Does anyone know where I could find an SO-239 (UHF female) to binding post adapter? I tried ordering this one, but their payment processing appears to be broken. (I tried two different credit cards.) #AmateurRadio #HamRadio
Finally finished my in-depth experimentation on toroid baluns last night. Turns out that the simplest solution is often the best: a traditional transformer acting as a voltage balun did the trick!
I was a bit dismayed with the narrow bandwidth of my system with the copper pipe dipole with a 4:3 step-down ratio (it hit the center of 6m, but the SWR at the FT8 frequency wasn't as good), but but changing to 6:3 (5:3 didn't work at all) brought the resonant frequency down and got one of the best SWR readings I've seen. 👍
My plan is to have a switch on the balun to select between the 4:3 and 6:3.
After playing around with reconfiguring the autotransformer balun and trimmer caps, it really looks like my copper pipe dipole (meant for the 6 meter band) is too long. It really wants to resonate at 49 MHz and I can get the SWR down to ~1.2 at that frequency. I'll have to cut it some when I get time. 👍 #AmateurRadio #HamRadio
I've been using it on 6m prior to all this with a twin coax transformer that @DD8SF recommended and it's been fine. Pretty wild that it was too short all this time. :P
Our HOA is having exterior maintenance done and our stack of units is next. That means no outdoor antennas for probably a few weeks. #AmateurRadio #HamRadio
Finally made some real progress on the magloop after adding a 100 pF capacitor in parallel to the 5-250 pF variable capacitor…at least on 80m. Now there's too much capacitance to hit 40m.
The SWR on 80m is really good. When I tested FT8 at 100 W, it was around 1.1. :D
Aw man, something just fried. The SWR jumped from 1.1 to way high out of nowhere. I'm guessing it's "The Doohickey" since that switch probably wasn't really rated for 100 W. :P
Time to build a new one that includes what I learned building the first one! I'll still use the same coil and so on, but I'll have to cut the switch out and toss it. The upside is that I already ordered a pair of beefy switches, using one for disabling the magloop's fixed capacitor and having an extra one, so that means I won't have to wait as long! :3
Went through the entire feed line with my NanoVNA and couldn't get it to reproduce, but as soon as I tried transmitting at 100 W, the problem came back. 100% a power capacity issue that the former's low output can't trigger. #AmateurRadio #HamRadio
@ai6yr peer tube theoretically uses a peer to peer protocol, so everyone watching a video also shares it. How effective is that in the real world? Usually I'm the only one watching a video at that time.
It doesn't "work" yet because I used the "circumference / 10" formula to determine the length of the curved rod in the gamma match, rather than using it to determine the distance between the two terminals where the gamma match joins the main coil. :/
It's much more promising than earlier things I've tried to get this antenna working (coupling loop, toroid coil, etc.).
Was having a weird problem on 2 meter where the SWR reported by my analog SWR meter was around 1.1, but my transceiver was reporting 2.5-3! I tried replacing the cable with two new ones I crimped, of more or less the same length (around 2 feet), but the problem remained. :(
When I put in a pre-made 3 foot cable in, the problem went away! :/
The weirdest thing is that I crimped all of the cabling between the SWR meter and antenna, so is the length of the transceiver–SWR meter leg the issue? :(
1/2 Connectors and feed line do need to NOT be resonant partials of the frequency in use. The feed line to the antenna also should really be at least a 1/4 wavelength (pretty easy to do with 2m).
1/4 wavelength at 2m is about 19", but everything in the vicinity, connected or not, has SOME influence on resonance.
Does this mean your cables were to blame? It's possible.
Even though the cables I crimped are 26" and 28" in length, I still feel like the length might be the issue here. None of the other cables I made had such a negative impact, but they were further from my transceiver on the feed line.
My first exposure to the idea was from another ham who WAS an electrical engineer, mentioning that in his gigahertz world, even PC board trace lengths were critical.
2/2 The other possibility is a poor connection in one of the crimps or soldered tips. I've found (my unscientific experience) that behavior that changes with power level is sometimes a connection issue.
This video, which becomes a favorite of all hams who see it, will help show why coax length matters. EVERY connector is an impedence change, which causes reflected energy.
I did run into the power issue with another cable I made for HF a couple days back that was caused by there not being enough solder in a coax pin, but that taught me to be more careful at that part.
I don't think the SWR changed with power in this VHF case, so I feel like that might not be it here.
Sorry, I should have been clearer...your SWR meter works by sending an RF signal, very low power. Then the radio transmits at a much higher level, which is what can lead to a different result. As long as you're checking the solder quality of the centers in your connectors, you're doing the right thing. I've overlooked that more than once.
Thanks. I think we might be talking about two different things here. The SWR meter I'm talking about is one of these. It displays what's happening on the line rather than generating its own signal.
@W6KME "EVERY connector is an impedence change" -- I was under the impression that both BNC and N connectors preserve the 50 ohms characteristic impedance, unlike UHF/SO239 which don't. Thoughts ...?
@tswartz07 @gmoretti A couple of other possibilities: if the cables are *too* short, you might be below the minimum bend radius and shorting the center conductor (or almost shorting). And it's also worth checking the cable and connectors to verify no 75 ohm stuff has snuck in.
In my case, the cables weren't bent because I'm using 90° connectors at each device along the line. :3 Oh, I also always check to make sure there's no continuity between the center conductor and shield right after soldering. 👍
Anyone know what the correct way of mounting one of these vacuum variable capacitors is? I'm assuming that the top and bottom parts with bolt holes are the two electrodes, but I'm not sure. :/
I don't know for certain, but the physics of capacitors would suggest that you're showing it 'correctly oriented' where a push rod or other mechanism would turn the top rod to move the plates closer together or further apart. The big non-vacuum ones rotate to adjust the amount of surface plate that is adjacent but doesn't change the spacing of the plates.
On our #simplex group last Wednesday there was a 5mw contact on 446.500 FM from Cerritos down to San Diego. I was able to QSO with San Diego at 50mw and me at .5 watt on a Yaesu FT-60.
How in the world do I do that, though? dsd doesn't support reading WAV files, DSD+ is a Windows application, and dsd-fme seems to not support reading files at all despite claiming being able to.
Input/Output options:
-i <device> Audio input device (default is pulse)
/dev/dsp for OSS audio (Depreciated: Will require padsp wrapper in Linux)
pulse for pulse audio signal input
pulse:6 or pulse:virtual_sink2.monitor for pulse audio signal input on virtual_sink2 (see -O)
rtl for rtl dongle (Default Values -- see below)
rtl:dev:freq:gain:ppm:bw:sq:vol for rtl dongle (see below)
tcp for tcp client SDR++/GNURadio Companion/Other (Port 7355)
tcp:192.168.7.5:7355 for custom address and port
m17udp for M17 UDP/IP socket bind input (default host 127.0.0.1; default port 17000)
m17udp:192.168.7.8:17001 for M17 UDP/IP bind input (Binding Address and Port
filename.bin for OP25/FME capture bin files
filename.wav for 48K/1 wav files (SDR++, GQRX)
filename.wav -s 96000 for 96K/1 wav files (DSDPlus)
(Use single quotes '/directory/audio file.wav' when directories/spaces are present)
Needed a tube bender for my next project, but my local hardware store was out of ones that could handle ½" tubing, so I had to order from McMaster–Carr.
#AmateurRadio #HamRadio
Neil E. Hodges
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