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Ricebox for AM?




 
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ke7trp
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« Reply #25 on: October 31, 2011, 01:35:41 PM »

Forums and email are very impersonal.  Its hard to tell if someone is being a jerk or not and often times arguments insue.  The meek can hide behind the keyboard and act like a lion. 

I worked a person on this forum that is very tough on people here.  Short one liners. I know more then you ect ect.  Then when I worked him on the air, I realized that he was a pretty nice normal guy. 


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KX5JT
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« Reply #26 on: October 31, 2011, 04:06:06 PM »

It's true that intent and humor are often misjudged on forums.  Glad you figured out I was an okay guy Clark.  Grin
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AMI#1684
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« Reply #27 on: November 01, 2011, 06:54:27 AM »

Another thing to think about using Transceivers in AM mode is the resting carrier output and modulation.
ALL 100 W PEP SSB transceivers will need to be adjusted to 25 watt carrier in AM. And your microphone level has to be adjusted so that there is NO ALC activity. ANY ALC in the AM mode and your positive peaks are gone and flattened out.
Being that you broke your rule not to use your radio on AM, do not try to get into the electronics to disable the ALC or the SWR foldback circuits.
This was done to an old work horse transceiver of mine a TS440 and some mods to the filter networks. It had B'cast quality audio and easily made 130% pos peaks,,,,thank you Dave,,,W2WV.
With careful adjustments in regards to carrier setting and audio, a lot of the transceivers in use really have very nice TX audio. Some are unbelievable.
Fred
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Fred KC4MOP
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« Reply #28 on: November 01, 2011, 07:31:33 PM »

Thanks, Fred.  Smiley
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73 Mike 
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« Reply #29 on: November 02, 2011, 04:35:48 PM »

This is one question that I never could reconcile.   My Icom 718 runs 40W of carrier which seems high, but the rule of thumb is that the PEP power of a double sideband AM signal is 4 times the carrier power.    What if the ricebox is SSB with an unbalanced modulator with the SSB filter still in the circuit, would that mean you can run the carrier at one-half the PEP power.   Is that what Icom does when it sets the AM carrier to 40W.    They seem to work OK at that level as long as you keep the mike gain below the ALC tripping level.   I never did quite figure this out but have never had problems running the 40W of carrier.   Lowering the carrier power doesn't seem to improve anything.   This has been covered before but I never saw a good explanation.
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ke7trp
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« Reply #30 on: November 03, 2011, 11:07:52 PM »

At a 40 watt carrier the Icom cannot fully modulate the signal.  If this is ok for you or band conditions allow it, Then great.

The ALC is to agressive and will not allow 100% modulation from a low carrier of 25 watts.  The most mine will produce is about 50 watts from a 25 watt carrier.

You can open your icom and adjust/modify your rig.  However,  I do not want to modify the rig.  The solution is to use the external ALC device and simply plug in the unit to the ALC jack. No mods and the problem is solved.

You can then run Any carrier level you wish, With producing the full 100 watts output when modulated on AM.

This device really shines when using a typical Ham amplifier with Tentrodes or high power Triodes that does not want much drive.  My amp only wishes to have about 15 watts of AM carrier as Drive.  I can then modulate the rig and adjust the mic gain until I have 100 % modulation while watching my station O scope. This is not possible with out the ALC device.  From 15 watts carrier my icom will not reach anywhere near 100%. 

On air testing produces from my friends IC756Pro 2/with 4cx800 x2 amp, shows a very strong increase in audio and clarity.  This is expected since his rig goes from 750 watts pep to 1500 with the device inline and his Carrier is fully modulated. 

C
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« Reply #31 on: November 03, 2011, 11:14:41 PM »

At a 40 watt carrier the Icom cannot fully modulate the signal....

What if the Icom was only transmitting one sideband?

Somewhere recently, I read that a certain Icom transceiver only transmitted ONE sideband on AM. (I don't know if that's really the case or not.) If that is true, is the four-times-carrier rule still true?
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73 Mike 
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ke7trp
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« Reply #32 on: November 03, 2011, 11:20:37 PM »

I cant speak for all Icoms. My 756 Pro uses both sidebands.  I can see them on the transmitting Spec scope. At 40 watts, Carrier. It can only modulate to the 50% range or so.

C
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K3ZS
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« Reply #33 on: November 04, 2011, 08:17:32 AM »

The ALC box would be a good addition, but I only use the Icom on AM for emergency use, i.e. before the tubes warm up on the AM rigs.
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K4RT
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« Reply #34 on: December 01, 2011, 03:45:39 AM »

Following up, I built the circuit referenced in this thread and connected it to my Yaesu FT-920 transceiver.  I modulated the carrier using voice then a 1000 Hz tone.

Judging from the transceiver's ALC meter, the ALC was unaffected by the voltage output of the circuit (and there was no change in the waveform on the scope) until the circuit output reached approximately 4 VDC (about the level of the internal ALC voltage).  At that point, the ALC meter pegged and the transceiver power output went to zero, with a corresponding disappearance of carrier waveform on the scope.  Several tests produced the same result.

I'm wondering if similar results were obtained by others who have tried the circuit and where they went from there. I'm reluctant to test further for fear of damaging the transceiver's ALC.

Brad K4RT
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Brad K4RT
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« Reply #35 on: December 01, 2011, 12:56:43 PM »

Looking back over my "log notes" (scraps of paper) over the last several weeks, out of 47 AM contacts, only 3 were using vintage boatanchor equipment. The rest were using solid-state transceivers, class E rigs, Elecraft, and Flex rigs.

My ricebox is now older than my Johnson 500 was when I used it. 
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W2VW
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« Reply #36 on: December 01, 2011, 01:00:01 PM »

Not sure if that circuit works on Yaesu radios.

It is reported to work on several Icoms.

Following up, I built the circuit referenced in this thread and connected it to my Yaesu FT-920 transceiver.  I modulated the carrier using voice then a 1000 Hz tone.

Judging from the transceiver's ALC meter, the ALC was unaffected by the voltage output of the circuit (and there was no change in the waveform on the scope) until the circuit output reached approximately 4 VDC (about the level of the internal ALC voltage).  At that point, the ALC meter pegged and the transceiver power output went to zero, with a corresponding disappearance of carrier waveform on the scope.  Several tests produced the same result.

I'm wondering if similar results were obtained by others who have tried the circuit and where they went from there. I'm reluctant to test further for fear of damaging the transceiver's ALC.

Brad K4RT
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Pete, WA2CWA
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« Reply #37 on: December 01, 2011, 02:47:20 PM »

I would read these threads:
http://amfone.net/Amforum/index.php?topic=25323.0
http://amfone.net/Amforum/index.php?topic=24495.0
And AM in Icom DSP rigs: http://www.ab4oj.com/icom/dsp_am.html
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
K4RT
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« Reply #38 on: December 01, 2011, 10:45:35 PM »

Pete,

I had reviewed the two amfone.net threads, but the AB4OJ link is new to me. I'll check it out.

73,
Brad K4RT
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Brad K4RT
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« Reply #39 on: December 02, 2011, 05:23:33 PM »

One thing about the meters ...

It could be the meter you were using that showed no movement may have been an averaging meter, and not a true peak reading meter. On AM you would not see any movement on the average meter.

Do I have that right? I think so.

John
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Pete, WA2CWA
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« Reply #40 on: December 02, 2011, 05:55:47 PM »

One thing about the meters ...

It could be the meter you were using that showed no movement may have been an averaging meter, and not a true peak reading meter. On AM you would not see any movement on the average meter.

Do I have that right? I think so.

John

Depends on what kind of rig you were running on AM.
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
Steve - K4HX
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« Reply #41 on: December 02, 2011, 05:59:11 PM »

I've talked to quite a few guys running FT-101s. Some of the early ones would be 40 years old now! Even the ones made at the end of the line (not the ZD models which were more like a 901 than a 101) are now 30+ years old.


Looking back over my "log notes" (scraps of paper) over the last several weeks, out of 47 AM contacts, only 3 were using vintage boatanchor equipment. The rest were using solid-state transceivers, class E rigs, Elecraft, and Flex rigs.

My ricebox is now older than my Johnson 500 was when I used it.  
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Todd, KA1KAQ
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« Reply #42 on: December 02, 2011, 06:10:16 PM »

a 101EE was my first amateur rig back in the early 80s. Wonder where it is now?

Before the Flex came along, the 101 was probably the best sounding if not most prolific ricebox found on AM. An incredible amount of good audio with minimal effort. Hearing N3DRB booming into VT with his at a whopping 25 watts a few years back still amazes me. I was sure he was on a big plate modulated rig.
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known as The Voice of Vermont in a previous life
KX5JT
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John-O-Phonic


« Reply #43 on: December 02, 2011, 06:12:39 PM »

One thing about the meters ...

It could be the meter you were using that showed no movement may have been an averaging meter, and not a true peak reading meter. On AM you would not see any movement on the average meter.

Do I have that right? I think so.

John

I see a little wiggle on mine. 
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AMI#1684
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« Reply #44 on: December 02, 2011, 06:50:37 PM »

Bill, W3DUQ was the first one I every heard using a 101 on AM. His was modded for hi-fi and lots of positive peaks. This was in the late 70's or early 80's.


http://amwindow.org/tech/htm/ft101.htm
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ke7trp
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« Reply #45 on: December 02, 2011, 08:52:08 PM »

KC6MCW has those mods done to his FT101.  He runs outboard studio mic with some audio proc gear.  Its better sounding then most big BC transmitters I have heard.  The only issue with doing this is that they will be a good 25KC wide and will not have any internal limiting. 

Even stock with a Shure 444 mic they are just fantastic.  Most of them will do 150 positive if not 175 so the use of a scope is a must.   There is no ALC action on AM.  It will fly.   

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Steve - K4HX
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« Reply #46 on: December 02, 2011, 08:59:32 PM »

Quote
There is no ALC action on AM.

Excellent point. This is what really lets the positive peaks soar.
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Ralph W3GL
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« Reply #47 on: December 03, 2011, 03:25:34 AM »


Speaking of Bill's (W3DUQ) FT101ZD, I have that rig sitting on a shelf in my shack.

Back a year or two ago when my TS440 died and the TS940 was out of town, Dave
(K3ZRF sk) donated it to the WFD cause.  With the TS440 back in operation and the TS940 back in my possession, the 101 was retired in ready reserve, so to
speak...

Yeah, it produces good peaks of 125% and more with little effort on AM and the receive is not too shabby as well...
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73,  Ralph  W3GL 

"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other"     Ed Morrow
Steve - K4HX
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« Reply #48 on: December 03, 2011, 10:40:34 AM »

I have DUQ's FT-101F.
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