The significance of digital modes...


G3SPL
 

It strikes me that modern digital modes are truly transformative in ham radio and probably more so than most technical developments since I was first licensed in 1963.
 
The biggest factor is the use of continuous waves - constant power level with miniscule frequency shifts to modulate the messages to be signaled. For most of my amateur radio career, I have been plagued by interference problems - to TVs and hi-fi equipment of neighbours and indeed my own family's gear.  I have never been able to live in a country estate, set far from other homes and with room for an extensive antenna farm.  Hence, my operations have been limited by the fear of, or actually causing, interference to neighbours' TVs and in more recent times, to computer and all the other electronics that are around in people's homes now.
  
Most of the transmission modes I have used over the years involved variation in RF power level, e.g. AM (in the 1960s), SSB, CW (morse code) and even PSK31.  One mode I used which had a constant envelope power was RTTY.  However, to make contacts on that mode required a significant power level which itself could easily cause interference problems. Similarly, FM transmission on VHF, although better than AM because it is constant envelope, could cause interference to TV, like "patterning" on the picture.
 
Modes such as FT8 allow the use of low powers due to the capability of decoding messages down in the noise with error correction to cope with HF propagation variations. This is taken to another level with the WSPR mode where very slow data rates allow world wide signalling with a watt or less of transmitter power.
 
The JS8 mode (using app JS8Call) is particularly useful. It allows "proper" QSOs with other hams, at a rate similar to morse code signaling - and similar to RTTY and PSK31, given that those modes often require repetitions to get over propagation problems, like QSB and QRN. It allows free text conversations, which I enjoy more than the "computer to computer" interactions of modes such as FT8.
 
A big plus point for these new digital modes is that transmitters can be made simpler - as evidenced by the QDX, for example. The difficulty of providing a linear RF amplifier for modes like SSB (and PSK31) is absent. This makes for simpler and more efficient RF power stages.  
The fact that you can realistically make contacts with, say, the 5W output of a QDX is another big plus in my book. Recently in the UK, amateur radio operation has been curtailed by the requirement to keep exposure of people to RF fields within strict limits.  This does not apply for transmit powers below 10W so I choose to keep to that limit to avoid having to jump through the hoops to prove that my transmissions will not lead to "harmful" levels of RF in the area.
 
As an aside, I find this concern for limiting exposure to RF somewhat amusing. I spent much of my 40 year career in broadcast transmission on HF sites with multiple 250kW transmitters feeding into antennas with up to 16dB of gain. I have had probably thousands of hours in very high RF fields, and come to no harm.
 
Anyway, I am thrilled to be able to finally "do" amateur radio without the worry of causing interference to my neighbours. Viva digital!
 
--
Peter Lee
G3SPL


Mark KB0US
 

In general, the digital modes have significantly reduced the cost per contact particularly for DX contacts.
 
An hour of FT8 operating a day will yield about 5,000 contacts per year with a QDX and wire antenna. Boost the power to 40 watts and you're competitive with every other station in working DX.
 
This low cost per contact greatly reduces the barrier to entry particularly for youth. 
 
Once you've "gotten your money's woth," it's much easier justifying upgrading equipment and antennas.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


Ed G8BQR
 

The "calling frequency" is also the working frequency in many modes - the whole "band" in one audio bandwidth.
No more "tuning High to Low" for signals, and listening to bacon frying, whilst wondering if there really is any enhanced propagation.
Incidentally, the main reasons I re-activated my call, plus the possibility of using HF - the QDX is an added, very welcome, bonus :-)  Regards  Ed  G8BQR


 

On Wed, Nov 30, 2022 at 02:52 PM, Ed G8BQR wrote:
and listening to bacon frying,
Ah, more like the *smell* of Top Band ;-)
 
--
- 73 de Andy -