I've been listening on the bandsfor a while and quite frequently I hear a few HAM Operators (also known as Amateur Radio Operators) complaining about their noisy receivers, especially people that just started to use the new ICOM's based on SDR technology, i.e. IC-7300 and the IC-7610.

I live in a fairly populated area with quite a few Amateur Radio Operators (AROs) close by. Some of them with the same Transceiver outfit as me however, their antenna system and location differs quite a lot from mine. My antenna system is a non-resonant dipole (RX/TX 40 - 6 m), a 1/2λ 80m inverted L (TX 80 RX below 3 kHz) and a few RX only antennas (H-field and E-field), and yes I live in suburbia and yes I've been lucky to be able to get these antennas into the air (I do dishes and other house chores). However, what I have noticed is the some of my local AROs, which have either better antenna systems and/or a better location then me, seem unable to "hear" as well as I seem to do, i.e. making a bidirectional contact with ease. It can't be only my antenna system or my location, my QTH is surrounded by houses which are higher then my dwelling and the only clear path (no obstructions) I have is into the WNW @ about 280° - 320°). Some of my local AROs are using BEAM's on 40 m and have clear take off 360° etc. . So what could it be?

I might be wrong but could it be that the Operators don't know about their radios Receiver Improvement Arsenal (RIA)? I.e. using the RIA to get the best Signal out of the Noise out of the receiver at the current receive situation, i.e. the CONTACT? Yes, that's what I mean, the CONTACT. Isn't that the what we try to achieve, "making the contact" ?

This is not a blurb about technical specs, this is more a HOW TO get the best SIGNAL to NOISE performance out of your receiver to make/enjoy the contact.

PLEASE NOTE: I do not talk about the "OH NICE SIGNAL 59+20", sounding like John Laws and are > 3 kHz wide and are splattering (IMing), no I'm talking about stations that are in or just above your received noise floor.

If we look at the test specs of these radios (ARRL/Sherwood/Farson) one thing is very clear, they have BIG EARS, i.e. the Minimum Discernible Signal (MDS) of the IC-7610 starts at about -122 dBm and goes to over -140 dBm.

I like to see my noise floor at my QTH go that low (with antenna connected of course), but according to ITU P.372-12 the noise floor at my QTH should be about -91 dBm at 7 MHz (S6), it's actually a bit better by 6dB most of the times, but a far cry about the RX prowess of the current crop of Amateur Radios (sorry about the technical digression).

To show you what I'm talking about I've been taking some screen shots to show what can be achieved by applying the BASIC tool set our RIA provides (most amateur radio transceiver/receiver have those).

I'll be using an SDR-IQ with SpectraVue Ver. 3.39 and SBSpectrum Ver. 1.31 to show the effects of the below Receiver Improvement Arsenal (RIA):

• • • • • • • • • RX-filter bandwidth

                • RF-GAIN control

                • RX-Attenuator

                • AGC

Used appropriately, these basic tools will help us to hear signals, which are low in signalstrength, better.

What do I mean to hear a signals that are low in signalstrength better.

Well our channel receiver bandwidth, the frequency bandwidth the receiver is listening too, is using about 3 kHz of bandwidth for an SSB signal. However, if the good operator is transmitting his SSB signal at 2.4 kHz bandwidth and who doesn't, we have 600 Hz of noise added to out receiver. Which means we now receive a 2.4 Khz SIGNAL + 600 Hz of NOISE in our selected channel bandwidth. So, the first thing to do would be to remove the NOISE in our receiver by changing the receiver bandwidth to as close as possible to the transmitted bandwidth. By removing the NOISE we should be able to hear the SIGNAL better.

OK, enough words here are a few pictures to hopefully demonstrate what can be done to get a signal out of the noise floor.

Pic1 shows the setup parameters I've used for the demonstration and the current 7 MHz noise floor (summer) at my QTH at around 14:30 AEDT, a fairly quiet day.

OK, enough words here are a few pictures to hopefully demonstrate what can be done to get a signal out of the noise floor.

At the above picture, Pic2 we can see clearly what happen if we narrow the RX-bandwidth, the signal pops out of the noise. And at Pic3 below we see the opposite, i.e. widening of the RX-bandwidth, the signal starts to disappears into the noise.

This is what the professionals call the Signal to Noise Ratio (SNR). As we can see if we reduce the receivers bandwidth, i.e. limiting SIGNAL+NOISE ingress, we improve the SNR. The net effect is that the SIGNAL we are interested in, SOUNDS clearer/louder.

Another very good tool is the Automatic Gain Control, the AGC. Most modern Amateur Radios have the ability to adjust the TIME CONSTANT (ATTACK TIME) for their receivers AGC. Pic4 above displays the effect of having the AGC disabled and then enabling the AGC, the noise disappears and the signal pops up. It is worth while playing around with the AGC, I have three different settings on my radio for different noise events/modes. The grey area show to much gain, riding (manually altering) the RF-GAIN can also help, but as I did here, enabling the AGC improves the SNR (see further down for more on AGC).

As mentioned above, switching the AGC off and riding the RF-gain can improve our listening pleasure. Above at Pic5 I'm adjusting the RF-gain settings manually (riding the RF-Gain) to bring the signal out of the noise.

Pic6 above shows us a combination of AGC and riding the RF-gain. Look at the signal pop out! (I wish it always would be that easy).

Instead of riding the RF-gain we can take a short cut and add predefined attenuation (ATT). Most Radios have the ability to add attenuation in predefined steps, some in 6dB steps others in 5dB. See the effect in Pic7 above.

Take a look at the above picture, Pic8, can you see the AGC in action?

As soon as the signal (the CW) stops, the AGC increases the rx-level, depicted by the grey noise which becomes darker in color. This is where you experiment with your AGC time-constant and set it up to suit your operating preference.

So, as you can see we have a great arsenal of tools available to BETTER our receivers ability to get the desired signal out of the noise, or to phrase it more appropriately to ease the HSP between our ears to only work on the SIGNAL and not needing to apply filters to remove the noise (limited HIPS).

Again, I used a CW signal for display purposes only, this will work equally well for SSB and some DIGITAL modes like PSK and RTTY.

However, what it can't do though is get stations out of the mud that use muddy audio, i.e. to much BASS or slurred CW. For that the HPS needs more HIPS and apply rigorous handshaking i.e. 5/9 sorry I had some noise can you repeat .... again ..... had noise again please repeat ....

On 80m and 40m I have between 18 dB and 12 dB attenuation, atmospheric noise levels are high on these bands, start with whatever you feel comfortable with then adjust the AGC. Next I'd setup the filter bandwidth to remove the higher pitched noises, noise above 2.4 kHz and low rumble noise, the noise below 200 kHz. My RX filters are set at 2.8 kHz, 2.1 kHz and 1.7 kHz for SSB, low cut at around 100 - 200 Hz for example: my 2.1 kHz filter bandwidth is setup as 200 - 2300 kHz.

Play around with the setting until you find a setting that sounds right to you. These are setting that work for me, but not necessarily work for you.

This is basically setting the overall system gain, which includes the gain from your antenna systems (Antenna, Cable, ATT, LNA etc.), to the current receive situation which will be different for each situation i.e. the mode of operation, what antenna is being used, the frequency of operations, the operator (HSP and HIPS), time of day, band condx etc. etc.

However, as you get familiar with your radios available RIA, you will get, not only more and more pleasure out of your receiver (station) as you get proficient with that tool-set, but you also will manage to finish more bi-directional contacts.

Let me mention a few more RIAs that are not in the standard RIA. An additional AF tunable filter (Equaliser) can help in reducing noise and Digital Noise Reduction Systems (NR) either at the IF or AF.

However, it is better to reduce the noise before it hits the AF stage of your receiver. I found using a decent speaker, or two if your transceiver has two receivers is also another good way to improve your listening pleasures. Or, of course using a good pair of headphones.

And one more little secret. The use a different antenna to the in use for the current contact ( the TX antenna) could also improve the SNR. However, I will elaborate on that at a later stage.

73 and good DX.