AM station

When I started in amateur radio most people were on AM (amplitude modulation) even on HF.  

In recent years there has been a bit of an AM revival especially on the lower HF bands. At one time AM was very popular as the gear can be simple and it is an effective mode. 

Its main drawback on HF is it is wider than SSB and power is wasted in the carrier. On the plus side RX gear can be extremely simple yet effective. See my Fredbox and Sixbox transceivers.

I saw this AM station on the internet. It made me feel quite nostalgic. 

Sadly, many have never used AM or experienced it.

The disappearance of AM broadcasters

Many AM broadcasters are closing down. 

In 10 years' time the MW and LW broadcast bands may be empty of AM stations. This is a great pity as many of us came into RF via simple MW and LW crystal sets. These are easy to make.

Many AM shortwave broadcasters are also closing down as many now prefer to access these stations via the internet. This is also cheaper.

In 20 years' time I wonder what MF and HF will sound like? I suppose much of this spectrum will be kept by the military "just in case" it is ever needed if the satellites were jammed or destroyed.

It seems the shortwaves will largely be abandoned. In this case, I do hope amateurs (or licence free services) are granted access to a wider array of frequencies. Not that I can see it ever happening, but wouldn't it be great if we were granted access to all of HF at low power on a non-interference basis?

2m Fredbox QSO

This was in 2011 and shows me in QSO with the 10mW 2m AM Fredbox. Many years ago I had a cross channel QSO with it handheld. These days it is hard enough having an FM QSO on 2m!

See https://sites.google.com/view/g3xbm4/home/vhfuhfmicrowaves/homebrew/fredbox. 

The death of AM on the amateur bands

Although there are still a few AM nets on some bands, the mode has mostly been replaced by FM and SSB. This is a pity as in years gone by people "chanced" on amateur radio by listening on short wave.  I well remember hearing amateurs on 160m AM many years ago. I remember copying G4PJ 4 miles away on a crystal set in the 1960s when he was on AM.

These days, people can no longer just chance on amateur radio. Our hobby has changed and the way newcomers "find" the hobby will be different. Modes like FT8 may be fine for working DX, but it is unlikely to be an introductory route for newcomers. As a person with a poor voice, I quite like FT8 and WSPR. At the same time, I am conscious that these modes cannot be ways in to the hobby.

AM had many advantages: gear was simple, ex-PMR radios were practically being given away and signals could be detected by very simple detectors. The simplest was just a diode detector. As I recall weak signals were better on AM than FM.  Of course AM carriers could be a real nuisance. 

Many today have never experienced AM, which is sad.

Even MW/LW broadcast AM is being phased out.

Several of my designs in the past were for simple AM transceivers. See my website at www.g3xbm.co.uk or my free PDF book for details.

VHF AM

When I first came on VHF, most activity was on AM. These days what phone activity exists is SSB or FM with AM quite rare. 

In some ways, this is a pity. AM gear used to be able to be picked up very cheaply and homemade AM gear can be very simple. I have to confess that I am rarely on AM these days, preferring FT8 as my voice is poor. I come on 2m and 70cm SSB for activity contests and once a week on a 2m FM net.

See https://sites.google.com/view/g3xbm4/home/vhfuhfmicrowaves/vhf-am .

Amplitude Modulation (AM)

When I was first active, AM was the main mode on all bands. On HF this was replaced by SSB and, in very recent times, FT8 has become very popular. On the VHF bands most use FM, although there are fewer coming on just for a chat as there are now (free) alternatives on the internet.

Now I am not saying AM is brilliant, but the gear is often simple and low cost. There has been a growing interest in AM on bands like 160m, 80m and 10m. If you have never played with AM, you don't know what you are missing! At one time, ex PMR AM gear was practically being given away.

On 2m, the centre of AM activity is 144.550 MHz.

I get the feeling that most people have a dim view of AM, not least our national society, the RSGB. In my view this is totally wrong. Like other modes, AM has its place. Just listen above 29 MHz when 10m is open.

See https://sites.google.com/view/g3xbm4/home/vhfuhfmicrowaves/vhf-am .

Forgotten!

Since I released my free G3XBM Project Scrapbook, I have already thought of some things that I have left out! 

In the early 1970s, when still living in Cambridge, I made a 2m AM rig based on the Pye PF2AMB. It had a RX that I could tune and, I think, 6 crystal controlled TX frequencies. It was in an aluminium box covered in wood effect Fablon.  In the photo taken in the 1970s (when I had hair) it is the rig with the black and white meter to the right of the EC10 receiver,  I used to have a weekly sked on CW with G5UM in Leicester. Jack used to write the VHF column in RadCom. He was a really nice man.  The rig produced 500mW on AM.  It was also used once in the PW QRP contest, with some amazing results. 

I also made a 100mW AM transmitter with very pre-emphasised speech and heavy clipping. This was extremely punchy and effective.

In the photo, the rig on the bottom right was a 10m 1W CW TX. It was my first experience of HF, with a loft dipole. Later, I made a 10m PA to increase the power. I think this was to 25W. It was far too much for me!

At the time, my 2m antenna was a hand rotated, 2 element, HB9CV in the loft, that I could turn from the operating position.

Sadly, I no longer have schematics for these rigs, but I shall add reference to these in the next edition, by which time I might remember more, HI.

Fredbox 2m QRP

It seems hard to think this tiny rig was designed and built so long ago (1974?). It was rebuilt a few years ago and still works. It must count as one of my favourite all-time rigs. 

I would not recommend trying to exactly copy it, but use it as a source for your own designs. Some years ago, I know one club did a PCB for a version with a loudspeaker amplifier and loudspeaker. I forget who this was.

In its day it had several 100km QSOs handheld and even one of 160km to France handheld even though just 10mW AM. These days, most local QSOs are on FM. In its day, it was a very small rig and much smaller than commercial handhelds.

See https://sites.google.com/view/g3xbm4/home/vhfuhfmicrowaves/homebrew/fredbox .

10m Tenbox

With 10m again becoming a good DX band, it does not seem right talking about a simple cross-town natterer for 10m!  Mind you 10m is often a daylight DX band and there are plenty of times when it is dark when the band is totally unused.

Derivatives of this simple radio might make an ideal 10m cross-town natterer. Just above 29MHz would be an ideal spot with plenty of space and very low chances of causing anyone else problems. This receiver has heard USA AM stations with just a base loaded whip on the car, although I would not recommend it for serious DX work.

In my mind I see a rig a bit like a tiny Heathkit Twoer (remember these?) with a tunable RX and crystal controlled TX. On a suitable PCB it could make a nice club project. Improvements would include an AF amplifier to drive a loudspeaker and maybe a very simple linear to bring the power up to a few watts of RF.

I cannot imagine the rig costing much more than £10-20. Put it another way, how many cups of coffee or beers will that be?

See https://sites.google.com/view/g3xbm4/home/hf-mf-and-lf/homebrew/10m-am-tenbox .

10m AM

 One of the pleasures of the last solar peak was hearing the USA AM signals just above 29MHz. One of the beauties of 10m is its size. With 1.7MHz of bandwidth all modes can be accommodated without issues including FM and AM.

AM operation

It is some while since I was on 2m or 6m AM. 

There has been something of a revival in AM, although AM should not be used on busy bands. There are AM nets on 160m, 80m and 40m. I am looking forward to again hearing 10m AM from the USA just above 29MHz.

See https://sites.google.com/view/g3xbm4/home/vhfuhfmicrowaves/vhf-am .

Amplitude Modulation

Although I have not used AM recently, partly as a result of my poor voice, I can see the attraction of the mode. It lends itself to home brewing and in the past I have designed and made several AM rigs. At one time they were practically giving away ex PMR AM rigs.  

The Fredbox and Sixbox are examples of AM rigs I have designed and made in the past.

Southgate News has announced the formation of an AM Amateur Radio Society.

See http://www.southgatearc.org/news/2021/april/announcing-the-formation-of-the-amplitude-modulation-amateur-radio-society.htm#.YIgZpGjYrrd .

My thanks to Steve G1KQH for pointing this out.

2m AM QRP

10 years ago I had a QSO with my Fredbox transceiver on 2m AM as the photo shows. 

I still have the Fredbox, but sadly there is little AM still on 2m. 

In its day, AM was an effective mode on 2m. These days there is far less chatting. Apart from organised nets on FM and contests there is, sadly, less activity. Many now prefer the "rubber stamp" exchanges with FT8.

Nanowaves

As you will have seen, after a very long break, I took my first tentative steps back into optical communications yesterday. 

Before my stroke, I enjoyed going out in the field to see how far I could cover, especially over the horizon using QRSS (very slow CW) with PC decoders. 

Much greater distances would have been possible, then my health got in the way. 😕 

All the gear was home made. This was one of the attractions: all the gear was simple, including the test gear. 

This is a field of experimentation open to everyone. You may find some ideas on my main website.

See https://sites.google.com/site/g3xbmqrp3/optical

AM activity

This is very late! There are still a few hours left if you want to give HF AM a try.

See https://amqsoparty.wixsite.com/mysite

2m AM QSO - 100 miles - 10mW - halfwave whip

My  XYL was looking in our loft for some pictures and came across my mobile logbook that I had not seen for over 7 years. I have never managed to get in our loft since my 2013 stroke. 

In the logbook is my Fredbox QSO across the Channel with 10mW and a halfwave whip on 2m AM in 1976. This was one of my all-time best ever QSOs. See logbook page photo below.

Years later the Fredbox was revived and used for some local QSOs again.

See https://sites.google.com/site/g3xbmqrp3/vuhf/fredbox .

AM operation

These days many on the air have never used AM (amplitude modulation). Many prefer FM or SSB for chats.

Certainly, I get the impression that our national society, the RSGB, is anti-AM. They have continued not to put 144.55 as the AM frequency of choice in 2m bandplans. They continue to have the fatuous remark about AM users being mindful of bandwidth, when well set-up AM often occupies less bandwidth than FM. I also found out that one RSGB official had no idea there was a preferred slot for AM on 10m! I get the impression that they haven't a clue!

AM has its place on less busy bands. It also lends itself to easy homebrewing. To me, it seems a shame that AM is hidden away. It is not the best mode for many reasons, but well modulated AM on 10m is a real joy to hear.

See https://sites.google.com/site/g3xbmqrp3/vuhf/2am

2m AM

These days there is very little AM on 2m whereas at one time it was the only mode! The RSGB seems to have an aversion to AM and the 2m AM centre of activity (144.55MHz) appears as a begrudging footnote in the band plans every year. They bang on about worries over adjacent channels when AM transmissions usually occupy less spectrum than FM!!

AM can be quite effective on weaker signals than FM. Often AM gear (ex-PMR) can be found very cheaply. AM has a place and many newcomers are often totally unaware of this mode.

See https://sites.google.com/site/g3xbmqrp3/vuhf/2am

AM QSO party - Jan 2020

Southgate News reports on an upcoming AM activity contest towards the end of January. On some bands there is plenty of space for AM. This concentrates on HF AM.  There is little doubt that SSB is a better DX mode and takes up less bandwidth, but there is still a place for AM.

See http://www.southgatearc.org/news/2019/december/january-2020-am-qso-party-in-europe.htm#.Xe6ju-iTLnE

2m AM

When I first came on to 2m, AM was the main mode. During the 1970s, FM gradually took over. Also, the Liner-2 got people on the band with SSB. I would say the late 1970s and early 1980s was a golden age on 2m, with G8s gaining access and plenty of activity. Quite a few people used the Liner-2 and a 9 el Tonna antenna.

Although the use of AM on 2m is way down on those early dates, it can still be found. 144.550MHz seems to be the centre of activity. AM is often better than FM and narrower bandwidtth, although the RSGB "experts" seem not to know this!

Often, second hand ex-PMR AM rigs can be obtained very cheaply.

See https://sites.google.com/site/g3xbmqrp3/vuhf/2am