HT-220 UHF Frequency Tuning

Last update: 5/12/00

I make no claims to technical accuracies. USE AT OWN RISK.

WARNING: FCC license required for transmitting on frequencies covered by the HT-220.

NOTICE: HT-220 cannot be certificated for transmitting in the Family Radio Service (FRS) bands.

WARNING: Amateur radio license is required for tuning, adjusting, and operating transmitters on the Amateur radio bands.

Michael Wright, K6MFW
Website Editor

HT-220 Frequency Bands

UHF is split into three bands: 406-420, 450-470, and 470-488 MHz.

The UHF is divided into more discrete groups depending on the IF (2nd oscillator) crystal. These are,

Carrier Freq	IF Crystal Freq
406.000 - 420.000 450.000 - 450.675 450.700 - 451.150 451.175 - 451.475 451.500 - 452.500 452.525 - 453.675 453.700 - 460.725 460.750 - 461.025 461.050 - 461.750 461.775 - 461.925 461.950 - 462.200 462.225 - 464.750 464.775 - 465.275 465.300 - 466.000 466.025 - 466.725 466.750 - 467.250 467.275 - 468.175 468.200 - 468.675 468.700 - 470.000 470.000 - 488.000	12.155 11.245 12.155 11.245 12.155 11.245 12.155 11.245 12.155 11.245 12.155 11.245 12.155 11.245 12.155 11.245 12.155 11.245 12.155 11.245

Frequency Calculations

Fo1 =	(Fc - F1) / 9
Fc =	Carrier Frequency =	406 -- 420 MHz or 450 -- 488 MHz
F1 =	1st IF Frequency =	11.7 MHz
	F1 = F2 + Fo2	(for 11.245 MHz crystal)
	F1 = F2 - Fo2	(for 12.155 MHz crystal)
Fo1 =	1st Oscillator Frequency =	48.700 -- 50.922 MHz (for 450 -- 488 MHz carrier freq) or 43.811 -- 45.366 MHz (for 406 -- 420 MHz carrier freq)
Fo2 =	2nd Oscillator Frequency =	11.245 MHz or 12.155 MHz
F2 =	2nd IF Frequency =	455 kHz

Tuning the HT-220

You can order crystals to the desired frequency from either ICM (www.icm.com or 1-800-725-1426) or Peterson Radio at (712) 323-7539. ICM will calculate the actual crystal frequency for the operating frequency you specify for the HT-220. Cost is typically $15 and delivery is about 2 weeks. After soldering the crystal in place, you still need to tune the radio for optimum performance.

Sorry, no transmitter conversions or alignments here.

HT-220 UHF Reciever Alignment

Following is from HT-220 UHF manuals 68P81061A80-0 and 68P81001C83-K

Test Equipment Required per Motorola manual:

1. Motorola S1052B DC Multimeter with RF probe or equivalent.
2. Motorola S1051C Transistorized AC Voltmeter or equivalent.
3. Motorola S1067A Transistorized Audio Oscillator.
4. Motorola S1056A-9A or TU546 Series Test Set with 455 kHz crystal or equivalent crystal controlled oscillator.
5. RF Millivoltmeter - Millivac Model MV828A.
6. Motorola S1319A FM Signal Generator, or equivalent.
7. Motorola NLN6689A Tuning Tool Kit (or equivalent non-conductive adjustment tools).
8. Motorola TEK-23 Power Supply or equivalent.
9. Motorola NKE6003A Tune-up Kit.
10. Motorola NKE6007A Tune-up Cable - used for the remote antenna mounting speaker-microphone option. However, on the standard remote speaker-microphone models, the NKE6007A Tune-up Cable may be used to make audio measurements when used with the NKE6003A Tuneup Kit.

Note

The NKE6007A Tune-up Cable must be used when aligning receiver with signal generator in order to simulate the actual impedance of the antenna. With the remote antenna mounting speaker-microphone option the NKE6007A Tune-up Cable must be used instead.

Receiver RF and IF Stage Gain Measurements Chart

Caution: Connect a 39-ohm resistor in series with the audio output jack when servicing with a power supply and AC operated test equipment. Paralleling test equipment chassis grounds can bypass the audio output internal load R54 when making AC or DC measurements and damage the audio output transistors.

			Readings in Volts			DC VTVM
Step	uV Input	Meter Point	Lab. RF Voltmeter	AC Voltmeter	DC VTVM (With RF Probe)	T1 Detuned	T1 Tuned
1	Noise	Emitter Q2	0.42	----	0.43	----	----
2	Noise	M1	----	----	----	4.0	2.5
3	Noise	Emitter Q4	0.90	----	0.80	----	----
4	Noise	Base Q5	0.10	----	0.01	----	----
5	10,000	Collector Q1	0.09	----	0.05	----	----
6	1,000	Collector Q3	0.085	----	----	----	----
7	1,000	Base Q5	0.12	----	0.01	----	----
8	100	Collector Q5	0.48	----	0.35	----	----
9	50	M2	0.03	-30 dbm	----	----	----
10	Noise	IC1, Pin 4	----	-35 dbm	----	----	----
11	1,000	Y2 Input	0.10	----	0.015	----	----
12	1,000	Y3 Output	0.13	----	0.025	----	----

Notes:

• Connect the Motorola S1319A FM Signal Generator to the radio set using the Motorola NKE6003A Tune-up Kit and/or NKE6007A Tune-up Cable, as applicable.
• All measurements are taken using 15.0 vdc input.
• When measuring rf voltages, connect the ground clip to the nearest ground point at the element being measured.
• For noise readings, the signal generator frequency must be set to a frequency removed from the carrier frequency.
• Steps 1 and 3 provide a measure of oscillator activity.
• Steps 2 and 4 provide a measurement of high and low oscillator injection.
• In steps 5 through 10, repeak the coils as necessary for a peak reading. The tuning of the coils may be different for each type of meter.
• After completing the stage gain measurements, retune the receiver according to the receiver alignment procedure.
• All readings indicated in the chart are for a normally operating receiver.
• A malfunctioning receiver will cause readings to differ.

Step	Input	Meter Point	Readings
1	100 uV	M4	-13 dbm
2	100 uV	Emitter Q7	-12 dbm
3	100 uV	Base Q12	-40 dbm
4	100 uV	Emitter Q15	+16 dbm
5	100 uV	Speaker	+15 dbm

Notes:

• Connect the Motorola S1319A FM Signal Generator to the radio set using the NKE6003A Tune-up Kit and/or NKE6007A Tune-up Cable, as applicable.
• Modulate the signal generator with a 1000 Hz tone (and on "PL" models, the proper "PL" tone) adjusted to 3.3 kHz peak to peak deviation. Tune the signal generator to the carrier frequency (zero reading at test point M4) and set the RF input signal to 100 microvolts.
• The readings shown in the chart are taken with an AC Voltmeter.
• All measurements are taken using a 15.0 volt dc input.
• Adjust the volume control for rated audio output.

Step	Input	Meter Point	AC Voltmeter	DC Multimeter
1	Noise	Collector Q8	+8.5 dbm	----
2	Noise	Collector Q9	----	0.8 v
3	Noise	Collector Q10	----	2.0 v
4	Noise	Base Q11	----	0.6 v

Notes:

• Turn squelch control fully clockwise.
• Connect the Motorola S1319A FM Signal Generator to the radio set using the NKE6003A Tune-up Kit and/or NKE6007A Tune-up Cable, as applicable.
• All measurements are taken with 15.0 vdc input.
• For noise readings the signal generator frequency must be set to a frequency removed from the carrier frequency.

Step	Test Equipment	Meter	Adjustment Point	Procedure
1	DC Power Supply	----	----	Adjust power supply for 15.0 v.
2	DC Multimeter, Portable Test Set with 455 KHz Crystal	M3	T3	Unsquelch radio. On "PL" models, turn "PL" off. Connect the 455 KHz output of the test set to M2. With the DC Multimeter, monitor M3 and tune T3 to a peak. Typical reading is 2.0 v.
3	DC Multimeter, Portable Test Set with 455 KHz Crystal	M4	L11	With the setup in step 2, monitor the discriminator output at M4. Tune L11 for zero volts. This setting should be within ±0.01 VDC of zero volts. Disconnect the 455 kHz output of the test set from M2.
4	DC Multimeter	M1	T1	Tune T1 for minimum reading.
5	DC Multimeter, FM Signal Generator	M4	Signal Generator	Set FM signal generator to 50,000 uV and adjust to the desired frequency. Monitor M4 for zero volts.
6	AC Voltmeter, FM Signal Generator, DC Multimeter, NKE6003A Tune-up Kit and/or NKE6007A Tune-up Cable	M2	L2, L5, L6, L7, L9, L10, T2	Tune T2, L5, L6, L7, L9, L10 and T2 (T2 tuned for comp. side) for a maximum reading at M2. Keep the M2 reading below -30 dbm by reducing the signal generator input. Retune the coils to make sure they are peaked. Note: L9 and L10 should be tuned to second peak. Monitor M4 for zerovolts.
7	DC Multimeter	M4	L1, L3 L301 thru L306 as applicable	Use the base station transmitter or a frequency standard as a signal source, adjust warping coil L1 (for 1 and 2 freq. models) or L301 (for multi-freq models) for a zero DC voltage at M4. MULTI FREQUENCY MODELS Use above procedures substituting L3 for L1 (2-freq models) or L302 thru L306 (multi-freq models).
8	AC Voltmeter, FM Signal Generator, NKE6003A Tune-up Kit and/or NKE6007A Tune-up Cable	Speaker	Signal Generator	Adjust the volume control for an output voltage across the speaker-microphone of 0 dbm (noise only -- no signal input). Increase the input signal until the noise is reduced to one tenth of the reading with no signal input (-20 dbm). Read the attenuator scale in microvolts. This is the 20 db quieting sensitivity and should be less than 0.5 uV. TWO-FREQUENCY MODELS ONLY: Check the 20 db quieting on the other frequency. Both channels should have a 20 db quieting sensitivity of less than 0.5 uV.
9	FM Signal Generator, NKE6003A Tune-up Kit and/or NKE6007A Tune-up Cable	----	Signal Generator	"PL" MODELS ONLY Set carrier squelch to threshold level. Turn "PL" on. With the signal generator modulated with proper "PL" tone, squelch should open if the output of the signal generator is increased above 0.25 uV.

Notes

• All slugs should be tuned to the peak nearest the printed circuit board unless stated otherwise.
• On two-frequency models, set the Frequency Selector Switch to F1.
• Use the nonmetallic tuning tool supplied in NLN6689A for tuning all coils and transformers.

I make no claims to technical accuracies. USE AT OWN RISK.

WARNING: FCC license required for transmitting on frequencies covered by the HT-220.

NOTICE: HT-220 cannot be certificated for transmitting in the Family Radio Service (FRS) bands.

WARNING: Amateur radio license is required for tuning, adjusting, and operating transmitters on the Amateur radio bands.

Michael Wright, KG6BFK
Website Editor

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