Amateur radio antennas, circuits, techniques and related topics. By Peter Parker VK3YE/AK3YE.
Newer material appears at https://vk3ye.com and https://youtube.com/vk3ye .
A quick video demonstrating the capabilities of the JS8Call digital mode in a contact with VK6LMK. It's like FT8 but is conversational, allowing free text contacts. In this video I start off with 5w, then go down to 16mW, to see how it works over a 2500km path on 3.5 MHz.
On the weekend I visited Melbourne's Telstra Museum as part of Open House. It has working displays of phone and exchanges. I think you'll enjoy the video.
Yesterday we looked at double sideband suppressed carrier on HF. Today it's AM's turn. AM is the original voice mode amateurs used. We still use it, though not to the extent that we did before SSB arrived in the 1950s on HF and FM on VHF in the 1960s.
It's not a very efficient mode for QRP. And phase distortion on HF can bend signals around so they lose readability. But if you are running reasonable power and if conditions are stable then AM can have a warm sound.
AM contains a carrier plus the two sidebands. The carrier acts as a blanket that smothers band noise (if the signal is strong enough). That differs from SSB where you might still hear band noise in between voice peaks.
AM isn't much of a DX mode. But it can be good for local and semi-local contacts on bands like 160, 80, 40, 10, 6 & 2 metres. Most modern transceivers still transmit it so give it a go when you're hearing good signals from your contacts. Here are some of my AM transmitting videos.
40m AM
160m AM
160m AM with a kite antenna
Local 160m AM activity around Melbourne
Have you had an AM contact? How did you find it? Please share your thoughts below.
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How many of you have operated double sideband (suppressed carrier) on HF?
Not many, I'm guessing.
DSB had a brief 'golden age' around 1960 when SSB was taking off. Like SSB it had no carrier and you could tune it in on an SSB receiver. But it was easier to generate, with no crystal filter or phase shift networks required.
It's had a second renaissance amongst builders, particularly those using direct conversion gear. A DSB transmitter is basically the reverse of a direct conversion receiver and you can use many of the same parts if you wanted to build a transceiver.
While a DSB signal is difficult to hear on a homebrew direct conversion receiver, the chances are that you'll be talking to people on commercial SSB gear. In may cases they won't know you are even transmitting two sidebands unless you point it out.
Here are some videos of DSB gear.
Beach 40 40m DSB rig. Very simple. This is the first of several videos.
Using the OzQRP DSB rig from the beach
DSB isn't just for voice. Here I'm transmitting 30m WSPR DSB.
Have you tried DSB? What have been your experiences? Please leave your comments below.
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QRP and contests aren't necessarily things you think would go together. All the bedlam. And all the high power stations. You might think that as a QRPer you wouldn't stand a chance.
But look at it this way. Let's say that only 10% of the calls you make, when replying to stations, are successful. Either the other guy comes back to someone stronger or they fail to hear you at all.
During normal band conditions during a usual operating session you might only call ten stations and make one contact.
Whereas during a contest everything is packed in. You might have the chance to call 100 stations in the same amount of time. If 10% hear you then that's ten contacts in the bag. It's a numbers game. There's many more opportunities to call and therefore to get contacts than during a non-contest time.
Ah, but there's competition from other, stronger stations. Yes, true. But contest contacts are very short. Once they're done you get another chance to call a minute later. The motivation to get points is very strong - some people are willing to struggle with a weak QRP station to get a signal report and contest exchange even though they wouldn't hold a ragchew as it's just too hard.
The types of people on during contests are often top operators with good stations. Possibly in the country with a low noise floor. Which means they're more likely to hear you than someone in the 'burbs with a low dipole. Even if someone stronger does call you may be audible underneath in which case the calling station might take another listen.
To summarise, QRP can work in contests. You might not get a top score but you can still do quite well. And smaller sprints or locally-based contests can be excellent also. Here's a few videos demonstrating how QRP can work during contests.
The Commonwealth Contest - a DX oriented contest
A short local 80m contest
Another short contest
A 2019 Field Day contest
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Amateur radio has so many specialty interests. There's even specialties within specialties. Some of the topics are more obscure than the subforums you see on amateur radio discussion groups you see on eHam, QRZ or Facebook.
Where do you find them? At one time many special interests gathered on Yahoo Groups, with their own little email groups. You can either receive messages as emails or read them as threads online. And there was a files section where you could post reference articles and pictures.
Sometimes Yahoo Groups has been unreliable. That caused many to switch over to groups.io . There's a huge number of groups on various aspects of amateur radio. Here's one search. Try other specialities or locations for groups that match your interests. Some groups allow you to read their messages as a visitor while others need you to sign up (it's free).
What interesting groups have you found? Please leave your finds in the comments section below.
PS: Thinking of buying a shortwave receiver? Browse these links. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.
PS: Enjoy these well-reviewed books on various amateur radio topics. They're available for under $US 5 each in electronic form. Or you can get them in paperback. Visit VK3YE Radio Books to find out more.
When you ask people the first project that got them interested in radio was, 'crystal set' is often mentioned. For a younger generation it was probably 'FM bug'. Yes, wireless microphones were (and are) great for both learning and pranks. Their sensitivity can be surprising as can their transmitting range. There's amateur radio uses as well. For example you could use one as a short range link to allow you to monitor shack equipment from the house.
If you want to relive the bug-building experience, here's a few links to try.
One of the items picked up at the recent hamfest (see yesterday's post) was a UHF frequency counter. It worked but was off frequency. Adjusting the trimmer capacitor helped but not enough. Here's how I got it on frequency.
"Hamfests aren't as good as they used to be". That's a common lament. Is it true? Or is it because hams tend to accumulate junk with age and there's less and less they really need.
Anyway here's some finds at a local hamfest held on Saturday. I also test some of them. I think this has been one of my best hamfest hauls.
PS: What have been your best hamfest finds? Please share them in the comments below.
Many beginner amateurs start off with a VHF/UHF handheld FM transceiver (or more recently) one also featuring digital voice modes. Experiences with this shape their view of what VHF/UHF frequencies can do. That is a reliance on repeaters and local communications unless an internet link is involved. Later on they may get on the HF bands to work longer distances. Others may have started on HF, remained with this as their first interest and only got VHF for local FM contacts. People in both groups have missed out VHF/UHF SSB and the experience of their attributes.
These videos have been collated to indicate what is possible on 6m, 2m and (to a lesser extent) 70cm SSB. All involve contacts with low power and basic antennas. Yet the distances achieved often exceed that normally achieved on FM, even with repeaters.
Why is this so? The first thing is that per watt SSB is more efficient than FM. This is because of SSB's narrower bandwidth and the characteristics of FM which make it great when signals are strong but less readable when signals are weak.
Secondly (on average) SSB operators have better stations, antennas and equipment than average FM operators. It's not true in all cases but many FM operators only need to access repeaters and talk locally on simplex. A small improvement to antenna gain will often go unnoticed. Whereas SSB operators who work direct to each other, often over extended distances, will notice even small increases in gain. The combination of a taller mast and substituting a small beam for a vertical will increas your singnal by 10dB on a band like 2 metres. Another 10dB gain is possible by increasing power from (say) 30 to 300 watts. That's good but if you combine that with a distant station who likewise improves their antenna and output power by similar amounts then there's a massive improvement in signals between the two stations.
And I haven't even factored in other upgrades such as lower loss feedline, masthead preamplifiers, portable locations or modes even more efficient than SSB such as CW and the increasing family of digital modes used on VHF/UHF.
Facets of VHF/UHF SSB vary and can include DXing, contesting, local nets, satellite communication, experimentation, antenna work, aircraft enhancement, EME (moonbounce) and more. Activity is not always immediately apparent but if you listen and tune around long enough as well as familiarises yourself with local patterns you will find it.
Video demonstrations
These videos show what's possible with VHF and UHF SSB with low power and modest antennas. In all cases I'm running 5 watts or less. Antennas used have included small loops on 6m and, on 2m and 70cm, dipoles or small beams. In no case am I transmitting from great heights. Some contacts have been made pedestrian mobile. Typical ranges for this are 30 to 100km, with over 2000km occasionally possible on 6 metres during sporadic E openings.
6 metres pedestrian mobile
VHF/UHF Field Days (mostly 2m SSB)
2m SSB portable results in response to an alert that the band was open
Pedestrian mobile 2m and 70cm SSB
Equipment and antennas
I've used a Yaesu FT-817 as this suits my style of portable work. Larger 'All-in-one' HF/VHF/UHF transceivers typically include at least 6 and 2m SSB. Antennas vary greatly in size but even a small beam is enough to get you started.
Operating
Operating is quite different to both HF and VHF/UHF FM/repeaters.
If you were to turn on at a random time, the chances are that you will hear no one at all. In many areas there is activity but it's harder to find than on HF. It may be heavily based on nets and regular operating periods during the week. For example here in VK3 we have a 70cm SSB net on Monday evenings (7:30pm 432.310 MHz), a vertically polarised 2m SSB net on Tuesday evenings (7:30pm 144.310 MHz), a Wednesday evening 2m SSB horizontally polarised net (8:30pm 144.150 MHz), a Thursday evening 6m SSB net in Bendigo (9:00pm 52.250 MHz) and aircraft-enhancement activity on weekend mornings. That doesn't include other spontaneous activity. So you're pretty much guaranteed activity on most days if you're around at the right time.
To improve your chances, familiarise yourself with beacons, calling frequencies, local field days and nets including looking up club newsletters, joining social media groups and searching the web. And not to mention old-fashioned tuning around and asking people you work.
What have been your experiences with VHF/UHF SSB? Please leave your comments below.
PS: Enjoy these well-reviewed books on various amateur radio topics. They're available for under $US 5 each in electronic form. Or you can get them in paperback. Visit VK3YE Radio Books to find out more.
Regenerative receivers infuriate some but fascinate me. Badly built ones can squeal and drift but a well built set, picking up signals from around the world with just one or two transistors, is a thing of beauty.
If you are not familiar with a regenerative receiver they use positive feedback (regeneration) that increases a circuit's gain. This also increases its selectivity to allow it to better pick signals out. And when the detector is lightly oscillating it produces a beat signal useful for receiving CW and SSB signals.
Here are some regens I have tried.
Listening with an HF regenerative receiver
An older HF regenerative receiver (but still solid state)
OK this is a pretty arcane topic that might not interest that many.
And I had forgotten about this video until reminded by a comment in a Soldersmoke blog.
But I'm quite proud of it. Especially the analogue transparent plastic graphics and sound.
Watch it if you like to know a bit more about direct conversion CW transceivers and the receive/transmit frequency shifts they need to function properly.
PS: Enjoy these well-reviewed books on various amateur radio topics. They're available for under $US 5 each in electronic form. Or you can get them in paperback. Visit VK3YE Radio Books to find out more.
I've owned a variety of receivers over the years. Good and bad. Here's a few words about them and accompanying videos. Most aren't current models so you'll need to look on the secondhand market to find them. Note that some of the early videos are a bit blurry but they get better later on.
Astor radiogram
The one that started it all for me. Had three shortwave bands - 19, 25 and 31 metres - so I could only hear broadcast stations (and WWV). But its bandspread was good so tuning was easy.
National Panasonic GX3
The standard 1970s receiver with AM, FM and a shortwave band or two. Terrible frequency readout and tuning resolution and they can drift a bit. But work with SSB with a BFO at signal frequency.
Optimus Extended Range receiver
Basically Radio Shack/Tandy answer to GE's Super Radio - but apparently not as good. Good for broadcast band reception.
Sony SRF-59
A tiny receiver but a very special design. Incredibly good AM broadcast band performance. Prized by lightweight DXers.
Digitech AR1748
This is the big chunky receiver you see me using in the first photo. Quite good for AM and FM but not having a BFO limits its use on shortwave.
Digitech AR1780
This is my current 'go to' general coverage portable receiver. I like it. It has a wide tuning range (more than stated in the instructions) and is quite sensitive, selective and stable. Its only annoyances are its memories are difficult to use and it seems to draw a bit of current from the batteries when switched off.
PS: Interested in buying a new receiver? Browse these links. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.
PS: Enjoy these well-reviewed books on various amateur radio topics. They're available for under $US 5 each in electronic form. Or you can get them in paperback. Visit VK3YE Radio Books to find out more.
The very popular FT8 mode has its place for 'rubber stamp' exchanges but isn't a chat mode.
News crept out of a more conversational version called FT8Call where you could enter free text.
That morphed into JS8Call.
It was under development for a while.
Now you can download the release version and start chatting keyboard to keyboard under weak signal conditions.
What's JS8Call like? Watch this video, of my first JS8Call contact, and find out!
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Probably the cheapest multiband HF SSB amateur transceiver you can get is the uBitx, designed by Ashhar Farhan VU2ESE. It's a kit but with the main board assembled. You just need to find a box and solder up the connections to the external power, speaker, antenna, microphone, and key sockets. And make a few other adjustments (which can be a bit tricky).
It's not perfect. Operating isn't as smooth as say a Yaesu FT817 or 818. But the kit has been refined over time. This portable session is a taste of what it's like on-air.
A lot has been written online about the uBitx. I've done a few videos myself. I've put together a few of the best resources about it on my website here.
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