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 permissable 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 - KaySeeks

Pages: 1 ... 71 72 73 74 75 76 77 78 [79] 80 81 82 83
Equipment / Re: The best undercover fm antenna on the market
« on: January 24, 2018, 2102 UTC »
Vertical dipoles do well on FM.

Pretty sure that most commercial FM broadcast in the US is vertically polarized anyway so conforming to that makes sense if you want to attract listeners.

Back "in the day", I think I used an antenna that was a combination of horizontally and vertically polarized (because that's what I had available) with much, much less than 1 Watt and I think the range was about 1.5-2 miles (~2.5-3 km) but the TX was on a hill. Your mileage may vary, as they say.

And, the answer is YES. But... (always there is a "but")

Yes, there always is a "but..." because, if you have been around enough, you will know that there always is a trade off.

As some have noted, the Rds of the the IRF520 is approximately half that of the IRF510. That improvement will not come without a price and that price is speed - the input and output capacitance is approximately double that of the IRF510 and it is slower as a result. That may or may not affect you.

Similarly, the IRF620 has a slightly higher Rds than the IRF510 and IRF520, but it can sustain twice the Vds of the IRF510 and IRF520 and that trade off means that the input and output capacitances increase (thus it is slower), but not to the same degree as the IRF520. That may or may not affect you.

Now from the "more than you wanted to know" department:

I have not decapped any of these to look at the insides but I'm fairly comfortable in saying that these probably share a common die layout and they just make metal mask or wirebonding options to add or subtract elements. The doubling of the Vds probably means that they just stack the equivalent of two IRF510s in series into the same package (essentially), thus doubling the sustaining voltage. Similarly, to halve the Rds, they essentially parallel two IRF510s but that of course means that the input and output capacitances double. This is the trade off I spoke of. There is no such thing as a "free lunch" in this sort of configuration.

Why would they do it this way? It's cheaper to manufacture in this manner and you cut product development costs by essentially spawning multiple products from one common element. There are customers that want more Vds capability than the IRF510, there are others that need more current capability than the IRF510; this gives them the option of addressing all those markets with less engineering activity.

I fast forwarded through the video but as an ADS user, I'm pretty sure that he hasn't included full parasitics, based upon his schematic at the end (which I post a link to below). He has some transistor parasitics and the microstrip model includes some as well but it isn't complete, e.g., bondwire parasitics. That will have some effect.


In addition, I suggest that you want to look here for info from a guy that has built a lot of QRP Class D, E and F stuff.

I quote from MOSFET Class D/E/F amplifiers - Part 2, page 4, bottom of the second column and leading onto the third column: 

The   second   point   with   the   above equations is how the switching losses are  frequency  dependent,  due  to  the  term "2fo." This is why most Class E circuits on  the  internet  are  only  for  160M  or  80M, as even a sloppy job of designing the circuit and using a sinewave drive (equations) will   still   yield   high efficiency...This  is  also  why  those  scaling  these amplifiers for 20M have had disappointing  results,  as  the  switching  power  losses double as you double the operating frequency.

... next week, when Pai hopes to convene the scheduled January 30 meeting and start rolling back his Democratic predecessorís Net Neutrality policy.

Seems to me that the tom foolery never stopped.

Pretty strong in Western NY State too, of course. I have the frequency as ~6924.98 KHz, for what it's worth.

0014 - Jimmi Hendrix song
0020 - quick SSTV image
0021 - All Along the Watchtower. Down to SIO 343. Background noise is picking up.
0025 - More JH.
0028 - quick SSTV, into more JH. Signal slowing fading.
0037 - more SSTV
0038 - "PeeWee" CW ID over the SSTV image
0049 - off

FM Free Radio / Re: FM Pirate Stations in Chicago?
« on: January 20, 2018, 0157 UTC »
the FCC office is located 8 mile southeast of me. (snip) There is a bunch of antennas on the roof. (snip) Being this close, I wouldn't dare do any FM pirating.

Let us know when their trucks aren't in the parking lot though, OK?  :D

The RF Workbench / Re: Any DDS 200 watt AM Transmitters or kits
« on: January 19, 2018, 0318 UTC »
Another thing you can see when you peer closely at the carrier of some of these rigs is FMing....
...If you watch the carrier while the station is on the air, you'll observe two things. When there's no modulation, the carrier is narrow, as you'd expect. When there's modulation, it becomes extremely wide and variable, due to the carrier frequency moving around with the audio modulation.

I do a bit of listening to Dutch and Greek MW pirates for entertainment.

Most of them have stable transmitters (stable enough) without a hint of major issues. Some are horrible. Some clearly have some sort of steady-ish low-frequency AM or FM on them, making the carrier wide. Some have some pretty serious FM issues. If my receiver's synchronous detector comes out of lock every time your transmitter exceeds 0% modulation (i.e., anything other than a dead carrier), then you might just have a problem with your transmitter.

I wonder what became of that Dumb Bunny?

He's back and using a computerized voice.  ;D

Another alternative is the good-old-handy-dandy CW IDs. PeeWee style....

Utility / Re: 4XZ Israeli Navy 4331 kHz 0500 UTC 16 Jan 2018
« on: January 18, 2018, 0022 UTC »
From what I understand, what I captured is the signal in "idling mode" and that it occasionally sends classic number station-style five number groups.

Correct. I have heard both but most of the time it is "idling".

Huh? / Death
« on: January 17, 2018, 2343 UTC »
There sure is a lot of death going on here on this board. Maybe we should change the name?

I get the idea, you don't want to use you real voice. But maybe get someone else to record it? Disguise your voice?

Voice scrambling is an option, though that has its limits too. Too much scrambling will be similarly unintelligible.
This is not an endorsement. I have never used these but here are some ideas:

In lieu of that, operators using a computerized voice should repeat IDs several times, slowly. It gets tedious if you try to use it for all spoken words but it helps when it comes to IDs.

The RF Workbench / Re: A 500 watt Class E amp
« on: January 15, 2018, 2105 UTC »
Stupid stuff happens no matter how good the protection system is, but this should take care of the majority of failures.

I find that I spend as much or more time on protection circuitry and thinking through fault issues than I do on the intended function.

Longwave Loggings / Re: Take Off to the Great White North
« on: January 15, 2018, 2059 UTC »
I once had a girlfriend who was from the far S.W. corner of Minnesota... I'd advise you to stay far away from those beacons. The women are good looking but they all sound the same.

Interesting that the women all (seemingly) must have spoken in CW. Did any of them have a better fist than the other? Was one better at straight key than the others? It's OK to tell me these private details. No one else is here reading them.

General Radio Discussion / Re: Propagation
« on: January 05, 2018, 2148 UTC »
There's a propagation section to this forum. I suggest that this go there.

Pages: 1 ... 71 72 73 74 75 76 77 78 [79] 80 81 82 83

Item image   Communications Receivers - Principles & Design by Ulrich L. Rohde and TTN Bucher