On the exciter shorten the following coils: L301/L311, L302/L312, L303/L313, L304/L314, L305/L315, L306/L316 and L307/L317. The older models have paper coils and are somewhat easier to modify but tend to slip and require Teflon inserted between the slug and coil sleeve. The later models use plastic coils and are preferred because you don't have the slippage. The plastic and paper have different number of terms.
Paper Coil - 19D416859G4
Plastic Coils - 19D430230G4
To calculate the number of turns to remove
|
Coil No. |
Original Turns Paper Coils |
Calculated Turns to Remove |
Original Turns Plastic Coils |
Calculated Turns to remove |
Actual turns removed. |
|
T101,T102,T103 |
33.5 |
9.28 |
33.5 |
9.277 |
9 |
|
T104, T105 |
11.75 |
3.25 |
14.5 |
4.016 |
4 |
|
T106 |
7.5 |
2.08 |
7.5 |
2.077 |
2 |
|
T107 |
7.5 |
2.08 |
7.5 |
2.077 |
2 |
|
T108,T109,T110 |
4.75 |
1.32 |
4.5 |
1.246 |
2 |
|
T111 |
5.25 |
1.45 |
5.5 |
1.523 |
2 |
|
T112 |
5.5 |
1.52 |
5.5 |
1.523 |
2 |
More information on coil modification.
The taps are left unchanged
If L102 is 27 micro henry, it should work fine, if is is 38 micro henry, replace it with a .22 micro henry
Tuning Excitor
|
Using DC Volt Meter with High Impedance |
Tuning Coils |
Readings from Dave's 1997 conversion taken with Fluke DVM |
|
Pin 2 & Ground |
Peak T101 |
2.42 |
|
Pin 1 & Ground |
Peak T102,T103 |
2.01 |
|
Pin 3 & Ground |
Dip T104 Peak T105 |
1.13 |
|
Pin 4 & Ground |
Peak T104,T105 Dip T106 Peak T107 |
1.61 |
|
Pin 7 & Ground |
Peak T106,T107 Dip T108 Peak T109 Dip T110 |
2.08 |
|
Pin 5 & Pin 6 |
Peak T105,T106,T107,T108,T109, T110 |
0.63 |
|
Using watt meter |
Peak T111 & T112 |
330mwatts@235mamp |
You can increase the power output 40mw by removing the resistor between T112 and RF Jack and replacing R147 (the resistor satnding on it end across from T111) a 36 ohm resistor with a 1/4 watt 10 ohm resistor
Tuning the exciter using a spectrum analyzer
The example I will use is 223.38. The fundamental frequency is 224.38/12 or 18.698 Q106 triples the frequency by amplifying the second harmonic to 56.095. Q107 doubles the frequency to 112.190 by amplifying the first harmonic. Q108 doubles again to 224.380.
Using a sniffer, set the spectrum analyzer to approximately 55 MHz – 57 MHz . Sniff around T101 and tune T101, T102, and T103 for maximum. Next move up to 112.190 and tune T104 and 105. Now move to 224.38 and Tune T106-T112.
Use the procedure above to get a power measurement and tune for maximum output power. You can also tune as per the manual once you do the above procedure to get meter readings.