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.

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.


Messages - redhat

Pages: 1 ... 29 30 31 32 33 34 35 36 [37] 38 39 40 41 42 43 44 45 ... 106
541
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

542
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

543
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

544
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

545
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

546
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

547
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

548
North American Shortwave Pirate / Re: X-FM 4095 AM from 4085 AM 0127 UTC 17 Feb 2019
« on: February 17, 2019, 0206 UTC »
Quote from: MrMomB (LED) on February 17, 2019, 0159 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

549
Equipment / Re: RA0SMS vs PA0RDT Active Mini Whip - RA0SMS is Very Noisy - Why?
« on: February 15, 2019, 1103 UTC »
If the schematic I'm looking at is correct, there are only two active devices in the antenna, a dual gate mosfet, and a bipolar transistor.  The mosfet does a voltage to current conversion, and the bipolar transistor is used to drive the line.  Both devices should be biased as class A to minimize distortion.  If the bias is incorrect, or if the front end mosfet is damaged somehow, odd behavior, images, or other distortion products can be present, especially in the presence of strong RF or AC fields.

+-RH

550
General Radio Discussion / Re: Plate pirates target ham radio operators in Corner Brook
« on: February 14, 2019, 1412 UTC »
Quote from: Pigmeat on February 14, 2019, 1406 UTC
It's not surprising. Mike Hamar straightens up just enough to make Possum Lake's police force and things start disappearing. The son of Bambi Bazooms goes bad again.

They don't have these problems in Port Asbestos.

"I'm a man, and I can change, if I have to, I guess..."

+-RH

551
QSLs Received / Re: XFM QSL 2x
« on: February 12, 2019, 1748 UTC »
I just noticed that the date on the Thanksgiving QSL is incorrect.  I will have corrected once sent out in a few days.

...oops

+-RH

552
Huh? / Re: Green New Deal
« on: February 12, 2019, 1221 UTC »
Quote
We tried to make him ride in the back with Al's pet goat, but the goat wanted nothing to do with him. We usually ended up tying him to the roof.

Who, Ernie, or the goat?

+-RH

553
General Radio Discussion / Border blasters and goat glands, an unlikely american radio story
« on: February 09, 2019, 2244 UTC »
The professor ran across this article a few weeks ago.  Its a good one!

http://www.ominous-valve.com/xerf.html?fbclid=IwAR2y_g_1mYT2MSGxP625erNnBSZhpspc2l3JtrJb3hSvqGUtmh0rJoomobY

+-RH

554
Peskies / UNID 6990KHz LSB 2-9-2019 0840z
« on: February 09, 2019, 0854 UTC »
On with OM doing long mic checks, then very long repetition of the word 'annita' very strong, pushing S9+10dB

+-RH

555
Equipment / Re: The SW200 LPAM, Part #15, Amateur Radio AM, Audio Processor.
« on: January 28, 2019, 0251 UTC »
Quote from: Kage on January 28, 2019, 0027 UTC
On a funny side note, I have heard of stations using their retired analog processors just for the studio talent since it's real-time and let them hear that "radio sound" in their headphones while using the new digital processor at the transmit end so to trick the DJs and not anger them with the delayed live processed audio ;D

In the industry this is known as a 'talent processor' and became more common when HD arrived 15 or so years ago.  Even the analog portion of an HD signal is delayed by 8 seconds or so to match the coding and buffering delays present in the HD chain.  I've worked around the processor latency problem by monitoring off air for the control room speakers, but whenever a mic is turned on, a macro sets the monitor feed to program.  Dirty but it gets the job done.

+-RH

Pages: 1 ... 29 30 31 32 33 34 35 36 [37] 38 39 40 41 42 43 44 45 ... 106