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Mantle
May 15, 2004


Why does it have to be HF though? Won't I be able to use the same protocols over VHF or UHF?

Here's a group doing packet radio networks based on LinBPQ

http://tarpn.net/t/faq/faq_tarpn_features.html

Mantle fucked around with this message at 22:14 on Apr 28, 2020

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Motronic
Nov 6, 2009


MOTRONIC FOR MODERATOR, MAKE AI GREAT AGAIN


Grimey Drawer

Mantle posted:

Why does it have to be HF though? Won't I be able to use the same protocols over VHF or UHF?

Here's a group doing packet radio networks based on LinBPQ

http://tarpn.net/t/faq/faq_tarpn_features.html

It doesn't HAVE to be at all. If you're near enough to one of those nodes to hit them on VHF/UHF go for it. I just haven't seen that kind of thing as anything other than super isolated and local anymore.

From their home page:

quote:

The TARPN group, about 250 hams as of Feb 2020

Not discouraging you at all, but understand that you need to be in a very specific area(s) for this to work. And I'd worry more about antenna cost/feasibility than radio cost.

The Hambulance
Apr 19, 2011



ASK ME ABOUT MY AWESOME STARTUP IDEA


Fun Shoe

longview posted:

Stringing a dipole along wood will definitely de-tune it, possibly severely depending on the type of wood and the moisture content.
At higher powers you could end up arcing into the wood, posing a fire risk.

From what I know, the ends of a dipole are more sensitive to nearby objects and have a higher voltage than the feed-point, so they would be more important to keep free.

Thanks! I have the room to string it up so it doesn't touch anything, it's just going to be more work. Not as much work as doing it twice or an attic fire though.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


when longview says "higher powers" we're talking like 600-1000 watts.

A 100w radio into a dipole made of insulated wire is virtually zero risk.

Motronic
Nov 6, 2009


MOTRONIC FOR MODERATOR, MAKE AI GREAT AGAIN


Grimey Drawer

Partycat posted:

Do we have enough people and tech to resurrect a SAARS net on a brandmeister group ? I have a hotspot and DNR portables , and some are linked into allstar, fusion, etc

Anyone frosty enough to do this? I dusted off the MD380 as well and have my hot spot running again.

CapnBry
Jul 15, 2002

I got this goin'

Grimey Drawer

If I have a Random Wire Antenna with a 9:1 unun feeding it, do I need to design an antenna tuner for matching the 50ohm to 450ohm impedance of the antenna or is it supposed to be virtually a 50ohm load already? I'm looking to pick up another variable capacitor to play with matching and I'm trying to determine how big it needs to be at max. Does the imaginary part of the impedance dominate the calculation when the unun is already trying to match the feed impedance? All of this is really low stakes just messing around experimenting and learning for fun on receive-only or lower power TX (10W max).

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


It's supposed to be 50 ohms on the coax side of the unun, yeah.

Build yourself a simple LC tuner and goof with it!



Note that you can add one switch and VASTLY increase an L network's range as so:



Max capacitance helps you out on lower bands, but quite often your limit isn't how big the C goes, but how small it goes. No variable cap goes to 0 pF and most of my 500 pF air variables get down to like, 20, 30 pF.

You could also add a SPDT switch (on-off-on, 3 position) and two fixed value caps in parallel with the main tuner cap to extend range. Some of the little qrp tuners do this with 250 pF and 500 pF caps to stretch them out on the lower bands. Tuning gets sharp, though.

CapnBry
Jul 15, 2002

I got this goin'

Grimey Drawer

Jonny 290 posted:

It's supposed to be 50 ohms on the coax side of the unun, yeah.

Build yourself a simple LC tuner and goof with it!


That's exactly what I was doing yeah! Building the coil is easy enough with just some winds of wire and a few taps, but I was going to order a capacitor and I didn't know how big it would need on the top end to tune 80, 40, and 20 meters. I guess it doesn't make all that much difference since even at 450 ohms it doesn't look like I'd ever need more than 500pF. I'm trying to find a nice two gang version with like 250pF each so I can mess with switching them in and out and hopefully doesn't look like it spent half a century at the bottom of a lake. Also for not a lot of money because I am cheap as hell and not from overseas because I am impatient. Oop found one on eBay finally, 30-300pF and 30-500pF sections with a 4:1 knob and hard stops on either end for just $14 shipped woohoo tuner baby.

CapnBry fucked around with this message at 19:08 on May 3, 2020

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


Is cap size a concern? are you trying to make this Itty Bitty?

Cause, if not....




Last hamfest I bought out the entire stock of a guy that stripped down a bunch of milspec antenna tuners. That's 500 pF and good for probably 3-5 kV.

I'll mail you one for the cost of shipping if you like, I just gotta figure out how to do curbside UPS/USPS pickup.
(I paid $5 for it i seriously don't give a gently caress)

CapnBry
Jul 15, 2002

I got this goin'

Grimey Drawer

Jonny 290 posted:

I'll mail you one for the cost of shipping if you like, I just gotta figure out how to do curbside UPS/USPS pickup.
Oh man that's awesome of you! I had browsed like 15 pages of them on eBay this morning and gave up but I was reinvigorated by your post and managed to pick one up already. I appreciate the offer, that was super nice of you. Size doesn't really matter to me at this point, I'l just loving around, but I'm definitely keeping my eyes peeled for a vacuum variable capacitor that someone is unloading because at some point I'm going to want to try to put 100W or more into these things for funsies.

I was wondering if the antenna you took a picture of with your (original) DJI Mini was your antenna or your neighbor's, but now I guess we've answered that question too.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


Glad you were able to get something ordered! No prob at all.

--
Oh no that poo poo is all mine. I'll take a better video soon with full lowdowns on all my antenna setups

The big tall one with the cross pieces and all the wires is a full size 40 meter 'folded monopole'. It's by far the best antenna I've ever built, the thing is an absolute rock star on 40 meters. 2:1 SWR curve is between 6900 and 7350 kHz.



Just like the last image, except the center wire is chainlink fence top rail and conduit, and I don't have the cross wires in the middle. The benefits are that it has very wide bandwidth, and the mast/pole/whatever is grounded, so installation is very simple and doesn't require any insulators. I've just got it bolted to the actual fence on the property. The 'hot' side of the coax goes to the wire cage.


Small AM broadcasters often run folded monopoles as they have slightly higher feed impedance than regular 1/4 wave verticals, and they can use a simple grounded tower for the main support, instead of running an insulated base

Jonny 290 fucked around with this message at 19:38 on May 3, 2020

CapnBry
Jul 15, 2002

I got this goin'

Grimey Drawer

Jonny 290 posted:

The big tall one with the cross pieces and all the wires is a full size 40 meter 'folded monopole'. It's by far the best antenna I've ever built, the thing is an absolute rock star on 40 meters. 2:1 SWR curve is between 6900 and 7350 kHz.
I love messing with antennas and building them just seems like magic. I'm very excited to get my NanoVNA V2 to put some numbers to the things that I can only see as "well this sucks" or "oh man really good" currently. I built a 40m spiral loop antenna that just doesn't work very well but the bright side was that it had a 8-25pF variable capacitor and after 3D printing a little knob for it, I could SEE the bandwidth and tune of the antenna in the waterfall. It made me giddy with delight to see physics working and I am excited to improve and build more.

So am I looking at this diagram correctly that in like the 5-wire, all 5 wires are active elements? How long (wavelength-wise) is each section? It is too big to fit in the area I have but I'd be interested to know more about it.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


You can build a folded setup for any band!

The outer four wires are connected to the center conductor of the coax. The pole and the fence (and my few ground radials) are connected to the shield.

Because it's technically a 'fat' conductor (RF thinks it's a 3 foot diameter metal pipe instead of a few wires) it's shorter than a full quarter wave at 40 meters by about six feet or so.

The best antenna building is just experimenting and trying to dial in what you got. I rarely build from hard dimensions, but model something up in software, see if it'll barely work, then build it IRL and tweak it to match.

The Hambulance
Apr 19, 2011



ASK ME ABOUT MY AWESOME STARTUP IDEA


Fun Shoe

Jonny 290 posted:

You can build a folded setup for any band!

The outer four wires are connected to the center conductor of the coax. The pole and the fence (and my few ground radials) are connected to the shield.

Because it's technically a 'fat' conductor (RF thinks it's a 3 foot diameter metal pipe instead of a few wires) it's shorter than a full quarter wave at 40 meters by about six feet or so.

The best antenna building is just experimenting and trying to dial in what you got. I rarely build from hard dimensions, but model something up in software, see if it'll barely work, then build it IRL and tweak it to match.

What software are you using to model the antennas? Apologies if you have said before.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


Prepare to dive headlong into early 2000s ham software land

https://hamsoft.ca/pages/mmana-gal.php

It's a quirky program that takes some time to learn, but it works well.

mycomancy
Oct 16, 2016

Not keeping silent about crimes committed by the government of China is racist!

Jonny 290 posted:

Prepare to dive headlong into early 2000s ham software land

https://hamsoft.ca/pages/mmana-gal.php

It's a quirky program that takes some time to learn, but it works well.

Hahahahahahahaha that website is a treat!

Totally Reasonable
Jan 8, 2008

aaag mirrors


this is a DR DOS household.

The Hambulance
Apr 19, 2011



ASK ME ABOUT MY AWESOME STARTUP IDEA


Fun Shoe

mycomancy posted:

Hahahahahahahaha that website is a treat!

I always get a chuckle out of the ham websites. It's like website development screeched to a halt in 1998. Then I remember that the hobby is mostly grey-beards (myself included) using tech that was state-of-the-art in the early 1900s.

Jim Silly-Balls
Jun 6, 2001

Fondle my shiny metal ass


The Hambulance posted:

I always get a chuckle out of the ham websites.

Username, post, avatar TRIPLE THREAT

taqueso
Mar 8, 2004









Fun Shoe

I found another use for SDR in the car, tire pressure monitoring

Jim Silly-Balls
Jun 6, 2001

Fondle my shiny metal ass


Do it while you can. A lot of cars are eschewing typical TPMS systems in place of just comparing wheel speeds when driving in a straight line, which gives you essentially the same data (is a tire flat?) with less hardware cost

taqueso
Mar 8, 2004









Fun Shoe

My car is old enough it doesn't even have TPMS, I'd be adding it to my new wheels. The cheaper method you mentioned has some major issues with all of the tires being inflated to the wrong pressure together doesn't it?

Jim Silly-Balls
Jun 6, 2001

Fondle my shiny metal ass


Yep but

horse_ebookmarklet
Oct 6, 2003

can I play too?


Grounding and bonding, oh great. Just trying to design before I buy.

First, I have been seeing some conflicting information on having a single point ground versus a multiple grounding electrodes. People seem to be arguing that having a single point ground is fine for antenna and satellite systems, and it will be fine for 100w PEP HF, and it greatly simplifies the design (Jim W6LG youtube videos).
This doesn't strike me as reasonable (having no RF ground, just the existing system ground), but at this point I'm so confused I don't know what is reasonable anymore. Given that, I blindly went ahead with what I perceive as a traditional multiple electrode design, but I guess I don't really feel confident in this.

With either system, how do I avoid a ground loop at the power supply? In the below image, aren't I creating an enormous ground loop? i've seen (what I believe is very bad advice) to use a cheater plug to avoid this...



My setup is fairly basic and I won't be installing tower. I probably should have already bought the ARRL general license manual I suppose, might answer this?

Zaepho
Oct 31, 2013


So a couple days ago I decided to play of 40M. Keyed up and kicked in my tuner at 100W CW. I know I should have started lower but it's been a while. And then the power went out.

Just our house, tripped a dozen breakers in the panel. Figured.. That's weird.. Lets do it again! and keyed again at 5W CW into the tuner. A different half dozen circuits tripped.

Halp! What Do?

I've been able to run 100W SSB previously with no issue, did the lovely builders grade breakers go bad, is my non-existent station ground to blame. Wat Do?

Seriously, what is my next step?

Progressive JPEG
Feb 19, 2003



Are they GFI breakers (with test buttons) or regular breakers?

xergm
Sep 8, 2009

The Moon is for Sissies!

What's your antenna setup? You could be getting RF back into the house.

I had a similar issue on 40m when I was using a G5RV before switching to a true doublet. 40m digital would start to set off the CO detector upstairs.

It may not have been an issue with SSB because your effective power may have been lower since it's modulating with the audio; CW is full blast when keyed.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


99% chance you have either gfi breakers or those newfangled arc fault breakers. They both hate the poo poo out of RF.

There's a ham goon that successfully exploded their Nest thermostat via 40m RF. 40 meters is notoriously good at causing house wiring to freak out.

Zaepho
Oct 31, 2013


Progressive JPEG posted:

Are they GFI breakers (with test buttons) or regular breakers?

Regular, go out to the breaker box in the garage and flip off and back on type breakers.


xergm posted:

What's your antenna setup? You could be getting RF back into the house.

20m dipole in an inverted V, the top point is hanging off the eaves, coax comes in a window and goes to a tuner before getting to the radio.

Jonny 290 posted:

99% chance you have either gfi breakers or those newfangled arc fault breakers. They both hate the poo poo out of RF.

There's a ham goon that successfully exploded their Nest thermostat via 40m RF. 40 meters is notoriously good at causing house wiring to freak out.

I'm guessing it's the arc fault breakers causing the trouble. the GFCIs spread around the house weren't an issue. I'll have to find some time to see if I can reproduce on 20m and/or 20m at lower power or different mode when the wife/kids won't riot at me breaking the house electrical.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


Half size dipoles (i.e. a 20m dipole on 40m) have super low feedpoint impedance and can poo poo all kinds of RF back down the coax shield. Do you have a choke balun (air or ferrite) at the feed?

longview
Dec 25, 2006

heh.


I'm playing around with my new all digital AM/SSB demodulator board for the 1970s Mackay receiver (sister card to the RNNoise/DSP board I built in 2018)

Anyone have any suggestions for neat DSP-friendly noise reduction tricks I can pull to improve reception?

What I've got so far:
* PLL carrier tracking for AM-sync reception
* AM/DSB/SSB quadrature demodulator for AM
* The combi demodulator also runs a costas phase feedback loop inside the DSP to maintain a constant carrier phase for the demodulator (in addition to the external carrier tracking)
* CW/SSB modes is just a synchronous demodulator with adjustable LO (radio has crystal IF filters for those modes, I plan to set the digital IF filters to match the crystal filters in the final system)

Today I tried a way to reduce the effects of AGC pumping when DXing. The issue is carrier fading causing the received signal to be over-modulated (solved by using a synchronous demodulator), and the other issue is AGC pumping when the carrier fades.
My solution so far is to use a very narrow band pass filter to select only the carrier frequency of the AM signal, I do this anyway to feed the PLL carrier tracking with a low noise signal.
Then I measure the envelope power in the carrier frequency range, and divide it by the total envelope power of the signal.
After some scaling+limiting I use this signal to control a tunable low pass filter. Controlling the audio level is also an option but IMO it sounds worse.

A side benefit of this is that when the radio isn't tuned to a station (within +-100 Hz), the output is attenuated a lot, acting almost like an AM squelch.

longview fucked around with this message at 17:06 on May 11, 2020

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


Wish i had insights on that one but it'd be like a toddler telling an f1 driver how to apex the turn


Unrelated:



Just ordered this. Time to see if I can get some wires WAY up in the trees.

motoh
Oct 16, 2012

The clack of a light autocannon going off is just how you know everything's alright.

Spending more time at home and away from work is crushing my learning, so it's time to fix up my lab bench and get back into the hobby. I have my tech license, and a wouxun handheld, but I'd like to pick up a benchtop transceiver, antenna, and some tools. I'm mostly a repeater hound. Any suggestions?

Jim Silly-Balls
Jun 6, 2001

Fondle my shiny metal ass


Jonny 290 posted:

Wish i had insights on that one but it'd be like a toddler telling an f1 driver how to apex the turn


Unrelated:



Just ordered this. Time to see if I can get some wires WAY up in the trees.

Jonny please donít murder your Mavic.

Remember the software for them was written with the stock weight in mind, nothing more, nothing less.

This doesnít mean that the software canít compensate for extra weight, but youíll need to be super careful as youíre not just hauling extra weight, youíre dealing with the line catching wind, dragging on the ground, etc.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


Yeah it'll be 5 pound monofilament and a 1oz sinker i think. i'll be careful!

wolrah
May 8, 2006
what?


I've always thought it'd be cool to run a power line up and basically use a multicopter in a tethered mode as an easily deployed temporary "tower". Rather than using the copter to hook a wire over a tree or whatever, just have it hold the wire as long as you need it. Ground station powers it normally, the batteries onboard are kept just to allow for a safe landing in the event of loss of ground power.

It seems like that would be a great solution for hams that can't put up proper outdoor antennas for one reason or another, if it could be done at a reasonable cost. And I guess if FAA regs allow for such a thing.

Jonny 290
May 5, 2005

[A]sk me about OS/2 WARP


experimentation has been done with tethered drones, and the coolest part is because they are not legally UAVs (due to the tether) as long as you dont violate airspace or go up 700 feet or w/e I think you're in pretty fine shape.

It'd be easy to run one as a tall HF vertical. DC-DC converter to shove a couple hundred volts up a twisted pair, DC-DC converter at the drone to bring it back down to 5v or 11.8v or whatever it needs, then use an RF injector to put your 75 meter hollering on both wires. I'd think the main concern would be lifespan of the motors at that point.

Sniep
Mar 28, 2004

All I needed was that fatty blunt...



King of Breakfast


Fun Shoe

wolrah posted:

use a multicopter in a tethered mode as an easily deployed temporary "tower".

and you hit PTT on 40 and the thing falls from the sky immediately

poeticoddity
Jan 14, 2007
"How nice - to feel nothing and still get full credit for being alive." - Kurt Vonnegut Jr. - Slaughterhouse Five

wolrah posted:

I've always thought it'd be cool to run a power line up and basically use a multicopter in a tethered mode as an easily deployed temporary "tower". Rather than using the copter to hook a wire over a tree or whatever, just have it hold the wire as long as you need it. Ground station powers it normally, the batteries onboard are kept just to allow for a safe landing in the event of loss of ground power.

It seems like that would be a great solution for hams that can't put up proper outdoor antennas for one reason or another, if it could be done at a reasonable cost. And I guess if FAA regs allow for such a thing.

I briefly mulled over a portable system for generating hydrogen to fill a balloon to lift an antenna in emergencies, but every option I've come up with involves dangerous chemicals or a ton of electricity. (And yes, I'm aware hydrogen is an explosion risk.)

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taqueso
Mar 8, 2004









Fun Shoe

Cool, cool. So what happened after you continued despite those dangers?

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