A modern HF radio is a marvel of technology. But often they are so complex that a lot of the controls never get touched! Or if they do, people are unsure what exactly they do and use them incorrectly.
So let’s look at some of the functions on a modern HF radio and how you can use them.
Anyone coming from a CB background will be pretty familiar with the squelch control. It basically turns off the audio on the radio until a strong enough signal opens it. Squelch can be very useful (if not essential) as the continuous hiss of a blank FM channel can be very annoying.
Squelch is used somewhat less on SSB as the background noise is generally quieter, but there is no reason why you couldn’t use it. If you are monitoring a specific frequency on your radio for hours on end it can be useful to squelch the audio on SSB to help retain your sanity!
The HF bands can be quite noisy at times and digital noise reduction can be a way of making the audio easier on the ears. The best approach is to engage the noise reduction button and then advance the noise reduction gain knob until you get the effect you are looking for. If you advance it too far the chances are that you will end up with very muddy audio, sounding like someone has their head in a bucket!
If you have a whistle or tone on your received signal a notch filter can be used to remove it. The tone can be due to a heterodyne of two signals mixing or someone tuning up. The approach is to switch on the notch filter and rotate the control until the tone vanishes or is attenuated. If the tone frequency changes you will need to re-adjust the control.
Some radios have an auto notch feature that can automatically track tones and remove them without you needing to touch the controls.
A notch filter can adversely affect the quality of the received audio so should not be left switched in if it is not required. Also, listening to a CW or PSK 31 transmission with auto notch engaged can be totally self-defeating as the rig does its best to remove the very signal you are trying to listen to!
Receiver Incremental Tuning or Receiver Independent Tuning is a way of changing the frequency your radio is listening to without affecting the transmit frequency. It can be very useful on SSB if someone comes back to your CQ call and is not quite on your frequency.
By engaging the RIT and tweaking the control slightly you can make their voice more intelligible. If you moved the main VFO dial the chances are that they would change their radio and you would be back where you started.
The only problem with RIT is forgetting that you have engaged it. If you then subsequently move up or down the band to call someone else you will be off frequency. So either switch it off or set it to 0.00 kHz offset
Webmaster note- Personally I think the Rit is an instrument of the devil, I avoid its use all the time. How many times have you listened to a net where several of the participants have a the RIT engaged and each are netted on a different station — chaos and unintelligibility on a large scale.Forgetting to return the control to zero once used could account for your lack of HF success with the RX shifted possibly, by up to to 5KC either way, could lead you to wonder why there are no responses to your CQ calls!
The Automatic Gain Control is often misunderstood. Received radio signals can vary wildly in their strength, from very weak to incredibly strong. With AGC the radio will try to adjust itself to deal with these vastly differing signal strengths.
On the whole it does a good job, but you can help it. Usually you can choose between fast AGC and slow AGC. This affects the speed at which the radio will adjust itself when listening to different signals. While slow or medium AGC may be fine for SSB transmissions, you may find with CW or PSK31 that you miss the first one or two characters of a transmission as the AGC fails to react quickly enough when moving from a strong signal to a weak one.
Fast AGC tends to work better with digital modes, but it is worth experimenting. AGC can be a personal thing—I prefer a slow setting.
All rigs work in different ways, but most will let you adjust the width of the IF filter. Other older radios may have different crystal filters that have the same net effect. These effectively cut down how much of the “band” you listen to at once.
Typical values for SSB tend to be 3.6 kHz or 2.7 kHz. The first setting is a broad filter that will give you excellent received audio quality. However, if the band is busy you may find that you suffer from adjacent channel interference and the 2.7 kHz setting might be better. With most modern radios you can even narrow this down even more, but if you go much below 2.4 kHz the audio will start to deteriorate.
If your radio lets you set up three different width settings for SSB then 3.6, 2.7 and 2.4 kHz would be a good choice
For CW and digital modes you might want to opt for narrower filters. CW enthusiasts usually go for 500 Hz or 300 Hz, although modern Software Defined Radios (SDR) can even be used down to about 50 or 25 Hz on CW with no “ringing”. Other people prefer to engage a 1000 Hz filter so that they can hear other stations that might be close by, using their brain to filter out the different signals.
The correct filter for digital modes, such as RTTY and PSK 31, will depend upon the mode itself and how busy the band is. A good choice would be set up three—say 500 Hz, 300 Hz and 200 Hz—and select whatever works best for you at the time. But setting a 3.6 kHz width would also let you hear signals that are close, but not exactly on your frequency.