Ham Radio

Sounds intersting!
Do you have more details on this?

Try this link: http://www.arrl.org/digital-modes It introduces RTTY, PSK-31 and others. RTTY is the old protocol and it just transmits to any radio listening in. PSK-31 is more like a computer modem in that a radio receiving the signal can check for transmission errors and ask for a re-transmit of portions of messages that do not come over cleanly.

As per the FCC, if you are in the US, you can make up your own protocol so long as the specs are "published" somewhere. So there are a number of other systems out there.
 
I've messed around with the SDR dongle a bit. Mostly I've used it for monitoring local analog ham conversations. I need a better antenna setup than the crappy mag mount I have running right now.

Good luck with that SDR trunk program. How'd you build the quarterwave, by the way?

@skullmask One of these bulkhead SMA connectors:

shopping.jpeg

and 5 pieces of copper wire cut to 3.3 inches. Solder the 4 radials into the 4 corner holes and the center mast into the center conductor. You'll want to measure and trim the center mast so that you get 3.3 inches from the flange to the tip (for 850MHz). Bend the radials down so they are at a 270 degree angle to the center mast. It should look like a pyramid with a spire on top. Plug your coax onto the mating side of the connector and you've got a quick and dirty antenna. You can crimp a ring terminal to the end of the center mast so you can hang the antenna up by a string. Just take the length of the ring terminal into account, as it will add to the effective length of the antenna. This works well for uhf and vhf too using a BNC instead of the SMA shown.

I'll get out to the building soon and snap a pic of mine & post it.
 
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@skullmask - Here ya go. Sorry for the delay. I did this with 26awg solid copper wire, but 14awg or so would work just fine. I'm just receiving, so nothing too precision here. If I were transmitting, I'd be a little more precise and avoid the splitter.

I've got the SDRs running with Unitrunker & DSDPlus and can monitor trunked systems from 45 miles away. Pretty cool.
 

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skullmask

Sparrow
@skullmask - Here ya go. Sorry for the delay. I did this with 26awg solid copper wire, but 14awg or so would work just fine. I'm just receiving, so nothing too precision here. If I were transmitting, I'd be a little more precise and avoid the splitter.

I've got the SDRs running with Unitrunker & DSDPlus and can monitor trunked systems from 45 miles away. Pretty cool.

@Sargon2112 Neat setup. I guess the hook at the tip of the antenna makes for a convienient method of hanging it up. I haven't seen dual SDRs set up like that before though. Is that so you can continuously monitor the trunked system's control channel with one while listening on working channels with the other?

This weekend I resumed messing with the HF set again. I bought a USB cable and connected my PC to the USB port on the Icom IC-7200 which has a built in sound card. Using Hamlib and fldigi I was able to work some stations using a digital mode called PSK31. Some US, some Canadian. I even briefly saw a few Spanish and German stations, but they could not receive me.

I'm really liking the digital modes. The constant hiss of background noise of phone SSB grates on me after a while. And its super hard to reach anyone since the band conditions are so bad. But with PSK I can just pick out a signal on my PC's waterfall display and type out messages, and they often get through whereas my voice does not.
 
@Sargon2112 Neat setup. I guess the hook at the tip of the antenna makes for a convienient method of hanging it up. I haven't seen dual SDRs set up like that before though. Is that so you can continuously monitor the trunked system's control channel with one while listening on working channels with the other?

This weekend I resumed messing with the HF set again. I bought a USB cable and connected my PC to the USB port on the Icom IC-7200 which has a built in sound card. Using Hamlib and fldigi I was able to work some stations using a digital mode called PSK31. Some US, some Canadian. I even briefly saw a few Spanish and German stations, but they could not receive me.

I'm really liking the digital modes. The constant hiss of background noise of phone SSB grates on me after a while. And its super hard to reach anyone since the band conditions are so bad. But with PSK I can just pick out a signal on my PC's waterfall display and type out messages, and they often get through whereas my voice does not.

Yep, the purpose of the dual SDRs is as you said. One is parked on the control and the software decodes the data, pointing the second SDR to the working channel. It's technically not scanning anything, it's just being pointed to the working channel like any other radio in the system.

These RTL-SDR dongles run hot as hell, I haven't measured it, but they have to be over 85C internally, judging by the exterior temp. I'll be pulling them from those cases and potting them in a thermally conductive epoxy to a heatsink for the final rig. Will probably double the life, if not more than double it.

I intend to get my FCC license this fall, if any nearby testing is being held with Covid scaring everyone. I've been into this stuff too long not to have it and I would enjoy the PSK stuff you described, especially on HF.
Right up my alley. Not to mention having use of the multiple 440, 2 meter and 6 meter repeaters in the surrounding areas.

What antenna setup do you run on your HF rig? Are you running a pre-amp to hear those European stations or just a good beam?

Cheers.
 

skullmask

Sparrow
What antenna setup do you run on your HF rig? Are you running a pre-amp to hear those European stations or just a good beam?

I have a few different setups. I started out using a homebrew version of the Buddipole and Buddistick, which I based off the following video:


Written instructions are included in the video description. A few things I did different from this guy was that I made the balun like he did, but installed three eyelets on the sides, and a threaded base on the bottom so it could act as a guying point and platform for either the vertical or horizontal elements. I also built a dedicated vertical instead of reusing the horizontal elements since I could go longer with the whip and use a smaller coil, with the hope that it would be more efficient on the lower bands. The whip elements and other needed parts you can't find in a hardware store can be found at buddipole.com.

I haven't bothered messing around with beams yet, just standard dipoles. I also have another simple balun set up with terminals for wire dipoles, with elements cut for 40 and 80m that I can swap between. I put them all up using painters poles. I don't have a permanent setup, just portable stuff I can run a cable to from the kitchen window.

As for the pre-amp, I've messed with it before but didn't bother for PSK31. To be honest with as high as the noise floor on HF has been, all the preamp does is amplify the noise too so I haven't seen much use for it. On the other hand, I've seen an improvement in signal quality using the attenuator on occasion, especially on voice SSB.
 

skullmask

Sparrow
@Sargon2112

So, I finally decided to buy some RTL-SDR dongles for playing with scanning trunked systems. I ended up buying some dual dongle enclosed setup off eBay but in hindsight I'm thinking that wasn't the best idea. When the package arrived it looked ok, but when I tried using it one of the dongles would keep dropping out after a few minutes. Unplug and replug seemed to fix it but it would just drop out again.

I ended up tearing the thing apart (carefully) and bypassing the active usb splitter. Turns out the usb splitter it came with was defective. With the dongles plugged into my pc directly it worked fine. Just for the heck of it I took out an old usb hub I had lying around and plugged the dongles into that. It used the same chipset as the defective splitter but worked fine, so it isn't some weird issue with the chipset.

Without the enclosure the dongles actually run pretty cool. I think the reason these things tend to run hot is while they are enclosed in the metal box, the air around it doesn't circulate so it tends to heat up. So far I haven't had any issues with noise due to the lack of any shielding of the board...

A more worrying issue I had with it though was the poor quality of the soldering. There was a huge blob of solder on the power on indicator LED that almost shorted out the pins of a transistor on the dongle board. Fortunately it was a cold solder joint so it didn't short out. I wound up just removing it and cleaning it up with some solder wick.

The splitter for the antenna itself also had cold solder joints. I wound up reflowing those as well. From the looks of it whoever is putting these things together doesn't know how to solder properly and likely doesn't have the proper tools to do so. For those who don't know, a cold solder joint happens when the surface one intends to apply solder to isn't heated above the temperature required to melt solder. So solder just piles up on top of it without actually whetting to it. While it may appear to be a good connection, they inevitably fail and are mechanically weak. It looked like the type of work you get when using a cheap radio shack soldering iron and some basic rosin core solder without any additional flux. If I were to do it all over again I would have just ordered some rtl-sdr dongles and built an antenna splitter myself.

I emailed the seller, and politely explained the issues I found. I probably voided their warranty by ripping the guts out of their enclosure and reworking their shoddy soldering joints, but I do want to put the thing back together again and I think it was just a faulty active usb splitter. So I asked them to send me a replacement splitter so I can try putting this back together. Lets see how it goes.
 

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@skullmask, great post. When I read it, I couldn't resist opening up one of my RTLSDR dongles to have a look. The soldering looks good on this one. It has a thermal transfer pad on the back of the boards, which doesn't do much to help the heat issue, as there is only partial contact with the case. There is a small array of vias under the processor, intended to transfer heat to the back, but it's just too compact, and little to no convection, as you pointed out. I'll run these without the cases in my Raspberry pi trunker though. I can't knock them too much though, as these are great devices for the price. I tried to snap a pic, but I need to reduce the size to attach it.

I returned an NHRC repeater controller once, over crap solder joints. It was all through hole stuff too, doesn't get much easier, yet 75% of the joints were cold. I emailed them, like you did here, explained things and had pics. They sent a replacement, which was better, but still, it was obvious the tech(?) who populated the board did not understand soldering. I just cleaned up the second one myself and still have it, 10 years later. They had a great design, but bad workmanship can kill a great design quickly.
 

skullmask

Sparrow
@Sargon2112 I have no idea who manufactured the boards, or where they come from. I heard back from the seller, apparently that's an IR sensor not a transistor. And apparently the blob was meant to be there according to them, as it is supposed to connect the neg lead to both pins 1 and 2. I dunno why they didn't just bend the neg lead 90 degrees and solder the leg directly to both those pins. Big blobs to bridge pins is just so sloppy.

Apparently the term "cold solder joint" doesn't register with them. I get the feeling they are working with some sort of 30w radio shack soldering iron with a crap tip, and just piling blobs of solder on top of the surfaces being soldered. I was able to fix the joints myself in 30 sec with some liquid flux and a decent Weller iron.

The units are made by a group called PatriotWaves. Made in 'murrica, but most likely all from made in china parts. I started using the suspect splitter again, which has no identifying marks so I don't know who made it. It appears to be working a bit better now. I have had it running several hours before I ran into that issue again. This time it continued to work as it was the non-control channel dongle that stopped working. Apparently SDRTrunk can work with just one dongle, it will automatically shift the SDR around to fit as many working channels into the 2.4mhz bandwidth as it can. But I really need two to cover it all. What I think is happening is that one dongle is randomly dropping briefly, then reconnecting afterwards. SDRTrunk cannot reacquire the SDR after the connection gets disrupted, so a restart is required. I can simulate this by unplugging an sdr then plugging back in. Does the same thing I'm seeing with this suspect splitter. Could be the dongle itself that's dropping out, so I'll just keep testing.

It would be nice if we started making things in America again. But not if people keep half-assing it on workmanship.
 
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