AM on Flex 5000

[ka4koe]

I am currently running a Flex 5000a into an SG-500 amplifier for a good 100 watt signal. However, as well all know, the Flex folks do not go into a lot of detail with regards to documentation.

I have run the audio setup routines as outlined in W1AEX's excellent webpage, with regards to mic, equalizer, leveler, and AGC levels.

My question is that I have no idea what the AM carrier level adjustment actually does. This level is adjustable from 0 to 50.

Thanks!

Philip
KA4KOE

[kb3ouk]

That just sets the carrier level to whatever amount of power you want. The Felx is somewhat unique since it's always putting out 100 watt pep sidebands, then you can adjust the carrieranywhere from 0 to 25 watts, you don't want to go over 25 watts. This way actually allows you to adjust the percentage of modulation by changing the carrier level, less carrier means more modulation.

[ke7trp]

No..   It does not mean more modulation. The 100 watt pep sidebands remain the same. It means you are changing the carrier level. 

Depending on your watt meter, You would want 3 to 4 times the carrier value to the peak value in the AM mode.    Its best to use the output scope to set the carrier and audio levels.

Its best to use an O scope to set AM transmitter.  Watch the drive into the amp... The Flex has a poor performing transmitter section in terms of IMD and into a low drive solid state amplifier, you can really take out sections of the band if not adjusted correctly.  People running them around me tend to splatter alot in the AM mode.

C

[kb3ouk]

The percentage of modulation is the ratio of peak sideband power to carrier. 100% modulation is 4 times the carrier, so at 25 watts the peaks would be at 100 watts, so that's 100% modulation. Since with the Flex the sidebands are fixed at 100 watts, dropping the carrier power changes the carrier to sideband ratio. If the carrier output is backed off to 15 watts and the sidebands remain at 100 watts, that is around 130% modulation.

Read this closely: http://amfone.net/Amforum/index.php?topic=27012.msg205463#msg205463

[ka4koe]

Now, you two fellars are just makin' my punkin' haid hurt bad. Need a consensus!

[Steve - K4HX]

Rob, W1AEX seems to be the Flex AM expert. I'd seek his advice.

[kb3ouk]

That's why I posted the link to the exact post where he describes the function of the carrier control, everything that I've posted so far in this topic has basically been a reinterpretation of the information in that post.

[flintstone mop]

OK we're stuck in a groove here. You would adjust the carrier so that you have a power out from the SG unit of 125 watts. 4X 125 watts = 500 watts PEP. which is the max power of the SG unit.
TIME for a DUMMY Load for the info in this post.
To get a little headroom and not hit the amp for everything its got adjust the dead carrier,,,no modulation,,for let's say 110 watts with the DRIVE control on the main screen. What is your PTT?? Got that wired into the Flex?? The DB-9 connector?? Not sure.what Flex did for the 5000.
AM Audio is in the set-up (Transmit) screen. Adjust as wide as the software allows. There will be the usual warnings that you are not being a good neighbor selecting wide audio. The SDR 5000 might be less bandwidth than the SDR 1000 or SDR 3000.
Set AM carrier level for 25watts. This is important. Any other setting really screws up the amount of modulation in the Flex.!!!
You will adjust for lower power depending how much drive the SG amp needs to give you 110W carrier. Hopefully nothing over 25watts.
The mic level is set so that your audio NEVER goes over 0dB.
The forward power meter in the powerSDR software has a menu to see the various audio stages in the Flex. Clik on it and the menu will show all of the monitoring points.
The ALC menu should read a little bit of movement as you talk.
You can EQ your TX audio. Listen to yourself and determine what kind of audio you want to TX.
The COMPANDER button on the main screen really makes the tx audio increase without overmodulation.
DO NOT clik on DX. That is for speech audio and breaking through pile-ups in contests or DX. SSB.
If it's right, your QSO's will receive a lot of nice comments. Flex is capable of plenty of modulation. I'm not familiar with a SS amp running AM mode.
Fred

[ka4koe]

I actually don't hit it that hard. With my power supply (2 big gell cells), I get 400W on a good day. I usually dial it back to 90-100W carrier.

Drive is 21.
Carrier Level is 25.

Not exceeding 0 db on any of my adjustments. I've done it enough times that I don't need to follow the procedure as its learned.

You are the first person to explain the difference between compander and compressor (DX). Like I said, the Flex documentation leaves a lot to be desired.

Thanks for the clarifications. They are appreciated.

Philip
KA4KOE

[N2DTS]

Back a while, the PSDR software used to have the carrier control adjustable from 0 to 100.
And you could set it to 90 and get 110% modulation with a sine wave.
Set it to 80 and you could get 120% modulation, ect.

It just reduced the carrier, not the sideband power, which is nice for having lots of audio on the carrier, or running into an amplifier.
When they changed it to 0 to 50, I think something else changed and it did not seem to sound or work the same.
At the same time, the audio levels in PSDR seemed to get much more critical if you wanted good sound.
Latency did go down though...

[W1AEX]

Hi Phil,

Your conclusion that the documentation is a bit light for AM is very true. They gave us an almost infinitely adjustable tool and then kind of left it to the user to figure out. At any rate, the carrier level setting for AM is very much misunderstood and to make it even more exasperating, it behaves differently from version to version as Flex has adjusted the scaling factor to correct a few mishaps along the way. So... if you are using version 2.3.5 the optimal carrier level setting will be different than what you would select for version 2.5.3 to attain the same performance.

There's some good advice in the thread already, but I'll throw my 2 cents in. As Shelby (KB3OUK) said the Carrier Level allows you to control the ratio of power in the sidebands to the amount of carrier. At the highest carrier level setting (for some versions that is 100 and in the current version it's 50) you can't reach 100% modulation in the positive direction without over-driving the audio and distorting. You'll hear signals that suffer from this frequently with a lot of the SDR stuff on AM and of course the quick conclusion is that SDR is crappy. But the fact is, many guys using SDR never bother to go through it and set it up optimally. So, as Clark (KE7TRP) suggested, the easiest (and probably the best) way to set this is to use a scope.

Keep in mind that the "Drive" control on the left side of the PowerSDR GUI comes into play here as well. Typically, when driving my pair of 3-500's (using PSDR version 2.5.3) my Drive slider is set to 15 and my Carrier Level is set to "45". When set this way, my amp produces ~150 watts of carrier and with my voice and my audio gain settings this produces a clean waveform with peaks up to 125% and nothing even remotely approaching the baseline. If I increase the Drive slider so that I am producing a 250 watt carrier the scope still looks very nice with good looking peaks up to 125%. When I advance it further than that, the Flex 5000 PA runs out of headroom and I begin to see evidence of flat topping at the exciter level. Your voice, and your gain settings at each stage in PowerSDR will no doubt produce different results. Once you set your Carrier Level to produce the positive peaks you are looking for, you shouldn't have to adjust it again. One thing to keep in mind is that if you select a Carrier Level that is too low your signal will begin to sound like double sideband with an AM detector. You'll get reports that you sound gritty and distorted. If you are using version 2.5.3 your setting of "25" might be doing this. I found that anything less than 30 caused this with my setup. At any rate, it’s really not a cookie cutter kind of adjustment as everyone's voice and microphone behavior differs, but keep an eye on the scope and you’ll be fine.

There is a complete test equipment software suite inside PowerSDR that allows you to sweep the Flex 5000 so that you can see for yourself that the transmitter is flat from 20 Hz to 20,000 Hz. If you choose to use hardware to test it, you will get the same result. You can also set the bandwidth of your AM signal to anything from 0 kHz to 40 kHz. Whatever audio you feed into your Flex 5000 will be faithfully reproduced in any voice mode, but only if you set up PowerSDR optimally. You can make it sound like a Valiant, an Apache, or pretty much anything you want right up to broadcast quality.

Clark (KE7TRP), I’m not sure where you came up with that UN-SMUG generalization about IMD! When it’s set up correctly, the SDR stuff is fairly spectacular in that department. That being said, I wonder how many SDR rigs are actually optimally setup? I can easily make my Flex look very nasty with just a few mis-adjustments. From what I see on my panadapter my guess is that there are quite a few SDR rigs out there that are very poorly adjusted. One of the best things about the SDR platform is all the adjustments a user can make, and one of the worst things about the SDR platform is all the adjustments a user can make. (Think about that for a moment...) When you tune across AM signals like those produced by Chuck - K1KW (Flex 5000), Bill – W1LLY (Flex 5000), Frank – WA1GFZ (HPSDR), Al – W1VTP when he doesn’t wander from the mic! (Flex 5000) or Dave AC2IQ (homebrew SDR - check his amazing stuff out on QRZ) along with many other SDR users, even the most skeptical observers would have to admit that they sound fairly spectacular and their signals look very smug on a scope and on a spectrum display.

73,

Rob W1AEX

[flintstone mop]

hmmmm
Thanks Rob
I'll check out your tips for carrier levels and the settings in set-up for AM carrier. They seem to conflict with each other. I have an SDR 1000 and using PowerSDR 2.3.5. I do not know if it was a glitch BUT you must have PwerSDR 1.8.6 installed before 2.3.5 will work. Says so in the Flex site.
The thing I have noticed is setting the AM carrier for 100W in the set-up screws everything up. Even though I am driving my amp with 9W. I have an AL1500 and that is all I need to get a 300W carrier.
Lousy modulation with the set-up on 100W. Return it to 25W and all is well. I see the Power Out Meter on the Amp really swinging the munkey.
So I will do some playing here to maximize the modulation. So far, I get really nice reports on the TX audio. Minimal EQ and slight compression from my Symetrix 528E. I have proper levels throughout the Flex where they are supposed to be. I am not using the Flex EQ in TX. The bandwidth is set for 0 for low freq and 6500 for max high freqs.

[W1AEX]

I'll check out your tips for carrier levels and the settings in set-up for AM carrier. They seem to conflict with each other.

Hi Fred,

There were several versions of PowerSDR where the scaling for the AM Carrier Level setting was broken. Keep in mind that the numerical AM Carrier Level setting was never intended to correspond to power output in wattage. When they corrected an issue with the FM power settings somewhere along the line it disabled the scaling factor for the AM Carrier Level setting. This made it possible for users to set the Drive control to 100 and the AM Carrier Level setting to 100 and produce a 100 watt carrier with no headroom left for modulation. It was a disaster for those who didn't understand what was going on. Fortunately, that debacle has been corrected.

Actually, both controls do work together rather than in opposition. Keep in mind that the "Drive" control has a different function than the "AM Carrier Level". Use the "AM Carrier Level" setting to control the ratio of power between the sidebands and the carrier. It's a clever way to allow you to determine the maximum size of your positive peaks. Then use the "Drive" slider in the PowerSDR front panel GUI to control the overall power output of the rig.

Let's say your AM Carrier Level is set so that your signal has a nice clean waveform with positive peaks up to 125% and you have the Drive control set to produce a 5 watt carrier. By adjusting the Drive control so that your carrier power rises to 10 watts or 20 watts your observed waveform will look the same on the scope (but bigger of course) because the increase in carrier and sideband power will be linear, until you reach the point where the PA runs out of headroom (100 watts PEP) and then you'll begin to see signs of flat-topping. Not a problem for you with the AL-1500 which needs very little drive to reach 1500 watts PEP but with an amp like mine (pair of 3-500's) it's important to watch the scope to make sure the Flex doesn't run out of headroom when driving the amp to higher power levels. To be honest, I like the asymmetry that is possible, but I think my stuff sounds best if the Flex 5K is restrained to no more than around 125% positive peaks. It sounds clean, it does not get anywhere near the baseline so you don't get into the wavelet issue, and I have plenty of headroom for the power levels I like to run.

Another important thing to remember is that at the request of many users, Flex moved the data for a few settings from an area of the database that went across all your TX profiles into the area of the database where settings are stored for each individual TX profile. This means that things like Mixer settings and the AM Carrier Level are no longer universal changes, they are now stored within each TX profile you create. You can have a TX profile set up for 100% positive peaks, and with a click of your mouse, you can load a different TX profile that is set to run 125% positive peaks. As I recall, this change took place with version 2.3.5 but I'm not absolutely certain. People who are not aware of this may find that the AM Carrier Level they set up last Tuesday is gone if they switch to another TX profile, so it's important to keep track of what your version does.

I have two TX profiles that I run for AM. One is a 9.998 kc wide profile with DSP settings of 0 - 4999. The 4999 allows me to operate on 7.295 MHz without PowerSDR squawking that I have reached the band edge. The other profile I use is a 12 kc wide profile with DSP settings of 0 - 6000. Both profiles use the same 10 band EQ settings with the compander set to "5" and the ALC climbs up to around -1 dB on peaks. Fred, I completely agree with you about staying away from the DX compressor for AM use as its range of adjustment seems to be above anything useful for the AM mode. If you go to the link below and scroll down to the second video that's at the bottom of the page, you can hear how it sounded when I sampled it with my setup:

http://www.w1aex.com/psdr_rec/psdr_rec.html

Both of my profiles use a TX buffer size of 4096 to provide a steep brickwall skirt on the signal. That's largely a matter of user preference but I think it's more neighborly to run that way. Some guys set the TX filter bandwidth to 40 kHz and control their TX signal width in their audio chain and that works just as it does with plate modulated rigs. With the scaling factor present in the PowerSDR 2.5.3 version I use an AM Carrier Level setting of "45" with both profiles and run anywhere from 10 - 20 watts out of the Flex to drive my pair of 3-500's to between 150 ~ 250 watts of carrier output depending on band conditions.

73,

Rob W1AEX

[flintstone mop]

Hi All.....and Rob
A few discoveries here with my Flex. Power settings and profiles for different modes ok here. Plenty of mod audio on the carrier.
BIG difference in audio quality by shooting only slightly processed audio from my Symetrix ( some compression from Symetrix, EQ turned off in Symetrix) then goes into the sound card (FA66) and now using the Flex EQ.
The recording and play back through the Flex software is out of this world. I'll have to look closer into my R390A and whatever has been going on there. The I.F. may not be at its best according to what I hear between the FLEX recording and what I monitor from the 390A. Just running the FLEX at 18 watts. So the receiver is not overloaded from using the amp and legal limit going into the dummy.
The recorder function pretty much tells it all.
Hell!! I might just plug my Marshall mic into the FA66 and let it really run wild!! The FA 66 can provide phantom power. ......Here we go!
Mic into FA-66 card and the Flex is the BOSS. What a difference!! Completely open full audio. Very smooth and plenty of modulation!! Makes life a lot simpler. Thank You Rob
Fred

[WA3VJB]

...to operate on 7.295 MHz without PowerSDR squawking that I have reached the band edge.

I have wondered how people stay in any kind of comfort zone when they dial up that high in the AM Zone.  It's one thing to risk being out of license class subband (like when down low) but another to be out of the allocation.

[W1AEX]

I have much less confidence in my old Viking rig Paul. It usually drifts down and then settles down which is a good thing when working the top end of 40 meters. Unfortunately, the VFO has the random magical ability to jump up a kHz or two which makes life a little exciting. It's on my list of things to correct in the distant future. Of course, there's also those random sibilant peaks that can flicker out beyond the band edge. I bought a RANE VP-12 that Blaine N1GTU was willing to part with and it has a pretty effective de-esser but it's not exactly a brick-wall effect! Ah well, we all do what we need to do to get on the air...

Rob W1AEX

[W2VW]

I have much less confidence in my old Viking rig Paul. It usually drifts down and then settles down which is a good thing when working the top end of 40 meters. Unfortunately, the VFO has the random magical ability to jump up a kHz or two which makes life a little exciting. It's on my list of things to correct in the distant future. Of course, there's also those random sibilant peaks that can flicker out beyond the band edge. I bought a RANE VP-12 that Blaine N1GTU was willing to part with and it has a pretty effective de-esser but it's not exactly a brick-wall effect! Ah well, we all do what we need to do to get on the air...

Rob W1AEX

Excellent reasons to sell out and go ssb.

[Steve - K4HX]

Yep. On LSB you can get on 7299 or maybe even 7299.5 kHz if you are clean.

[W2VW]

Yep. On LSB you can get on 7299 or maybe even 7299.5 kHz if you are clean.

I'm clean as a Safeway chitlin.

[Steve - K4HX]

HA!   

[K1JJ]

Or, since a dead carrier has zero bandwidth, park on 7.29999999999999999  and don't say anything.  FB OM.

[Steve - K4HX]

Not much different from some QSOs I hear.   

Or, since a dead carrier has zero bandwidth, park on 7.29999999999999999  and don't say anything.  FB OM.