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Author Topic: HF rigs that transmit well on A.M.  (Read 1394 times)
KB9WIS
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« on: November 15, 2003, 11:58:07 PM »

On occasion, I like to hear the old timers on 160 meters transmit on A.M..  From my experiences, only the "older" tube rigs transmit legible AM audio in this emission.  I've tried my newer ICOM rig on A.M., however the results very quite disappointing.., in comparison to my older Yaesu 101.  The ICOM's reports were very distorted audio with reverse linearity upon modulation.. (even when reducing the carrier).  Perhaps it's just a Newer ICOM thing/glitch.


Has anyone ever attempted to utilize a newer HF solid-state rig on A.M. with satisfactory results?  If so, which rig have you had success with?



73's,

Kb9wis
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OBSERVER11
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« Reply #1 on: November 16, 2003, 09:27:21 PM »

it is all in the design. Newer rigs are SSB transmitters, they get AM by inserting a carrier. Older rigs have a huge modulation transformer where 50% of your output is the job for the modulation transformer. You are not going to find the added weight and expense of a modulation transformer in a 5 pound mobile radio.
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K0BG
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« Reply #2 on: November 17, 2003, 04:22:42 PM »

I don't particularly like AM for one very good reason; spectrum space. With today's technology, 2, 3, and even four QSOs can be made using the same space as AM. This says nothing of the efficiency differences between the two modes.

Alan, KØBG
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WA2CWA
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« Reply #3 on: November 17, 2003, 07:16:51 PM »

See my answer to your question over on the Boatanchor forum where you also post the question.

And you don't need a large modulation transformer to sound good. Many of todays rigs sound great on AM with little to no effort.

Most of the current crop of rigs on the market today now include the AM mode. Some of the SSB signals I've heard on the bands recently take up as much space as an AM signal. AM is here to stay with more and more operators discovering this neat and fun mode. Hey, when they throw out the CW requirements, and expand the phone segments, there will be more room for SSB, AM, and the digital modes. Digital AM and SSB are right around the corner.

Pete, WA2CWA
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KB9WIS
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« Reply #4 on: November 17, 2003, 11:46:18 PM »

Pete,


Thanks for your input..  It was insightful..  However, back to my question though.. Hi,hi...  Have you tried any newer solid-state rigs that actually sound decent on AM?  If so, what were their model numbers?  Did any of them have DSP?  I tried a newer ICOM with poor results, so now I have to switch back to my old Yaesu 101 whenever the urge to talk on AM creeps up..



73's,


Kb9wis
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WA2CWA
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« Reply #5 on: November 18, 2003, 04:22:21 AM »

Did you read my response on the Boatanchor forum? I've been using the 756 PRO II on AM with excellent results. Also have used the Icom 706 MK IIG on AM, mostly on 6M and 10M with good results. My older Kenwood Twins T-599D/R-599D also sound great on AM. Kenwood TS-2000, TS-870, and TS-850 are also great rigs to use on AM.
Pete, WA2CWA
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VE2DC
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« Reply #6 on: November 19, 2003, 05:46:52 PM »

My IC751A was hard to get to sound right... my present IC781 sounds fine... but do turn off the compressor...

AM is fun up around 29. 0 - 29.2MHz where there is lots of room.
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KZ1X
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« Reply #7 on: November 23, 2003, 07:55:28 PM »

Which rig were you using, specifically?  You only mention 'newer.'

My 756PROII sounds fabulous on AM when adjusted properly.  Add in some gain afterwards, and I'm on par with the plate mod rigs of yore.

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KB9WIS
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« Reply #8 on: November 23, 2003, 08:18:05 PM »

I've tried an Icom IC718.  The receiver sounded great, however the TX has poor with distorted TX audio, and the wattage would swing "backwards" instead of "forward" regardless of RF drive/carrier and/or audio levels..  Played with this a lot, however I could never get it to sound decent..  Are you referring to the Icom 756 pro 2's receive or transmit characteristics on AM?  I would love to hear it on the bands (as I was considering purchasing one of these rigs in the near future..)
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WA2CWA
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« Reply #9 on: November 23, 2003, 10:14:03 PM »

Given that your query is post on three different forums, we seem to be going around in circles.
"...and the wattage would swing "backwards" instead of "forward" regardless of RF drive/carrier and/or audio levels.. This is Icom's current design and it's not a bad thing. This characteristic does not induce distorted audio on transmit, it actually helps to reduce any distortion, especially if you're driving a linear. Are you using Icom's stock microphone for the 718? As far as I can see, none of Icom's microphones are designed for high fidelity AM audio. Next time you work someone using a 756 PRO/PRO II, as them to switch over to AM. It's a push of one button. The only other adjustment that may be required is to reduce the power output to 25 or 30 watts. Even with the RF power control set to maximum (40 watts on AM), it's difficult to tell if there's any distortion on the AM carrier unless one is using a microphone tailored for SSB operation. As Steve, WIK, stated on one of the other forums, even with properly operated plate modulated rigs, the RF doesn't swing forward. Controlled carrier rigs, when transmitting, will exhibit this characteristic.
 I've used my 756PRO II on AM since May 2002 and never have had a "bad" audio report either barefoot or driving a linear.

Pete, wa2cwa

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W8JJI
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« Reply #10 on: December 02, 2003, 06:29:19 PM »

My icom 746 pro sounds very nice on AM.  No matter where I set the carrier it does not seem to affect any charactaristics of the transmitted audio, and I don't know why. But that's good !
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HAMRAD
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« Reply #11 on: December 03, 2003, 11:03:44 AM »

The Icom 706MKII and MKIIG both work great on AM. These will show forward power output as you modulate. Just set power out at 20 to 30 watts and you'll get about 80 watts or so on voice peaks. The original 706 works as well but the audio has a tinny sound. I am sure there is a fix for it but if your going to get one get the last two versions. Of course if you want GREAT sounding AM audio buy a Yaesu FT 102!!
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KB9WIS
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« Reply #12 on: December 03, 2003, 11:49:19 PM »

Hamrad and W8JJI,


Thanks for your replys.  That's interesting that the 706MK2G have "foward" wattage with modulations peaks..  I would like to hear one someday..  


W8JJI,


I noticed you stated the 746PRO does well on AM.  Does the audio have "forward swing of wattage" or is it negative (similar to what my IC-718 would do)?  What bandwidth settings did you have the AM transmitter set to, to sound well on AM?
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W0JX
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« Reply #13 on: December 10, 2003, 07:52:25 PM »

I have a year-old FT-1000mp Mk V Field which I have used on 160 and 80 meter AM. I use an Realistic dual impedance mike I bought for $5 bucks at a hamfest. I get outstanding audio reports from the stations that I have worked. This is because I spent the time to find a local ham who also operates AM listen to my rig while I adjusted the equalization and DSP settings on the MP. Another key is set the output properly. A 100 watt rig is set for 25 watts out with no modulation.
It drives my Collins and BTI linears just fine with excellent results. Another good rig on AM is the Kenwood TS-850.

Regarding bandwith, most AM operation is "channelized,"
and not spread out all over the band. Therefore, spectrum use, in my opinion, is not excessive. Best of luck with your pursuit of "Angel Music."
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WA3VJB
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« Reply #14 on: December 31, 2003, 07:20:03 PM »

The Yaesu Mk. V is without a doubt the nicest sounding modern transceiver on AM today. Second place is the Ten Tec Jupiter.

Way down the list is the Icom 756 Pro II, whose DSP is apparently unable to keep up with the tasks associated with producing a carrier, two sidebands and good audio.

There is a transmitted audio syndrome known as the "ICOM Rumble," that the factory refuses to acknowledge. With respect to my friend Pete, WA2CWA, he can't hear it on his rig.

Please consider this sound file to hear the artifacts generated by not one but two examples of the Pro II, including Pete's...

http://amfone.net/audio/IC756-RumbleDemo.wav

It may not be irritating enough to forego the rig, but with other DSP based rigs like the Mk V successfully producing high quality AM, I have to wonder...

Paul/VJB
Annapolis
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