Messages

46

ID and Translation Requests / 4020kHz music station, pirate?

« on: December 02, 2019, 1531 UTC »

Tuning around last night around 10pm cst. Don't recall any stations on this frequency but know of pirates using frequencies nearby recently. Not sure what the music was, sounded a bit like rock that I couldn't identify but lots of fading.

47

The RF Workbench / Re: A 25W experimental transmitter for medium wave (AM)

« on: November 25, 2019, 0826 UTC »

This is a great thread, hooked me in right away.

Ok yes Kage, good stuff on your TX. The IRF640 is quite a forgiving Fet! I drive it with the old LuLu fave, 8 volts into the 74HC240 with a good 40 watts out @ 24 volts to the PA. Source for the 74HC240 is the usual DDS module, AD9850.
Ok yes, my modulator uses Class A also, which heats a small room LOL... but it sounds great! The audio driver is the LM 3886..its the biz. Working on the PWM version right now which will be on the air soon. Have worked it on MW and SW with great results.

Redhat..that is a cool layout man..love it. Neat. Cheers.

I used the LM3875 for a similar purpose. Was going to drive the whole transmitter off of the output at half rail voltage like the smaller shortwave transmitters people build do but found the chip became unstable doing so and couldn't see the load properly so it would kick into protection. Ended up using it as a driver chip instead into some beefy current transistors to hang the transmitter voltage on for modulation and that worked well. My main issue was that rail to rail voltage was somewhere up at 40+ volts (15-20vdc at carrier minus losses in transistor diode junctions) which is simply too high for most OP Amps as drivers, but the Texas Instruments LM38xx series can handle those voltages fine and act like a high powered OP Amp to buffer audio into the final modulator transistors.
I wonder how many of us who have used them for this purpose happened to get the free sample parts from TI?
Definitely overkill using such a chip for a modulator considering they were designed for high end HIFI amplification, but I just happened to have a handful laying around.
Anyway, didn't mean to derail the thread.

48

The RF Workbench / Re: A 25W experimental transmitter for medium wave (AM)

« on: November 22, 2019, 1536 UTC »

Medium wave is so easy to get on with minimal parts these days yet somehow I still over complicate my designs because I end up working around bin parts I happen to have on hand instead of purchasing what I need. Still happy with my 25 watt AM TX though that is class E utilizing a single IRF640 and the commonly found 3 chip PLL frequency generator circuit. That FET requires quite a bit more drive oomph though so I ended up using a totem pole bipolar circuit ahead of it, also didn't have proper fet driver chips on hand.
Then I went and got weird and modulated it with series class A instead of D and of course the heat sink for the modulator is the size of the rest of the transmitter including the PA that runs cool on a tiny slab lol.
Oh well, it gets the job done.
Your design is nice and clean, definitely a pro level build. Too bad I didn't see this a year ago when I started work on building my TX.

PS: I was wondering what I was going to use my set of 4 T130-2 cores for that didn't work out the way I intended for an 11m EFHW antenna, now you're making me want to fool around with another transmitter build or maybe linear PA for something to use them in

49

10/11 meters / Re: 27.385 Mhz

« on: October 30, 2019, 1656 UTC »

Same here in the midwest. Wish I had SSB on my transceiver but nice hearing some skip again especially after I got my antenna back up.

50

Equipment / Re: Antennae Maxims

« on: October 27, 2019, 2359 UTC »

4. You are an antenna

My antenna erection sure turned me into part of one the other night from those wonderful end fed standing waves.
Now what about the Gooch?

51

General Radio Discussion / Re: Having a radio station and lacking interest

« on: October 25, 2019, 0752 UTC »

Yeah I know TL;DR. I was just ranting. Just angry about the solar cycle I guess

52

General Radio Discussion / Having a radio station and lacking interest

« on: October 25, 2019, 0727 UTC »

Ever since I was a kid I wanted to be a radio DJ. I built small FM transmitters as a teen starting out with rigging in audio to the internals of another FM radio and using the local oscillator to rebroadcast a few houses down from mine. Grew up and pirated FM with higher power, got up to 10 watts or so on FM and a 40' tower. Covered most of my town. Had friends come over and we'd do shows and had the local Taco Bell guy a mile away call in just to hear his voice echo over the cell phone and his radio.

I got paranoid after a while and part of that was my own doing trying to get the word out and I was always getting high and/or drunk at the time. Had a bad cough syrup habit but that's another story. Anyway.. after learning not only did my friends know about our FM station.. the whole damn town knew which surprised me. Doesn't help it is a 11k population so word gets around, but not in the way I wished.

So I switched up, went to AM because my strength is electronics and having fun with electronics. Got on medium wave and still have it setup for the occasional power switch flip to start broadcasting. I'm saving it for winter though when conditions are best and FCC is stranded.

Thing is the lack of interest now. Radio in general is dying. Any of us who deny that are clinging to memories. I sure know I cling to those FM days in the late 90s to 2008 or so. I had a lot of fun then and we had a ton of listeners. I had a phone patch, aka: cell phone with cord spliced into the mixer, but hey.. it worked!
My point here is the medium itself is dying because in general most broadcasts on AM/FM are talk radio and music, and not good stuff. It's all syndicated garbage, no local calls, no requests.

Us pirates aren't doing so great either in my opinion and I know I will take hate for this but I tune into shortwave on 69xxkHz and it's always the same boring music I can get on FM radio, the DJs don't talk much and some of them resort to computerized voicing.
What happened to broadcasting with actual talk, maybe a friend or co-host? No offense to those who don't, I believe everyone with the ability should get on the air, but the programming has become stale lets face it. We get out our tablet computers or phone to see what song is playing if we don't know just to type up a reception report. Yeah hooray you emitted RF and we could hear it. There are some really good pirates still around and I won't name names, but they can carry a program and often blast a radio. So if you got low power make that programming count or else you just become another log note.

Sorry I don't mean to sound like a dick. I just remember pirates of the 90s and so, there was more effort rather than running a play list. I say this because I realized that is exactly what I was doing with my AM radio station on 1710kHz. Wondering why I didn't get more listeners, then sat back and thought... would I continue listening to this just because it's on the radio? 

I'm just wondering what is the way forward? I seem to be going backward with AM now instead of FM broadcast band pirating simply because it's literally getting to the point where FM radio has killed itself and no one wants to listen to Hotel California one more time without shooting their brains out. At least AM offers more fun, which is so damn backward when you think about it. What has become of all this?

53

Equipment / Re: 9:1 or 49:1 unun for end-fed long/random wire?

« on: October 16, 2019, 1404 UTC »

I'll get a 9:1 unun,and use a suggested random wire length to avoid half-wave and it's multiples then,that sounds like the best things I can get out of this setup.
I was only thinking about the 49:1 due to the random high impedance spikes a random wire can produce,and I tought it would be easier to match a super low impedance than a too high one.
Actually,the old one did a fairly decent job for me.Especially on the higher bands,where the 30m wire was at least 2x wavelength.It is true that it has some directivity,it may be deaf in some directions,and it may perform really well in others.
I don't want to live with this one antenna forever,but right now this should be fastest and easiest way to get on the air with somewhat decent signals.
Thank you for everyone,I can't wait to install it and see the results 

If you have a facebook account check out the group EndFedHalfWaveAntennas. Don't need to be a ham to join. They focus mostly on the non-resonant type EFHW transformer and antenna designs and are very active.

54

Equipment / Re: 9:1 or 49:1 unun for end-fed long/random wire?

« on: October 16, 2019, 0249 UTC »

The "9:1 UNUN" are for random length wire antennas fed at the end. 49:1 or other high ratio transformers are for resonant "cut to frequency" antennas like the traditional zepp/fuchs antenna.

Generally the 9:1 has far more loss as the transformer/core takes on heat to make the non-resonant antenna be of any use across wide bandwidths and are often deaf across some range of frequencies because of the nature of a random length of wire. A tuner will help with that but introduces even more losses. Worse yet people who know no better will think they are performing great because they always show the user a good SWR, but remember even a dummy load shows good SWR 
They have the benefit of being quick to throw up in the air and will get some signal in/out but are inefficient compared to resonant single/mono band antennas.

If you want a high performance monoband EFHW antenna you should always go with the 49:1 UNUN and cut the aerial to half-wave resonance and almost all your power into it gets out since it acts exactly as a traditional dipole, with the exception of being fed at the end.
The ratio doesn't need to be 49:1 2,400 ohm either, other ratios will transform to other impedance. Generally an EFHW will be in the range of 2,000 to 5,000 ohms at the very end of the dipole when resonant.
I usually go with a 3.2k transformation wire winding ratio of 8:1 which is a final impedance conversion of 64:1 (50ohm * 64 = 3.2k ohm). Antenna diameter and height above ground makes a difference here. Generally the fatter the radiator the lower the final impedance at the end. Thin wires might need as high as a 81:1 out at 4k ohm. Remember the large ratio number is the coil winding ratio squared, so for a 9:1 wire winding you end up with a 81:1 impedance conversion, not to be confused with a 9:1 UNUN for non-resonant types that convert to ~450 ohm.

Whew think I typed that all correct. Check out http://www.aa5tb.com/efha.html for info on the traditional high performance resonant EFWH.
For random wire non-resonant types plenty of plans and examples exist online but keep in mind there is no free lunch as they say, being non-resonant and wideband means they might perform as good as a wet noodle on some bands and somewhat acceptable on others, but any wire in the air is better than nothing.

55

Equipment / Re: To weep hole or not to? That is the question..

« on: October 12, 2019, 2227 UTC »

Any penetration on top of a "weatherproof" box is a potential failure point.
If you decide to go with a weep hole, make sure it is small enough to prevent entry of yellow jackets, spiders, etc.

Looks like I typed too soon. After a little reading it sounds like a weep hole is actually required because a perfectly sealed box will build up condensation. After pushing the top of my old match box into a glass of water there was no leak. Looks like the few tablespoons of water in it built up from condensation alone over the seasons since I didn't build it with a bottom weep hole.

Now the question is how large of a hole? My match unit is small since I am using a toroid this time instead of air coil so guessing it won't need to be any larger than a coffee straw opening, small enough to keep bugs out for sure. Wonder if that might be too small?

56

Equipment / To weep hole or not to? That is the question..

« on: October 12, 2019, 2103 UTC »

Replacing my old EFHW antenna match box I built a few years ago. It progressively climbed in SWR slowly over time until it became unusable.
Took down the vertical today and disconnected the box, opened it up and you guessed it.. water came gushing out.
Thought for sure I had that thing waterproofed well with RTV silicone but the antenna mount bolt is on top so rain ran down the antenna pole on top of that bolt and nut and somehow worked its way through the bolt threads into the box even being on there as snug as I could twist along with sealant.

So would it be advisable to make my new box waterproof with some other method/sealant or have a bottom weep hole to let water out?
This raises another issue in that humidity could get through the weep hole causing its own damage so not sure which is better practice in proofing it.
Luckily my coax didn't get water down it, or not enough to damage it but I definitely checked it with a dummy and meter to make sure and crossed my fingers.
I'm worried if the weep hole is at the bottom which is where my coax will connect that it will let water out which can then drip towards the coax connection. Thinking of maybe gluing a tiny tube into the hole so it runs past the connector

Ugh Midwest weather season is brutal on antennas 

57

Huh? / Re: Rip Taylor is dead.

« on: October 07, 2019, 0405 UTC »

RIP Taylor

58

The RF Workbench / Re: Stretchyman 40w GaN TX is sick

« on: October 07, 2019, 0354 UTC »

And this is why I don't sell my old homemade transmitters to people. I've been asked before but always feared something like this would happen and I don't even build on a professional level like stretchy does. Oh those multiple pops... sure someone wasn't making microwaved popcorn in the other room? I could use some reading this thread.

59

Huh? / Old TV reception phenomenon

« on: September 27, 2019, 1057 UTC »

Many TV repairmen from times past have a story many of them have experienced along with some ordinary TV viewers while alone where when tuning the rabbit ears and touching the antenna just right they would see the usual signals of distant stations go out of sync.

Once in a great while through the rolling signals they would see a fuzzy or oddly distorted colored live video of themselves, or even childhood memories or family events that would roll up the screen only for a moment that could never quite be tuned in before it would vanish to static. Only problem is there were never any video cameras or recorders in the room and the image seemed to come from a position in the room or past event where no camera could possibly be.

Most people who have noticed this phenomenon would refuse to tell anyone about it in fear others would think they've gone crazy and often couldn't shake the creepy feeling that something unexplainable is watching them while they watch it.

60

Equipment / The greatest radio ever, teh Bell Howell 9 band prise

« on: September 23, 2019, 2146 UTC »

I spelled teh on purpose.
Yeah here is all the glory of this $1 radio I just bought at the thrift store. It has world band, so... You know how radios are, if it has shortwave you have to buy it because we're suckers.

Well this little goofball of a radio covers medium wave from 530 to 1610kHz or so, talk about a killer for me. I listen to the X band AM mostly. To make things a little more gentle though it does have a barn door IF stage which makes AM listening like listening to FM if you don't mind going out into the deep woods to hear a broadcast far away from your local 50kw. It's easy to modify though to cover up to 1710kHz as I found by a simple adjustment on the 4 gang capacitor variable, but don't expect the readout to be right of course.

FM is even better, it actually performs as good as my breadboard FM radios. It almost has the ability to have selectivity if you hold it just right.

Oh and did I mention shortwave? This has the feature but I think they forgot to enable it. I picked up Havana and oooooh weeeee!

Okay I'm giving this little radio a harsh time. It's cute, performs okay for camping, and for being a radio that was a gift if you purchase other crap prizes on TV then voila. It at least has no birdies and after opening it up and damn near breaking the antenna connection from only removing the cover that is held together by... get this... ONE SCREW, and clips, I adjusted the 455kc oscillator and touched up the 4 screw tuning capacitor for peak. It's on par with dollar store gizmos and well it had shortwave... who will let a cheap radio with shortwave sit around for $1? Gumballs cost that much these days. I say we replace gumballs with shortwave radios! 



BTW that arrow pointing to that screw, that is literally the ONLY screw holding the thing together, it's all plastic clips  besides that one real loooong screw lol.