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Modulation Probs with deskmic
Topic Started: Sunday, 30. August 2015, 10:10 (359 Views)
SleepyDragon
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26 Charlie Tango 1094

Hello,

I was on Mid band USB chan 27 and had a report of bad modulation..... After a few quick checks I found this....

The bad modulation only occurs on USB/LSB and not AM or FM
The bad modulation only happens with the deck mic and NOT the original mic from the radio.

Any Ideas what this could be (Battery perhaps)

Chris
[marq=Proud to be running 100% legal, unmodified radios on standard power.]Proud to be running 100% legal, unmodified radios on standard power.[/marq]

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Nubster
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26 Charlie Tango 050

What microphone is it ? (ie: what make and model)
Was you running any extra power when using SSB ?
What radio are you using ?
Edited by Nubster, Sunday, 30. August 2015, 10:32.

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Nik Gnashers
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26 Charlie Tango 573

Battery is the first thing I would check, but if the modulation is perfect on FM/AM then it suggests another issue.

I used to have issues on SSB in one of my old mobile setups, where my modulation was bad, but on FM/AM it was fine. It turned out to be an RF problem, and a different mic sorted it.
I think it 'might' be the same for you, if your outputting more wattage on SSB, which is why the RF feedback only causes an issue on SSB, as your power is lower on AM/FM.
I guess one way to try this is to use lower power (if that's possible with your setup) on SSB, and if the problem is cured then your 'fun' trying to cure RF-in-the-shack issues begin.
Clip-on ferrites on as many things as you can in the shack, and especially the Desk Mic lead may just cure it.
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SleepyDragon
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26 Charlie Tango 1094

Nubster
Sunday, 30. August 2015, 10:29
What microphone is it ? (ie: what make and model)
Was you running any extra power when using SSB ?
What radio are you using ?
The Mic is a SADELTA EchoMaster plus Classic, the echo is turned off on it as it the rodger bleep
The Radio is a Albrecht ae75000, standard unmodded, running on standard power, 4w am/fm and 12wSSB which is driven from the radio, there are no amps.

the antenna is plugged into a low pass filter which then goes into the radio, no swr meters or anything else in the coax line.
[marq=Proud to be running 100% legal, unmodified radios on standard power.]Proud to be running 100% legal, unmodified radios on standard power.[/marq]

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SleepyDragon
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26 Charlie Tango 1094

Nik Gnashers
Sunday, 30. August 2015, 11:23
Battery is the first thing I would check, but if the modulation is perfect on FM/AM then it suggests another issue.

I used to have issues on SSB in one of my old mobile setups, where my modulation was bad, but on FM/AM it was fine. It turned out to be an RF problem, and a different mic sorted it.
I think it 'might' be the same for you, if your outputting more wattage on SSB, which is why the RF feedback only causes an issue on SSB, as your power is lower on AM/FM.
I guess one way to try this is to use lower power (if that's possible with your setup) on SSB, and if the problem is cured then your 'fun' trying to cure RF-in-the-shack issues begin.
Clip-on ferrites on as many things as you can in the shack, and especially the Desk Mic lead may just cure it.
I think you may be right, I'm going to take it to knights, see if they can make sure it's wired right for my radio, perhaps there are some spare wires in the plug picking up the rf
[marq=Proud to be running 100% legal, unmodified radios on standard power.]Proud to be running 100% legal, unmodified radios on standard power.[/marq]

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Nubster
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26 Charlie Tango 050

OK Chris as Nik said yeah the first thing you would check would be the battery , but you would get the same reports on AM /FM if the battery was knackared , sometimes if you have the mic turned up too much on SSB that can cause the radio to be over driven hence you sound like you are under water to people who are listening so try backing off the mic vol on the mic a bit when on SSB first or failing that or instead back off the mic gain on the radio (if you have a mic gain on the radio where you havent got to mess about going in to a menu to do it ) a bit when using SSB , another thing is that the saldelta is a old school mic and your radio is a new school and sometimes I have noticed some old school stuff does'nt like working with the new school radios in certain ways ie: OK on FM but cr@p on AM & SSB or they just dont want to work at all, I had a Astatic 575M6 Teardrop( old school mic) once worked perfect on my old school radios I had but just didnt want to work on a new type radio I had, found out it was somthing to do with a lot of the newer radios use what is called a elerect mic and that takes power from the radio and older power mics use a battery to power them so non comatable with some newer radios ,another thing have you tried it with out the low pass filter in line cos TBH I dont know why you have that cos in the moderen day the chance of you giving TVI is Nil TBH cos modern equipment ie: T.V's and such have far superior filters on them then what we had back in the 70/80's when we really needed a TVI filter on, cos I have used TVI filters before and sometimes I found they caused more agro than what there worth , just another thought does you radio have a built in echo and talk back on it like all these Anyclones cos if it does I've heard from some who have those type of radios that even though you think the talkback or the echo is off its not 100% off and that can cause problem with modulation with a non standard mic
Edited by Nubster, Sunday, 30. August 2015, 15:11.

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SleepyDragon
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26 Charlie Tango 1094

FIXED !


Thanks for the advice everyone . It looks like I've sussed it out, looks like it happens when the radio's mic gain is on full whilst the desk mic is plugged in, by turning the radio mic gain to half was and the desk mic on 1 (it goes from 1 to 10) it sounds great again. I guess there is only so much bandwidth on SSB.


Chris
[marq=Proud to be running 100% legal, unmodified radios on standard power.]Proud to be running 100% legal, unmodified radios on standard power.[/marq]

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Deleted User
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It sounds like you were over driving the audio stage. ......................
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