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Messages - IQ_imbalance

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91
Equipment / Re: RF circuit help....
« on: June 16, 2020, 1641 UTC »
My NanoVNA finally arrived.  As expected, the diplexer chops down on the 200-400Mhz sensitivity. The top scan is my DJ-130, the middle scan is the UHF (~800-900 MHz) yagi, and the bottom is the combined feed from the diplexer.  What's curious is that the amount of attenuation around 300 MHz doesn't appear too massive (within a log at least) yet i've lost a 380 MHz system.   Still playing around with it.....

92
Equipment / Re: RF circuit help....
« on: June 12, 2020, 1450 UTC »
A VNA is in my future.  Going to have to make some educated guesses about the component values as they’re not marked but we’ll see.  Given that the only UHF I’m really interested in is toward the upper limits of the current configuration hopefully I’ve got plenty of room to tweak the VHF section without affecting UHF

93
Equipment / RF circuit help....
« on: June 12, 2020, 0219 UTC »
Hi all.  I purchased a diplexer so i could run a VHF and a UHF antenna into the same feedline.  Seems to work well, but I didn't notice that there's a gap between the two bandpasses (VHF 47-230 MHz, UHF 470-862 MHz).  Unfortunately there's a 350 MHz system i'd like to receive, so I'm wondering if i can tweak the circuit to fix this...ideally by shifting the VHF bandpass from 47-230 MHz to 47-400 MHz (or thereabouts). 

I did my best to trace the circuit (damn tiny surface mount components!!!)  Can anyone make heads or tails of this, and suggest somewhere i might start to try and figure out how to modify the VHF bandpass?  I'm fine w/ the UHF settings, so hopefully i just have to do something to the VHF leg.


94
Equipment / Re: Vertical antenna build questions
« on: June 06, 2020, 1754 UTC »
Don't forget to weatherproof the elevated end like crazy (and a drip loop might still be a good idea) if you're using F-connectors and RG-6.  Ask me how I know.....

95
Equipment / Re: Up the discone!!
« on: June 06, 2020, 1752 UTC »
....and it wasn't the 550 cord.  Turns out i didn't waterproof my connectors adequately and while it works great at HF and VHF, it's practically deaf on UHF (~800MHz).  I can see a weak signal on my afedri but it's not nearly good enough for my scanner to decode.  Tried whacking a few feet of coax off the ends but still no-go.  Going to scrap the coax (no big deal, picked up several hundred feet for cheap) and start again once I get some additional coax-seal...apparently 'waterproof' F-connectors only do so much.....

96
Equipment / Re: Vertical antenna build questions
« on: June 06, 2020, 0241 UTC »
Probably doesn't matter, but ran into this while researching how to insulate my hanging discone...

http://www.repeater-builder.com/antenna/tree-antenna/tree-antenna.html

There's some fellow near Glenelg that has one of those fancy 4-corner vertical setups, along with a whole host of other antennas

The countryside in that part of MD is thick with folks from (ahem) places w/ lots of RF experience......

97
Equipment / Re: Up the discone!!
« on: June 06, 2020, 0236 UTC »
another lesson learned.  550 cord is a great RF insulator while dry, but when it gets wet...not so much.  Was wondering why everything got quiet after a few rain showers....

Will install a PVC insulator to deal with this issue tomorrow.

98
Equipment / Re: Up the discone!!
« on: June 01, 2020, 1612 UTC »
Some additional data....apparently the DJ-130 can survive free fall from about 40' onto a deck.  20lb test line does NOT hold up well.

Good news though, the 550 cord arrived and i used it to hoist the antenna back up.  As long as the squirrels don't eat it, and the branch holds, I think i'm in a good place.


99
Equipment / Up the discone!!
« on: May 15, 2020, 0010 UTC »
Today I started my little project to get some elevation on my DJ-130 discone.  It’s been mounted on a 2nd floor deck, but I want to try and raise it above the roofline if possible.

Its new home will be a tree so I broke out the fishing pole, lead sinker, and slingshot. I was pleasantly surprised to manage to get the line on a decent branch without the lead sinker breaking any windows or heads.  So far so good....

Next was to swap the 20lb test for something more substantial.  Unfortunately the 550 cord I thought I had was nowhere to be found beyond bits and pieces, but nowhere near the length necessary.  Amazon to the rescue, but that means it’s in a holding pattern for now.

100
SDR - Software Defined Radio / Re: SDR recommendation......
« on: May 13, 2020, 2350 UTC »
I'll second the afedri recommendation...very happy w/ mine (it's the HF/VHF version).

With 5 acres you could set up a pair of loops and phase them....that might be fun. 

101
Equipment / Re: Grounding A Radio
« on: May 13, 2020, 2317 UTC »
Make a big ol' "Enemy of the State" faraday cage and ground it to that.   ;D

J/k....you probably just need a counterpoise, so run some wire around the perimiter of the room or (as ThaDood pointed out) stuff it under the carpet!

102
Equipment / fun toys (digital multimeters/oscilloscopes)
« on: May 12, 2020, 1918 UTC »
Just putting this here....i'm a fan of things that leverage the damn expensive hardware i carry in my pocket...
https://pokitmeter.com/
https://www.oscium.com/oscilloscopes/imso-204

103
General Radio Discussion / Radio to the rescue!!
« on: December 29, 2019, 0133 UTC »
https://www.sciencemag.org/news/2019/12/us-tests-ways-sweep-space-clean-radiation-after-nuclear-attack

104
North American Shortwave Pirate / UNID 6955 USB 0205 UTC 08 Dec 2019
« on: December 08, 2019, 0212 UTC »
S3-S5.  SIO 444.
0205: Stray Cats Rock this Town
(another stray cats song, then some metal...)
0210: rap
0211: Popeye twist.  still SIO 444.
0213: guitar instrumental..Parisiene Walkways?
0216: Radio Ga Ga
0218: OTA



105
HF Mystery Signals / 7335 and 7365kHz CW? 20191116 0216 UTC to ???
« on: November 16, 2019, 1614 UTC »
Maybe CW?  Broadcast on 7335 and 7365 kHz 20191116 0216 UTC until ?????.  Captured from central MD, but also noted on Kiwis across eastern US (didn't check western US).  TDoA suggested SE US, maybe Florida....

Someone on HF chat commented that these are Radio Marti freqs.....


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