5 Nov 2012

December's Practical Wireless

The December 2012 edition of "Practical Wireless" has my article about the 2m AM Fredbox and the 6m AM Sixbox transceivers that are described in more detail on my website. These simple QRP VHF transceivers proved to me that you don't need to spend lots of money to make simple transceivers that work. Both have produce interesting QSOs: the 2m Fredbox had several 90km QSOs with one at 160km, despite being only 10mW output and using just a whip antenna!

Today there is not that much AM activity on the bands but I think this is a great pity as the mode has a lot to offer. I do hope the RSGB can be (eventually) persuaded to add 144.55MHz as the AM calling/working frequency in the band plan. It is mentioned (almost lost) in the foot notes, but it needs to be properly shown. For some reason the RSGB seems to have a problem with 2m AM.

I hope others will build simple AM gear for 144.55MHz or crystal up some ex-commercial PMR radios and again enjoy the fun of 2m AM. Second hand AM gear for 4m and 2m can often be obtained for just a few pounds as no-one wants it.


David Cope said...


The RSGB has a problem with AM. Period. Most hams have a problem with AM. Period. AM has no central focused "marketing" within the ham community to counter the F.O.D against AM. AM needs to be curated as a heritage mode (IMHO) and it deserves it's own part of the spectrum - anywhere except the current ham bands so it can operate with out constant "monkey chatter" from SSB in it's full glory. Short - it needs a protected WARC type band.

David, G8JGO

Roger G3XBM said...

Several VHF bands have PLENTY of space for a few AM channels and their users. At 5-6kHz per user it is not a bad mode in terms of spectral efficiency compared with FM. Even on 10m, apart from around sunspot maximum the band occupancy is such that AM is a mode to be embraced and used. it's fun!

David Cope said...

VHF yes. HF no (apart from 10M and even then in a large contest SSB'ers think nothing of operating in the AM window). In the states they have a bit more spectrum (e.g. 75m) where 3880knz and 3885knhz tends to be quite free of SSB interference (or at least when I listened).

I would still argue that a small number of spot frequencies across the shortwave spectrum (outside of ham bands) allocated only for AM would be an incentive to keep the mode vibrant and alive and free from other amateur QRM. Given that each band has (usually) a common watering hole for AM (when it's clear of SSB) and that most AM tends to favour a co-operative round table discussion format then such a change would not be to much of a challenge. Still, it's all academic anyway - there is as much chance of pigs flying as there is of getting reliably clear (HF) AM frequencies.

I tried operating 144.55MHz AM (Burndept ex-PMR) - putting out CQ on a regular basis for a month and had no takers (as well as extensive monitoring - no AM heard only an FM net). Used to enjoy a local net on 145.375MHz, but alas I've moved QTH out of range of that - but I'm not to far from you now Roger! (IO91XX) so when I can get an antenna up maybe re-equip for 2M AM :-) (I have 4m AM currently - and actually heard some activity using an indoor aerial - too weak to make out callsigns)

Anyway - well done on getting your Fredbox published - hope it spurs someone on - I should go and get the magazine that person could be me! :-)

73. G8JGO.

Tiégui said...

Hello Roger,
look at the duct mode propagation for tomorrow : http://www.dxinfocentre.com/tropo_eur.html#hour42

Should we try a QRP QSO in SSB. Running here 2W on a magnetic loop antenna. Like in this QSO with OK1DOL :

73 from Thierry, F4EOB.

Roger G3XBM said...

Thierry, no 2m antennas up at the moment, sorry. Roger G3XBM

Roger G3XBM said...

Well just a vertical V2000.

Tiégui said...

Anyway, the propagation wasn't good today. Maybe for the next time.

73, from Thierry.