Evening all. So I have a perceived need to go bigger than my Lincoln 2+ and I want to have room to grow. I have run 12 feet+- of American made high strand count 6 gauge wire to a 120 amp Anderson connector. My Lil President came with abysmal factory tuning. Am- 2-6 watt dk swinging to 22. I thinking a straight 6 2879c box with ssb won't over tax my current wire as it will be woefully under driven. Any thoughts? Also, Carl Built or Hopper. Carl's prices are about 300 ish below Hoppers. Guesstimate as Hopper doesn't have the 6 2879c mobile listed. Quick math comparing base 2879 vs 2879c. Any help would be great. 73s
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Mobile 6 pill analysis paralysis
- Thread starter Big Al 413
- Start date
Never could understand the reason for a linear with six transistors.
If it's configured as a two-by-four, that's just a bad idea. This is roughly twice the drive power four transistors should get. A one by four should last longer and sound better.
Then again, if it's a straight six, same question. Since the basic circuit is a push-pull pair of transistors, combining two of those will double the power. Combining two of those gets you four times the power of that first push-pull pair.
But going from four to six is only a half-again increase. Considering how receiver meters work, the difference between a straight four and a straight six just won't make a significant difference to the receiver's S-meter at the other end.
A straight eight would be my first choice for that radio. Just my two cents.
73
If it's configured as a two-by-four, that's just a bad idea. This is roughly twice the drive power four transistors should get. A one by four should last longer and sound better.
Then again, if it's a straight six, same question. Since the basic circuit is a push-pull pair of transistors, combining two of those will double the power. Combining two of those gets you four times the power of that first push-pull pair.
But going from four to six is only a half-again increase. Considering how receiver meters work, the difference between a straight four and a straight six just won't make a significant difference to the receiver's S-meter at the other end.
A straight eight would be my first choice for that radio. Just my two cents.
73
While going from a 4 to a 6 pill is not a noticable change, your going from 22 Watts to several hundred, is huge.
With a SSB box, an 8 pill will require more current for the same drive and produce less output too. You have the loss of two more splitters and combiners, plus the bias current of two more transistors.
Also, under driving a transistor amp will cause it to run less efficient as its output impedance will be higher than 50 ohms. Causing more RF voltage to be dropped across the transistors and more power to be dissapated in them.
Under driving a no tune solid state amplifier, only causes it to run less efficient and typically will not reduce dissipation untill you're below 1/3 to 1/4 normal power output.
This fact makes it difficult to simply under drive a larger transistor amplifier with the thought of just adding more drive later. The best efficiency happens when the drive matches the amp so that its output runs close to 50 ohms. Honestly, in this case, that would be a four transistor amplifier.
With a SSB box, an 8 pill will require more current for the same drive and produce less output too. You have the loss of two more splitters and combiners, plus the bias current of two more transistors.
Also, under driving a transistor amp will cause it to run less efficient as its output impedance will be higher than 50 ohms. Causing more RF voltage to be dropped across the transistors and more power to be dissapated in them.
Under driving a no tune solid state amplifier, only causes it to run less efficient and typically will not reduce dissipation untill you're below 1/3 to 1/4 normal power output.
This fact makes it difficult to simply under drive a larger transistor amplifier with the thought of just adding more drive later. The best efficiency happens when the drive matches the amp so that its output runs close to 50 ohms. Honestly, in this case, that would be a four transistor amplifier.
Well ide love to go with a straight eight and driver but I'm not upgrading the entire electrical system and adding batteries/super caps to handle that much power. I figured the straight six (and later on plus driver or hot radio) would be just under maxing out my 160 amp alternator and 65 series battery. I get the incremental difference between 900 and 1400 peak watts, but I'm going from 22 to X. Not from 900 to 1400. Why not shoot for a little higher of a start to begin with? Anywhos, going to settle with the 4x 2879c box. Will work well with what I have and can handle a radio with more grunt as well. Now to ponder a Carl built, Fat boy, or Hopper. Thus far Carl's price looks the best, haven't heard back from Rooster in TN. yet on a Fatboy. Thanks Shockwave and nomadradio for the thought food. Anybody had any recent experience with those Carl built or Hopper boxes? Couple guys in area run Fatboys and they seem good
Hey Shockwave -
This statement surprised me. I always assumed that the output impedance of an amp would be the same regardless of input drive. I run a 1 x 4 amp on the "low" setting. SSB only, never AM. 600 watt amp, but only about 250W peak. If the amp's output impedance is not 50 ohms in this case, and not a good match for my antenna would it be best to install an antenna tuner to match them up ??
- 399
I bought a straight 6 from Hopper and have no complaints thus far with it. Took a few weeks longer to get but stuff does happen.
It would be most effective if the tuner were installed directly on the output of the amplifier and before the signal passed through any 50 ohm coax. In this way you could tune the output impedance to match any given drive level, just like a tube amplifier.
The output impedance is (in general) V^2/(2*Po). The factor of 2 is based on the class of the amplifier. The lower the conduction angle the lower the factor 2 will be approaching one lower conduction angles. If you are running SSB, your output impedance is continuously changing (all over the map) with low power the impedance is high as Po approaches zero, when Po is higher the output impedance drops as the power increases. You design the output circuit for the maximum power transfer and anything less will not be an ideal match. 15*15/2*100 for example is 1.125 ohms. Your radio has the same issue, Some people believe that the 50 ohm output impedance is absolute, that is far from the truth. There are some really good explanations in Motorola publications.
Z (Impedance) = E (Voltage) / I (Current)
"given 100 watts of output from a fixed 50 ohm transmitter into a 50 ohm load, how....,"
https://www.worldwidedx.com/threads/959b-ssb-swr.262386/page-2#post-772389
"given 100 watts of output from a fixed 50 ohm transmitter into a 50 ohm load, how....,"
https://www.worldwidedx.com/threads/959b-ssb-swr.262386/page-2#post-772389
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If we only had 50 ohm devices 
, 2SC2879 is far from 50 ohms, more like 2 ohms.
, 2SC2879 is far from 50 ohms, more like 2 ohms.
Well, to go back to start...
Most output networks are simply a transformation - to take the low-impedance output and allow it's power to be transferred to the antenna output - whatever ohmic impedance you want it to be.
IN older tube sets, the voltage component output of the tube made it ideal for "ladder line" and other high-impedance output networks.
Transistor designs required it low-voltage - high current output to be transformed into a working component of equal voltage and current - so this made things more closer to 50 or 75 ohm impedance.
So in a way, we had to settle for 50 ohm to make the current munchers and the voltage zappers to work together - so they created this ohmic / impedance mess of 50 or 75 ohms with 50 ohm being more favorable for Low- end MHz range (kHz - Lo-VHF) while the losses in the 75 ohm being more favorable for VHF-Lo onto UHF.
IMO - it's seems that to the end user, the home brewer types that could use anything were left to themselves - but for the commercial endeavor, it had to be standardized, which took away all of our developer fun - so we got stuck with A99's and Siros' while others that could benefit from the voltage component better (READ: Home-made antennas) used Gizmotchy - Inverted - V - Cane-pole and End-Fed favored that group.
So now, to make your own, Radio - that's a no-no, but antenna? Well, that now has to fit in the box of what that Radio we cannot make, to suit our needs. It - has to fit in / match in - so it then becomes our Carborundrum - we're stuck with the Radio and it's platform for impedance - not what we could use in making our amp to suit our needs.
Most output networks are simply a transformation - to take the low-impedance output and allow it's power to be transferred to the antenna output - whatever ohmic impedance you want it to be.
IN older tube sets, the voltage component output of the tube made it ideal for "ladder line" and other high-impedance output networks.
Transistor designs required it low-voltage - high current output to be transformed into a working component of equal voltage and current - so this made things more closer to 50 or 75 ohm impedance.
So in a way, we had to settle for 50 ohm to make the current munchers and the voltage zappers to work together - so they created this ohmic / impedance mess of 50 or 75 ohms with 50 ohm being more favorable for Low- end MHz range (kHz - Lo-VHF) while the losses in the 75 ohm being more favorable for VHF-Lo onto UHF.
IMO - it's seems that to the end user, the home brewer types that could use anything were left to themselves - but for the commercial endeavor, it had to be standardized, which took away all of our developer fun - so we got stuck with A99's and Siros' while others that could benefit from the voltage component better (READ: Home-made antennas) used Gizmotchy - Inverted - V - Cane-pole and End-Fed favored that group.
So now, to make your own, Radio - that's a no-no, but antenna? Well, that now has to fit in the box of what that Radio we cannot make, to suit our needs. It - has to fit in / match in - so it then becomes our Carborundrum - we're stuck with the Radio and it's platform for impedance - not what we could use in making our amp to suit our needs.
- we'd have a much different back yard and/or farmers field
- containing - an antenna Farm that could be seen from Satellite...
the series equivalent input and output impedances of a 2SC2879 represent complex impedances due to the capacitive reactance present.
output Z = R1.45 -jX1.0
output Z = sqrt Rsq + jXsq
output Z = sqrt 2.1025 + 1
output Z = sqrt 3.1025
output Z = 1.761391495380854 ohms complex output impedance
input Z = R1.45 -jX0.95
input Z = sqrt Rsq + jXsq
input Z = sqrt 2.1025 + 0.9025
input Z = sqrt 3.005
input Z = 1.733493582335972 ohms complex input impedance
ref. toshiba 2SC2879 specifications data.
input impedance matching to a 50 ohm source is accomplished using C1, C2 & L1.
output impedance matching to a 50 ohm load is accomplished using C3, C4 & L2.
ref. Fig. Pi TEST CIRCUIT
output Z = R1.45 -jX1.0
output Z = sqrt Rsq + jXsq
output Z = sqrt 2.1025 + 1
output Z = sqrt 3.1025
output Z = 1.761391495380854 ohms complex output impedance
input Z = R1.45 -jX0.95
input Z = sqrt Rsq + jXsq
input Z = sqrt 2.1025 + 0.9025
input Z = sqrt 3.005
input Z = 1.733493582335972 ohms complex input impedance
ref. toshiba 2SC2879 specifications data.
input impedance matching to a 50 ohm source is accomplished using C1, C2 & L1.
output impedance matching to a 50 ohm load is accomplished using C3, C4 & L2.
ref. Fig. Pi TEST CIRCUIT
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Should never overlook the antenna system on top of everything.
The 2879c parts are wholey different from the 2879. So part values are different. Really only matters if you rely on a service tech that knows what values go where but not why. Only say that because people who can't build or fix their own gear can't seem to find someone to fix their gear in a timely fashion.
I'd go with an 8 pill standard 2879hg box and ask for a set of matching spare finals (hfe) they're cheap! Maybe get 4.
Make sure your guy is using metal clad caps on the output transformers. Today's silver micas, besides not being the best part for the job in general. Are crap!
The 2879c parts are wholey different from the 2879. So part values are different. Really only matters if you rely on a service tech that knows what values go where but not why. Only say that because people who can't build or fix their own gear can't seem to find someone to fix their gear in a timely fashion.
I'd go with an 8 pill standard 2879hg box and ask for a set of matching spare finals (hfe) they're cheap! Maybe get 4.
Make sure your guy is using metal clad caps on the output transformers. Today's silver micas, besides not being the best part for the job in general. Are crap!
Do you see what you guys did? Big Al asked a simple question and you guys went all geeky on him. Yeah, we all know how to do the math and quote the equations, but when it comes down to keying the mic and seeing what Mr. Bird has to say, all he wanted was an opinion on a winning combination of radio and amp size. I do agree with the "Six Pill Conundrum" though. I am stuck with a Carl Built and two different radios for drive, a Stryker SR-955 that peaks at 70 watts and an RCI 99N2 that peaks at 185 watts. The Stryker only tickles the amp and gives me 450 watts Bird Peak. I am afraid to plug the RCI into the amp due to having an Asymod System integrated into the circuit and it produces 25 watts DK (non adjustable), so do not want to take chances of running too much DK into the 6-pill amp.