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Top Gun Modulator

D

DTB Radio

Well-Known Member
Sep 14, 2005
1,059
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Carlisle, PA. USA
www.dtbradio.com
I'm posting this to see if we can get some good technical discussion going of this somewhat controversial modification/module. I've done a bit more study recently, and here's what I've found:

The top two photos are from a magnum S9, tuned to exactly the 4:1 ratio, full power, 100% modulation. The first two photos are without the Top Gun, the second 2 are with the Top Gun. The photos will speak for themselves to you fellow techies, so I won't go into detail on what's shown. I will note that NO settings were changes on either the 'scope or analyzer during the test, other than center position on the analyzer (to keep the signal roughly centered on the screen). The photos with Top Gun on show increased audio harmonic distortion, which is showing up as a "clipped" audio signal in the scope photo, and as a much wider sideband (and much higher IMD) in the analyzer photos. No gain in the usable sidebands is seen. I ran the same tests with the radio set for about 2 watts key, and basically the Top Gun just seems to artificially turn the radio up to full power while modulation is present, then let it fall back to the 2-watt key level when modulation is not present. I didn't bother to post those photos because the TG photos at 2-watt key are all but identical to the high-power photos without the TG.


Before Top Gun:

pretopgunscope.jpg

pretopgunspec.jpg


After Top Gun

topgunscope.jpg


topgunspec.jpg





Now before everyone and his brother starts posting lots of opinions based on just using their radio, let me say that I'm not looking for non-tech postings on this one. I want to hear input from actual techs with experience in testing radios with the TG feature either built-in or added, and hear what their test results were. Also, I understand that most power meter shows more power with the TG than without, but the photos above show that there isn't any more power developed. I want to hear from any techs who actually have seen more power developed on an analyzer and 'scope, as well as those who have basically seen the same thing I have.
 

DTB Radio said:
Now before everyone and his brother starts posting lots of opinions based on just using their radio, let me say that I'm not looking for non-tech postings on this one. I want to hear input from actual techs with experience in testing radios with the TG feature either built-in or added, and hear what their test results were. Also, I understand that most power meter shows more power with the TG than without, but the photos above show that there isn't any more power developed. I want to hear from any techs who actually have seen more power developed on an analyzer and 'scope, as well as those who have basically seen the same thing I have.
Click to expand...

I can't comment on TOP GUN, but ARF had a modulator built into their ARF2001 that seems about the same.

Increases the apparent modulation on AM... We all know how that is accomplished (read distortion)... On SSB, it might do something.

If the manufacturers want real processing, they need to either process the RF, and use it to control the feedback in the audio circuit, or convert the audio to RF, and apply RF clipping at that level, then reconvert to audio.

Suffice to say, neither is cheap, nor will it find it's way to CB.... At least, not since the 70s :)

--Toll_Free
 
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DTB, I have the scope, but not the spec analyzer. If you send me a spec analyzer I can test out the top gun and post my pics, too :)
 
JustinDePolis said:
Toll Free, not to hijack the thread, but I think it would be easy to do this properly. Even something like a couple diodes, an OP-AMP, and a audio bandpass filter could do the job, and proper feedback using a well designed AMC circuit. Sure, it's not the best way, but it would be better than anything out there right now, do you agree.


<<snip>>
Click to expand...

I agree 100 percent. I think the secret to doing this is to use high speed diodes... Remember, we are using this to control an audio frequency amp, but rectifying it at the RF level, so those diodes should be able to switch at the frequency of the carrier..... Sidebands (we hope) aren't +/- megaherts :) I think a couple years back we all learned this with bias schemes.

Anything that will increase the avg modulation will be a boon to CBers... Of course, clipping (like Lou's circuit does) does a good job (I just think his needs more drive on the output)... But sample it at RF, and you're actually helping the transmitted signal, not shaping the input to the modulator based upon a predetermined level the original engineers designed into the radio...... (this would help when moving the carrier control around A LOT.... Your processor would let you set a modulation level, instead of audio input level like the mic gain does now.... Whereever you put your carrier, the modulation will track, and the amount of "processing" you set should never change with different carrier levels.....)

Anywho.. Ima stfu now. Thread hijack over :)

--Eye Uh Toll Uh
 
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Jericho Willie said:
I want to post something here but I'm not sure what your definition of a Tech is? Do I need a degree in RF Engineering or would that over qualify me?
Click to expand...


I've found that a technician is usually the one that makes the engineers prototype work in the first place.


Go read rec.radio.cb and search my posts for some of my signature lines related to Engineers... :)


--Toll_Free
 
i have built a bunch of processors/clippers over the years mainly from discrete components but even a few vogad chips have been tried,
for me by far the most effective was rf clipping,
more expensive to do yes but if you use a decent bandwidth filter and set it up correctly i think they work great and tend to sound sweeter and clearer than the typical compressed nasal sound of most simple audio based compressors even when running relatively high levels of compression,
to my ears no audio based compressor i ever heared comes close to a well setup rf clipper if your main concern is to be heared and understood under the most difficult conditions,
want to bust a pileup hit the 18db button on the datong and punch a hole in the woollybacks muffling away on the ft1000 subwoofers and most important is that all the subwoofers hear your only using an old ft7 with a modified cb amplifier ;)
 
Jericho Willie said:
I want to post something here but I'm not sure what your definition of a Tech is? Do I need a degree in RF Engineering or would that over qualify me?
Click to expand...


My general definition of a Tech, within the confines of this thread at least, is someone with some kind of formal electronic education (college degree or extensive military training), and at least 10 years experience in the field of AM communications. I would also consider someone without any "formal" education, but who has, for 10 years or more, worked with and studied under another person who is recognized nationally as a leading person in the field of AM communications.
 
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bob85 said:
for me by far the most effective was rf clipping,
more expensive to do yes but if you use a decent bandwidth filter and set it up correctly i think they work great and tend to sound sweeter and clearer than the typical compressed nasal sound of most simple audio based compressors even when running relatively high levels of compression,
to my ears no audio based compressor i ever heared comes close to a well setup rf clipper if your main concern is to be heared and understood under the most difficult conditions...
Click to expand...

How true. My "state of the art" Yaesu FT-857 has audio processing and cannot hold a candle to the punch I get from my 30 year old Kenwood TS-820S with it's RF processing.The Kenwood does the processing at the TX IF level so it works at about 455 KHz regardless of the operating frequency.
 
TG modulator is designed to dead key low, and provide a power control proportional to the modulation amplitude. The end result is low dead key, CLEAR transmit audio, with a max peak power output. Some people on CB like this type of artificial "forward swing". It's a result of the myth that something must be wrong with your CB if a receiving station see's "backward modulation" on their s-meter. I find this modification annoying as hell, as it makes the squelch circuit pop on and off with each word.:bdh:
 
arf compressor

The arf 2001 radio uses a feedback servo loop and solid state transformerless modulator to achieve 18 db's of rf corrected compression.


Browning Raven and a couple other tube radios I cannot think of right now used a "opto-compressor" circuit. Basically a light connected to the modulator output and a light sensing optic that looks like a nuvistor tube connected to the compression circuit.

Many SBE radios had a very good compressor built in. They used expensive .1uf electrolytic caps for bypass and these would go bad (dry out) and many would bypass the compressor instead of repairing it. CPI also had a very good compressor built in.

Most Browning tube bases have a built in clipper / filter. Cliiper / filters are generally considered louder than compressors.

Tram d201 have a semi assymetrical soft compressor and clipper

Regency Range Gain and Imperial had DSBRC (double sideband reduced carrier) Low dead key, lots of swing and LOUD just my 2 cents
 

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