Buryflex all the way to K3?
Locked
 
|
I'm doing some rewiring of my shack and the antenna runs. I'm going to order
some BuryFlex which will be used as the main runs to both of my antennas. I'm trying to minimize the number and type of connections while doing all this. I don't yet have any BuryFlex as my previous runs were RG213 (Wireman CQ110) so I don't have a feel for its flexibility. RG213 is pretty stiff. I'm wondering if I can bring two BF lines up to the back of the K3/10 or will that be like connecting two anacondas to a church mouse? My alternative would be to make a couple of RG8X jumpers for the last few feet. thanks jim ab3cv ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
> I'm doing some rewiring of my shack and the antenna runs. > I'm going to order > some BuryFlex which will be used as the main runs to both > of my antennas. > I'm trying to minimize the number and type of connections > while doing all > this. I don't yet have any BuryFlex as my previous runs > were RG213 (Wireman > CQ110) so I don't have a feel for its flexibility. RG213 > is pretty stiff. > > I'm wondering if I can bring two BF lines up to the back > of the K3/10 or > will that be like connecting two anacondas to a church > mouse? Jim, two points: 1.) We should always have an entrance bulkhead ground at the building cable entrance that is bonded to the mains ground. This is where 99% of the lightning protection will occur. Why not run a small cable from there to the K3?? 2.) The loss at HF and even lower VHF in barrel connectors or connectors in general is immeasurable without very special methods. There is some bad information on Internet about it and some real wild myths, but the loss in a typical moderate to good PL259-barrel-PL259 is about .05 dB or so at 30 MHz, and less on lower frequencies. When I test connectors here at HF, I actually have to do it thermally with a few kilowatts of power!!! The loss is almost always too low to measure accurately on a $35k network analyzer at HF, even on a PL259/SO-239 combination. Unless you are on UHF or working EME on 144 MHz, there is very little reason to avoid changing cable sizes inside the dwelling. 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by Jim AB3CV
Thanks all for the input. I'll just run 8X jumpers from my bonding panel to
the K3. The operating point is on the first floor directly above the basement service entrance and bonding panel with polyphasers so it will only be 10ft. Now to order a bunch of coax and connectors. 73 jim ab3cv ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Buryflex all the way to K3?
|
|
Good choice. My first (and probably last) experience with BuryFlex is that
it should have been named SortaFlex. It's pretty stiff compared to Belden 9913F7, which is a dream to work with in comparison. (IMHO, of course. I know some people don't like it.) At HF and 6m, though, ten feet of 8X will be perfect. Bill W5WVO -------------------------------------------------- From: "Jim Miller" <[hidden email]> Sent: Sunday, May 30, 2010 1:37 PM To: "Elecraft Reflector" <[hidden email]> Subject: Re: [Elecraft] Buryflex all the way to K3? > Thanks all for the input. I'll just run 8X jumpers from my bonding panel > to > the K3. The operating point is on the first floor directly above the > basement service entrance and bonding panel with polyphasers so it will > only > be 10ft. > > Now to order a bunch of coax and connectors. > > 73 > > jim ab3cv > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by W8JI
On Sun, 30 May 2010 15:13:19 -0400, Tom W8JI wrote:
> There is some bad information on Internet >about it and some real wild myths, YES. That said, some of the "misinformation and myth" is based on the use of cheap, no-name junk connectors sold at hamfests and on the internet, often by "respected" ham vendors. >When I test connectors here at HF, I actually have to do it >thermally with a few kilowatts of power!!! Some of these junk connectors will fail the power test. I learned that the hard way, having bought a bunch of the junkers and put them in my station. One coax elbow overheated with 1.5kW in the first hour of contest operation, and failed (to the extent tht my Titan amp got very unhappy). It was VERY hot, because the internal connection for the center conductor was a tiny spring! My rule, learned the hard way -- stick to first quality, name brand connectors. Amphenol isn't cheap, but that's all I buy. If I were a mfr with a decent lab (like Tom, or W2VJN) and could do serious testing of other products, I might add other mfrs to that list. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by Jim AB3CV
On Sun, 30 May 2010 15:37:23 -0400, Jim Miller wrote:
>Thanks all for the input. I'll just run 8X jumpers from my bonding panel to >the K3. One thought. If you're going to operate SO2R and run power, you should probably use the bigger coax for the jumper, because the more robust shield can help interstation crosstalk. I did that in my shack for that reason, and it made a difference. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
> One thought. If you're going to operate SO2R and run
> power, you should > probably use the bigger coax for the jumper, because the > more robust shield > can help interstation crosstalk. I did that in my shack > for that reason, and > it made a difference. I'd be very surprised if that had anything to do with shielding Jim. Try this experiment if you have a network analyzer and an amplifier. take 30 feet of RG8X and wrap it tightly against another cable, but treat the ends properly. Terminate the amplifier end and measure cross talk signal on the other with the opposite end terminated. You'll measure virtually no crosstalk, certainly much less than -80 dB, with nearly any cable. Even very crappy Radio Shack cable that you can see through the braid is surprisingly good. After making dozens of measurements here, I concluded the major problems I had were from antennas coupling to antennas (even at 1000 foot spacing) and how connectors were mounted on radios and amplifiers, and things like BNC and phono connectors. I need to expand this page, but here is some actual data comparing coupling at 1/2 mile between antenna to ingress through the shield of one type cable. I think we far overestimate shield ingress. The real problem is poor connector mounting and grounding. (Sound familiar?) We use RG8X no problems, but I have cleaned up the grounding of connectors on all my RF equipment and panels. 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
Thanks all! My K3/10 is almost always running at 5w CW.
I'm really surprised and grateful for the great ears and enormous patience DXers have shown responding to my puny signal. I did note that the 70ft run to my dipole via RG213 was right on spec when I measured it at 0.5db of loss. But the 20ft of jumpers I had ate another 0.6db. I can eliminate those and will do so now that I'm aware of their penalty. I know it only means a fraction (pick a number...) of an S unit but when the DX on the other side of the world has to ask for a dozen fills I'll be happy to know I've done as much as I can to lessen their pain a bit. ;-) Best so far is an FO in French Polynesia and VQ in Diego Garcia with 5W and a 80ish foot wire dipole at 50ft in Maryland. 73 jim ab3cv ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by W8JI
On Mon, 31 May 2010 18:59:20 -0400, Tom W8JI wrote:
>After making dozens of measurements here, I concluded the >major problems I had were from antennas coupling to antennas >(even at 1000 foot spacing) and how connectors were mounted >on radios and amplifiers, and things like BNC and phono >connectors. You're certainly not wrong about what you call "grounding" and I call pin 1 problems. :) I do have an HP 3590D spectrum analyzer sitting in the shack, and put a simple loop on it to look at 2nd harmonics from my Ten Tec 425 amp and 160M vertical. It was about -44 dBc when I started, and I got it down to the rated -50 dBc by doing nothing more than changing coax jumpers. Now, I trust your engineering, and your measuring may be better than mine. :) 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by Jim Brown-10
> My rule, learned the hard way -- stick to first quality, name > brand connectors. Amphenol isn't cheap, but that's all I buy. > If I were a mfr with a decent lab (like Tom, or W2VJN) and > could do serious testing of other products, I might add other > mfrs to that list. > We used Kings double-crimp coax connectors for all our products and installations that went into the global mining industry where reliability and ruggedness were of paramount importance. These were selcted after a lot of testing, though admittedly not at 1.5 kW levels. 73, Lyle KK7P ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by Jim Brown-10
> I do have an HP 3590D spectrum analyzer sitting in the
> shack, and put a > simple loop on it to look at 2nd harmonics from my Ten Tec > 425 amp and 160M > vertical. It was about -44 dBc when I started, and I got > it down to the rated > -50 dBc by doing nothing more than changing coax jumpers. Something else was going on Jim. Not shielding. We cannot accurately measure harmonic suppression with a probe or loop unless the probe or loop is somehow frequency compensated for sensitivity as frequency changes. In short, the "antenna" used on the analyzer has increasing sensitivity for a given flux level with frequency. As I recall a very small loop open terminal voltage is about 8*10-6th times F times loop effective area. So your loop has 6dB more sensitivity as frequency doubles, although it could in practice be much more or even somewhat less because of other effects that might unintentionally compensate or enhance the change. More likely you changed the impedance presented to the tank circuit on the second harmonic. Changing 80 meter impedance at the 160 meter tank can radically affect harmonic suppression. Harmonic suppression will be less with a low impedance terminating a pi network on the harmonic, and greater with a higher impedance on the second harmonic. Just changing the velocity factor (electrical length) of the cable a small amount can change the level of the harmonic significantly. When we want to measure something, we have to be careful to actually measure what we think we are measuring. :-) Case in point, I have a 2nd harmonic stub on my 160 antennas. It is in a calculated sweet spot 1/4 wavelength on 80 meters from my amplifier pi-network loading capacitor. This makes maximum possible 80 meter Z across the load cap on the 160 amplifier, so the loading cap looks like a more effective short on 80. By altering nothing but distance of the stub from the amp to 1/2 wave on 80 meters on the 160 feeder, the harmonic suppression decreases 10-15 dB. Even the length of the cable to the matching system affects the harmonics, and each matching system is different! Changing cable electrical lengths will change harmonic levels significantly, even without a harmonic suppression stub in the system. 73, Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
On Mon, 31 May 2010 21:00:32 -0400, Tom W8JI wrote:
>Something else was going on Jim. Not shielding. >In short, >the "antenna" used on the analyzer has increasing >sensitivity for a given flux level with frequency. Agreed. But there's more -- my amp, a Titan 425, has an L network output, and there's a stub about three feet of coax from the output. Thanks to antenna switching, I can't get closer than that. So I'm looking to see some additional harmonic suppression, and so far I don't. That is, I don't see suppression when I add the stub. I'm confident of the stub tuning -- it was cut in a 50 ohm system (HP generator and HP analyzer), and tweaked at the 2nd harmonic. More on that below. >More likely you changed the impedance presented to the tank >circuit on the second harmonic. The coax I was changing was between the K3 and the amp. >Changing 80 meter impedance at the 160 meter tank can radically >affect harmonic suppression. Yes, and this is not generally understood. It's a general characteristic of all passive networks. >When we want to measure something, we have to be careful to >actually measure what we think we are measuring. :-) Yes. >Case in point, I have a 2nd harmonic stub on my 160 >antennas. It is in a calculated sweet spot 1/4 wavelength on >80 meters from my amplifier pi-network loading capacitor. >This makes maximum possible 80 meter Z across the load cap >on the 160 amplifier, so the loading cap looks like a more >effective short on 80. By altering nothing but distance of >the stub from the amp to 1/2 wave on 80 meters on the 160 >feeder, the harmonic suppression decreases 10-15 dB. Even >the length of the cable to the matching system affects the >harmonics, and each matching system is different! Changing >cable electrical lengths will change harmonic levels >significantly, even without a harmonic suppression stub in >the system. As it happens, the primary reason that I've been working on this is to study the effect of stub placement, with exactly these effects in mind. :) And I fully understand exactly what you're saying. But the source is not the only boundary condition contributing to the impedance along the line -- the antenna does as well. In this case, it's a vertical about 30-40 ft of RG8 away. It looks like 50 ohms at the fundamental. I haven't measured at the 2nd harmonic, but I'd bet the Z is prtty high. :) If you look at my website, you'll find a first draft of a tutorial on coax and stubs that addresses this issue. Any comments you might have would be appreciated. http://audiosystemsgroup.com/Coax-Stubs.pdf 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
Jim,
You say that foam dielectric is more costly and provides no benefit at h-f. If you are only considering dielectric loss this is true, but the lower effective dielectric constant allows (requires) a larger center conductor (for the same overall diameter) which fulfills your "big copper" idea. On a related note, this increased center conductor diameter also requires special connectors sized for the cable. Wes ps. Your first draft says, "Second draft" If you look at my website, you'll find a first draft of a tutorial on coax and stubs that addresses this issue. Any comments you might have would be appreciated. http://audiosystemsgroup.com/Coax-Stubs.pdf ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by Jim Brown-10
Hi Jim,
I gotta get back to work but...... >>More likely you changed the impedance presented to the >>tank >>circuit on the second harmonic. > > The coax I was changing was between the K3 and the amp. When we measure a change in a complex soup of interactions and fields formed by the interactions, we might never really know what we really changed or how we changed it. There could be a half dozen things going on, including that the actual harmonic never really changed in level at all. Collins fell into this trap with the unneutralized 30L1. The 30L1 amp, because it lacks neutralization, has inherent instability and regeneration problems. They started playing with coax between the amp and exciter, saw changes, and came up with a long fairy tale about 180 degree phase inversions in the coax between the exciter to amplifier coax. Unfortunately the conclusion they reached can be fully disproven in a matter of just minutes by observing the same things they did in a different way. Anyone thinking the coax shield has such a large effect needs only directly measure egress or ingress through the shield to see how little worry about the shield at HF is actually warranted. We are in a thick soup of radiation from our antennas, and even the worse cable shields "leak" far less than the fields from direct radiation. Far more important are common mode currents from poor antenna design, poor cabinet bonding, poorly thought out groundplanes, bad PC or wiring layouts, and poor connector mounting. Coax shields are way down the "problem" list at HF. 73 Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
«
Return to [K3]
|
1 view|%1 views
| Free forum by Nabble | Edit this page |