Messages

91

Equipment / Re: Super Sized MW Loop Antenna Mark 3

« on: May 31, 2019, 1712 UTC »

The effect of self-capacitance is that you can't tune a loop above some frequency

So it is mostly just adding capacitance to the LC circuit, thus lowering the tuning range.

92

Equipment / Re: More Wire, Higher Wire, Longer Wire

« on: May 31, 2019, 1708 UTC »

I think my comment stemmed from seeing quite a few people (usually on the Facebook SWL groups) complaining about not hearing stations others are reporting, especially the pirates.

Ah, now I follow you.  When I say I enjoy DX with the portables, what I mean is I enjoy seeing what they can do and maximizing their performance.  They have a coolness factor for me not unlike the fascination I feel when I see an old muscle car.  Before I began SWLing, I would spend time with the KX3 monitoring ham chatter.  Compared to any of my portables, the KX3 is the superlative receiver, but I just don't find it as fun to use!

I'm certain I'll eventually arrive at a dedicated SDR monitoring station.  I have an rtl-sdr that I used for UHF/VHF monitoring, and was blown away when I realized I could have it recording several channels at once, limited mostly by the computer I was using.  I saw a forum post at an FM and TV DXing site detailing recording a whole 10Mhz of broadcast FM during a sporadic E opening for later analysis, like you do for SW pirates.  This is powerful stuff.

93

Equipment / Re: More Wire, Higher Wire, Longer Wire

« on: May 29, 2019, 2114 UTC »

That's a great observation and question. 

Several reasons come to mind:

1) I enjoy portability. My first personal electronics were a Sony Sports Walkman that I took with me everywhere and I used until it finally gave out. I also preferred portable gaming systems to wired ones when I played vidya.

2) I am interested in off-grid comms, so I prefer battery-op radios, even for RX-only.

3) I enjoy comparing the various radios against each other.

4) I'm interested in preserving them and passing them down.  My little girls already have their own (RF-1170) in their room and are discovering a love for radio.  I intend to make a "radio room" with a museum feel to it.

5) I love the styling of all of them.  I would have a hard time picking a favorite, and while I've never had the collector's bug before now, I think it has taken hold.

When you say "nice communications receiver" I assume you mean something like an Elecraft K3, or top of the line Icom, Yaesu, or maybe something older like the Drakes that are highly praised.  These are amazing radios, but they can't be carried from room to room or out on vacation like a shortwave "boombox."  And there is a certain "fun factor" that I cannot explain, but I'm sure you understand what I mean, that I find in the several portables I now own that my KX3 does not have. 

If I decide to get more serious about radio performance, I've decided I'll go the SDR route.  Based on posts I've read of yours, I'm sure you appreciate this.  My understanding is that you need to start spending 5 figures to outclass a powerful computer with a good SDR attached.

94

Amateur Radio / Re: HAM Radio FUNgus

« on: May 29, 2019, 2040 UTC »

do statistics on him to see how many huhs per qso are on average, peak, etc.

 :')

Please put a graph up. 

It didn't take long for my wife to start saying things like "today I got muh tires replaced, and I spent some time watching the paint dry, but first I sat down and looked at muh lawnmower blades, before getting some gas for muh automobile" when she sees me scanning.  I have to counter with "if you listen long enough some of these guys discuss engineering stuff."  To which she rebuts "you've told me how depressing it is when you hear the old timers discussing their lives."

I wouldn't say it's my favorite aspect of the hobby, but I do enjoy listening to technical conversations between the more engineering-minded. However, I've heard far too many conversations between extremely old men recounting their long lives, discussing how they were radiomen during WW2 or Korea, how they met (and when they lost) their wives, what they did for a living in their long-ago retired profession.  It depresses me on a deep level, especially as it comes disembodied from the ether late at night, like whispers from a couple of ghosts.

95

Equipment / Re: Super Sized MW Loop Antenna Mark 3

« on: May 29, 2019, 1948 UTC »

What's the effect of the self-capacitance, though?  I assume it's more than "it just lowers the tuning range," and I figure it must lower Q, but don't know the physics behind it. If you are trying to achieve highest Q, is it best to increase or decrease the inductance of the coil and make up the rest with capacitance?

I'm having a hard time finding answers to this online.

96

Equipment / Re: More Wire, Higher Wire, Longer Wire

« on: May 29, 2019, 1944 UTC »

My true "first" is a CountyComm GP-5 SSB, and I remember thinking "this is going to f**king ROCK" when I hooked about 70' of speaker wire I'd strung on the ceiling to it.  There were images and ghosts EVERYWHERE across that thing and I immediately started looking to upgrade.

The Tecsun was my first serious world band radio, but I made some rapid acquisitions in the last month.  I now own an ICF-5900W, RF-2200, RF-1150, and ICF-2010.

I have ferrite-wound isolating transformers at the receiver and antenna ends.  I suspect this adds some attenuation, and most certainly it protects from static buildup.  There was only one night a couple weeks back where the Tecsun started having image problems, I assume from frontend overload.  Signals were just booming in.  I either did not see this issue with the other radios, or the issue was resolved by switching to "local" from "DX" on the offending frequencies.

I feel like Rain Man, but one of my biggest joys currently is A/B/C/D/Etc testing these radios and seeing how they stack up.

97

General Radio Discussion / Re: Are you under 30 and how did you get interested?

« on: May 29, 2019, 1905 UTC »

I just turned 40, and like a time capsule opening, my interest in SWL and focus on learning the EE details of radio TX and RX has sprung forth.

In the mid-80's I saved my allowance for a couple years and purchased a yellow Sony AM/FM and cassette Sports Walkman.  I've always been interested in listening to music, and this allowed me to tune in to an FM station that played some forward-thinking music (techno was just blossoming at the time) as I fell asleep.  I also enjoyed recording things to cassette and listening to them later.

In the early 10's I got involved in ham radio.  My driving force is off-grid comms, QRP is my biggest interest.  Very recently I've started collecting "vintage" receivers, cleaning them up and seeing what they can pull in.

...I am not into it to make contacts or to do other ham-like activities...The physics of it just makes me really happy...

I feel mostly the same.  I don't enjoy VHF/UHF repeater ragchew, and the idea of SW contesting doesn't interest me.  My biggest thrill is designing a new (and hopefully improved) antenna system, then testing it out.  In that regard, I enjoy seeing if I can make a few contacts from time to time with my modest 15 watts. But mostly, I've become addicted to continually improving my wide-band SWL receive systems.

I'm a big fan of electronic music, both listening to and producing.  I'm a yank and a bit young, and so I missed the UK rave explosion.  But even more sadly, the US doesn't have the FM pirate culture the UK still has.  That brings me to the final point:  I detest the state of AM/FM and even SW broadcasting in my locale and realize I may need to be the change I want to see.  If you know what I mean.  And I think that you do.

98

Equipment / Re: More Wire, Higher Wire, Longer Wire

« on: May 29, 2019, 1803 UTC »

Josh,

Thanks for the detailed information.

In other news, I had major storms last night and so was stuck listening to AM on inside antennas.  I've only just begun SWL in earnest April 1st of this year when I received my Tecsun PL880, and so this was a first.  I learned that the static crashes begin well before the first flash, and I was using this as a cue to look out the window in order to see some bolts.

99

Equipment / Re: Super Sized MW Loop Antenna Mark 3

« on: May 29, 2019, 1754 UTC »

I haven't worked with the copper tubing yet.  I took straightening it for granted.

The design for my "furniture-grade tuned loop" includes a 9PST rotary switch in order to select between 1 to 9 (the full coil) windings.  I'm hoping I can grab some meaningful SW with less windings, but my SW experiments on the large ferrite assembly were failures. I want something clean for the splices between the loop wire and the wires leading to the switch and I settled on cutting segments of this copper tubing, placing it in the drilled hole, passing the coil wire through, and drilling a hole in the part of the tube sticking out for the wire lead to the switch. 

Now that I say all this it seems like a lot of work for very little payoff.

100

Equipment / Re: Super Sized MW Loop Antenna Mark 3

« on: May 29, 2019, 1553 UTC »

If you are concerned about weatherproofing the ferrite, it's not difficult to seal the ferrite assembly inside PVC tubing.  In fact, the RGP3 construction assumes this. 

It may be worth a quick experiment using one of your rods for the inductive pickup.  The small amount of ferrite, relative to the coil area, probably doesn't measurably increase the gain of the large loop.  However, my understanding is that an inductive coil concentrates the magnetic field lines near the central axis, and I believe a rod in the center would concentrate that even further and allow for a small, neat coupling coil directly on the rod.

Have you considered refrigerator copper tubing?  With 7' sides at 4 turns, I have you at roughly 112'.  It shouldn't be too difficult to sweat them end to end.  A quick price check at Home Depot shows 20' of 1/4" OD copper tubing at about $15, so 6 of those runs you about $90.  It's perhaps a bit pricey for an experiment that may not pan out, but once you finalize your design it's something to consider.

101

Equipment / Re: Super Sized MW Loop Antenna Mark 3

« on: May 29, 2019, 1337 UTC »

That's cool stuff.  I've now built two tuned loops for BC AM, and the increase in gain as I increase size has me planning even bigger loops.

I recently built an RGP3 (a large loopstick made of several smaller ferrite rods) and have meant to experiment by placing it in the central axis of my largest tuned loop.  I'm not clear on the relationship between the distance of the coil to the ferrite core, or of the area ratios between their respective cross sections.  It probably wouldn't help increase nulls, but my gut tells me it would give even more gain, and if nothing else, it should allow for a turbo-charged small inductive winding for the antenna lead.

Maybe you have some ferrite rods and might experiment 

***EDIT***

I've been researching how to increase the efficiency of tuned loops and am not clear on what wire spacing on the coil does for performance (I suppose Q, in this case).  I understand the closer the wires in the loops, the higher the capacitance, but what does that really mean overall?  In particular, my RGP ferrite is about 14" long, but the coil is currently about 3" long, and I wonder if it is worth trying to spread that out over most of the ferrite length.  I'm also planning a 4' cross-arm tuned loop, I have it calculated at 9 turns.  I intend to make it out of hard wood, stain it, make it really nice like a piece of furniture.  Currently I have it planned with .5" spacing, but if it doesn't make much difference, I would like to change that to .25" for weight and size reasons.

Can someone weigh in on this?

102

Equipment / Re: More Wire, Higher Wire, Longer Wire

« on: May 29, 2019, 1322 UTC »

This is meant for wide-band receive, so a traditional mono-band dipole is probably out for now.  I have some 300-ohm window line available, I'll look into the T2FD.

Josh, regarding the resistor for static discharge, would that be in addition to the ferrite isolation transformer at the antenna side? 

103

Equipment / Re: More Wire, Higher Wire, Longer Wire

« on: May 24, 2019, 2154 UTC »

Thanks for the reply.

Seeing as this is for receive only, if I hung a wire over the tallest branch I can snag, let it drop straight vertically, would this be an improvement over the longwire?  Would it require a ground rod? Or whatever counterpoise I can muster?

My understanding is that for RX purposes, we are trying to deliver the highest signal voltage as compared to ground as possible, so a RF ground rod provides that "zero" against which the antenna can be compared. But a counterpoise is needed for TX because of EM fields within a wavelength of feed point. I have zero experience with verticals, but I can say that once I added my mess of wires as a "ground" to my random wire, there was a noticeable increase in signal strength.

It has been fun and rewarding so far, but my next steps will be more costly, time consuming, frustrating (I'm not very good with my wrist rocket) and its appreciated when the experience of others prevents the frustration of failure 

EDIT:

Regarding the 9:1, I'm ready to experiment, I have two other mixture types, and enough to try 1:1, 1:4 and 1:9.

104

Equipment / More Wire, Higher Wire, Longer Wire

« on: May 24, 2019, 1911 UTC »

While I enjoy experimentation, I must balance cost and return, as I'm sure the vast majority of you do, as well.  I preface with this to head off the "just try it and find out" replies!

Over the last two months I've grown and improved my SWL antenna system passing through the following phases:

1) A long wire strung as straight as possible along the ceiling from one corner of my house to the other on the second floor,
2) 80' or so of wire outside the house leading off into the trees and connected directly to the center conductor of rg59 that makes ingress into the house to a wall plate, and a jumper leading from the plate to the radio,
3) Adding a 1:1 ferrite binocular isolation transformer between the coax center/shield and the radio's two antenna terminals,
4) Adding a 9:1 ferrite toroid isolation transformer, one winding connected to antenna wire and ground, with ground being a short wire leading to and soldered onto to a pile of old audio cables that are sitting on the ground (covered with woodchips for marital bliss), and the other winding to coax center/shield.

The final refinement I am considering is to add 100' or so of wire into the air, and push the coax connection off into the woods with a proper Earth RF ground.  The thing is, the steps I've taken so far have given me a very strong S/N, I'm very happy with the results. However, 15Mhz and up is very quiet, and I realize that is probably due to propagation conditions, and probably also my ferrite choices for the transformers.  I also have a lot of fading on some SW frequencies, but my understanding is more wire won't help that, and this requires tricks like diversity receive, antennas that are a wavelength apart, etc.

I'm interested to hear if anyone has made a similar jump and heard a noticeable difference by adding that last 100', and moving it terminus that extra 50' from the house.

105

The RF Workbench / Re: Loop Stick Ferrite Physical Connections

« on: May 09, 2019, 1332 UTC »

spacing the coil from the cores

In fact I do mean to try this before I commit to the final enclosure.  I more thoroughly experimented with coil position along the ferrite core length last night, and the sweet spot seemed as hard to hit as did tuning the cap without a vernier.  Based on a mental running average of the DBU and DBV reported by the pl880 it seemed the highest gain was achieved just off of center.  However, a new variable entered in:  because the coil sleeve doesn't currently fit snugly over the ferrite core, the central axis of the coil can pitch and yaw out of parallel with the central axis of the core. 

If the wire distance from the ferrite isn't noticeably detrimental to performance, I am considering trying to engineer a sliding mechanism for the coil to create a second form of tuning in addition to the usual variable cap.  Think about the pump on a shotgun:  I envision the core tightly packed inside a PVC tube, and another PVC cuff wound with the coil that fits snugly on the outside of the tube and slides along two metal rails, and these will make the appropriate connections to the coil and cap to complete the LC circuit.

It may not be worth all the extra work, but it sounds fun to try and fabricate it.