541
Propagation / Re: Solar Activity, or lack thereof
« on: March 02, 2019, 2031 UTC »
Time to break out the longwave transmitter, apparently.
+-RH
+-RH
Shortwave Pirate Radio In North America And Around The World, And Other Signals That Go Bump In The Night
We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations.
Always consult with the appropriate authorities if you have questions concerning what is permissible in your locale.
Anyone want to take them to court?
+-RH
More bang for the buck (or watt) as they say...
+-RH
Did you consider that many 'part 15' stations are run by former pirates, busted or not? Many folks have a brush or two with HF, and perhaps the station in question has as well.
It is also entirely possible that someone else has used that name for their station, and serendipitously there is a part 15 station using the same name. There currently is no Wiki article for this station, maybe you should make a page for them and 'set the record straight'...
+-RH
Send me some reception details and a postal address and I'll send you one.
Thanks!
+-RH
Show Posts
This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.
542
The RF Workbench / Re: Beginner class D design
« on: March 01, 2019, 0411 UTC »
I would leave a small amount of R in series with the gates for two reasons;
1. it helps dampen any tendency of the network and other strays to ring (Better drive waveforms).
2. should a transistor failure occur, it prevents the output of the driver from going complete short circuit. I have lost a few drivers due to transistor failure, No more once a little R was added. I'm using three 10 ohm 1206 resistor in parallel to make a wider low L resistor, and also spread the dissipation.
+-RH
1. it helps dampen any tendency of the network and other strays to ring (Better drive waveforms).
2. should a transistor failure occur, it prevents the output of the driver from going complete short circuit. I have lost a few drivers due to transistor failure, No more once a little R was added. I'm using three 10 ohm 1206 resistor in parallel to make a wider low L resistor, and also spread the dissipation.
+-RH
543
General Radio Discussion / Re: Six Things Broadcasters Should Know about the PIRATE act
« on: February 27, 2019, 0011 UTC »The Eighth Amendment to the United States Constitution states: “Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted.” This amendment prohibits the federal government from imposing unduly harsh penalties on criminal defendants, either as the price for obtaining pretrial release or as punishment for crime after conviction.
Anyone want to take them to court?
+-RH
544
General Radio Discussion / Re: Six Things Broadcasters Should Know about the PIRATE act
« on: February 26, 2019, 2208 UTC »So, basically what they're saying in the bill is that these stricter measures only apply to AM and FM pirates? I always liked HF better anyway...
More bang for the buck (or watt) as they say...
+-RH
545
The RF Workbench / Re: Beginner class D design
« on: February 26, 2019, 2100 UTC »
40% on, 60% off. The idea is that the drivers are better at turning the fets on than off, due to miller and reverse transfer capacity in the mosfets. As such, the duty cycle will be stretched, and if not compensated for, cross conduction occurs in which for a very short time, there is a dead short across the PA voltage source which destroys the transistors. The way around it is to introduce dead time. I use the circuit out of a Nautel NX-50 PA module to accomplish this. The idea is that two drive signals are compared, one normal, and one delayed by a fixed amount. The two signals are compared, one by NOR, and one by AND. This produces two signals with a fixed amount of dead time, which prevents cross conduction. Some experimentation will be necessary to find out what amount of dead time produces best efficiency, but 10-20nS should work. I believe I used the DS1100z-40 in this application and its working well.
The reason the NCP driver has two output pins is to allow you to tailer the gate resistor values for optimum rise and fall times, usually using a smaller resistor for the low side.
Whenever checking your input drive waveforms, be sure to look at them with a dual channel scope so you can verify that overlap is not occurring (phase A CH1, phase B CH2).
+-RH
The reason the NCP driver has two output pins is to allow you to tailer the gate resistor values for optimum rise and fall times, usually using a smaller resistor for the low side.
Whenever checking your input drive waveforms, be sure to look at them with a dual channel scope so you can verify that overlap is not occurring (phase A CH1, phase B CH2).
+-RH
546
General Radio Discussion / Re: Minnesota to decommission NDBs starting in 2019
« on: February 26, 2019, 1539 UTC »
All the more reason to have your own cesium beam clock, I suppose.
...I have always wanted one!
+-RH
...I have always wanted one!
+-RH
547
The RF Workbench / Re: Beginner class D design
« on: February 26, 2019, 0526 UTC »
It is theoretically possible, however, getting conventional devices to switch that fast (100x carrier frequency to achieve 99% modulation) is almost impossible.
+-RH
+-RH
548
The RF Workbench / Re: Beginner class D design
« on: February 25, 2019, 1743 UTC »
I'm using IXDN614 drivers. The waveforms looked better with these drivers than the '4452's. 15-20V should be fine, I think your bigger problem is the overlap in the PA due to 50% duty cycle drive.
I've also had problems with some RF slugs indicating greater than 100% efficiency when input/output power is calculated. This is more noticeable with higher power slugs when measuring at less than 75% full scale, as the linearity deteriorates at the lower half of the scale.
+-RH
I've also had problems with some RF slugs indicating greater than 100% efficiency when input/output power is calculated. This is more noticeable with higher power slugs when measuring at less than 75% full scale, as the linearity deteriorates at the lower half of the scale.
+-RH
549
The RF Workbench / Re: Beginner class D design
« on: February 24, 2019, 2150 UTC »
How are you introducing 'dead time' into the phases of the RF drive? At 7MHz, you will need about 40% duty cycle on each phase to prevent cross conduction (shoot through). This could be one of the reasons for the relatively poor efficiency on 7 MHz.
+-RH
+-RH
550
General Radio Discussion / Re: hfundergrounds wiki pirate list error
« on: February 23, 2019, 0231 UTC »Quote
Also, I haven't examined the list closely but am curious how many part 15 stations you might have listed there. Do you not distinguish between legal unlicensed operators and pirates?
Did you consider that many 'part 15' stations are run by former pirates, busted or not? Many folks have a brush or two with HF, and perhaps the station in question has as well.
It is also entirely possible that someone else has used that name for their station, and serendipitously there is a part 15 station using the same name. There currently is no Wiki article for this station, maybe you should make a page for them and 'set the record straight'...
+-RH
551
The RF Workbench / Re: Beginner class D design
« on: February 19, 2019, 1800 UTC »
I've tried both 43 and 61 material ferrites, not much difference I could note, although with your higher harmonic power I could see some difference in this application, 43 may be better.
I would try something similar to this, wound with coax, shield grounded only on the load end http://www.communication-concepts.com/rf2000-transformer/
+-RH
I would try something similar to this, wound with coax, shield grounded only on the load end http://www.communication-concepts.com/rf2000-transformer/
+-RH
552
The RF Workbench / Re: Beginner class D design
« on: February 19, 2019, 1630 UTC »
In order to get clean switching, you really need to hit the gates of SiC fets with 15V or greater. 18-20V seems about optimal, any less and RDSon comes up pretty quick and will deteriorate your efficiency and cause excessive heating.
Also, are your power measurements before or after the lowpass filter? Without a filter, power is likely to read substantially higher due to large amounts of harmonics, which on conventional class D is going to be quite high.
Not sure what your output transformer looks like, but hopefully the primary is made out of large-ish copper tuning to reduce Q and therefore excessive ringing due to circuit strays. I would try and do something similar to what is found on solid state VHF PA's where some semirigid line is bent into U shapes and the shields soldered together. This will also help maintain impedances and keep ringing down.
+-RH
Also, are your power measurements before or after the lowpass filter? Without a filter, power is likely to read substantially higher due to large amounts of harmonics, which on conventional class D is going to be quite high.
Not sure what your output transformer looks like, but hopefully the primary is made out of large-ish copper tuning to reduce Q and therefore excessive ringing due to circuit strays. I would try and do something similar to what is found on solid state VHF PA's where some semirigid line is bent into U shapes and the shields soldered together. This will also help maintain impedances and keep ringing down.
+-RH
553
General Radio Discussion / Re: Rebuilding a Piece of the First Digital Voice Scrambler
« on: February 19, 2019, 0146 UTC »
You can keep the Tang, but if you've got a few greenies laying around I'll trade ya 
+-RH
+-RH
554
QSLs Received / Re: XFM Christmas Show eQSL
« on: February 17, 2019, 1249 UTC »
And with that, 2018 is 'in the can'. We issued 152 QSL's for 9 shows.
Thank you all for your listenership, and we'll see you at the next show!
+-RH
Thank you all for your listenership, and we'll see you at the next show!
+-RH
555
North American Shortwave Pirate / Re: X-FM 4095 AM from 4085 AM 0127 UTC 17 Feb 2019
« on: February 17, 2019, 0206 UTC »01:53 Nine Inch Nails
Hi from Niagara Falls NY
Have you a S-6/7 tonight
How do I sign up for the disk?
Send me some reception details and a postal address and I'll send you one.
Thanks!
+-RH
