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Topics - i_hear_you

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1
10/11 meters / 11 meters is active 0320 UTC 25 July 2019
« on: July 25, 2019, 1524 UTC »
I'm tuned to 27025.  A guy is calling "579" and mentioned he's still on a dipole.  He's now razzing the "new kid" who has been "quiet lately."

2
Amateur Radio / Frequency Band Etiquette
« on: July 17, 2019, 1553 UTC »
Tip of the hat to IZS4 for the title.

About a month back I was calling CQ on 14230 and someone broke in informing me that is a SSTV channel.  I apologized and QSY.  However, during a contest weekend I heard stations stomping all over 14230 and 14233 on SSB phone.  I've also heard non-contest SSB phone QSOs taking place on these frequencies with SSTV over top.

What is good form here?  Avoid them for phone?  Use them for phone but QSY if asked?


3
Equipment / Waterproof Project Boxes
« on: July 15, 2019, 1449 UTC »
I'm looking for ideas on waterproof, nonconducting, strong (can handle the stress of wire antenna mounting points) and "machinable" (I have a Dremel) containers to use as the feed point for dipoles and elevated verticals.  It needs to have room for large coax chokes, I think a 4" cube would be perfect, but haven't found one yet.  I've turned up ABS and polycarbonate units with rubber gaskets that fit the bill, but not for under $20/piece.

Maybe I just have to shell it out, but figured I should ask here first.

4
Equipment / Multiple Radio/Antenna Safety
« on: June 28, 2019, 1901 UTC »
I'm looking into my first mobile install with a CB and a VHF radio.  I've also just acquired a second HF radio and am interested in using one for "ears" and the other for mostly TX.  I'm looking for some advice, feedback, and/or life experience regarding ensuring systems don't harm each other.

Questions I have:

-For radios and antenna systems in the same band (e.g. 20m) what sort of distances between TX and RX antennas are generally safe, and where on the wattage spectrum does danger of the TX hurting the RX radio approximately begin?  I've been using the pl880 with the antenna retracted and only TXing at most with 15w to test my sound, but I've been paranoid I'm hurting the pl880.  I intend to be TXing with 100w.

-For radios and antenna systems in different bands (e.g. 11m and 2m) the same question as above, and this will be on a vehicle so spacing will be tighter.  I don't suppose I have to worry much about the 4w from CB hurting the VHF, but what about 75w going the other way? Also, are transistors less vulnerable to damage from something like this if they aren't in use?  Would turning the CB off while using the VHF help protect it?

-Recommendations for a TX/RX radio switch are appreciate, or inline attenuators for the RX radio.  I believe these would allow one to blast away on TX and ensure a damaging voltage doesn't make it to the RX radio, but I have no experience here.

5
General Radio Discussion / Eham Offline!?!
« on: June 27, 2019, 1325 UTC »
I noticed last night that the forum was broken due to some missing PHP library, but now it seems the whole site is down.  Ouch!

6
Are 1/4" or 1/8" audio jacks and plugs contraindicated for field-swappable connections between coax connector and antenna terminals, or between coax connector, the coax ends of a toroid-wound choke and antenna terminals at QRP?  I'm looking for a way to quickly and easily swap or remove different chokes/baluns/isolators into the watertight junction box feedpoint of a vertical.

EDIT:

Same as above but with RCA?

7
Equipment / Vertical antenna SWR diagnosis
« on: June 14, 2019, 2112 UTC »
I just hung and tested a new 20m minimal vertical with peak about 22', feed point just over 6', and two raised radials sloping down to about 2' at the ends. Coax terminates to a UHF connector, which is hooked to a choke made of twin power cable wrapped through two stacked 31-material ferrite toroids for 13 turns. I am using 25' of rg8x for current testing.

I originally cut all three wires for about 17'. Initial SWR measurements showed a nice dip to 1.5 around 13 mhz, so I "shortened" each wire by about 6" by bending them back on themselves at the end insulators. SWR was now dipping at around 13.250 mhz, so i bent back another 6". Another check showed the same SWR dip at 13.250, so I didnt bother to shorten it yet again.

Any ideas what might keep the lowest SWR where it was after the second shortening? The wire is solid bare 18 AWG, so it makes electrical contact where it loops back and wraps itself. Could the toroid choke be causing it? Or my length of coax?

8
Equipment / Multiple dipole positioning
« on: June 03, 2019, 2010 UTC »
Hey all,

Awhile back I purchased a four-way remote antenna switch kit from the bay and intend to hang several dipoles cut to frequencies of interest.  The idea is a long run of coax to the switch, with the shortest possible coax lengths to the antenna feed points.  What sorts of orientations would minimize negative interactions between four dipoles?

9
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.

10
The RF Workbench / Loop Stick Ferrite Physical Connections
« on: May 07, 2019, 1935 UTC »
I'm building a ferrite loop stick comprised of two larger "rods" of 12 bundled rods, stacked end to end.  Each bundle of 12 is currently held tightly together with electrical tape on both ends.  I lined them up, then wrapped some more electrical tape over the joint.  There is the slightest of mechanical play between the bundles, but not within the bundles.

As I was checking the loop for proper inductance together with my air variable, I was also rotating the radio + ferrite assembly to test changes in signal.  I noticed some occasional wild oscillations of signal while handling the assembly, and I assume it is due to the imprecise and intermittent physical connections where the bundles meet in the middle, right where the coil currently sits. 

Any input on whether I should:

1) Move the loop to one end where it would then reside on a solid segment of ferrite ,
2) Put some Penetrox A between the bundles,
3) Figure a way to make that center joint mechanically stable.

Regarding these points:

1) I tested sliding the coil along the ferrite.  I don't know the EE theory here, but it seems the gain was highest with the coil in the middle, and I think I read that the inductance changes based on the position.
2) It seems intuitive to use a conductive paste between ferromagnetic materials, but I can't shake the feeling that's not how it works.
3) It will be tough, but not impossible, to get some stabilizing dowels inside the plastic cuff I am using.



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