Suggestions on who to tune my Galaxy 98VHP

[BooDaddy]

Ok... lemme ask a few more questions. I am looking at getting a bench setup for basic tinkering (on low end radios at first of course.. LOL)

What do you all think about this: http://www.dosy.com/products/tc4002psw.php

and how about some suggestions for some good beginners equipment? Dummy loads, oscilliscopes, freq counters and such..

Is this a good oscilliscope:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=330216636348&ssPageName=STRK:MEWA:IT&ih=014

I know its off topic, but I figured you guys could help

 

[hotrod]

well far as the dosy meter=saave up your money and get a bird43 or coaxial dynamics
for a dummyload ya can buy online dummyloads checkout [universalradio.com]
the other equiment ya listed im not sure where 2 get it new.could check ebay

 

[freecell]

the scope you linked to won't do the job.

 

[4600turbo]

"Buy a 8 pill Class C amp. Davemade, Fatboy, Xforce and or worldwide. and be done with it."

no, it's stupid advice. Class C Amplifiers are designed for FM and CW operation.
you've been brainwashed by comp amp builders. Class C Amplifiers are not designed to be used with transmitter modes of operation incorporating asymetrically modulated waveforms because of the inherently high levels of distortion. if you're using them for AM/SSB operation then you're the ones using the vacuum cleaners.

Give me a break like no one uses these amps for AM. LOL

 

[BOOTY MONSTER]

http://www.smeter.net/amplifiers/classes.php

 

[4600turbo]

4600turbo: [ returns to banging his head on the wall ]

 

[AudioShockwav]

Good link Booty.
There are and will allways be those who run class c amps on modulated modes such as AM and SSB regardless of the outcome.
And there will always be those who drive the snot out of them to get every possable watt on the meter, no matter if other radio users have to suffer, both in band and out of band, from the result.
Lets hope everyone will read the info provided and make there own decision as to what is best.
For me, it is a clean station, I want to respect the other radio operators around me by running a station that will not disrupt their fun while operating my own.
And to get back on the subject of the question, Yes, the radio can be set up properly to run the Amp, and do it cleanly.
Both Richard, and Jack have given you good info.


73
Jeff

 

[freecell]

"Give me a break like no one uses these amps for AM."

and all the ones who do don't know or understand anything about Amplitude Modulation.

 

[BOOTY MONSTER]

"Give me a break like no one uses these amps for AM."
i guess every one has herd their parents say.............. " if everyone else jumps off a cliff are you ? "

 

[freecell]

and into the same category we can lump amplifier dealers who sell 32X2SC2879's claiming 8000W while referring to them as "LINEAR". what's really sad is that the same guys who use class c amplifiers believe it.

or the dealer will list it as 32X2SC2879's @ 3.2KW and then when you follow the link you see crap like this:

"Driven Power (RMS) 3200 Watts Driven Power (PEP) 6400 Watts"

like the old saying goes, ""If you can't dazzle them with brilliance, then baffle them with bullshit"....but now they've gone one better, now they just rely on total confusion.

then they provide further evidence in their advertising thay they don't have a clue by making comments like: 200W carrier 500W peak, revealing to the thinking world that they know nothing about AM.

and you want to slam 160W into 4 or 8 2SC2879's? do you know how to read? are you able to comprehend what you read? just exactly what part of the word "maximum" are you having a problem with?

http://www.firecommunications.com/trdbase/2sc2879.pdf

input power MAX. 10WPEP

 

[freecell]

and you can forget about trying to justify these ridiculous ratings by stating that "well they're running them class c and that's more efficient"....that doesn't fly either when you consider the FACT that maximum efficiency for class ab1/2 can be as high as 62.5% and class c is seldom if ever higher than 85%, the difference there being about 22.5%. the problem with that entire line of thinking is that an increase from 3200W to 8000W represents an increase of 250% so don't even go there.

 

[BooDaddy]

So since the max inpupt wattage on a 2SC2879 is 10w PEP, I would not want to drive a Texas Star DX1600 (8 x 2SC2879) with more than 80w PEP correct?
Now, I am going to make an stab and say that good modulation would be 4x your carrier (at max modulation) So, a 20w carrier would be good.

Let me know if I am wrong... I am learning....
A "maxed out" feed to a DX1600 would be a 20w carrier (dead key) modulating to 80w PEP.

An ideal feed would be 10w carrier and max modulation of 40w PEP.

I have also learned that the 98VHP can be easily tuned to do 10w carrier when the power knob is all the way down, and with the power knob all the way up, it is a 65w carrier. This is actually the suggested settings from CBtricks.com:
http://www.cbtricks.com/radios/galaxy/dx98vhp/dx98vhp_trans_adj.htm
Look about halfway down on the page where it says AM CARRIER POWER

Does this sound right?

and into the same category we can lump amplifier dealers who sell 32X2SC2879's claiming 8000W while referring to them as "LINEAR". what's really sad is that the same guys who use class c amplifiers believe it.

or the dealer will list it as 32X2SC2879's @ 3.2KW and then when you follow the link you see crap like this:

"Driven Power (RMS) 3200 Watts Driven Power (PEP) 6400 Watts"

like the old saying goes, ""If you can't dazzle them with brilliance, then baffle them with bullshit"....but now they've gone one better, now they just rely on total confusion.

then they provide further evidence in their advertising thay they don't have a clue by making comments like: 200W carrier 500W peak, revealing to the thinking world that they know nothing about AM.

and you want to slam 160W into 4 or 8 2SC2879's? do you know how to read? are you able to comprehend what you read? just exactly what part of the word "maximum" are you having a problem with?

http://www.firecommunications.com/trdbase/2sc2879.pdf

input power MAX. 10WPEP

 

[freecell]

"........80w PEP"

you'll end up using < or = 40WPEP. 5W in results in approximately 100W out for a single 2SC2879, give or take depending on the particular hfe-beta grouping of the devices used. the minimum device gain is 13db..

db = 10LOG(Pout/Pin)
db = 10LOG(100/5)
db = 10LOG(20)
db = 10(1.301)
db = 13.010

 

[BooDaddy]

So, in theory, it would be as simple as setting up the 98VHP to exactly as mentioned on CBtricks.com=

power knob on low = 10w carrier, with max modulation (which i am thinking would be about 30-40w PEP)

Then I could run the 98VHP on low power to drive the amp, and then when the amp is off, I could run my radio on max power for "local talking" and have a 65w carrier and around 200-225 peak...

Am i correct in assuming that at 100% modulation you are at 4x your carrier (minus the inefficiences of the radio itself, which would actually be about 3 to 3.5 times carrier)??

"........80w PEP"

you'll end up using < or = 40WPEP. 5W in results in approximately 100W out for a single 2SC2879, give or take depending on the particular hfe-beta grouping of the devices used.
the minimum device gain is 13db..

db = 10LOG(Pout/Pin)
db = 10LOG(100/5)
db = 10LOG(20)
db = 10(1.301)
db = 13.010

 

[freecell]

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........