it not what you see,...... its what you hear
function equally well???? try to load an 11 meter amp on 160:headbang
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Difference between ham amps and cb amps
- Thread starter linearone
- Start date
it not what you see,...... its what you hear
function equally well???? try to load an 11 meter amp on 160:headbang
Build in band switching? Are you serious? And an output filter too huh. Would Wizard know how to do that and if he did would he be willing too? I think not.
I think if someone put a wizard amp on the ham bands the spectrum analyzers in the high end rigs would tell some bad tales and the person using said Wizard would be severely scolded.
After reading this tread I'd like to point out a few things I've seen. First, I think the 8877 gets a bad rap. Sure it has a fragile grid but the peak emissions that oxide coated cathode provides are amazing. With just an optocoupler watching the grid I was able to hold 7KW on the Bird from a single 8877.
I was trying to see what the tube could take and planed on blowing it up. Sounds crazy but I had a supply of surplus plasma RF generators that ran the tube donated to me as scrap. I didn't mind hooking one up to a 10 KVA pole pig to find the limits.
I thought the tube would blow up that day. To my surprise it handled over 7000 volts on the plate and stayed together being used several times a week for a year! One day it finally killed the tube and when I took the tube out it was blue in color from the extreme heat.
The grid was running well over 100 ma and the plate dissipation was far exceeded. Very bad practice for amplifier building but it sure was an enlightening test that revealed unexpected capabilities with the "fragile" 8877.
On the topic of 50 KW mobiles, they do exist on 11 meters. It is true their outputs do not reach the proper peaks to reproduce true AM. That would take 200 KW peak. More important is the RF exposure levels to the operator and those around. This is a very serious risk at these power levels and you are fooling yourself if you think you've come up with any safe way to transmit 50 KW with an antenna that has a center of radiation at essentially ground level.
The lucky ones have had the chance to connect headaches or blurred vision to the RF exposure and stopped. Not everyone will have the early warnings. Most have no clue how many times over the safe limits this RF exposure is.
I have nothing against 11 meter operators and have had some good fun on that band too. Hams are not going to convince 11 meter operators that their amps are better for many reasons. The main reason is the dollar to watt ratio and the fact ham amps are often not big enough
1.5 KW PEP is little more then a driver on this band today.
It's way too hard to convince someone who owns a working Wizard that the amp has serious design flaws. The mind set of "it works so it must be right" is difficult to erase. That's why those who know how to build quality 11 meter amps seem to be absent in the marketplace. They gave up on trying to find customers who knew the difference and were willing to pay for it.
Looking at Wizards site today I noticed he still uses copper strap to feed B+ to the tubes where there is no skin effect but continues to use simple wire to tie the anode to the PI network where the skin effect would benefit from copper strap. If that doesn't say "I have no clue about how RF works" I dunno what does. Almost seems like he makes an effort to get as much RF into the power supplies as possible.
I was trying to see what the tube could take and planed on blowing it up. Sounds crazy but I had a supply of surplus plasma RF generators that ran the tube donated to me as scrap. I didn't mind hooking one up to a 10 KVA pole pig to find the limits.
I thought the tube would blow up that day. To my surprise it handled over 7000 volts on the plate and stayed together being used several times a week for a year! One day it finally killed the tube and when I took the tube out it was blue in color from the extreme heat.
The grid was running well over 100 ma and the plate dissipation was far exceeded. Very bad practice for amplifier building but it sure was an enlightening test that revealed unexpected capabilities with the "fragile" 8877.
On the topic of 50 KW mobiles, they do exist on 11 meters. It is true their outputs do not reach the proper peaks to reproduce true AM. That would take 200 KW peak. More important is the RF exposure levels to the operator and those around. This is a very serious risk at these power levels and you are fooling yourself if you think you've come up with any safe way to transmit 50 KW with an antenna that has a center of radiation at essentially ground level.
The lucky ones have had the chance to connect headaches or blurred vision to the RF exposure and stopped. Not everyone will have the early warnings. Most have no clue how many times over the safe limits this RF exposure is.
I have nothing against 11 meter operators and have had some good fun on that band too. Hams are not going to convince 11 meter operators that their amps are better for many reasons. The main reason is the dollar to watt ratio and the fact ham amps are often not big enough
1.5 KW PEP is little more then a driver on this band today.It's way too hard to convince someone who owns a working Wizard that the amp has serious design flaws. The mind set of "it works so it must be right" is difficult to erase. That's why those who know how to build quality 11 meter amps seem to be absent in the marketplace. They gave up on trying to find customers who knew the difference and were willing to pay for it.
Looking at Wizards site today I noticed he still uses copper strap to feed B+ to the tubes where there is no skin effect but continues to use simple wire to tie the anode to the PI network where the skin effect would benefit from copper strap. If that doesn't say "I have no clue about how RF works" I dunno what does. Almost seems like he makes an effort to get as much RF into the power supplies as possible.
I have noticed that alot of 11 meter folks run as much power as their pocket will allow because they can,without thinking of rf exposure to themselves or others,and not caring how clean their transmission is....
Where most hams run no more power than needed and care about the quality of their transmission...sure some amateur amps have the ability to do 1500+ watts....but most of those that I have had any contact with just let them idle along at 800 or less watts so the amp is not being run wide open
Sure amateur amps cost a good bit more,but in most cases they are filtered as they should be to control out of band harmonics and are usually over built for their power rating.... as where CB amps have little or no filtering installed and are being pushed for all they are worth and then some
Give me an amateur amp any day
Where most hams run no more power than needed and care about the quality of their transmission...sure some amateur amps have the ability to do 1500+ watts....but most of those that I have had any contact with just let them idle along at 800 or less watts so the amp is not being run wide open
Sure amateur amps cost a good bit more,but in most cases they are filtered as they should be to control out of band harmonics and are usually over built for their power rating.... as where CB amps have little or no filtering installed and are being pushed for all they are worth and then some
Give me an amateur amp any day
I might be Mack,I never claimed to know it all,but from what I have personally seen.. what I posted above for the most part is true..I fully realize that not every 11 operator will run their equipment all out nor will every ham let their equipment idle along....
there are both good and bad in both hobbies...I was just expressing my personal experience *shrugs*
there are both good and bad in both hobbies...I was just expressing my personal experience *shrugs*
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I notice there is lots of talk about harmonics with amps. The biggest difference between tube ham amps and CB amps as it pertains to interference is direct RFI not related to harmonic content. Perhaps we need to discuss the difference between these two main types of interference.
It's been a long time since most interference complaints dealt with harmonics in the average household. Harmonic interference shows itself only at multiples of the fundamental frequency. It will show up on radio and television equipment operating close to the harmonic. Only effecting those frequencies while other pass trough perfectly. The prime example use to be TV channels 2 and 5 when it came to CB. All other channels worked fine.
Today's problems are by far mostly RFI and have nothing to do with harmonics. They can't be cleaned up with a TVI (harmonic) filter. For RFI to take place all we need is for rectification of the RF signal to take place in any electronic equipment. Since it's not frequency selective it can effect more types of equipment including computers, door bells, phones, intercoms, alarm systems and sound equipment. Many effected devices don't even contain RF circuitry.
Ham amplifiers are absolutely better in this key area of RFI reduction then CB amps. Things that reduce RFI in most ham amplifiers include proper RF layout that shields all other components from the RF compartment. Double front metal walls that shield meter openings from letting RF out. RF bypassing on leads leaving the RF compartment and any wires leaving the amp like the AC line cord.
By using methods of proper design you can prevent nearly all RF energy from being radiated at any source other then the antenna. By using normal CB design you can let tons of RF escape right out of the cabinet and worse yet let it go right down the AC line and turn all the electrical wiring in your house into one big RFI transmitting antenna.
Simple test for Wizard owners, hold the antenna of a field strength meter close to the AC power cord or meter on the front of the box. Does it read unusually high in these areas as compared to the side of the amp where it's easily shielded well? Even the simple build it yourself SB-220 had all of these issues under control.
It's been a long time since most interference complaints dealt with harmonics in the average household. Harmonic interference shows itself only at multiples of the fundamental frequency. It will show up on radio and television equipment operating close to the harmonic. Only effecting those frequencies while other pass trough perfectly. The prime example use to be TV channels 2 and 5 when it came to CB. All other channels worked fine.
Today's problems are by far mostly RFI and have nothing to do with harmonics. They can't be cleaned up with a TVI (harmonic) filter. For RFI to take place all we need is for rectification of the RF signal to take place in any electronic equipment. Since it's not frequency selective it can effect more types of equipment including computers, door bells, phones, intercoms, alarm systems and sound equipment. Many effected devices don't even contain RF circuitry.
Ham amplifiers are absolutely better in this key area of RFI reduction then CB amps. Things that reduce RFI in most ham amplifiers include proper RF layout that shields all other components from the RF compartment. Double front metal walls that shield meter openings from letting RF out. RF bypassing on leads leaving the RF compartment and any wires leaving the amp like the AC line cord.
By using methods of proper design you can prevent nearly all RF energy from being radiated at any source other then the antenna. By using normal CB design you can let tons of RF escape right out of the cabinet and worse yet let it go right down the AC line and turn all the electrical wiring in your house into one big RFI transmitting antenna.
Simple test for Wizard owners, hold the antenna of a field strength meter close to the AC power cord or meter on the front of the box. Does it read unusually high in these areas as compared to the side of the amp where it's easily shielded well? Even the simple build it yourself SB-220 had all of these issues under control.
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True about harmonics not being an issue due to cable TV and other changes.
Harmonics are however still a big issue where the antenna no longer acts as a load for them.
Feedline radiation is alive and well in many of these cases.
Time to make a thread of everything it takes to make a popular CB amplifier into a "ham" amplifier.
Harmonics are however still a big issue where the antenna no longer acts as a load for them.
Feedline radiation is alive and well in many of these cases.
Time to make a thread of everything it takes to make a popular CB amplifier into a "ham" amplifier.
HiDef,that is pretty easy....
Step 1 ....find the nearest trash can and carefully place the CB amp into it .. then set trash can out for the garbage truck to pick up in the morning :tongue:
Step 2 ..... Start looking at Amateur amps and find one that works for you
Step 1 ....find the nearest trash can and carefully place the CB amp into it .. then set trash can out for the garbage truck to pick up in the morning :tongue:
Step 2 ..... Start looking at Amateur amps and find one that works for you
I'm almost certain this break in harmonic interference is only temporary and will be back to haunt us soon. The FCC didn't vacate most VHF low band TV frequencies for nothing. They couldn't wait to sell it off to new over the air services that won't be sent via closed loop cable TV. Once these frequencies are reallocated there will be all types of new services that will be happy to receive harmonic interference all over again. Oh...and the fastest way to make a popular CB amp into a ham amp is to jack the tube out of the socket and slide a real amp under it.
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