Topics

1

General Radio Discussion / Empty HF frequency band for emergency coms

« on: January 17, 2021, 2208 UTC »

First of all, I'm not sure if I'm in the right section, so feel free to move this.

OK, so I am preparing for a societal collapse I purchased some HF ham radio transceivers. I am on my way to getting my license, however, I will need to use this as a means of communication for some people without licenses.

Assuming the system had collapsed, what HF frequency range should I plan to use that doesn't contain any military or other communications currently? Is there an empty range you could give me? A no mans land. I'm looking for something in the range 3.5 - 10 MHz cause I need to cover a 100 mile distance. My calculations show that 5 - 6 MHz would be the best choice also taking into account those people's lot size. Don't tell me just use ham anyway cause it'll be jammed.

Of course there's the pirate frequencies, but a range is something I'm looking for, not a specific frequency.

Understand that this is only to be used during emergency, so I just want to make sure I'm not interfering with anyone.

Thanks

2

Equipment / Would this dual antenna design work?

« on: August 04, 2020, 1441 UTC »

So at some point in the not too distant future, I'm going to purchase a new property with more space. I want to put up an antenna system with two antennas. One for shortwave and one for mediumwave (both for TXing and RXing). I want the minimum number of towers/supports for cost and size. The shortwave will be an inverted V and the mediumwave, inverted L. I want to insulate the base of the tower and drive it for mediumwave and for shortwave, I want to attach an inverted V to the top of the driven tower. Will this work or do I need another tower to support the V so I don't get interference or other problems? I won't TX on both at the same time if that helps.

Maybe you have a better idea?

(Note that the inverted V is not parallel with the L; it is perpendicular. It just looks like that cause I can't draw 3D.)
Here is a diagram:

3

Equipment / DRM pirates

« on: July 23, 2020, 0244 UTC »

I've been looking into DRM recently and I found these products which seem more like something a pirate might use:
http://www.nti-online.de/edrg30.htm
http://www.nti-online.de/edrg30usb.htm

I am a bit confused about the process though. It seems to me like this may actually just be an SSB transmitter cause it looks like the PC is the source of the actual DRM signal. Is that how most DRM systems work, or do the professional transmitters generate the DRM inside them?
Are most DRM signals actually an SSB signal rather than AM? Could you generate the DRM on a PC and just feed that into an old fashioned AM transmitter? Yes, it would be less efficient, but does it work?

I am trying to decide what I'm going to do with my next shortwave transmitter. Do you think a super wide 15 kHz analog SSB signal made with an SDR would be better than DRM?

4

Equipment / Higher highs and lower lows on MW TX antenna

« on: July 13, 2020, 0817 UTC »

Compared with a MW broadcasting station, my antenna produces higher peaks and lower troughs at all times and all listening locations. Why is this? Does this have to do with angle of radiation? It is interesting that during the peaks, it's actually better than a number of MW stations at the same distance, but it dips so deep that it can't be heard sometimes. Would making the vertical section longer improve this? I always thought that angle of radiation simply has to do with the distance covered, but maybe it's more than that. If it's not angle of radiation then what is it?

5

General Radio Discussion / Why is there a gap between 7 MHz and 13 MHz?

« on: June 19, 2020, 2100 UTC »

When looking at the pirate radio logs here as well as the list... https://www.hfunderground.com/wiki/List_of_Pirate_Radio_Frequencies

You can see there is nothing noted in this range. I can understand why much higher frequencies are not used cause they are not very reliable. But in this range, I would expect easier antenna installation with a higher efficiency at lower heights. Also much shorter for smaller lots and increased daytime range. Maybe the doughnut is too big (bad local)? By doughnut, I mean the empty area between the groundwave and the skip zone. Is there just no space for it? I don't know this band too well.

6

Bacon, BBQ, Beef, And More / Frankie's Free Range Meat

« on: June 19, 2020, 1923 UTC »

I am not affiliated with them, but I know the guy cause he has a youtube channel about nutrition and about some conspiracies I don't necessarily agree with, but a good guy. Hopefully, you don't mind this advertisement Chris
With the current beef supply limits in the US, I figured it would be good to let people know about this source. They sell in bulk at some of the cheapest prices online. All grass fed mostly from NY farms or Australia. He complains about not making much money from his low costs (and it's not just a marketing ploy). In addition, most everything is sourced directly, so there should be no supply chain issues unless too many people purchase.

https://frankiesfreerangemeat.com/

7

General Radio Discussion / Pirate radio laws outside the US

« on: June 05, 2020, 0405 UTC »

Most pirates are in the five eyes countries. What are the rules like in other countries? Like Europe and Asia mostly. I know China would be pretty harsh, but what about the other Asian countries? Is anyone here from a European country and can explain what the scene is like there? (I am not necessarily talking about FM, but rather SW and MW.) In Asia, the countries I'm not sure about are Vietnam, Thailand, Laos. Clearly China would be insane, but these other countries aren't fully communist, so I wonder. I tried using google translate to find sites in other countries, but nothing obvious comes up. Maybe it's just non-existent and unexpected and therefor safer?
Not that I plan on doing it.

8

SDR - Software Defined Radio / TDoA_service - Hams or FCC?

« on: June 01, 2020, 0304 UTC »

Recently I was listening to a pirate broadcast and this user called "TDoA_service" was entering some SDRs and set to the same frequency of the pirate station. Is this something that pirates typically experience from curious ham operators or is this the FCC?

9

Equipment / Outdoor tuner or switch

« on: May 27, 2020, 0411 UTC »

I'm trying to figure out how I'm going to make my inverted L antenna switchable. This may seem simple, but let me elaborate.
My antenna as is, is just an L with a shunt coil to ground. This allows me to operate very well on only one frequency +-20kHz. Now I want to make another system to make this antenna usable on shortwave with a tuner.

I could just remove the shunt and make a full fledged L or Pi network tuner outdoors. This will probably be very time consuming with the weather proofing, etc. So basically what I think I want to do is put a switch outside to switch out the inductor and then use a normal ham tuner indoors. I know I could probably just re-tune the outdoor shunt inductor, but this will be a hassle to get it right with the tuner indoors also hooked up to it.

10

Propagation / Poor conditions (noob)

« on: January 13, 2020, 0402 UTC »

Hey,

I'm not a noob to radio, but propagation (other than the more obvious non-planetary/solar noise stuff) has not been something I really understand very well. I do understand the solar cycles to some extent, but I am curious about the more frequent changes in propagation that can be seen on a daily or weekly basis. What is the biggest determining factor in that?

I noticed the last couple days that the propagation has been some of the worst I've seen since I started listening about a year and a half ago. What is causing this and when is it likely to clear up?

11

General Radio Discussion / WQFG689 antenna

« on: December 20, 2019, 0847 UTC »

I've been wondering what the antenna for WQFG689 looks like. Does anyone have a picture or has seen it before? (I did try looking it up and I was unable to find anything on google.)

I find it surprising the coverage that it has. No other TIS covers so much. It goes hundreds of miles and I never hear any other TIS on 1710. I assume they are limited to the usual 10W of power, so their antenna must be really good.

12

The RF Workbench / Question about stretchy 350W SiC deck

« on: December 02, 2019, 0203 UTC »

Hey stretchy,

I am back at the shortwave transmitter again. I've had it working great below 4 MHz, but now I am back to trying to make it work higher again. I thought I had it at 87% efficiency, but I looked on a spectrum analyzer and it's terrible. When I run it next to the filter, then it's great, but only 76% efficiency @ 6.8 MHz. I am almost 100% sure it has to do with my broadband output match.

Anyway, I'm thinking about buying your SiC RF deck. The 350W one with 4 fets I believe. How much would that cost?

I know you use those T200-2s. What else do you have to match the output beside the transformer?
Yours is not wideband, right? you have to tune it to the band?

13

General Radio Discussion / Direction finding of a skywave signal

« on: October 29, 2019, 0906 UTC »

With all the shortwave pirates here, I am curious about how easy it is for the FCC to direction find a skywave signal. I would assume it is much harder than for VHF bands. Is it really even practical to do on a vehicle?

14

The RF Workbench / C-QUAM stereo on PWM TX

« on: October 29, 2019, 0045 UTC »

Hi,

Redhat, your mention of c-quam with a PWM transmitter got me interested, so I thought I should make a separate thread about it.

As I understand it, you modulate the PWM as you normally would with left and right channels mixed together. Then for the c-quam, you need a device that will offer a phase modulated TTL square wave and you feed that in where you would normally have your crystal oscillator?

Do such devices exist? Could a regular part 15 100mW c-quam transmitter have this extracted from somewhere in the circuit or do I need to build my own device that produces it?




As a side note: It also got me thinking - what would happen if you got two PWMs and fed each side of the amp separately (assuming push-pull design)? would it make an ISB type stereo?

15

The RF Workbench / NCP driver sucks

« on: October 13, 2019, 1749 UTC »

I'm on my 4th revision of my PCB and the first one was the best. On the first one, I used TC4452 because I didn't know about the IXDD614 at that point. After that I found out about the NCP and thought it would be better than the 614 and so I built my last three PCBs based on it. It was a big mistake and I wasted so much time on it and now if I want to use the 614s, I have to basically start over at square one. So I am giving up for at least a year. It pisses me off because I'm not the type to be able to put something like this down, but it's not worth it to get angry over something like this.

BTW: The waves going in and out of them are square as can be (as square as the crystal source which is connected with very short straight traces).

So what's wrong with them?
1. They get dangerously hot at 12V and above - they may do 15V with a heatsink on top, but they were emitting a smell like they were about to pop (and I did pop several).
2. The datasheet (especially the truth table) is either just really confusing or the design is just wrong. Based on the truth table, there is no way to use the inverting input as the output will always be low. I found this to be the case in practice also.

So yeah, I think it will work with GaN cause they only need about 8V, but if you got it working with SiC at higher voltages, then you must have magical powers.

So for now, I'm just going to use my original design board that works good below 5 MHz. I guess I won't be on the 'fun' band any time soon lol 

EDIT:

Here's the datasheet: https://www.onsemi.com/pub/Collateral/NCP81074-D.PDF

Truth table page 5.