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Suggestions on who to tune my Galaxy 98VHP

freecell said:
unfortunately it doesn't work that way. the transistors produce slightly higher gain at lower input drive levels and the gain begins to drop as drive is increased. you'll find that the carrier level from the transmitter will be noticably less than 10W to produce 200W of carrier from the DX1600. if you'll look back at the beginning of this mess you'l remember that TS states that 4W in produces 175W out........
Click to expand...

Ok. I think i am starting to see the big picture. So, if i were to input 10W carrier to the dx1600, I would get 450w carrier out. This would be a little higher than what I should run it at as the amp would be swinging around 1300 PEP. Ideally the amp should swing around 800-900 PEP to keep it stable, and non-distorted on AM.

Or am I wrong, and would it be ok to drive a DX1600 with 10 watt carrier?

Another question... am i correct in assuming that in theory, 100% modulation is 4x the carrier (minus any ineffeciencies) .

And am i correct in thinking this way because you are effecively doubling (100% increase) the amplitude on BOTH the peak and trough of the wave from the carrier?
 
BooDaddy said:
"Ok. I think i am starting to see the big picture. So, if i were to input 10W carrier to the dx1600, I would get 450w carrier out. This would be a little higher than what I should run it at as the amp would be swinging around 1300 PEP. Ideally the amp should swing around 800-900 PEP to keep it stable, and non-distorted on AM."

begin at 4W carrier and stop when carrier out from the DX1600 reaches 200W. modulate the transmitter and adjust AMC for at or just under 800WPEP.

"Or am I wrong, and would it be ok to drive a DX1600 with 10 watt carrier?"

"Another question... am i correct in assuming that in theory, 100% modulation is 4x the carrier (minus any ineffeciencies)."

when Peak Envelope Power reaches 4:1 or when power output increases to at or under 6db. above the carrier. when you see that you're looking at AM done properly. if you're measuring AVG. power then you're looking for 1.5:1 peak to carrier or a 1.76db. increase in power above the resting, unmodulated carrier.

"And am i correct in thinking this way because you are effecively doubling (100% increase) the amplitude on BOTH the peak and trough of the wave from the carrier?"
Click to expand...

you look that over and think about it some more then re-ask the question again later.
 
Last edited:
get a good external power meter than can handle 2000 or more watts . http://www.palstar.com/pm2000am.php . put it between your amp and a properly tuned antenna that can handle the power . key the mic and adjust the deadkey from the amp to 200 watts . speak into the mic in you normal voice (dont whistle) and see what your modulation spikes are measuring . 800 watts is what you want to be clean and get the most of the amps ability and design . no doubt you can get more but at the expense of increasingly higher ammounts of distortion and bleed over , not to mention heat . heat is not an electronic devices friend .
 
freecell said:
you look that over and think about it some more then re-ask the question again later.
Click to expand...

Ok, so in this example, if we put 10w carrier to the dx1600 we would get a 450w carrier out (taken from: http://www.firecommunications.com/dx1600.txt )

If we managed to get a 4:1 from the setup, that would in theory have the amp doing 1800 PEP (which we know is impossible).

So, with a 4w carrier from the radio, we get a 175w carrier from amp making 700 PEP.

Im just ballparking but it looks the amp is basically multiplying the radios carrier by 45x (very ballpark). so a 5w carrier would be around a 225 carrier from the amp. This would also mean at 4:1 the amp woud do 900 PEP.

now, I am kinda worried that I wont be able to get my radio to do 4-5 watt carrier when on the lowest power setting. Has anyone of you guys been able to get a 98VHP down to 4-5 watts carrier on the lowest power setting?
 
I cant return it to myself :) I bought it from a distributor... I sell radios on my site.

But, I am not going to be able to do what I would like:
turn the amp off and run the radio at max power (200 watts PEP) for local talking
Or turn the amp on, turn the radios power down and use the amp for DX'ing.

I just wonder if the radio will actually be OK running a 4 watt carrier... meaning no distortion or oscillation. I havent bought a watt meter yet, so I cant test it out.. LOL.
 
hmm... is it possible to put the 3db padding on a switch so that it can be turned off when not running the amp?
I am assuming the 3db would effectively take the 10w carrier and attenuate it to 5w? Am i correct?
 
Ok, this thread has been beaten to death, burried, dug up and beaten to death again, rotted into a stinky puddle, and then beaten to death some more. Plenty of good stuff, but enough is enough already.

It boils down to this: IF the 98 is tuned correctly, you CAN use it without difficulty to run the 1600. If it were mine, I would set the low-power side up for between 5 and 8 watts dead-key, make sure the AMC is set correctly, and go with it. The radio WILL sound both loud AND clear if it is done correctly, both barefoot and through the amp. The main thing is to make sure the amp and the radio both have enough juice to suck on while operating.


I think the original question was who would be good to set it up. 8541 would be good, Fire Communications would be good, I can certainly do it, and I'm sure there are some others who are every bit as good as the others mentioned. 8541 and myself are two of the three techs/shops that Galaxy will recommend to work on their equipment.
 
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Yeah, I gotta agree DTB... but i will have to say.. I have learned a metric crap ton of info from this thread.
So much so, that I have bought a Dosy 4002-PSW to learn with. I cant afford a Bird right now, but I am going to try and get one later on.
I think i may put the 98VHP on the bench and have a look. I deffinately gotta fix the carriers on it. They are all out of whack.
 
I will give the 98 a tune this weekend, and I am going to try and get a watergate... and maybe even a video watergate for you guys to check out and make sure my homework was correct~~

Thanks again!
 

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