Amateur Radio

Possible Causes

• •Wrong CTCSS/PL tone
• •Offset incorrect
• •Insufficient power to reach repeater
• •Repeater offline

Diagnostic Steps

1. 1.Verify CTCSS tone matches repeater requirements — check local repeater directory
2. 2.Confirm offset direction and frequency (standard 2m offset is −600 kHz, 70cm is −5 MHz)
3. 3.Increase power output or relocate for better line of sight
4. 4.Try transmitting without tone to hear if repeater responds
5. 5.Check if repeater is listed as active on repeaterbook.com

Possible Causes

• •Microphone gain too high
• •ALC compressing audio excessively
• •Wrong mode selected
• •RF feedback into microphone

Diagnostic Steps

1. 1.Reduce microphone gain in radio menu
2. 2.Check ALC meter — should peak in the upper third, not peg continuously
3. 3.Verify correct mode — FM for VHF/UHF voice, USB for HF above 10 MHz
4. 4.Move microphone cable away from feedline to prevent RF feedback

Possible Causes

• •Antenna not cut to correct length
• •Ground system inadequate
• •Feedline has water ingress
• •Antenna too close to metal structures

Diagnostic Steps

1. 1.Measure antenna length and compare to calculated resonant length
2. 2.Check counterpoise or radial system for vertical antennas
3. 3.Inspect all coax connectors for moisture and corrosion
4. 4.Use antenna tuner to match on non-resonant frequencies
5. 5.Move antenna away from metal gutters, downspouts, and structures

Possible Causes

• •RF entering shack on power lines
• •Feedline radiating near equipment
• •Ground loop in audio cables
• •Operating near resonant frequency of audio cables

Diagnostic Steps

1. 1.Add ferrite cores to all cables entering shack — power, audio, USB
2. 2.Check that coax shield is properly grounded at single point
3. 3.Use balanced audio connections where possible
4. 4.Reduce power output temporarily to confirm RF is the cause

Possible Causes

• •Band closed due to propagation conditions
• •Wrong time of day for chosen band
• •Solar disturbance affecting ionosphere
• •Antenna not effective for target distance

Diagnostic Steps

1. 1.Check current band conditions on DXMaps.com or PSKReporter — confirms whether the band is open
2. 2.Match band to time of day — 40m and 80m are night bands, 10m and 15m are daytime bands
3. 3.Check solar flux index (SFI) and K-index — SFI below 70 or K-index above 4 indicates poor HF conditions
4. 4.Try a different band — if 20m is dead, try 40m or 17m which may be open

Possible Causes

• •Low transmit power
• •Antenna not transmitting despite receiving
• •Feedline or connector fault on transmit path
• •Operating simplex when station is on a net frequency

Diagnostic Steps

1. 1.Verify transmit power output with a wattmeter — confirm power is actually reaching the antenna
2. 2.Check SWR on transmit — high SWR reduces effective radiated power significantly
3. 3.Listen for your own signal on a second receiver or WebSDR to confirm you are actually on frequency
4. 4.Try calling CQ on a clear frequency rather than calling a specific station who may not hear you

Possible Causes

• •Auroral propagation on higher HF bands
• •Aircraft scatter causing rapid fading
• •Multipath propagation on short skip paths
• •Ionospheric disturbance

Diagnostic Steps

1. 1.Flutter or rapid fading on 10m–20m often indicates auroral or disturbed propagation — check K-index
2. 2.Try a lower band — 40m and 80m are less affected by ionospheric disturbance
3. 3.Switch to a digital mode such as FT8 which handles fading far better than SSB
4. 4.Note time and band — compare with solar data to identify propagation path

Possible Causes

• •Local noise source masking signals
• •Antenna not resonant on chosen band
• •Antenna tuner not engaged
• •Band genuinely closed in your direction

Diagnostic Steps

1. 1.Check noise floor — if S-meter is consistently above S5 with no signals, a local noise source is masking reception
2. 2.Tune the antenna tuner and verify SWR is below 2:1 on the chosen band
3. 3.Try a directional antenna or beveridge receive antenna to null local noise
4. 4.Confirm band is open using WebSDR — if signals heard on WebSDR but not locally, the problem is local noise or antenna

Possible Causes

• •Audio interface level too low
• •Wrong audio device selected
• •Computer clock not synchronized
• •Software not in receive mode

Diagnostic Steps

1. 1.Check audio input level in WSJT-X — the waterfall should show visible signals and the level meter should be active
2. 2.Verify the correct audio input device is selected — must match the interface connected to the radio
3. 3.Synchronize computer clock to within 1 second using an NTP client — FT8 is extremely time-sensitive, off-by-2-seconds = no decodes
4. 4.Confirm WSJT-X is in receive mode and the correct band/mode is selected

Possible Causes

• •Transmit audio level too high causing splatter
• •Wrong frequency offset
• •Computer clock not synchronized
• •Too much competition on popular frequencies

Diagnostic Steps

1. 1.Check ALC meter during FT8 transmit — ALC should barely move, high ALC causes splatter that makes your signal unreadable
2. 2.Verify transmit audio level is set correctly — FT8 does not need high power, 25–50W is typically sufficient
3. 3.Confirm computer clock is synchronized — even 2 seconds off causes your transmissions to be ignored
4. 4.Try transmitting in the second half of the 15-second cycle — many stations call in the first half

Possible Causes

• •WSPR not uploading spots to internet
• •Wrong callsign or grid square entered
• •Transmit power setting incorrect
• •Band not active at chosen time

Diagnostic Steps

1. 1.Verify WSJT-X is configured with the correct callsign and Maidenhead grid locator
2. 2.Check internet connectivity — WSPR uploads require an active internet connection
3. 3.Confirm transmit power in watts matches what is entered in WSJT-X — reported power is in dBm but entry is in watts
4. 4.Check WSPRnet.org directly to see if your spots are appearing — may be a display delay

Possible Causes

• •Ground loop between radio, computer, and interface
• •Unbalanced audio connection
• •Interface not galvanically isolated from computer USB ground
• •Multiple ground paths through audio cables

Diagnostic Steps

1. 1.Use an interface with transformer isolation — SignaLink, Digirig, or similar isolated interfaces eliminate most ground loops
2. 2.Check that audio cables are as short as possible between interface and radio
3. 3.Try lifting the computer ground by using a USB isolator between computer and interface
4. 4.Add ferrite cores to USB cable and audio cables between interface and computer

Possible Causes

• •Power supply current limit too low
• •Voltage drop under transmit load
• •Power supply protection circuit tripping
• •Undersized wiring between supply and radio

Diagnostic Steps

1. 1.Verify power supply current rating — a 100W HF transceiver draws 20–25A on transmit, supply must be rated at least 25A continuous
2. 2.Measure voltage at radio terminals during transmit — should remain above 13.5V (12V nominal)
3. 3.Check power supply fan — a blocked fan triggers thermal protection causing shutdowns
4. 4.Use minimum 10 AWG wire between power supply and radio for runs over 1 meter

Possible Causes

• •Power supply generating broadband RF noise
• •Insufficient filtering on supply output
• •Supply noise entering radio on power leads
• •Supply switching frequency on or near operating frequency

Diagnostic Steps

1. 1.Try a linear power supply — linear supplies generate no switching noise and dramatically improve receive noise floor
2. 2.Add ferrite cores to power leads close to both the supply and the radio
3. 3.Install a 10,000 µF capacitor across the radio power terminals to filter switching noise
4. 4.Try a different power supply — some switching supplies are far noisier than others on HF

Possible Causes

• •Heavy load heating supply
• •Fan bearing failing
• •Ventilation blocked
• •Temperature sensor fault

Diagnostic Steps

1. 1.Check ambient temperature and ventilation around supply — allow at least 15cm clearance on all sides
2. 2.Reduce transmit duty cycle — constant key-down at full power overheats most supplies
3. 3.Inspect fan for debris blocking blades
4. 4.If fan runs at full speed even on no load, the temperature sensor or fan controller may have failed