Is there any current usage?
The only references I can find are the mentioned mobile use in Edinburgh, and a 10mW handheld that someone has built in Cambridge.
This suggests that current usage is V-pol, however, I would imagine that if we got any 2m AM SOTA going, that would generate more activity than what currently exists. So maybe we could select the polarisation to suit ourselves.
I am thinking of having a go with horizontal polarisation.
Tom M1EYP
In reply to M1EYP:
I have to say that whilst I appreciate the simplicity of the circuits to generate and demodulate AM, the engineer in me despises the inefficiency of the mode. It really is uber-naff.
The only sanctioned AM I’d support is if people are taking homebrewed valve rigs up the hills with them. Simple 160/80m rigs with a high-level modulated 807 PA, big heavy modulation transformers, vibrator power supplies and carbon mikes. For VHF either 829b or QQV 6-10/3-20/6-40 PAs are de rigeur. I mean who in there right mind would use solid state AM gear? It’s pants with a capital P!
Andy
MM0FMF
But who is in their right mind?
Not me, and your post only motivates me to progress the idea further Andy!
Tom M1EYP
In reply to MM0FMF:
Sorry Andy, can’t oblige - I sold my EL34’s and mod tranny a long time ago! I still have a 6/40A pa, but feel that the car battery required to power the kit just might be a limiting factor on most summits.
73, Gerald
In reply to MM0FMF:
By crikey, you tempt me, Andy…I’ve still got a 5763, would that count for a QRP rig?
Operated in plus fours, gaiters and ventile or tweed jacket with the antenna fixed on a shoulder-high alpenstock and the acivation recorded on a plate camera - wa-hey, back to the dark ages!
73
Brian g8add
In reply to G8ADD:
My plan to generate ideas and stimulate conversation to use am on sota; loosely disguised as frequency help needed on fm worked. It’s nice the way these things bounce around.
Frrequency! Freudian slip. Must be the cold.
mike g0hio
In reply to G0HIO:
Hi
144.550 has been suggested as a centre of activity for AM
http://homepage.ntlworld.com/lapthorn/vhfam.htm
and the Edinburgh group are mentioned here
http://www.rsgb.org/spectrumforum/pdfs/minutes/june07/AMSAT_UK_Spectrum_Forum_Report_2007.pdf
and from the new band plan
Note 8: The use of Amplitude Modulation (AM) is acceptable within the All Modes segment. AM usage may often be found on 144.550MHz although this frequency is not officially recognised within the 2M band plan. AM users are asked to consider adjacent channel activity when selecting operating frequencies.
Carolyn (G6WRW)
In reply to G6WRW:Hi All another place to try is 3.615 AM see link.Am can be used in the all modes section on any band but giving consideration to users on adjacent channels.To select AM on the ICOM IC706 from FM hold in the mode selector button for a couple of seconds.I think the FT817 is similar
http://www.gw2abj.co.uk/page10.htm ATB Geoff G6MZX
In reply to MM0FMF:
some settings adjustments are required to use the FT-817 on AM
It seems the stock AM settings sound horrible, you need to tweek the
AM_CAR and AM_MIC settings to get an improvement.
For those interested, it appears that the power should be limited to around 1 to 1.5 watts output using the carrier setting and then mic gain adjusted to provide best audio on test to suit individual voice characteristics. Allow some lee-way as I have been told that it is easy to over-modulate, especially if it is a case of shouting into the mic to overcome wind noise, etc.
73, Gerald
Postscript 30.01.09 14:00
I have just tried to adjust my FT-817ND (Nov 2007). The manual states that the power is preset at the factory at 1.5W, so there is nothing to adjust in respect of power on this version. The mic gain is preset at 50 - I read somewhere it is better set to 40 so I am initially trying it at that setting, though even 60 did not seem to over-modulate. The quality is not brilliant, but I was listening on a sideband receiver as I don’t have a dedicated AM mode receiver - sign of the times…