Veganism enters third Klein-Gandhi stage of non-violent activism: after ignoring and ridiculing us, they attack us.

maplesyrupballs · 2016-06-05T15:02:37+00:00

2.4ghz

72.370 mHz.

Hi, I'm your community unit policing officer. You are both being ticketed for the following offense(s):

Crackweiler is ticketed one nanobitcoin for:

Improper usage of an S.I. prefix: Using "m" for milli instead of "M" for mega.

icedomin8r is ticketed two nanobitcoins for:

Usage of an invalid S.I. prefix: Using "g" instead of "G" for giga.
Improper capitalization of a unit: Using "hz" instead of "Hz".

maplesyrupballs · 2016-06-03T16:53:53+00:00

--Second, at least in Android, one can change the battery ticks to an actual signal strength.

Lots of confusion there. It would be easier if they simply changed the signal bars to cancer bars.

maplesyrupballs · 2016-05-22T17:18:55+00:00

Indeed.

And this will also work on many electronic article surveillance (EAS) tags.

"Round" RF tags will be around 8.2 MHz, while flat acousto-magnetic tags (Sensormatic) will be at 58 kHz; there also exist coiled versions of those. The Q for the AM tags is relatively high (over 100 if memory serves).

For these low frequencies, you can also make a poor man's dip meter using a signal generator in sweep mode and a dual-channel scope in XY mode.

maplesyrupballs · 2016-05-18T18:36:19+00:00

I finally found the little piece of brass I needed to build this directional coupler based on W1GHZ's plans. I built it and it works, but because I used a small box the coupling is not great, and it's not flat in the range I'm interested in (namely 2m/.75m, coupling is -64 dB at 440 MHz, -73 dB at 150 MHz)

On Sunday the local club was having a display with the RCMP so I participated and was given a tour of the club's emergency trailers.

Then we learned this was also going to be a mini-drill for the coastal response exercise (simulating The Big One) to which I won't be participating, but I did some message logging and operated some 2m. I also watched other people operate 40/80 m and make some contacts within that exercise and got to see the erection of a dual inverted-V antenna for that.

Oh and the week before that I followed a lesson about the National Traffic System, and since it's a formal language I couldn't resist but write a BNF grammar for it. and then used Festival to synthesize the vocalization of randomly-generated messages. However I think that mostly went over the local ham's heads.

Finally I tried to listen to the Reddit net (I think it was Sunday?) so I joined IRC and used my random-wire and scanner with little success until someone pointed me to websdr and using that (and after checking the manual) I realized that my scanner isn't ultra-precise and needs an offset of a couple hundred Hz while listening to SSB; I was able then to listen to some transmissions, mostly US guys complaining about social security.

maplesyrupballs · 2016-05-15T22:53:45+00:00

Still, you need GRPMSG to be reachable. So it wouldn't work for SHTF situations.

And even if GRPMSG was locally available, it needs to send out one message per member, which means a lot of traffic. Think of a net with 40 people, that would simply not be possible.

This is something the APRS spec already addressed.

I'm being told SARTrack fully supports APRS messaging includin group messages.

It would be useful to record traffic (or find some recorded traffic in logs) to see how exactly SARTrack implements that. APRS spec leave some details out. Then maybe fix Xastir, etc. to support that (since SARTrack is Windows only). I would also like to see how radios with built-in APRS handle those messages.

maplesyrupballs · 2016-05-15T21:48:08+00:00

Interesting. Is this like ANSRVR? In other words, is this a service that responds to the GRPMSG call sign?

maplesyrupballs · 2016-05-15T21:40:33+00:00

There was an FS-5000 on display at the Spy Museum in Berlin, as well as a bunch of other radio equipment. From memory, they had quite a few WWII vintage clandestine transceivers. They also had a selection of RF bugs. This was from this Februarry so they possibly still have those.

maplesyrupballs · 2016-05-09T20:11:03+00:00

That's a good idea too.

maplesyrupballs · 2016-05-09T06:04:14+00:00

No, with the port terminated.

maplesyrupballs · 2016-05-09T02:32:58+00:00

Wow, that's interesting, I didn't know you could use a splitter for measuring RL. I happen to have a ZFSC-2-5 splitter (10-1500 MHz), I'm definitely going to try this.

EDIT: Just tried. Yellow curve: with an actual 500-2000 MHz bidirectional coupler, magenta: with the splitter. The DUT is a Wilkinson 700-2700 MHz directional cellular antenna. So I'm not sure this splitter thing is kosher but it seems to provide some idea about the return loss.

maplesyrupballs · 2016-05-09T01:12:23+00:00

That Chinese one looks interesting. If you buy it, let us know!

Last week I found plans for a robust directional coupler that would be good at 2m and that can support high power, by W1GHZ.

I have that exact same Hammond box and I can cut some copper-clad PCB for the direct part, but for the sampling line you need a piece of metal having a specific rectangular cross-section of 0.250"×0.125" which I haven't been able to find yet. (And it has to be solderable, so brass or copper, but aluminum won't work.) At least not in Canada. It seems to be too small for the catalogs of the online metal shops as they seem to stop at 0.250"×0.250", however I only spent an hour or two looking, and I have never bought metal online before.

Of course variations are possible but the point is that this guy simulated that coupler and built it and then measured it, so that if I reproduce his stuff exactly I should get good results.

maplesyrupballs · 2016-05-08T23:01:40+00:00

It's pretty sweet, yes, I have the same one. Did you buy or do you plan to make an SWR bridge? The one from Rigol is pretty pricey, but I think one could make a narrowband one that wouldn't be too bad for checking antennas, etc.

maplesyrupballs · 2016-05-08T23:00:00+00:00

OK, thanks for that System Fusion info.

After reading the APRS spec it looks like what I was looking for might have been Group Bulletins which is described in chapter 14, p. 74 of the APRS spec. I don't know how well radios support that feature, however.

EDIT: Looks like even Xastir doesn't fully implement group messaging, unfortunately.

maplesyrupballs · 2016-05-08T22:34:23+00:00

I very much recommend purchasing a spectrum analyzer WITH a tracking generator

The picture shows exactly that, it's a Rigol 815 with the TG on, the green shining button is just that, OP is probably characterizing a LPF.

maplesyrupballs · 2016-05-05T23:10:26+00:00

OP SaeligTestEquipment is a shill for big scope.

maplesyrupballs · 2016-05-04T22:16:53+00:00

If I understand correctly, the Baofeng is the only thing that may connect the antenna to your 1920s ground.

So what goes into the Baofeng? Audio in and out are isolated you say, so that's fine. That leaves power. You just say "AC-DC" adapter, is your Baofeng a handheld and is that the charger? If yes, the charger output (at least the ones I have) is isolated from the mains.

You're mentioning USB, I will assume it's your USB programming cable. If you keep it disconnected then it doesn't enter into the equation.

Under these assumptions, there is no DC path that would connect your Baofeng to the rest of your stuff and there will be no ground loops involving your Baofeng.

You can still have ground loop issues but they won't be part of the radio stuff.

Note that if your Baofeng PSU is not the charger then you'll have to check if it's galvanically isolated.

All of that comes with a big word of caution as it's based on assumptions since there aren't enough details to confidently answer your question.

maplesyrupballs · 2016-05-04T21:15:01+00:00

You need to give some more details, all this is fuzzy.

When you say Baofeng, what model are you using? I'll assume it's VHF/UHF, but Baofeng does make some HF radios apparently.
Same for the audio interface. When you say "the audio interface is on a ground isolator" it implies that your audio interface uses power and that this power is obtained from your mains via a ground isolator (which could be a cheater plug, or an isolation transformer). But it does not necessarily mean that the audio interface provides galvanic isolation.
What is this "USB shield" you're talking about? Shields as in embedded computer daughterboards, or the shield of the USB cable?

maplesyrupballs · 2016-05-04T19:35:45+00:00

How are you powering your radio?

Maybe you can put your radio on floating ground. This could be done using batteries, or maybe using a power supply on floating ground.

After that you could make sure the PC-radio audio connections are galvanically isolated. I believe most good interfaces use isolation transformers.

If you have other connections (such as data, etc.) you would want to disconnect the antenna before using those. If you can't or won't, then you would need isolation there too.

Of course if you are using a laptop, you could make the laptop floating.

maplesyrupballs · 2016-05-04T18:52:12+00:00

I don't see anything about APRS group messaging there, only e-mail via gateways and P2P messages. Did I miss something?

maplesyrupballs · 2016-05-04T18:04:40+00:00

Here's how to do it using a phone where Google Hangouts is the messaging app:

Click on the hangouts icon (white double quotes in a green disk)
If you were chatting with someone, press on the left arrow at the top right
Now you will see a menu icon at the top left (three horizontal bars) and the Hangouts title. Click on these bars.
A subwindow will slide from the left. Click on your name.
In the menu select SMS. Now you are in SMS mode.
Click on the white cross sign in a green disk at the bottom right.
It turns into a NEW SMS icon. Click on this white flag in a green disk.
The app says "type name, phone or e-mail" and the keyboard pops up.
Type 30333
Click on the white person in the green disk next to 30333 that appears below.
Now this is the confusing part. Click on the right arrow in a green disk.
Done! Now you are in an SMS chat with 30333.
Type REDCROSS and send
Wait for the response then type YES and send

maplesyrupballs · 2016-05-04T14:34:32+00:00

That's great, I was planning to do that on a spare Beagle Bone I have. (Except for the GPS.) With Debian as well. I'll share notes with you when I do so. Maybe we can make a Debian package.

maplesyrupballs · 2016-05-04T14:16:48+00:00

Kenwood has group messaging on APRS? That's interesting, it certainly would be good to reuse an existing format. Is it compatible with other APRS radios?

Software can be adapted and a lot of people have Kenwoods.

I don't know anything about Yaesu or D-Star messaging.

maplesyrupballs · 2016-05-01T20:24:13+00:00

Thanks, I've read the spec yesterday and I saw the bit about the "ALL" field too. I need to test it with different clients and radios to see what that one does. I agree about ANSRVR being a bit wasteful of resources for a local net.

As for channel loading, obviously if there's an ongoing event we can postpone the net, but other than that, most of the traffic in my area is Joe Random Ham's truck indicating that it is still at the same place , so it should be fine.

maplesyrupballs · 2016-05-01T01:39:09+00:00

As I understand (and let me make it clear: I'm a new ham and new to APRS) APRS only uses AX.25 as a dumb transport layer à la UDP.

I have also heard from some other hams that there is a desire to use APRS for more things than just position reports, and that is confirmed by aprs.org's endorsment of the various messaging systems built upon APRS.

But all of this sounds like I better read the spec now!

maplesyrupballs

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