SSB Carrier Supression

[Space Varmint]

Or I could attenuate the crap out of it and not mess with the mixer....whaa-Laa!

Anyway, the reason I had to do that was due to the noise also getting through the filter. The carrier signal needed to be much stronger than the noise or the filter would pass it as carrier. This was the reason for the access carrier.

I suppose there is a lesson here. Post mixer amps are very important in transmitters too. They are just necessary.

 

[Space Varmint]

And I took the amps and the ballanced mod & the crystal filter and put them in a separate shielded compartment. No need for a bead.

I redid the mixer and got inceredible suppression now and I made an output T network for the final and it is a thing of beauty! Perfect replication all the way through to the antenna. Problem is I only got one watt but my freq counter sees it when I talk it is so clean! One more driver stage. One more,,,lol.

 

[Space Varmint]

Well I'm pumping a full 5 to 6 watts running bare foot and I talked to a guy from Daytona FL today for about an hour. He said I was solid, and he could not believe the power I was running. I got her pretty well lined up now. I found I had some skin effect being amplified as part of my carrier. What I did was isolate the crystal filter and the balanced modulator into a separate grounded can and ran the carrier and audio in and the modulated signal out through coax. So taking the advice of the crew here, I put a bead on the center conductor of the coax which reduced the carrier some, then I put a small capacitance on the same point except I found I was not able to put it directly across the cable, it caused what appeared to electro-static noise, so I put it on the other side of a 2 inch wire right at the crystal filter output and acheived only carrier feeding the the crystal filter with no skin effect. This really cleaned up my signal to the point that the was carrier was to low from being over filtered through the crystal filter. So I widened the pass band slightly because it sounded like I was talking through a tin can. I still show zero output with no modulation on the output meter so I put it out there. I also went back to the PLL driver amps and fixed them to class A because I was showing something more toward class C output. This droped the gain a bit but was not much problem. I made a slight change in the mixer output filter to compensate for it.

I am trying to get some dx tonight with 5 watts...lol. Will give report back.

 

[Space Varmint]

Just got a 59 signal report from another country but the guy was cocky. He had a British accent.

 

[Space Varmint]

Notice the carrier level. This was taken right off the output of the final amp.

Just talked to Dallas Texas.

 

[Leftyretro]

You seem to be making more contacts over the air then on this thread lately? Too much QRM here most likely

Lefty

 

[Space Varmint]

Oh, you can see a couple of spots where it went peak to peak for a prolonged period...milisecs. I already fixed that. It was feedback.

 

[Space Varmint]

You seem to be making more contacts over the air then on this thread lately? Too much QRM here most likely

Lefty

LOL...and BCI (BritishCast Interference)<---Nigel

 

[audioguru]

I think I heard a cow in your movie. Can cows count?

 

[Space Varmint]

That was a radio man.

But any who, I'm gonna take her on up in power. I can't get enough contacts on 5 watts and I really don't need to hook up my 80 watter to it. I did yesterday briefly trying to call that guy from Belgium. OR4U...Gene was his name. The receiver is working great!

I got the output network set up for over 30 now but definately needs more drive. I'm gonna try a hefty buffer amp. I'm gonna use two MRF473's in a (get this Nigel)...a Darlington configuration. That should give me a good current boost.

 

[Space Varmint]

Hey Nigel, you should be delighted to know the Darlington didn't do squat. If anything I got a whole watt extra...lol. I through a Push-Pull in it and I'm still working with it but got 10 watts of clean duplicated power ot so far.

I seem to remeber something about that. After a certain power level buffers become useless. I guess it is because you are after voltage gain at that point.

 

[audioguru]

Usually a darlington transistor has very poor high frequency response. Useless for RF.

 

[Space Varmint]

Actually that might be the case at higher power levels. I'm using a Push-Pull right now. I hate ballancing these things. I had 10 watts and went for more and blew a transistor . So now I'm trying to re-balance another set (not a matched pair). I got the power but there is some trash coming off these.

 

[Space Varmint]

I just did something cool!

I pulled out the shielding I had around the final so I could work with it. Then i took the driver and ran it straight to the output network going to the antenna. Come to find out, I only got about 1/32th watt coming from the driver with no distortion. 1/8th watt when I over modulate and create trash in my signal. I think I will try putting the buffer back in to see if I get more power out of the driver. If so, just think what I will get from the final!

 

[Ross Craney]

Of course they have the same meaning. .

If you really are an audio guru you would know that two major design criteria for audio quality are Speach Transmission Index (STI) and Articulation Loss of Consanants (ALC)
Speach quality and speach intelligability are NOT the same thing

 

[audioguru]

Deaf people might hear 300hz to 3kHz.
Real people hear 20Hz to 20khz.

Speech has many important high frequency consonants sounds.
In my other post there is a test for intelligibility.

 

[duffy]

I think we're getting some cross-threading here - but those high frequencies are really important to speech quality. I don't know why people always focus on vowels and sonorants to the exclusion of everything else when this issue comes up. Stops and especially fricatives have significant spectral energy way up into the 10khz range.

 

[audioguru]

Have you heard an underwater throat microphone? Low frequency vowels only.
I can't understand speech from the thing.

 

[duffy]

Heh. Heard them and built them to trigger a vocoder-like gizmo in a guitar. Very mediocre.

 

[audioguru]

TV announcers used underwater thoat microphones. They sounded so bad that nobody could understand what they were saying.
The most important thing was that the microphones were hidden.

Recently the TV announcers and singers wear microphones on a boom in front of their mouths. Amazing very clear speech and singing.