HT-220 VHF 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

HT-220 VHF is split into three bands: 136-150.8, 150.8-162, and 162-174 MHz. The 150.8-162 version can be downbanded to the Amateur Radio 2-Meter band by modifying with capacitors.

Frequency Calculations

Fo1 =	(Fc - F1) / 3
Fo1 =	1st Oscillator Frequency =	39.733 -- 52.4 MHz
Fc =	Carrier Frequency =	136 -- 174 MHz
F1 =	1st IF Frequency =	16.8 MHz
	F1 = Fo2 + F2	(for 16.345 MHz crystal)
	F1 = Fo2 - F2	(for 17.255 MHz crystal)
Fo2 =	2nd Oscillator Frequency =	16.345 MHz or 17.255 MHz
F2 =	2nd IF Frequency =	455 kHz

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

Carrier Freq	IF Crystal Freq
136.000 - 138.500 138.501 - 142.000 142.001 - 147.000 147.001 - 150.800 150.801 - 162.000 162.001 - 170.000 170.001 - 174.000	16.345 17.255 16.345 17.255 16.345 17.255 16.345

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 VHF Reciever Alignment

Following is from HT-220 VHF manual 68P81006C35-O and 68P81001C63-G

Test Equipment Required per Motorola manual:

1. Motorola S1339A or S1340A RF Multimeter (or S1063A DC Multimeter with SLN6055A RF probe or equivalent).
2. Motorola S1053C AC Voltmeter or equivalent.
3. Motorola S1318A Series Signal Generator, or equivalent.
4. Motorola NLN6689A Tuning Tool Kit (or equivalent non-conductive adjustment tools).
5. Motorola TEK-23 Power Supply or equivalent.
6. Motorola NKD6001A Tune-up Kit.
7. Motorola NKD6001B Tune-up Cable - used for the remote antenna mounting speaker-microphone option. However, on the standard remote speaker-microphone models, the NKD6001B Tune-up Cable may be used to make audio measurements when used with the NKD6001A Tuneup Kit.

Note

The NKD6001B Tune-up Cable must be used when aligning receiver with signal generator in order to simulate the actual impedance of the antenna.

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
Step	uV Input	Meter Point	Lab. RF Voltmeter	AC Voltmeter	DC VTVM (With RF Probe)
1	Noise	Emitter Q2	0.40	----	0.40
2	Noise	Base Q3	0.06	----	0.03
3	Noise	Emitter Q4	0.90	----	0.90
4	Noise	Base Q5	0.06	----	0.03
5	10,000	Collector Q1	0.05	----	0.04
6	10,000	Base Q3	0.10	----	0.06
7	1,000	Collector Q3	0.30	----	0.20
8	1,000	Base Q5	0.11	----	0.06
9	100	Collector Q5	0.70	----	0.60
10	100	IC-1, Pin 10	0.03	-28 dbm	0.015
11	Noise	M2	----	-40 dBm	----

Notes:

• Connect the Motorola S1318A Series Signal Generator to the radio set using the NKD6001B Tune-up Cable.
• 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 chart 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

*M5 for remote spkr-mic models

Notes:

• Connect the Motorola S1318A Series Signal Generator to the radio set using the NKD6001B Tune-up Cable.
• 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	----	0.9 v
3	Noise	Collector Q10	----	2.0 v
4	Noise	Base Q11	----	0.6 v

Notes:

• Turn squelch control fully clockwise.
• Connect the Motorola S1318A Series Signal Generator to the radio set using the NKD6001B Tune-up Cable.
• 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	T6	Unsquelch radio. On "PL" models, turn "PL" off. Connect the 455 KHz output of the test set to the unused tap of L6. With the DC Multimeter, monitor M3 and tune T6 to a peak. Typical reading is +2.2 vdc.
3	DC Multimeter, Portable Test Set with 455 KHz Crystal	M4	L7	With the setup in step 2, monitor the discriminator output at M4. Tune L7 for zero volts. This setting should be within ±0.01 VDC of zero volts. Disconnect the 455 kHz output of the test set from the radio.
4	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.
5*	AC Voltmeter, FM Signal Generator, DC Multimeter, NKD6001B Tune-up Cable	M2	L1, T1, T2, T3, T7, T4, T5, L6	Tune L1, T1, T2, T3, T4, T5, and L6 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. On radios with two or more frequencies with separation of 0.3 to 2.0 MHz, remove signal and balance tune L1, T1, T2, and T3 on noise at M4 for equal noise readings on all frequencies. Note: T7, T4, T5, and L6 must be tuned carefully with the signal generator set to discriminator zero ±0.01 vdc.
6**	DC Multimeter	M4	L2	Use the base station transmitter or a frequency standard as a signal source, adjust warping coil L2 for a zero DC voltage at M4.
7	DC Multimeter	M4	L301, etc.	Repeat Step 6 for second through sixth frequencies as applicable
8	AC Voltmeter, FM Signal Generator, NKD6001B Tune-Up Cable	Speaker, or M5 for remote spkr-mic models	Signal Generator	Adjust the volume control for an output voltage across the speaker, or across a 39 ohm resistor in series with the audio output jack, for 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 0.35 uV. Repeat for all frequencies as applicable.
9	FM Signal Generator, NKD6001B 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 0.18 uV.

*After completing this step, look for the image frequency at 910 KHz below this setting as a check on the accuracy of the signal generator setting. Upon locating the inimage, turn to the proper setting for the carrier frequency.

**L2 reference designation applies to first oscillator coil of 1 and 2 frequency, internal speaker-microphone, or remote speaker-microphone models only. L301 reference designation applies to 2 frequency, internal speaker-microphone, or remote speaker-microphone models only. For reference designations of first oscillator coils applicable to other models, see assocaited internal, remore, or universal schematic diagram.

Notes

• Tune all slugs to the peak nearest to the circuit board unless otherwise stated. Use nonmetallic tool for T6 and T7.
• On radios with two or more frequencies, set the frequency switch to the lowest frequency.
• Turn the radio on and set the squelch control for maximum noise.

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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