frequency of 53Mhz into the radio. | + | |
| - | Turn the power adjustment to half way. | + | |
| - | Set the radio to receive and using the VCO test point set the voltage to 7� volts using the slug in the Rx vco inductor. The reason we want the voltage lower than the nominal 15V is the varicaps on the front end use the VCO voltage to tune, if we set the voltage too high they may not tune at 6M. Check the lowest frequency of operation (52Mhz) is above 5 1/2 V. | + | |
| - | Set the TX VCO to a similar voltage. See photo 8 for the VCO TP. | + | |
| - | Using a signal generator, adjust the slugs in the front end for maximum signal, starting at the antenna socket and working your way towards the front. | + | |
| - | Repeat 5 twice more. | + | |
| - | Adjust slug for maximum audio output (photo 9) | + | |
| - | Disable signal generator, set squelch level to 2 from the front panel, adjust the trimpot circled in photo 9 to allow squelch to mute. | + | |
| - | Select transmit and adjust the power out to 25W max. (photo 10). Check the current is less than 5.5A. (you will need to re-adjust with the lid on). | + | |
| - | While transmitting, | + | |
| - | Adjust the deviation on the control board to 5khz. (photo 11). If you cannot get enough deviation you will need to change the 68k resistor near the modulation balance trimpot to 22k. Ref photo 12. Dion, VK7DB informs me that there is some caps in paralell on the Audio path to the TX VCO. If you remove the first one you come to it drops the capacitance from 33p to 15p and he got 11khz of deviation out of the radio. I will look into the circuit diagram and circle the appropriate cap. He also had to play with the modulation balance after removing this cap. I have also thought about adding another varicap diode to the existing varicap on the Audio path in the TX VCO. I have not played with this however. | + | |
| - | + | {{ : | |
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| - | Photo 8 | + | |
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| - | Photo 9 | + | |
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| - | + | ||
| - | Photo 10 | + | |
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| - | + | ||
| - | Photo 11 | + | |
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| - | + | ||
| - | Photo 12 | + | |
| For our English friends, the above procedure will work when based on 51Mhz instead of 53Mhz. | For our English friends, the above procedure will work when based on 51Mhz instead of 53Mhz. | ||
| You should now have a very sensitive, powerful and stable 6M prm80 for minimal cost and a winters afternoon! | You should now have a very sensitive, powerful and stable 6M prm80 for minimal cost and a winters afternoon! | ||
| - | Specifications I ended up with. | + | ===== Specifications I ended up with. ===== |
| Frequency | Frequency | ||
6_metre_conversion_prm80.txt · Last modified: 2018/09/14 22:37 by vk3smb
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