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Question About Using AM mode on HF

AM on 75 does not include as many boat anchors as it did in the past. Home brew class E, flex radios, and modified rice boxes with an amplifier are gaining popularity now. I use to run a FT-101ZD however it was a little harder to get right then a FT-101E because you have to bypass the width crystal filter in AM to get receive bandwidth. In fact the optional FT-101ZD AM filter is 100% useless in RX without this mod.

I now use a Kenwood TS-940SAT with a modification I designed. The modification is done in two steps. First is removing AM modulation from the IF strip entirely and modulating one of the RF stages. The second deals with Hi-Fi and changing various caps and the feedback loop used on the mic amp IC. The results are amazing once you back the ALC down.

I've done this type of modification to many HF rigs made around the 1990's including the IC-781. Unfortunately I only took the time to fully document the procedure for the TS-940S. If anyone has one of these and is interested in the mod with pictures, Just send me a message trough this site. As good as the FT-101 series was on AM, the modified TS-940S is much better in terms of power and newer features.

The radio will easily modulate a 50 watt carrier to over 100% positive peaks. When the radio was undergoing this mod at one point I had the response opened up from 1 Hz to 100 KHz! I later bypassed the input to the audio amp to knock the high end down to just below 10 KHz to keep things within reason.

The mod has worked flawless in the 940's as I did about 7 of them for people a decade ago. All switching is done automatically off the mode switch in AM. The only function that is lost is the AM monitor in TX. That could be restored by adding a detector, I just never bothered. The mod is clean, nothing is hacked and it can be easily reversed although you'll never want to. By adding one switch the mod can be switched out on AM to compare the before and after effects of modulating the RF stage or IF stage.
 
Radio Tech said:
The 101 will have better sounding AM audio. I do not thisk I have seen a modern day rig that has good AM audio nowadays. Wonder why?

Most of the AM crowd runs the old stuff with big amps. Legal power of coarse.
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I must have slept thru this thread. Modern solidstate gear sounds crappy on AM for one very simple reason,they don't generate AM like they used. Good sounding AM is full carrier double sideband while the new gear today generates AM by using a full carrier and only one sideband, usually the upper side band, since both sidebands are unnecessary to convey the audio content.The result is a narrower "pinched" sounding signal that lacks the presence of full carrier double sideband AM. Whether the final is high level modulated or low level is irrelevant. Most people seem to confuse those terms and believe that low level modulation means something less than 100% when in fact it simply means that an RF stage "lower" in the chain, like a driver stage, has the modulation applied to it instead of the final stage. It amounts to the EXACT same thing as a "highlevel" modulated radio with an amp after it.
 
Captain Kilowatt said:
I must have slept thru this thread. Modern solidstate gear sounds crappy on AM for one very simple reason,they don't generate AM like they used. Good sounding AM is full carrier double sideband while the new gear today generates AM by using a full carrier and only one sideband, usually the upper side band, since both sidebands are unnecessary to convey the audio content.The result is a narrower "pinched" sounding signal that lacks the presence of full carrier double sideband AM. Whether the final is high level modulated or low level is irrelevant. Most people seem to confuse those terms and believe that low level modulation means something less than 100% when in fact it simply means that an RF stage "lower" in the chain, like a driver stage, has the modulation applied to it instead of the final stage. It amounts to the EXACT same thing as a "highlevel" modulated radio with an amp after it.
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I hate to disagree with anyone who has a kilowatt but this is plain incorrect.

Some military and marine rigs use one sideband with carrier. Almost all riceboxes use double sideband in the AM mode. There are only a few exceptions. The AM produced by a properly setup ricebox is AM just like an 807 modulated by a pair of 6L6s with. It is indistinguishable on a scope showing an envelope pattern.

One sideband with carrier will not produce low distortion with the diode detector used in 98% of hammy receivers.

Warmed over riceboxes are among the best sounding and least distorted AM transmitters in the Northeastern U.S.
 
I run AM alot on 80 and I use a ft101E w/ all AM mods and a TEN TEC TITAN 425. With this setup I can easily run 1500 peak with a 1kw avg out put(measured on lp100A) Thats with only 55watts of exciter power. Now that I have new tetrodes, with a full 115 watts in I see 3300 out!! But never run it that high, I just wanted to know..... But anyway with the 101 running damn near idle at 55watts out and the amp sleeping at 1500, I keep the mic gain down and use a Ten Tec 709. I get glowing reports and alot of folks think im running big iron. The key to nice audio is not to over do it and keep your bandwidth respectable!


Oh and to who ever said solid state rigs arent good on am, you should listen to a TS870 or Ten Tec orion/omni7. I think you would change your mind. I heard an omni 7 one night talking to a guywith an old globeking running a converted AM broadcast transmitter. The omni was hands down the best sounding. Technology is a great thing if your smart enough to employ it correctly!!
 
This thread has gone too far in the other direction.

Several of the newer rigs mentioned sound muffled on AM due to inadequate bandpass. 6KHZ spec filters are too narrow to transmit through on AM.

Others will not make 100% positive modulation due to software limitations.

Most riceburners need a few circuit changes to make decent AM. Anything with DSP that isn't a flex should be left off the list.

If some guy on the other end tells you your TS-2000 or 756 Pro sounds exactly like a plate modulated rig he is probably using a narrow receiver that needs a new audio output tube.

AM takes a little work unless you buy a Flex. No way around it.
 
I would like to find out how Yasue FT-2000 both sounds and works on AM since I do like to operate 75meter AM.

My Kenwood TS-950SDX sounds and works great on all modes using a heil GM mic but was looking to upgrade to a newer rig but do not want to drop the money if I cant do what I do now.. I had a TS-940 years ago and ssb worked great but AM was not good at all..
 
dxhound said:
I run AM alot on 80 and I use a ft101E w/ all AM mods
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And what mods are these pray-tell?

dxhound said:
Thats with only 55watts of exciter power. Now that I have new tetrodes, with a full 115 watts in I see 3300 out!! But never run it that high, I just wanted to know..... But anyway with the 101 running damn near idle at 55watts
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55 watts carrier? Near Idle?

dxhound said:
Oh and to who ever said solid state rigs arent good on am, you should listen to a TS870 or Ten Tec orion/omni7.
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I don't think anyone here would argue that SOME solid State rigs are capable of sounding good on AM, And I believe HiDef has put a proper perspective on this thread.

dxhound said:
I think you would change your mind. I heard an omni 7 one night talking to a guywith an old globeking running a converted AM broadcast transmitter.
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The Globe King is not an AM Broadcast transmitter.


dxhound said:
The omni was hands down the best sounding.
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I have a hard time taking anything seriously regarding AM from a guy who says ...............

dxhound said:
And just for your information, anything over %100 IS A FALSE /unrealistic number.
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And HiDef, I understand where you were coming from, (didn't at the start) and do agree with you....
 
MisterFatty said:
And what mods are these pray-tell?



55 watts carrier? Near Idle?



I don't think anyone here would argue that SOME solid State rigs are capable of sounding good on AM, And I believe HiDef has put a proper perspective on this thread.



The Globe King is not an AM Broadcast transmitter.




I have a hard time taking anything seriously regarding AM from a guy who says ...............




And HiDef, I understand where you were coming from, (didn't at the start) and do agree with you....
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I should have been clearer, 55 watts PEAK is near idle for the 101

The globe king is not a broad cast transmitter, hence why I said a globe king running a converted AM transmitter(as in the globe king is the exciter to the transmitter) You know what an exciter is dont you?????

And with almost all your coments, you have proven to me you are a classic golden screwdriver peak and tweaker, Git er done!

As for what my ft101e has done to it, The CW filter slot was modified for AM with some wiring changes to the band switch and filter board and a collins 7khz filter was adapted to the slot.

Most audio caps and a few transisters were upgraded as per the Foxtango AM modifications. Also a rebiasing of the Final PA for closer to class C amplification. SSB got a lil wider but still well within practicality and good practice. the trick is keep the ALC action to a minimum.

HI DEF, your assumption of the newer rigs not getting a true %100 modulated signal is almost definately correct. None of them utilize high level modulation. I was simply stating that with the software defined radios from tentec(and the Very wide ts870) they sound excellent.
 
dxhound said:
HI DEF, your assumption of the newer rigs not getting a true %100 modulated signal is almost definately correct. None of them utilize high level modulation. I was simply stating that with the software defined radios from tentec(and the Very wide ts870) they sound excellent.
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High level modulation is not necessary to reproduce natural asymmetry which shows up with good frequency response. Unbalanced balanced modulators do an excellent job of this. That's what many older ricers use. Plate modulators need low mod transformer ratios (when using a common supply) just to reproduce normal asymmetry. Many male voices can modulate easily to 140% positive without exceeding 99% negative if the bandwidth is correct.

I would not consider a TS-870 an excellent sounding AM rig. They sound OK but lack highs. If that's all I had then fine.
 
Most of what's here deals with opinion, and I'm not getting into that particular dog fight. I will say that the comments for signal bandwidth, 'practicality', and 'good practice', should be re-thought just a bit.
Do any of you happen to remember when th mode designator always included a number? CW was 'A1'. AM was 'A6E or J' IIRC, and so on. Do you happen to know what those numbers were? If you didn't, they were maximum bandwidth for that particular mode. They have not changed even if the mode designators have. Those numbers were in Khz, BTW. Does that tell you something about the acceptable bandwidth with 'AM' mode in the amateur services? It should. I'd also recommend that you NOT take my word for this, research it for your self. While you're doing that, you might also look for the acceptable band widths for FM, as in NFM and WFM, since those designatorsdon't tell you anything about their band width, just that they have one. It's all spelled out somewhere in the rules, you just have to find it. Makes for good practice with other questions like this!
Have fun.
- 'Doc
 
dxhound said:
And with almost all your coments, you have proven to me you are a classic golden screwdriver peak and tweaker, Git er done!
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Yes Mister Know-it-all..... gee 100% modulation means your radidio is clipping and flat topping....

I think you need to build some more "radar jamers"
 

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