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HF Radio communication so difficulties during Low SSN
It is true that most ham radio operators around the world in their quest for DX on HF radio find it exceedingly difficult during low SSN conditions at Solat Cycle minimas. Currently, as I write, we are negotiating low SSN conditions as we are making a transition from Solar Cycle #24 to #25. I agree that the difficulties are much greater during this phase in comparison to the high SSN phase. However, the question that is often asked is, are the HF bands practically dead? … The short answer is NO!

Can we still continue to make adequate radiotelephony SSB and CW DX contacts on HF during low SSN? …YES! … Do we need to fall back on ultra-weak signal modulation modes like FT8 to survive? … NO! … Those of us who give up on SSB phone or CW and find ourselves limited to FT8 are certainly doing something horrendously wrong. Most probably, the ham radio station setup is unsatisfactory… Hold on! I hear some readers saying, what nonsense are you talking about… I have a state-of-art, modern, and expensive transceiver – like FTDX-101D, FTDX-10, FT991A, IC-7300, TS-990S, TS-890S, TS-590G, etc… How can my setup be unsatisfactory or mediocre? Oh yes! It sure can be… What does a modern transceiver loaded with tons of DSP features really bring to the table? It enables you to negotiate congested band conditions with lots of activity in the form of near, adjacent, and overlapping interferences from strong signals, etc. When do these conditions occur? It happens when the SSN is high, DX propagation is great, and the bands are wide open… Not now under the currently prevailing difficult conditions. When you can’t hear any stations, and the bands appear to be quiet and placid, what could all the DSP features do to help you? Practically nothing. Under the present low SSN conditions, even a good old-fashioned, fully functional transceiver from the yesteryears would be equally fine. Even the older HF transceivers have equally good sensitivity.





Major issues leading to nadequate HF DX during low SSN
So, why can’t I hear any stations? The problem is not with the old or new jazzy transceiver. They are practically alike under low SSN conditions. The problem lies elsewhere. In all probability, it could be either or all of the following three things…

  • Lack of understanding of HF radio propagation.
  • Antenna not being high enough above ground to produce acceptable low take-off angle radiations.
  • Most importantly, a poor quality antenna setup which lets the coaxial cable (transmission line) pick up lots of noise coupled with excessive RF noise from home lighting, electrical appliances, etc in your house and immediate neighborhood.


Address these issues and you will be pleasantly surprised that you begin to work many more stations including DX even under low SSN conditions… Remember, the first and foremost thing is to be able to hear the DX before a two-way contact becomes possible… Let me explain the ramifications of these above-cited issues and how to resolve them… Read on!

Despite the important factors that I have listed above to achieve better HF radio DX capabilities during low SSN conditions, many ham radio operators fall into the trap of applying other means that may not be as effective. For one, opting for a higher gain antenna is usually the first thought. Remember, that such an antenna is always welcome but it will not do much good unless it is deployed in the clear at a greater height… Height above ground is the operative term and not so much the additional gain. Similarly, many think that a QRO HF Linear Power Amplifier would be the solution to their woes… Sadly, it is a misconception. It rarely does any good if your radio station is hard of hearing and is practically deaf due to elevated noise. Unless one hears the DX, what good is a linear amplifier? … I have compared some of these along with their pros and cons in the table below… Check it out!

HF band low SSN radio improvements

Amateur radio operators use various means of enhancing HF radio DX communication prospects. Of the different methods that are employed, this table shows the pros and cons of the 3 most common methods... Out of all three options, the decision to minimize RF noise floor at the receiver pays best dividend.



As I mentioned above, the difficulties in finding and working DX on HF bands during low SSN is usually due to a combination of antenna installation issues and also due to little or no understanding of how propagation conditions change with the change in SSN, selected band, and the time (day/night) of operation. In this article, I will deal with each of these aspects and attempt to suggest ways and means of mitigating the problems. Most knowledgeable and seasoned HF ham radio operators already know all this and therefore successfully negotiate the prevailing conditions to make regular SSB phone QSOs, both local as well as DX, even during the low SSN phase. My objective is to help all others also achieve this goal.

Start thinking beyond FT8 and leverage your station setup to begin working radiotelephony SSB DX more often by following a few simple but effective tips and tweaks described below...

As a matter of fact, I have written several articles on the adverse effects of poor antenna installations that result in unacceptably high receiver noise floors, and how to minimize them. I also have articles on the virtues of antenna height and low radiation take-off angles. Therefore, I will provide links to these detailed articles as extensions to our discussion while keeping the narrative brief in this article. Therefore, I will focus more on the differences in low SSN propagation conditions vis-a-vis that under moderate to high SSN scenarios. It is important to understand these aspects and learn to be able to find propagation openings rather than giving up and falsely concluding that propagation might not exist.

Now, let us expand our discussion on these three major factors that result in communication difficulties under low SSN conditions during the bottom ebbs of the 11-year Solar Cycles...


Understanding the dynamics of HF radio propagation under low SSN conditions
We need to understand that although the occurrence of HF band openings during low SSN certainly does get more restricted, the bands are definitely not dead. Therefore we must learn to find these band openings and operate during those times. On the other hand, during good SSN conditions, more bands tend to open up for a longer duration of time. Hence, the ham radio operators invariable stumble upon one or more propagationally open bands most of the time. They rarely miss propagation opportunities even if they do not understand much about how HF radio propagation works. This results in the general belief that the bands are open during good SSN... Whereas, during low SSN conditions, the random hit and miss approach to stumble upon band openings does not work well. This leads to the false notion that the bands might be dead.

Using a set of illustrations that graphically depict HF band opening prospects under both low SSN as well as moderate/high SSN will make this concept clear. Therefore, I will now present this set of illustrations along with an explanatory narrative... As examples, I have graphically projected HF radio propagation prospects for three different DX communication circuits. Similar logic would apply for any other HF DX path irrespective of whichever part of the world you live in.

The example HF propagation (band opening) projections given below are between the three following communication circuits...

  • Between USA and UK as would be applicable on 30th December 2021 for conditions of SSN 35 and SSN 150
  • Between India and Germany as would be applicable on 30th December 2021 for conditions of SSN 35 and SSN 150
  • Between Australia and Spain as would be applicable on 30th December 2021 for conditions of SSN 35 and SSN 150




In the above list, I have specified the date because the HF propagation prospects are also influenced by the season of the year. It is not the seasonal weather that affects propagation but the position of the sun's footprint on the surface of the earth in terms of the Latitude that makes the difference. Due to the inclination of the earth, as it revolves around the sun, the relative overhead position of the sun oscillates around the equator from the northern hemisphere to the southern hemisphere and vice-versa. This influences the ionospheric densities over different regions of the earth resulting in distinct alteration of HF propagation behavior.

Therefore, what we see in the following illustrations would not be the same during other months but would nevertheless follow a similar trend.

Without further ado, let us dive into the subject at hand...

The illustrations displayed below represent the HF propagation band opening prospects for three different example paths of DX communication. These graphical illustrations will provide a clear insight into band openings that would occur during two different conditions of SSN if they were to exist on a particular day. The illustrations are a plot of propagation openings over 24 hours (UTC time) plotted on the X-axis versus the frequency plotted along the Y-axis. The red and orange-colored regions represent good openings, while greenish and blue colors indicate no propagation. The red line plotted on the graphs represents the Maximum Usable Frequency (MUF) that prevails at any time.

USA to UK circuit HF propagation openings
The HF band openings for SSN 35 and SSN 150 are depicted below. During SSN 35 conditions, the 20m band opens up for a short while from 1300 UTC - 2000 UTC with moderate conditions. The 17m band opens for a shorter duration from 1400 UTC - 1800 UTC at best. All other bands are closed during the entire day. Therefore if ham operators choose any other time of day or band then they would have no success.

On the other hand, if the SSN were o be 150, then various bands 20m, 17m, 15m, 12m, and 10m would have strong openings for a wider period of time ranging between 1100 UTC - 2100 UTC to 1300 UTC - 1900 UTC. These openings produce much stronger signals over a wider time span. Moreover, 30m and 40m openings also occur between 0000 UTC - 1000 UTC or longer. Therefore, most operators easily stumble upon HF band openings during higher SSN conditions in comparison to low SSN... However, it clearly shows that the bands are not dead even during low SSN, it's only that one needs to know when the openings occur.

USA - UK low SSN HF band openings

USA – UK Circuit — This illustration charts the 24 hour HF radio propagation band opening prospects across all ham radio HF bands… The projections have been made for conditions of low SSN 35 as would have existed during the end of December 2021.

USA - UK HF band radio propagation openings

USA – UK Circuit — This illustration charts the 24 hour HF radio propagation band opening prospects across all ham radio HF bands… The projections have been made for conditions of moderate SSN 150 as would have existed during the end of December 2021.



India to Germany circuit HF propagation openings
I will present the graphs for this DX circuit path below without dwelling on explanations. The graphs should be self-explanatory and in line with the explanatory notes that I have provided for the USA - UK circuit case above.

The results are similar in the sense that stronger and longer duration band openings occur over more bands when SSN is high in comparison to what we achieve during low SSN. Therefore once again, people with very little or no understanding of finer nuances of propagation still manage to land into an opening, whereas, during low SSN, most often they miss the opportunities as they might be trying their luck on the wrong band at the wrong time.

India - Germany HF band radio propagation openings

India – Germany Circuit — This illustration charts the 24 hour HF radio propagation band opening prospects across all ham radio HF bands… The projections have been made for conditions of low SSN 35 as would have existed during the end of December 2021.

India - Germany HF band radio propagation openings

India – Germany Circuit — This illustration charts the 24 hour HF radio propagation band opening prospects across all ham radio HF bands… The projections have been made for conditions of moderate SSN 150 as would have existed during the end of December 2021.



Australia to Spain circuit HF propagation openings
Here are the graphs for this DX circuit path below without dwelling into explanations. The graphs should once again be self-explanatory and in line with the explanatory notes that I have provided for the USA - UK circuit case above.

The results are similar in the sense that stronger and longer duration band openings occur over more bands when SSN is high in comparison to what we achieve during low SSN. Therefore once again, people with very little or no understanding of finer nuances of propagation still manage to land into an opening, whereas, during low SSN, most often they miss the opportunities as they might be trying their luck on the wrong band at the wrong time.


Australia - Spain HF band radio propagation openings

Australia – Spain Circuit — This illustration charts the 24 hour HF radio propagation band opening prospects across all ham radio HF bands… The projections have been made for conditions of low SSN 35 as would have existed during the end of December 2021.

Australia - Spain HF band HF radio propagation openings

Australia – Spain Circuit — This illustration charts the 24 hour HF radio propagation band opening prospects across all ham radio HF bands… The projections have been made for conditions of moderate SSN 150 as would have existed during the end of December 2021.




Unacceptably high RX noise floor due to poor quality antenna and transmission line setup
S-meter noise floor HF radio receivers

This is a quick reference chart depicting typical Noise Floor levels that prevail across the HF spectrum which in turn adversely affects terrestrial HF radio communication.

Firstly, I wish to make it clear that a better antenna does not necessarily mean a higher gain antenna like a Yagi or a Cubical Quad. Even simple wire antennas like the Dipole can be great antennas. Go for balanced antennas like a Dipole, Inverted-V, etc, and avoid unbalanced element antennas like Off-Center Fed Dipoles (OCFD) and especially the absolute worst-case unbalanced antennas like the En-Fed Half-Wave (EFHW). The greater the asymmetry and unbalance, the greater is the RX local QRM noise problem caused by the unduly high Common-Mode Current (CMC) that could flow on the co-axial cable transmission line. The greater the CMC, the greater is the noise susceptibility and consequently the higher the noise floor on the receiver. The higher the receiver noise floor, the lesser number of stations copied by you. This is because a large number of available DX stations will drown below the RX noise floor and you won't even be aware of their presence.

Some might argue that an EFHW antenna is so simple and covers all HF bands. Isn't that great? well, not really! ... What's the point in having all-band capability when you might almost hear nothing on any band due to high noise and low SSN conditions? ... Think about it.

To be able to comfortably hear a radiotelephony signal, the Signal-to-Noise Ratio (SNR) must be at least +6dB. Good DX operators are however often able to comprehend and copy weaker signals with SNR as low as +1dB to +3dB... Whatever be your skill level, the bottom line is that SNR must always be positive by an adequate margin before you can copy it. Let us say, your noise floor is S7 on a particular band, then you would usually be copying stations with S8 or more signal strength. If the RF fading (QSB) is high, then one would perhaps need more than S8 to make it copyable... Now, on the other hand, you have a good, low CMC antenna system, the chances are that your RX noise floor might be S4. Under these circumstances, all additional stations that were present on the band at S5 to S8 level will now light up the band and be heard unlike in the previous instance of the S7 noise floor.

The difference between S7 (poor) and S4 (good) noise floor on your receiver would result in far greater benefit than what you might get by using any high gain antenna or having the DX station running a kilowatt linear. A high gain antenna might give you an additional 3-6 dB gain, or a DX operator's kilowatt amp may provide an additional 10dB at your receiver. Yet, they are no match for the improvement achieved by cutting your noise floor from S7 to S4. This noise floor difference amounts to 3x6 = 18 dB improvement. That too without robbing a bank and also not having to wait for only a kilowatt station to appear on the band but easily copy the majority of operators who work with typical 100W PEP.

To understand the finer aspects of what this means, please read the following articles...

How badly can high Local Ambient QRM affect HF Radio?Local ambient QRM (Noise) from various electrical appliances and other sources in the neighborhood often adversely affect HF radio communication. The negative effects of local QRM on an HF amateur radio station’s overall capabilities are usually far more pronounced than what most operators realize. The ability to address these noise issues may either make or break the radio station’s DX coverage efficacy.

Interpretation of S-Meter Noise Floor in HF Radio ReceiversThe magnitude of noise also varies with frequency. The lower HF radio frequency bands are more adversely affected. The higher frequency bands progressively experience lower noise levels. The 10m HF band is the least noisy, whereas the 160m and 80m bands are the noisiest. Further up, the VHF/UHF bands are subject to the very marginal influence of both QRN and QRM. Let us examine the estimated aggregate noise power density of combined QRN and QRM on various HF radio bands as might be experienced at different types of locations.




Increase antenna height to leverage low-angle radiation and enhance DX
Finally, make efforts to increase the height of your antenna above ground as much as you can. It would be worth the effort. The higher the antenna above ground, the better would be its low-angle radiation capabilities. The enhanced strength of low angle radiation thus achieved will amount to attaining higher gain from the antenna at low angles. This is another very important factor in significantly improving your DX capabilities, especially during low SSN conditions when most of the HF radio signals propagate and arrive at fairly low angles near the horizon. Unlike high SSN conditions when DX signals also arrive from higher angles in the sky, during low SSN, the high angle signal arrivals are almost non-existent.

antenna height and antenna gain

Comparison of radiation takeoff angle for maximum gain for an antenna installed a various different heights above ground level. As a consequence, the elevation section lobe pattern differs offering different long range DX performance.



Speaking of HF antenna height above ground, please beware that if you install the antenna above the roof of a tall concrete building, then the effective height of the antenna may not be work out to be the building height plus the height above the roof. If the roof-top is large enough, the effective antenna height might largely be defined by the height above the roof and not height above the street ground. This is because the large concrete building will have a RCC roof with steel rod mesh laid inside the concrete. This steel mesh acts as a virtual reflector for RF and simulates a virtual ground.

Read the following article for more information on the above cited facts...

Why might Antenna Height matter more than GainThough it may seem to be paradoxical at first sight, the fact is that very often the antenna height above ground might matter more than its published gain when it comes to HF band antennas used for DX operation. Long-range DX contacts on HF bands typically require long skips on optimally selected frequency bands for best results. To achieve this objective, the radiation takeoff angle (TOA) has to be quite low. Especially, under low SSN conditions (as is prevalent at the time of writing this post), when the ionospheric plasma densities are low and the slab thickness is also less, the higher TOA signals might penetrate the ionosphere to be lost in outer space. Low TOA signals from the antenna provide us with the best prospects.

Urban Antenna Height above ground – Facts & MythsThe most prominent and noticeable detrimental effect of urban antenna deployment is the overall deviation of the antenna radiation pattern compared to its theoretical textbook pattern. The antenna manufacturers usually publish technical specifications along with claimed radiation lobe patterns at various heights above ground. The technical design details available to homebrewers too always display the ideal pattern. This leads to general misconceptions about the actual realizable capability of the antenna in a real urban environment.



Low SSN - Why do most Hams find HF Radio so difficult? 1

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