getting started on AM

[w9avn]

Greetings:

I want to get started on AM but having trouble.
I use an FT 990 and a coax fed Butternut 9 band vertical antenna.
When I switch to AM from SSB all I get is heavily muffled transmissions, no matter
which band I use, time of day/night.  I tune to the AM frequencies and all filters are turned off.
What am I doing wrong?  Any help is appreciated.
Thanks,

Jim, W9AVN

[WQ9E]

Jim,

Your FT-990 should be fine for AM reception.  Make sure that the 2.4 filter LED is off when you select AM, otherwise push the button to extinguish the LED and this sets the AM bandwidth to 6 Khz.  Try tuning to a local broadcast station to get some experience tuning AM since this is easier given they transmit continuously.  The 2.4 Khz. filter can be used when interference is severe but the audio will be muffled.  In general the digital filter should be turned off for AM operation.

For transmit it appears there is an alignment preset for the carrier level so all you have to do is set the RF power to max (it is limited to 25 watts by the rig) and adjust the mic gain control for proper audio level.  Some of the other Yaesu rigs (i.e. the FT-1000 and FT-1000MP) have misleading instructions for setting up for AM which leads to distortion.  On these rigs the RF power should be set to max and the carrier level is set by the drive control.  Following Yaesu's instructions for these rigs results in severe distortion on AM and key clicks on CW but it appears they have the AM setup correct on the FT-990.

[KA0HCP]

W9AVN: Welcome aboard, Jim.  Bill

[steve_qix]

Welcome to AM!

Your rig will work well on AM.  Follow the instructions given by WQ9E.

Antenna-wise, a vertical is a poor choice for 75 meters or 160 meters.  Even on 40, it may be a poor performer.

For 75 meters (and 160) a dipole is definitely the best choice.  If you want to go simple, use a coax fed (fed at the center) dipole cut for the band (around 122 feet in length), and get it as absolutely high as you can get it off the ground (I wouldn't go higher than 90 feet, however for most 75 meter work) and as far from power lines and other similar RF obstructions as possible.  Don't bother with a balun.  Most stink.  If you're worried about feedline radiation, run the feedline through a bunch of type 43 cores, right at the center of the antenna.  This will decouple the line from the antenna.

Multiband with coax?  Connect multiple dipoles to the same feedline.  If you only have 2 dipoles, try to run them at 90 degree angles to each other if possible.

More elaborate systems involve open wire line and an antenna tuner.  If you go this route, stay away from low end tuners.  They consume power and burn out!

Again, welcome to AM!

Regards,  Steve

[kc4umo]

Welcome Jim.
For AM you came to the right place.
Not only are these good folks here but they are pretty darn smart and know their stuff.
Listen to what they tell you.

[w9avn]

OK, thanks for your input,I'll try your recommendations and let you know how
I make out.

Jim, W9AVN

[WQ9E]

Jim,

The Midwest Classic radio net gets started with a pre-net at 6:45 local time Saturday mornings on 3.885 and the net proper gets started at 7:30.  There are quite a few Chicagoland stations that check-in so if you need some help getting things sorted out that is a good place to find some local AM types.  And if you make it down to the Peoria hamfest later in September there are a number of us active on AM who will be there.

[K9PNP]

To add to what Steve said about antennas:  If you only have 1 support point with any height, make the dipole an inverted V.  That is my situation and it will normally do you a good job.  Use what assets you have.

Welcome to AM!!