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Author Topic: working on AM  (Read 1337 times)

Posts: 112

« on: January 30, 2010, 12:46:05 AM »

Being fairly new to HF, I've only worked phone on SSB.

I'm wanting to learn more about AM.  I still hear a few guys running AM on 75M.

What are the basics as far as band spacing so as to not interfere?

What's the normal frequency range on the bands for tx'ing on AM?

Do's and Do Not's?

I apologize, but, I just can't seem to find much about running AM on HF.

Posts: 5030

« Reply #1 on: January 30, 2010, 06:28:17 AM »

There was an article on AM ops in this months QST.

The general concensus is that you need a vintage boatanchor, like something from the 1950's, to crack the AM crowd. The QST article says to try it regardless. There are several frequencies for AM, that I was not aware of in the other bands, like 10M.

The bottom line is, I have a Yaesu FT-950 that puts out 25w on AM. Most of the boatanchors put out 100-200w of tube modulated power. I have never used my FT-950 on AM, but my guess is that it would not sound very good. I have no idea of what the modulation is set for. I did try an Icom 746 on AM on 10M once, just to try. The ham on the other end said it didn't sound very good.

Maybe from other here can shine more light. I also am nervous about running modern gear on AM, as I do not know how heavy it will tax the finals in a modern rig.

Posts: 4

« Reply #2 on: January 30, 2010, 01:38:04 PM »

Brian, a lot of the newer radios sound pretty good if set up correctly.  Here is a link to a great web group that is all about AM.

AMfone has helped me a lot, just reading the other information posted there I am learning a lot from these guys.  If you can't find the information you are looking for, just ask.  They have a section devoted to, "Modern Rigs" that I found useful.  If the radio has AM you most likely can get on AM without too much trouble.  The biggest problem I have found is not having enough power at times.  Anyway, check out the link.  Good luck.

Al, n7ioh

Posts: 493


« Reply #3 on: January 30, 2010, 01:59:56 PM »

My current AM rig is a Flex 5000 which is about as far away as you can get from a boatanchor. As indicated in the previous post, most of the current rigs on the market sound good on the air in the AM mode and only require you to press a button or turn a switch to the mode. I've worked several hams running FT-950's barefoot on 75 and 40 meter AM and they sound great. You'll find AM operation on many of the amateur bands including 160, 80, 40, 20, 15, 10, 6, and even 2 meters. Join the fun.

Pete, wa2cwa

Posts: 21764

« Reply #4 on: January 30, 2010, 06:15:08 PM »

In my experience, there's way more action on 75m and 160m AM than any other bands.

If the sunspots return in full force and we get good propagation on 10m, then there's quite a bit of AM activity on 10m as well, usually around 29.0 to 29.3 MHz.

Not much on other bands, although I do stumble across the occasional AM contact on 40m and 20m.  

But on 75m, the AM activity is mostly in the 3860-3890 kHz range, at least around here.  We have the AMI nets which center around 3870, weekly, with a lot of check-ins.

On 160m it almost seems "anything goes" and I hear AM activity almost anywhere above 1850 kHz and quite a lot above 1900.

Modern DSP rigs mostly sound terrific on AM if adjusted properly, and often sound a LOT better than "boat anchors" do.  DSP goes a long way to relieve the technical problems encountered with boat anchors.

But boat anchors will keep your shack warm at night and have that nice "glow" to them, so they're not going away any time soon!

Posts: 1042

« Reply #5 on: January 30, 2010, 10:04:56 PM »

Last summer I was working a guy using SSB, he was using AM - I switched my FT-897 to AM and was surprised at how well it worked without any adjustement - at least he heard me.

I'm thinking that while a BA would be a nice thing to have, it's not a MUST to do AM, unless you really need to have the big signal.

I suppose it's inconsiderate on a crowded band, but when there's room, AM does have a nice sound to it.

Posts: 1071

« Reply #6 on: January 31, 2010, 06:38:26 AM »

"What are the basics as far as band spacing so as to not interfere?"

I've occasionally worked AM on 80m using my Elecraft K3 and Acom 1000 linear. The K3 does proper double sideband AM and sounds good. Some HF transceivers offer AM as an afterthought and may not work well on that mode.

You don't say if you have a HF transceiver with AM, if you have it's easy enough to transmit into a 50 Ohm load and listen to it.

Many of the old boat anchor radios suffer from frequency drift and lack of frequency accuracy when VFO controlled, this wasn't much of a problem a few decades ago, but can be today. Also most do not include effective audio low pass filtering, which results in wide bandwidth transmissions (often out to  between 10 and 15 KHz either side of the carrier). You can solve both problems with either crystal control or a modern outboard VFO and the addition of an audio low pass filter.

With care, AM can be accommodated on bands such as 80m (especially during the day when propagation limits band use). I am not sure of the USA license conditions with regard to frequency stability and bandwidth, but you will need to be careful to not cause problems to other stations nearby.

73 Dave

Posts: 3331

« Reply #7 on: January 31, 2010, 10:37:46 AM »

If you ascribe to lofty heights, one of these Power Rocks from the early 80s:

tuned up to 1910 and fed into a 3/8 wave vertical would be the penultimate ham AM station.
Match it with a tricked-out Drake R4C, and you'd be where many wish to go.

Posts: 4464

« Reply #8 on: January 31, 2010, 11:11:08 AM »

I can tell you from experience the original Icom 756 will get excellent audio reports on AM when the speech processor is turned OFF.

Leave the processor on and it sucks more than a Hoover upright with a clean dust bag.

The end of the world will occur on April 23, 2018 ( the day after Earth Day. Go Figure ).  If you're reading this on April 24th look for updates coming soon.  If you're reading this after June first, fuhgedaboudit.....

Posts: 1012

« Reply #9 on: February 01, 2010, 10:31:34 AM »

My Tempo One actaully works FB on AM and im suprised. Its a tad noisy on the RX end but it works! Ive actually heard guys using modern rigs on AM such as the Flex 5000, Icom 746, and a smattering of other modern rigs as well. Just get on and have fun!!!
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