Re: regarding RF interference emissions
No doubt that BPL is Butte Stupid....
However that does not relieve DIYer of responsibility for not interfering with existing services or for creating RFI.
1-5 Mhz is used by AM broadcast, Amateur Radio and Foreign Broadcast. Emitting more than 100mW is strictly speaking (certainly in USA & Canada) is illegal. Euro rules are more strict.
And, it is bad practice to build things that knowingly emit RFI - plus it will get back into your system, and act like a parasitic would.
So DON'T DO THAT!!
rcavictim said:If one can assume policy by the actions of the regulators themselves then I see no evidence that the emission of huge amounts of radio communications killing EMI over a wide frequency range on a nearly globalwide basis is unlawful anymore. I give the accepted deployment of BPL (Broadband over Power Line) as my example.
B A S T a R D S !!!!!!!!
No doubt that BPL is Butte Stupid....
However that does not relieve DIYer of responsibility for not interfering with existing services or for creating RFI.
1-5 Mhz is used by AM broadcast, Amateur Radio and Foreign Broadcast. Emitting more than 100mW is strictly speaking (certainly in USA & Canada) is illegal. Euro rules are more strict.
And, it is bad practice to build things that knowingly emit RFI - plus it will get back into your system, and act like a parasitic would.
So DON'T DO THAT!!
The resonance coil and ran hot and melted the platic former and deformed, this detuned the circuit and started to overload the tube.
I did four attemts to make a new coil, all failed, tube went orange with all of them and ended with injury.
I have no probs at all with interference, i have ran the thing for a month with no complaints.
These things run in the 27MHz area which in sweden is an ameture band, you can send there as mutch as you want even without a license.
I did four attemts to make a new coil, all failed, tube went orange with all of them and ended with injury.
I have no probs at all with interference, i have ran the thing for a month with no complaints.
These things run in the 27MHz area which in sweden is an ameture band, you can send there as mutch as you want even without a license.
Interesting, this ought to be the way to go.Rodeodave said:
I built a horn out of plaster. In my case the plaster killed the resonance. Unsure whether it was an electrical or magnetic issue.
Could it be that tube? I temporarily had a 6550 working once.Tekko said:
I also used a cardboard tube as a former. It would get warm but wouldn't deform. (of course it is a small but manageable fire hazard.)
Yes it could be the tube.
When a tube is overloaded the cathodes emmitive layer boils off and sticks to the control grid, making the tubes life even harder as the grid gets less effective. This is an evil circle, so when i in a dark room discovered that the tube had started to glow very faint red it was probobly already too late, so my latter attemts on new coils set in the final shoot.
Tho its most likely the coils i used, they do not match the schematic by any measure, the resonance coil is too small and the RF coils has way to less turns, it should be 100µH, calculations reveals its around 20-25µH.
And when making they new coil attemts i slipped with the pair or pliers and hit my nose about 1.5-2cm from my right eye, god spared my eye but not the tweeter.
When a tube is overloaded the cathodes emmitive layer boils off and sticks to the control grid, making the tubes life even harder as the grid gets less effective. This is an evil circle, so when i in a dark room discovered that the tube had started to glow very faint red it was probobly already too late, so my latter attemts on new coils set in the final shoot.
Tho its most likely the coils i used, they do not match the schematic by any measure, the resonance coil is too small and the RF coils has way to less turns, it should be 100µH, calculations reveals its around 20-25µH.
And when making they new coil attemts i slipped with the pair or pliers and hit my nose about 1.5-2cm from my right eye, god spared my eye but not the tweeter.
Sorry to hear about your nose. I suspect the actual inductance is less important than the Q of the circuit. After all, the lower inductance with a correspondingly lower capacitance should produce an ideal coil that works at a higher frequency.
I hear that this can be done with mosfets. Just for the oscillator that is.
I hear that this can be done with mosfets. Just for the oscillator that is.
Even on 27 Mhz. there is a power radiation limit.
Ground and shield, it is good practice.
And if it is an amateur band and not a "Citizens Band" over there, you need a license. Technically you need a license here in the USA on CB too...
The criterion is not a lack of complaints, fwiw.
_-_-bear
Ground and shield, it is good practice.
And if it is an amateur band and not a "Citizens Band" over there, you need a license. Technically you need a license here in the USA on CB too...
The criterion is not a lack of complaints, fwiw.
_-_-bear
RF is RF
If u want succes follow the basic rules of RF power circuitry:
- HV ceramic capacitors for decoupling
- transmitting type tubes
- ceramic coil former (low dielectric losses)
- silver plated wire (low "skin" losses)
- RF shield, because you dont want your neighbors to kill you,
and 30~50 watts of RF power quickly starts to "boil" your head
(I'm serious about this ... personal experience)
------------------------
What we see now is like a dim image in a mirror.
If u want succes follow the basic rules of RF power circuitry:
- HV ceramic capacitors for decoupling
- transmitting type tubes
- ceramic coil former (low dielectric losses)
- silver plated wire (low "skin" losses)
- RF shield, because you dont want your neighbors to kill you,
and 30~50 watts of RF power quickly starts to "boil" your head
(I'm serious about this ... personal experience)
------------------------
What we see now is like a dim image in a mirror.
I remember last time I played with a 1200MHz transciever I was holding the output whilst transmitting (trying to match antennas). My hand felt like what I imagine being in a microwave oven feels like. I guess the RF probably spread throughout my body.
It took a few seconds to notice, then I felt like I may have sustained some strange kind of damage. What is your opinion as to that damage?
It took a few seconds to notice, then I felt like I may have sustained some strange kind of damage. What is your opinion as to that damage?
According to conventional wisdom, you probably sustained mostly a thermal load, in other words a slight increase in temperature, especially in your outer body layers, but probably short of an obvious burn. What did it feel like? There is some unproven suspicion that EM fields can also disturb transfer of ions (Ca, Na, Mg, K, etc) across cell membranes, but this not largely accepted. There is a related and raging debate on the safety of chronic cell phone transmissions close to the head. However, in your case, you probably suffered no significant long-term damage from your single experience.
Years ago, when I was a young RF engineer, several of my older colleagues had developed cataracts. They felt that this was due to exposure to high power microwaves that had heated their corneas. They likened it to heating raw clear egg “whites” until they turn white, due to denaturing of the constituent proteins. Again, unproven, but the number of cataract cases in that company among older engineers and technicians hardly seemed like a coincidence to me. I am very cautious around EM fields.
Years ago, when I was a young RF engineer, several of my older colleagues had developed cataracts. They felt that this was due to exposure to high power microwaves that had heated their corneas. They likened it to heating raw clear egg “whites” until they turn white, due to denaturing of the constituent proteins. Again, unproven, but the number of cataract cases in that company among older engineers and technicians hardly seemed like a coincidence to me. I am very cautious around EM fields.
Brian Beck said:
You know the way mains feels, that you can feel the frequency and know it's AC? It felt like AC, only at a much higher frequency, which is odd as I don't presume I could sense such a high frequency.
It started as a strange nervy warmth radiating from one point and into my fingertips. This was combined with a feeling of slight tension reaching through my hand and wrist.
Slightly OT...
I wonder if EM like your brain and rest of nervous system use can be affected by RF... I mean it's all just energy... If you hold a RF remote next to your head, it "reaches" further - same if you hold it next to car antenna... obviously. If you stand close to FM / AM Radio, of older type - it also gets interference, sometimes it gets better if you move closer... makes tuning a bear
Maybe my brainwaves are just a tad out there, like the post...
So the nervous tension you got from the transmitter, may be a case of resonating nerves... more likely it is because your nervous systems also use a.o. anions to cross synapses... so the tension might be a short slow down of neurotransmitters...
But then again I also feel the cellphone ear buzzing/glowing/slight headache thing... So I might be considered an odd one.
I wonder if EM like your brain and rest of nervous system use can be affected by RF... I mean it's all just energy... If you hold a RF remote next to your head, it "reaches" further - same if you hold it next to car antenna... obviously. If you stand close to FM / AM Radio, of older type - it also gets interference, sometimes it gets better if you move closer... makes tuning a bear
Maybe my brainwaves are just a tad out there, like the post...So the nervous tension you got from the transmitter, may be a case of resonating nerves... more likely it is because your nervous systems also use a.o. anions to cross synapses... so the tension might be a short slow down of neurotransmitters...
But then again I also feel the cellphone ear buzzing/glowing/slight headache thing... So I might be considered an odd one.
The transciever offers 10W into the ideal load. I had a direct electrical connection. I don't know what this added up to in my case but I seem to have gone into very mild shock for a short time IIRC but I am not sure whether this was a direct result, or just the thought of what I felt. I did feel a little groggy for a time afterward.
Word of Warning
Please guys don't wander off too far.
I believe all of us wants to build a working plasma tweeter!
During the experiments with my friend Ivan we found two serious issues:
1) Load matching: we used PL519 as oscillator, 600 V for B+,
120~140 V for g2, 15 turns on a 35 mm coil former.This is a
working setup but not ideal, perhaps the number of turns
had to be increased...
2)Modulation quality: altough we used heavy high-pass filtering
on audio signal, the unit is easily overloaded with mid
frequencies and starts to
distort, thus compromising dinamic range.this is perhaps caused
by inherent non-linearity of PL519's screen grid.In commercial
AM transmitters anode line modulation is used, i believe that
this is more linear.
As long as i dont get my babyes, i want to hear a few good advices regarding this modulation issue.
Please guys don't wander off too far.
I believe all of us wants to build a working plasma tweeter!
During the experiments with my friend Ivan we found two serious issues:
1) Load matching: we used PL519 as oscillator, 600 V for B+,
120~140 V for g2, 15 turns on a 35 mm coil former.This is a
working setup but not ideal, perhaps the number of turns
had to be increased...
2)Modulation quality: altough we used heavy high-pass filtering
on audio signal, the unit is easily overloaded with mid
frequencies and starts to
distort, thus compromising dinamic range.this is perhaps caused
by inherent non-linearity of PL519's screen grid.In commercial
AM transmitters anode line modulation is used, i believe that
this is more linear.
As long as i dont get my babyes, i want to hear a few good advices regarding this modulation issue.
Attachments
I found the same problem. I rigged up a sixth order passive xover at 2kHz and still could not get the drive. Maybe the valve was the issue (I may have been overdriving the screen). Try driving the screen (if this is how you are doing it), from a cathode follower. IIRC this helped a bit.
How far spaced are your turns? I found this to be critical, and 15 turns for me worked best on a 35mm former at a total length of 7-10cm IIRC.
How far spaced are your turns? I found this to be critical, and 15 turns for me worked best on a 35mm former at a total length of 7-10cm IIRC.
Just like Tekko and myself, you seem to have found this point a stumbling block. I figured I needed more power. I looked at Mosfets and considered pages from people looking to produce plasma midranges.
To be honest, the thought of sitting mere metres from a source of MW with enough power to traverse a city, was unnerving. Unfortunately, I decided to move on.
If someone were to find a way though, and could get good SPL's at a reasonably low xover point, safely and reliably (autostarting for eg), I might be inspired to take it up again.
To be honest, the thought of sitting mere metres from a source of MW with enough power to traverse a city, was unnerving. Unfortunately, I decided to move on.
If someone were to find a way though, and could get good SPL's at a reasonably low xover point, safely and reliably (autostarting for eg), I might be inspired to take it up again.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.