2m reciprocity and other assumptions

Foundations of Amateur Radio

Over the past nine and a half years I've been hosting a weekly radio net for new and returning amateurs. Called F-troop, it runs every Saturday morning at 0:00 UTC for an hour. Feel free to join in. The website is at http://ftroop.vk6flab.com.

In making the better part of six thousand contacts during that time I've learnt a few things about how nets work and how there are built-in assumptions about how a contact is made. There are several things that seem universally accepted that are not actually supported by the evidence and repeating them to new amateurs is unhelpful.

For example, there is an assumption that on 2m there is signal reciprocity. By that I mean, what you hear is what the other party hears. On HF, contrary to popular belief, this is also not universally true due to massive power and antenna differences and signal reports on FT8 bear that out - for example, my signal is often reported at least 9 dB weaker than the other station.

The reason that on 2m this isn't the case is because in general there is at least one other transmitter involved, the repeater. If you're joining in via a remote network, either via RF or via the Internet, there are even more times when this isn't true, but let's stay with the simple scenario of a single repeater and two stations.

If I'm using a base-station with a fixed antenna, my connection to the repeater is rock-solid. If you are using a hand-held and you're on the move, your connection to the repeater is anyone's guess. It could be great, it could be poor or even non-existent.

Not only that, the repeater is often using higher power, sometimes much higher. On average the repeaters near me are using 30 Watts, the highest uses four times that, the lowest uses 10 Watts. In contrast, a handheld uses at most 5 Watts, but more likely than not, half that.

Receiving a strong signal on a hand-held is simple, transmitting a weak signal to a repeater is not.

The point is, you might be hearing me as-if I'm sitting next to you, but I might be hearing you on the other end of a really scratchy and poor, intermittent and interrupted link.

If you add other repeaters and links with differing volume or gain settings to the mix, you get the idea that a 2m conversation may in many ways act like a HF contact.

That implies that there are plenty of times when you should use phonetics to spell your callsign and anything else of interest, despite the often repeated assertion that you don't use phonetics on 2m.

Another assumption is that 2m is less formal than HF. The people you talk to on 2m are likely to be local, perhaps people you've met at a HAMfest, face-to-face. You recognise their voice, you know their situation, their station and their habits.

On HF however, you have contact with people across the globe, most of whom you've never met, will never meet, have no idea about, let alone have a relationship with. That's not to say that you cannot have a friend on HF, I have plenty of people whom I speak with on HF, often during a contest, whom I've never met, but whom I speak with regularly on air. I can similarly recognise their voice, their callsign and know what to expect.

The point is that the more you look at the differences between 2m and HF, the more you realise that they are the same. Interestingly, as an aside, a contact on 10m or 15m can on plenty of occasions sound like a strong local FM contact.

My advice is to not think of 2m as a "special" band, but to think of it as an amateur band with a set of conditions. By law you are required to announce your callsign every ten minutes and at the beginning and the end of each contact. Note that this doesn't mean at the beginning and end of each over. In case that doesn't make sense to you, a contact is the whole conversation from start to end. Each time a station transmits during that contact is an over.

You should vary how you identify yourself, using phonetics or not, at the minimum required interval, or on every over, depending on the circumstances, not depending on the band.

Look forward to making contact with you on what ever band. You can get in touch via email, cq@vk6flab.com is my address and if you're into Morse, this podcast is also available as a Morse-code audio file.

I'm Onno VK6FLAB