View Full Version : Roast balun for dinner...
AE1PT
09-25-2012, 06:17 PM
http://ae1pt.com/photos/imh/roast-balun.png
Sad, isn't it? I was building a tuner table for quicktune of the new amp. Had just finished running new LMR-400 from the shack up to it to handle the wattage.
Balun is a Wireman type, supposedly rated at 2.5KW. The feed arrangement is about 30' of LMR-400 to the balun; ~50' of 450 ohm window line; and then 134' of dipole (67 x 2). Just a conventional doublet with a 4:1 current balun in the feedline. It seemed to be working fine at 300W, stayed that way at 500W, and then got real squirrely at 1KW. Whilst tweaking the reverse power (everything was well under 2:1).
The reflected power quickly rose up and pegged the needle. A quick look outside revealed nothing. 10 minutes later I tried again and replicated the first result. This time I went upstairs and looked at the balun box. Not much doubt that there was a little issue with it even before I opened it up...
My new dilemma. No way I am buying another of these. Obviously a full KW of continuous wave is not to its liking. There is no way to extend the window line and bring that into the basement. This leaves getting another make and spec of balun--or scrapping the doublet for now and getting a decent vertical in the yard before the snow drops.
Looking at this balun. Anyone familiar with it? I would be after the 'S' version. It has two toriods that are larger than the one in the Wireman that cooked.
http://universal-radio.com/catalog/antsup/5465.html
I have no real ideal on the vertical. It would have to be able to handle at least 500W of AM, and perhaps a bit more in RTTY mode. Any thoughts?
Ebay's yer buddy:
http://www.ebay.com/itm/4-1-Balun-for-Antenna-Tuners-For-10KW-Antenna-Tuners-Dr-Jerry-Sevicks-W2FI-/180903909098?pt=US_Radio_Comm_Antennas&hash=item2a1eb696ea
Your balun looks like it died from core saturation. Have a way to connect an antenna analyzer to the terminus of the balanced line and see what the system's impedance is at the frequencies of interest?
If the balun is truly rated at 2.5kw, and you managed to cook it with 1kw, I'd bet you have some severe impedances on certain bands. Fred's idea of getting an analyzer on the system is good advice. I also think that 50 feet of ladder line is not really enough to make the system present a reasonable impedance across all the bands.
What band did the balun fail on?
AE1PT
09-25-2012, 06:45 PM
I will borrow the club's analyzer tomorrow or Thursday.
The test was at 3.6Mhz. It has worked fine at ~100W since I reinstalled it here. The balun is new, as in my Tennessee QTH the window line ran directly to the tuner (Dentron MT-3000A). Although the plan is to put the wire 20' higher in the sky that will not add an awful lot of windowline, as there is already ~10 of slack in it now.
The twinlead comes down to the second story of the house, and from there makes the transition via coax to the basement.
I've used an MFJ-912 4:1 balun for several years now.
http://www.mfjenterprises.com/Product.php?productid=MFJ-912
I've run 500-600 watts of RTTY through it on several bands. I've run 1kw on SSB on several bands. I've never seen SWR rise, ever.
My 134 foot doublet is fed with 75 feet of 450-ohm ladder line to the balun, then about 15 feet of RG-213 to the tuner.
I hate when that happens.
By the way, smoked baluns taste best with a little teriyaki marinade, although I hear that some BBQ sauces really give them a kick...
OK, all kidding around aside... I was just reading the other day about someone who makes custom baluns, has been getting rave reviews. I'll see if I can find the link.
Might want to have a word with The Wireman about this. Don't know what your warranty is, but from the description, this is not a failure I would have anticipated. See what, if anything, they're willing to do about this.
FWIW, the only balun I have on an outdoor antenna at the moment is an old W2DU that I've had for a long, long time. Never had a problem with it. Did have another one that had a mechanical (not a balun) failure, the feeds to the dipole failed and snapped. But it was about 15 years old at the time, so I couldn't really complain!
Ah, here we go... http://www.eham.net/ehamforum/smf/index.php/topic,85201.0.html
Balun Designs (KZ5R) appears to be highly regarded. Couldn't hurt to talk to him... what's there to lose?
N2CHX
09-25-2012, 10:53 PM
That's designed to handle 2.5 kW? I'm not buying it. That thing is tiny. I've had to custom wind toroids for AM stations for emergency backup wire antennas and used cores way bigger that got pretty hot even at less than a kilowatt. 2.5 kW under perfect conditions maybe, but any kind of impedance weirdness and forget it.
Although the plan is to put the wire 20' higher in the sky that will not add an awful lot of windowline, as there is already ~10 of slack in it now.
How high is the antenna right now? I want to run a couple of calculations through the VK1OD TLLC program and I need a rough idea of the antenna impedance based on modeling it at a particular height in EZNEC.
Build an "ugly balun" out of 50 ohm feed line.
http://www.hamuniverse.com/balun.html
Build an "ugly balun" out of 50 ohm feed line.
http://www.hamuniverse.com/balun.html
That's a 1:1 current balun design. I suspect that Pat needs a voltage balun, and it has to be 4:1 (or greater) for his application.
Oh, I thought he was just isolating the (nasty) coaxial feed line from the (wonderful) ladder line.
Oh, I thought he was just isolating the (nasty) coaxial feed line from the (wonderful) ladder line.
He is, but you have to use a step-down transformer...unless the antenna/ladder line length happens to result in a relatively low feedpoint impedance (as is the case with a G5RV). It's possible to calculate dipole and balanced line length for a match at a given frequency but excursions far off either side of that value will see impedances begin to rise. So much so in the case of an extreme off-resonance condition that the balun core itself will begin to dissipate power due to incurred system losses. Which is what I suspect happened.
Yessah, cheap, lossy cores will tend to get hot. I can't remember where I ordered mine from when I was building my dual-L coupler, but they were not cheapies. I wrapped them in teflon tape. I've never ran more than 800W into it (1:1 current), but soon after the build and after a long-morning rag-chew, it was still cool as a cucumber. I plan to clean it up one of these days....yep, one of these days. And don't make fun of my "gater clips" either.
---
7393
He is, but you have to use a step-down transformer...unless the antenna/ladder line length happens to result in a relatively low feedpoint impedance (as is the case with a G5RV). It's possible to calculate dipole and balanced line length for a match at a given frequency but excursions far off either side of that value will see impedances begin to rise. So much so in the case of an extreme off-resonance condition that the balun core itself will begin to dissipate power due to incurred system losses. Which is what I suspect happened.
If I plugged in the correct numbers, a 134 foot doublet at 50 feet above ground should exhibit an impedance of 63 +j51 at 3.6 Mhz, at the feedpoint. According to VK1OD's TLLC online program, 50 feet of 450-ohm ladder line will transform that to an impedance of 1235 +j1212 at the 4:1 balun.
Small wonder the balun fried itself, assuming I have my numbers correct. Given Pat's resulting meltdown, I'd say I do.
Fooling around with some numbers, there are 2 choices:
The first is to increase the ladder line length to at least 75 feet (my configuration). This will take the feedpoint impedance above to 283 -j694 at 3.6 Mhz, at the balun. Obviously, this doesn't put nearly the strain on the balun as the original setup.
The second choice (and probably not a good one if using the antenna on higher bands) would be to shorten the ladder line to 35 feet. This will take the feedpoint impedance to 221 +j598 at 3.6 Mhz, at the balun. Again, less stress on the balun.
Then again, I could have totally fucked up the math.... ;)
AE1PT
09-26-2012, 02:03 PM
That's designed to handle 2.5 kW? I'm not buying it. That thing is tiny. I've had to custom wind toroids for AM stations for emergency backup wire antennas and used cores way bigger that got pretty hot even at less than a kilowatt. 2.5 kW under perfect conditions maybe, but any kind of impedance weirdness and forget it.
You know, I wondered the same thing when I opened it up. If there is an upside to this whole thing, it's that I am now coming to a whole new understanding of baluns. Funny how when some focused research is done things you thought you knew proved wrong--and in others the depth of ignorance was total? The great thing is that while stupid can't be fixed--ignorance can be cured with knowledge.
What I have concluded from this 'crash course' is that the Wireman balun is likely appropriate for use with a tuned, ladder line fed dipole--and is probably capable of 800W continuous input, with peaks to around 1.5KW. This is assuming no high or complex impedance's occur...
I also find that there are baluns that can be specifically engineered for antenna tuner usage, and the strange combination of impedance that may result with their use in finding a "match". A much larger toroid with different reactance and saturation characteristics is called for. Not the one I had. The suggestions made are being looked at. My guess is that the line is a little short, and that twisting about trying for a better match I caused the core to saturate. Pretty hard to recover from that by more adjustment unless the RF source is removed quickly.
I need to measure the exact length of the window line. Later today one end of the antenna will be let down and I can do that. Need to check something in the TenTec 'AcroBat' that is the center of the dipole and maybe do a little change there as well. As soon as I have the length and height measurements, they will be posted...
n2ize
09-26-2012, 02:20 PM
Pardon my ignorance but, if you are running "window line" why do you need a balun at all ? Can't you run it directly to a link coupled type of tuner ? Reason I ask is because I never had much luck with baluns, particularly if/.when I require a long duty cycle (such as when ragchewing on AM)... I destroyed more than 1 balun that way and I was running no more than 100 watts carrier each time. Balun was rated at least 1kw. On CW I had no problem. Short duty cycle all was well but otherwise they don;t seem to dissipate heat very well. That plus the fact that if there is heat indicates a power loss as energy is being dissipated as heat. Best for me was running the ladder line directly inside and directly to the tuner of link coupled type (coil and condensers but no balun inside).... Of course doing this is not always possible or practical I understand.
KG4CGC
09-26-2012, 03:04 PM
Pardon my ignorance but, if you are running "window line" why do you need a balun at all ? Can't you run it directly to a link coupled type of tuner ? Reason I ask is because I never had much luck with baluns, particularly if/.when I require a long duty cycle (such as when ragchewing on AM)... I destroyed more than 1 balun that way and I was running no more than 100 watts carrier each time. Balun was rated at least 1kw. On CW I had no problem. Short duty cycle all was well but otherwise they don;t seem to dissipate heat very well. That plus the fact that if there is heat indicates a power loss as energy is being dissipated as heat. Best for me was running the ladder line directly inside and directly to the tuner of link coupled type (coil and condensers but no balun inside).... Of course doing this is not always possible or practical I understand.
I don't know, John. Perhaps this will help though. I have an MFJ 948 antenna tuner. One of the output positions is switched for the use of balanced line. Inside is a balun for it. I suspect that since my radio has an output for a coaxial connector, the balun matches the impedances between coaxial cable and balanced line. The same balun also has a tap for a longwire option. I would never try to run balanced line from my coaxial connector. That just seems, irksome.
n2ize
09-26-2012, 03:17 PM
I don't know, John. Perhaps this will help though. I have an MFJ 948 antenna tuner. One of the output positions is switched for the use of balanced line. Inside is a balun for it. I suspect that since my radio has an output for a coaxial connector, the balun matches the impedances between coaxial cable and balanced line. The same balun also has a tap for a longwire option. I would never try to run balanced line from my coaxial connector. That just seems, irksome.
Okay, you are correct. I wouldn't suggest running balanced line straight out of the coax connector. However, I wasn't thinking that many of the present day MFJ tuners use a balun inside the tuner to match the unbalanced coax coming from the radio to the balanced line running to the antenna. I am using one of the old EF Johnson (link coupled) type tuners which uses an L/C network to match unbalanced to balanced. There is no balun inside the tuner nor anywhere along the feedline. it's entirely matched at the tuner without a balun.
This is what my tuner looks like this inside..
http://www.hamradio.me/wp-content/uploads/2008/07/mb_inside.jpg
AE1PT
09-26-2012, 03:21 PM
Pardon my ignorance but, if you are running "window line" why do you need a balun at all ? Can't you run it directly to a link coupled type of tuner ? Reason I ask is because I never had much luck with baluns, particularly if/.when I require a long duty cycle (such as when ragchewing on AM)... I destroyed more than 1 balun that way and I was running no more than 100 watts carrier each time. Balun was rated at least 1kw. On CW I had no problem. Short duty cycle all was well but otherwise they don;t seem to dissipate heat very well. That plus the fact that if there is heat indicates a power loss as energy is being dissipated as heat. Best for me was running the ladder line directly inside and directly to the tuner of link coupled type (coil and condensers but no balun inside).... Of course doing this is not always possible or practical I understand.
I had the window line running directly to the tuner in my previous shack in Tennessee. It worked great, but there was always a bit of stray RF wandering about on 15 and 10 Meters. Really obnoxiously so at 500-700W on the SB-200.
It would be possible to bring the line into the basement--down the side of the 2 story house, along the floor joists, and finally to the operating position. That would also add ~40' to the length of the window line. But it puts that line awfully close to far too many interconnects at the back of the bench. I have a type transmatch that has been modded for 50 ohm unbalanced (Johnson Matchbox) that I was thinking about running for AM use. More to think about. I just have a really sour taste about open line in the shack...
ab1ga
09-26-2012, 03:24 PM
And I always knew him as W6RCA... nice idea, though.
http://www.w5dxp.com/notuner.htm
Your balun was probably at a high-current point of the transmission line at that operating frequency. The high current caused the core saturation.
73,
KG4CGC
09-26-2012, 03:40 PM
http://i25.photobucket.com/albums/c79/bebop5/Aliens%20Guy/Tuner_zps8a5f1933.jpg
I've got a few big honkin' air variables (20KV plate spacing; 250pF butterfly being one of them), some vacuum relays and access to silver-plated tubing...stepper motors and controllers. One of these days - when I move and get a sloper or quadrature flat-top array in the air - I'm going to build a remote transmatch which will handle balanced lines sans the use of a balun.
John, 'ize may remember one of several designs which were popular years ago. The tricky/fun part will be the design and construction of a memory and band switch interface logic circuit so the radio/amp to which the thing is connected can command it to remote-tune for minimum reflected power.
It's a solution which may not work for everyone but those parts have been bugging me to do something constructive with them for years.
n2ize
09-28-2012, 03:55 AM
I had the window line running directly to the tuner in my previous shack in Tennessee. It worked great, but there was always a bit of stray RF wandering about on 15 and 10 Meters. Really obnoxiously so at 500-700W on the SB-200.
It would be possible to bring the line into the basement--down the side of the 2 story house, along the floor joists, and finally to the operating position. That would also add ~40' to the length of the window line. But it puts that line awfully close to far too many interconnects at the back of the bench. I have a type transmatch that has been modded for 50 ohm unbalanced (Johnson Matchbox) that I was thinking about running for AM use. More to think about. I just have a really sour taste about open line in the shack...
Yeah, I can concur. I used to like to keep the ladder line running as directly as possible to the tuner with a few routings around other wires and objects as possible. This often meant
keeping as much of it outside and as little of it inside as possible. One setup I had for a while involved running from the antenna to the attic, then into feed through insulators mounted on the attic window. Then into the shack via a hole in the closet ceiling. The tuner sat inside the closet on an upper shelf so as little ladder line as possible was in the actual room. When i needed to tune I had to reach up to the top shelf and dial the tuner while watching my meters at the same time. It was awkward but it was the only way I could keep the rf from overloading my compressor/limiter. Believe it or not the compressor/limiter was designed for AM Bcast use yet it was the most rf prone component in my audio chain. In later years I ran the ladder line.right in through the shack window and kept the tuner on the bench. Much more convenient that way. But by then I was using a different compressor/limiter that seemed less rf sensitive. Also made it possible for me to disconnect the antenna or at least throw it out the window when the sky turns bluish-grey and starts rumbling and flashing. But yeah, I know, keeping rf away from stuff can be very tricky...
BTW I have heard of some guys keeping the tuner out side and operating it remotely...
AE1PT
09-28-2012, 02:53 PM
http://ae1pt.com/photos/imh/newbalun.png
Here is part of the fix!
eBay was indeed my friend--as direct from the manufacturer was $6 more--not including the shipping. The core in this one is obviously much larger--and nearly three times the thickness. From all appearances, the entire build quality is pretty solid too. While I know that I can saturate this baby too--it's going to be a bit harder. From the design specs, this balun is designed to work with tuners--and deal with a wider range of impedences as a result of that. These are the internals of the tuner that it will hook to:
http://ae1pt.com/photos/imh/tuner.png
The quarter is thrown in for reference... :-D
So I did the measuring. The doublet is fed with 61' of window line, and elevated 45'. The dipole legs have 'stretched' out just a bit since I hung it, and now stand at 134' 5". I doubt that I am going to trim that out. What is going to happen is that the wire is going 20' higher in the air--and I am shortening the coax run to the balun down to 16'. With the added wire, this will put the WL at 75-80'.
Today I was at the place to pick up the antenna analyzer. Duh. I did remember to buy my advance ticket to the Elmira Hamfest tomorrow though...
Those Dentrons are good tuners. It's a real shame the company went belly up, but that's another story.
Those Dentrons are good tuners. It's a real shame the company went belly up, but that's another story.
I can tell you some stories regarding that.
I thought Dentron got bought by MFJ. Or does that count as going belly-up...?
KG4NEL
09-28-2012, 04:55 PM
I thought Dentron got bought by MFJ. Or does that count as going belly-up...?
He just does this now: http://caryaudio.com/
:)
AE1PT
09-28-2012, 05:09 PM
I thought Dentron got bought by MFJ. Or does that count as going belly-up...?
The story of Dennis Had...
He is the one who developed Ameritron--which of course now is owned by MFJ. Other companies he founded include Dentron, Amp Supply, and Cary Audio Design. Fred is right. There are some real stories about all of the companies--but especially ham equipment. Dentron and Amp Supply died of their own devices...
Depending upon where one is in the design cycle of Had's gear--one can have a gem or a lemon. I seem to be good right now with the 3000A and the LK-500ZB. As far as I know, they never underrated the parts... :clap:
P.S. On edit reading the previous post--Had retired just about three years ago. Who knows what he is cooking up now--but given his demeanor when amateur radio is mentioned it won't be anything there...
Depending upon where one is in the design cycle of Had's gear--one can have a gem or a lemon. I seem to be good right now with the 3000A and the LK-500ZB. As far as I know, they never underrated the parts... :clap:
They underrated the PS in the DTR-2000L. It's a shame, really. The 8877 would be much happier with 3,500 volts.
http://forums.qrz.com/showthread.php?166789-Ok-what-s-the-big-secret-about-a-DTR-2000L
Even though I don't use it anymore, I'm really impressed with the MT-3000A. Not giving mine up anytime soon, just in case I need a back up to the Palstar AT-1500DT.
AE1PT
09-28-2012, 07:38 PM
They underrated the PS in the DTR-2000L. It's a shame, really. The 8877 would be much happier with 3,500 volts.
That's a common complaint. Stuff a big ceramic in the case--and essentially design a 1KW amp around it. But it's still great quality on the components, and that is what I really meant about underrated. All of Had's stuff was built like little tanks...
Even though I don't use it anymore, I'm really impressed with the MT-3000A. Not giving mine up anytime soon, just in case I need a back up to the Palstar AT-1500DT.
Agreed! Mine will find a new owner at the estate sale... :cool2:
I thought Dentron got bought by MFJ. Or does that count as going belly-up...?No, Dentron went out of business. Ameritron got bought my MFJ. Amp Supply basically disappeared, as Dennis basically phased it out as he got into his audio business.
A lot of this is documented hither & thither on the web. Of course, there are some conflicting stories as well.
But I can still picture the look on KQ3T's face when he unpacked the MLA-2500 amp that Dentron had shipped to the store. No tubes. No top cover. They were on "back order" but never came. Dave ended up buying tubes from one of our gray market suppliers (EGE, which later got absorbed into HRO) & sold the amp at a loss to someone who was going to fabricate a new top cover.
ka4dpo
09-29-2012, 09:58 PM
Pardon my ignorance but, if you are running "window line" why do you need a balun at all ? Can't you run it directly to a link coupled type of tuner ? Reason I ask is because I never had much luck with baluns, particularly if/.when I require a long duty cycle (such as when ragchewing on AM)... I destroyed more than 1 balun that way and I was running no more than 100 watts carrier each time. Balun was rated at least 1kw. On CW I had no problem. Short duty cycle all was well but otherwise they don;t seem to dissipate heat very well. That plus the fact that if there is heat indicates a power loss as energy is being dissipated as heat. Best for me was running the ladder line directly inside and directly to the tuner of link coupled type (coil and condensers but no balun inside).... Of course doing this is not always possible or practical I understand.
Exactly. A KW Johnson MB would handle your amp and just about all of the mismatch you could hand it all day long. Course they don't do 160 or the WARC bands but any well designed link coupled tuner will do a much better job with a lot less loss.
KG4NEL
09-30-2012, 10:48 AM
Exactly. A KW Johnson MB would handle your amp and just about all of the mismatch you could hand it all day long. Course they don't do 160 or the WARC bands but any well designed link coupled tuner will do a much better job with a lot less loss.
Only reason I haven't bought one :(
n2ize
09-30-2012, 02:06 PM
Exactly. A KW Johnson MB would handle your amp and just about all of the mismatch you could hand it all day long. Course they don't do 160 or the WARC bands but any well designed link coupled tuner will do a much better job with a lot less loss.
i have the smaller 250 W matchbox and I have pumped considerably more than 250 W through it continuous keydown fully modulated AM and it handles it with no problem. No flash overs, no ,meltdowns, nothing burning. It's a great matching device, by far the best I have ever owned.
n2ize
09-30-2012, 02:10 PM
Only reason I haven't bought one :(
I have heard of some mods floating around to get the matchbox to tune down on 160 and on some of the WARC bands. Then again, link coupled tuners are pretty easy to build. Friend of mine bought a hombrew link coupled tuner at a ham fest. All the components were mounted on a wooden board and you used an alligator clip to tap the inductor. I'd imagine it wouldn't be hard to build one that will work on the warc bands. Or modify an existing Matchbox.
KG4NEL
09-30-2012, 09:46 PM
I have heard of some mods floating around to get the matchbox to tune down on 160 and on some of the WARC bands. Then again, link coupled tuners are pretty easy to build. Friend of mine bought a hombrew link coupled tuner at a ham fest. All the components were mounted on a wooden board and you used an alligator clip to tap the inductor. I'd imagine it wouldn't be hard to build one that will work on the warc bands. Or modify an existing Matchbox.
I think this looks badass, but I wonder if there's a way to cover 160 without having to swap out coils.
http://www.wz5q.net/index/shack_data/tuna.htm
Since I don't really have the tools or skill yet to do a decent metalworking job, a plexi-and-wood open chassis fits me perfectly :twisted:
n2ize
10-01-2012, 12:21 PM
I think this looks badass, but I wonder if there's a way to cover 160 without having to swap out coils.
http://www.wz5q.net/index/shack_data/tuna.htm
Since I don't really have the tools or skill yet to do a decent metalworking job, a plexi-and-wood open chassis fits me perfectly :twisted:
Looks nice. But, it might even be overkill depending on what power levels you are using. Plus the vacuum variables are going to be quite expensive, unless you already have them on hand oir can find them cheap at a hamfester. . You can probably scale it down and use 100-200pf air variables (with adequate spacing) and it will still handle a KW with no problems. Use a large enough inductor and alligator clip it to the appropriate part of the coil for each band.
I think this looks badass, but I wonder if there's a way to cover 160 without having to swap out coils.
http://www.wz5q.net/index/shack_data/tuna.htm
Since I don't really have the tools or skill yet to do a decent metalworking job, a plexi-and-wood open chassis fits me perfectly :twisted:Interesting. What kind of power does he plan to run through that... 10 kW or 20?
Seriously, I admire the work, and he admits the overkill in the text... but that's just what that is, overkill.
K7SGJ
10-06-2012, 10:29 PM
Interesting. What kind of power does he plan to run through that... 10 kW or 20?
Seriously, I admire the work, and he admits the overkill in the text... but that's just what that is, overkill.
Yeah, but if you got tired of radio, you could build a still with the parts.
XE1/N5AL
10-06-2012, 10:50 PM
Yeah, but if you got tire of radio, you could build a still with the parts.Or, just modify the existing design to serve a dual purpose. There's no reason why a ham can't operate with excessive power and alcohol levels at the same time.
K7SGJ
10-07-2012, 09:16 AM
Or, just modify the existing design to serve a dual purpose. There's no reason why a ham can't operate with excessive power and alcohol levels at the same time.
They do. There are special frequencies where the pickled ham basking in RF warmth can can be found.
They do. There are special frequencies where the pickled ham basking in RF warmth can can be found.
Start with the AM frequencies. ;)
ab1ga
10-07-2012, 04:18 PM
... Plus the vacuum variables are going to be quite expensive, unless you already have them on hand oir can find them cheap at a hamfester.
...
For that kind of money I'd just a soon buy a diffusion pump and build the whole thing in a vacuum vessel!
73,
So I did the measuring. The doublet is fed with 61' of window line, and elevated 45'. The dipole legs have 'stretched' out just a bit since I hung it, and now stand at 134' 5". I doubt that I am going to trim that out. What is going to happen is that the wire is going 20' higher in the air--and I am shortening the coax run to the balun down to 16'. With the added wire, this will put the WL at 75-80'.
So, what was the final outcome?
AE1PT
10-20-2012, 01:56 PM
So, what was the final outcome?
Outcome?
I mounted the new balun and am keeping everything below 500 watts. Not like I have gotten on the air much. In the interim I ordered another roll of window line, and a Saunders Zip Reel for my tennis ball launcher. The leaves finally fell out of the tree in the back that the other end of the dipole runs to--so I have a clean shot to the fork I am interested in which is about 25-30' further up the tree. I have to mount the Zip Reel yet--that may be a tomorrow project.
Once I raise the antenna on both ends, I have made my mind up to bring the window line all the way to the tuner. Project #214 has been building a new operating desk. The lumber for that was picked up this morning--and construction can start in about two weeks. The way I am setting everything up will easily lend itself to the line not being near other wires in back of the shelving system which will hold the gear.
I did borrow the antenna analyzer. MFJ-259. It may be the bomb for coaxial lines, but it is a POS for open transmission lines...
KG4NEL
10-20-2012, 11:37 PM
It has LCDs and things never imagined by users of open wire line. You're supposed to lick your fingers and feel how much current is going to the feedpoint :D
I did borrow the antenna analyzer. MFJ-259. It may be the bomb for coaxial lines, but it is a POS for open transmission lines...
MFJ offers an accessory package for the 259/269. Included are a couple of coils which attach to the antenna connector and turn the instrument into a grid-dip oscillator. Do you have access to such, or can you build a reasonable facsimile of the low-band coil? (I have the set and will provide construction details if you wish.)
After equipping the meter thusly, short the shack side of the ladder line with a coil made of 3-4T wire; its diameter should be close to that of the GDO coil and will inductively couple the instrument to the transmission line. You will then be able to read resonances and high-impedance points with it.
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