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Author Topic: Recently purchased a Johnson Matchbox...  (Read 3305 times)
K9SRV
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Posts: 121




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« on: August 02, 2012, 12:34:58 PM »

And have been thinking about antenna choices for multiband use.
Right now I'm leaning towards a 40 meter extended double zepp,
fed with 450 ohm ladder line right to the matchbox. I realize there
will be many lobes of gain and nulls as I go up in frequency.

Can anyone suggest a better alternative? BTW, the antenna will be N/S
exactly, but I will be able to swivel it a bit NW/SE in order to hopefully catch
some of the upcominng African DX-peds.

Thanks,
John
PS. I have NOT ordered ladderline yet. Any particular type from
the wireman that you guys would favor?
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WX7G
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Posts: 5920




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« Reply #1 on: August 02, 2012, 12:52:42 PM »

I would order the stranded wire ladder line from The Wireman, type 552.
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W5DXP
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« Reply #2 on: August 02, 2012, 03:50:58 PM »

Right now I'm leaning towards a 40 meter extended double zepp,
fed with 450 ohm ladder line right to the matchbox.

Technically, an EDZ (extended double Zepp) is a single-band antenna because the dipole length is defined as 1.25 wavelength. The formula for that length is 1200/f which would make it about 168 feet on 40m. Optimum length for 450 ohm ladder-line would be ~85' which would work well on 80m, 40m, 17m, and 10m. The other HF bands could present a problem for the matchbox which is not as wide a matching range as a CLC T-net tuner.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K9SRV
Member

Posts: 121




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« Reply #3 on: August 02, 2012, 06:05:13 PM »

Thanks a lot guys! Those bands would work well for me
as I have a 40 meter delta loop w/ a balun designs 4:1
that seems to work great on 20, 15. I have a Hamstick dipole
for 12, so the 40 EDZ would seem ideal to cover the bands I
cant work yet. Cecil, thanks for the 85 ft. advice! I knew ll lenght
would add to the equation, just forgot to ask the ideal size.

Thanks again!

John
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WB6BYU
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Posts: 13027




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« Reply #4 on: August 02, 2012, 07:11:12 PM »

Choice of feedline partly depends on the bands you are operating and the load impedance.
While stranded wire increases flexibility and CopperWeld(R) wire adds strength, both increase
the losses somewhat on the lower bands where the skin depth of the copper coating isn't
as thick in wavelengths.  The steel core will have higher hysteresis losses, particularly at
high currents (which you can get at a high SWR even if the load impedance itself is high.)
The stranded CopperWeld is particularly bad, as the copper on each strand is considerably
thinner than it would be on a solid conductor of the same overall gauge.  This is probably
most important for operation on 80m and 160m.

It just shows that choices aren't always as simple as they might appear.
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K9IUQ
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Posts: 1626




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« Reply #5 on: August 03, 2012, 05:09:27 AM »


Can anyone suggest a better alternative?

PS. I have NOT ordered ladderline yet. Any particular type from
the wireman that you guys would favor?

Sure. Your Matchbox was made for the "real True open wire feedline" not the glorified TV open wire feedline stuff on the market today. You can buy it here: http://www.trueladderline.com/index.html

Or you can make it yourself. It looks beautiful going up to your antenna and works much better than the faux TV ladderline being sold for transmitting.

I have used a 40 mtr extended double zepp (fed with the real openwire feedline) and it is a good antenna for 40 and 80 mtrs. However because of sharp lobes I actually prefer the old standby used by generations of oldtimers. Of course I am talking about the 130 ft doublet - fed with the real old timey open wire feedline - not glorified tv line.  Cheesy Cheesy

Many hams will tell you to worry about the length of the feedline. I have been using open wire feedline for 52 years on dozens of different antennas and have yet to measure the feedline. I use whatever it takes to get from the antenna to the tuner. Never any problems.....

Stan K9IUQ

« Last Edit: August 03, 2012, 05:14:58 AM by K9IUQ » Logged
K0ZN
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Posts: 1533




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« Reply #6 on: August 03, 2012, 09:51:47 PM »


Hi.

A couple of points....  I have been using 450 ladderline for years to feed various types of antennas from a Johnson KW Matchbox.  You will like the
MB.....  don't know which one you have, but they are similar. No matter what anyone tells you, the Matchboxes are still very, very good balanced line
tuners. The ability to re-set to a predetermined setting is the best there is; if you log your settings, you can QSY almost instantly.

The main down side is that the MB won't work on 30 M, but you can easily add some external C or L at the back of the box and fix that.
I shunt a coil across the terminals on 30 M and it works like a champ. (Actually, it will match a FEW loads on 30 m, but the range is very small).
17 M is no problem, but sometimes you will have to try both the 15 and 20 M position to see which gives the better match. 12 can be the same way
between 15 and 10 M....again, depends on the load. You also *might* have to experiment with line length to find a good match on a band, again,
depending on your antenna. I have a 128 ft. Center Fed Zepp/Doublet and I found a length of line that allows a match all bands but 30.
What a Match Box does not like is LOW impedance loads. My guess is that something around 47 ohms is the low end of what it will match.

I have used both 450 ohm balanced line and true 600 ohm open wire line. Could not tell any difference in operation or tuner operation. If you experience a difference it will more likely be antenna related.  All things being equal, I suppose 600 ohm line might be marginally better in some cases, but I would be amazed if you could tell it on the air.
I guess it is *possible* that the MB might have a fractionally wider range of matching with the 600 line, but it would be marginal.

Regarding Ladderline:  Mechanically, there is a BIG difference in durability and reliability.  DO NOT use the ladderline with the # 18 solid conductors.
It is very light, flaps and flies badly in the wind and will quickly get bad kinks in it. AVOID this stuff.  I live in an area with a lot of wind and often high
winds. By far, the best ladderline I found is the #14 (stranded) from the Wireman. It is heavy enough to handle high winds pretty well.  It will not kink or
take a bend set from wind. I have tried the Wiremans' #16 (stranded) but it seems to be just light enough that wind catches it worse. Electrically, it is
fine, but if you can possibly afford it, use the #14 stranded conductor ladderline. I guess, this is one of the advantages of open wire line; the wind doesn't
bother it nearly as much, but the down side is that mechanically, it kind of a pain to work with and support. One you get your line set up, you may find that
you need to add a few pieces of non conductive rope secured to something to reduce wind movement.

Rain can/will change your tuner settings at times. Part of this is changes in ground conductivity and part of it is the effect on the transmission line.
I guess in theory rain/wet line can have higher losses, but that likely is only an issue on

If you end up with some extra ladderline, DO NOT just pile it up on the floor in a rat's nest or coil. That will definitely cause some unbalance and
make problems. Keep any extra line "neat" and cleanly installed.

Lastly, also remember that ladderline or ANY balanced parallel line can have DANGEROUSLY HIGH VOLTAGES on it, especially if there is a modestly high to high SWR on the
line (which is common).  At legal limit, there is a VERY serious burn hazard with balanced lines. Make sure pets or kids or people cannot come in contact with it while
you are transmitting, especially, if you a running high power. Note also, that the points of high voltage will change dramatically by band.

Ladderline is my favorite type of line, all things considered, but you do have to give it a little TLC in the installation.

73,  K0ZN
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W5DXP
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« Reply #7 on: August 04, 2012, 07:37:41 AM »

I use whatever it takes to get from the antenna to the tuner. Never any problems...

Were you using a Johnson Matchbox?
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K9IUQ
Member

Posts: 1626




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« Reply #8 on: August 04, 2012, 10:09:22 AM »

Were you using a Johnson Matchbox?

Having used open wire feedline for 52 years I can not name all the different tuners I have used. From homemade to MFJ, Palstar, Murch, Heathkit, NYE Viking and many others I do not remember. Yes I had the baby Johnson Matchbox for a couple of years. Presently for the last several years I am using a TenTec 238B tuner. Except for some tuners not being able to tune 160 mtrs, I have not had any problems especially with Open Wire Feedline.

My very first antenna was a 40 mtr dipole fed with flat 300 ohm TV line. I was only 14 years old and was friends with the local TV repair guy. When I got my novice ticket the TV guy gave me some old used TV line he had laying around.

My xmitter was an Eico 720 put together by yours truly. I got a small knife switch from my TV friend. I put the TV line from the antenna in the center and the xmitter on one side and the RX on the other side. I thru the switch by hand to go from TX to RX. I could not afford a Dow Key coax relay. I did have one problem. The Eico 720 had a So-239 coax connector. Not to worry, I soldered a PL-259 onto the tv line and plugged it in. My ham shack was my bedroom on the second floor. I ran a 14ga wire to the bathroom faucet for the ground. I daisy chained this ground to all my equipment. Wink At that time I did not even know what an antenna tuner was, let alone own one.  Cheesy  My mother used to holler at me to get off the radio because I was wiping out her TV shows.  Cheesy Cheesy Cheesy

During the next year or so I got WAS and 70 some countries. I had a blast, working hams with enthusiasm. I lived hamradio then making hundreds of QSOes, even girls did not take me away from hamming. Then I had some on air hams tell me that what I was doing was wrong and my antenna should (would) not work.....  Cheesy Cheesy Cheesy

I have learned by doing mostly. I am aware that Antenna "Experts" will say measure your open wire feedline because certain lengths will give you problems. I am still waiting for those problems after using countless antennas with open wire feedline and never once measuring or caring how long the feedline is. It might be wrong and will not work but I do it anyway...   Grin Grin

Stan K9IUQ
 
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K7KBN
Member

Posts: 2764




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« Reply #9 on: August 04, 2012, 10:39:44 AM »

I had a friend in Hong Kong who referred to his antenna as an "AOG".  If you've ever read the fine print in an insurance policy, one of the dire, terrible things that the policy does NOT cover is commonly called an "Act Of God".  Or AOG.  An Act of God is something you wouldn't wish on anybody, and if it happens to you, sorry, but you're not covered.

His AOG antenna was a wire helically wound around a broom handle and fed against his steel balcony.  A real AOG, indeed, but I worked him from Las Vegas and across the Pacific to where the First Fleet area merged with Seventh Fleet (~160 deg. West).

George worked all over the world with that antenna, even though an SWR meter, if he'd had one, would have told him he couldn't possibly do it!
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73
Pat K7KBN
CWO4 USNR Ret.
K9IUQ
Member

Posts: 1626




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« Reply #10 on: August 04, 2012, 11:22:44 AM »

George worked all over the world with that antenna, even though an SWR meter, if he'd had one, would have told him he couldn't possibly do it!

Here is an update to my (true) story about my first antenna. After the antenna experts told I would not make contacts and possibly kill myself with my TV line fed antenna I bought a Western Radio all band trap doublet. Made in Kearney Nebraska. All band back then meant 80-10 meters and no WARC bands.  Cheesy

The Western Radio Trap doublet was an improvement in that it was coax fed. I don't know the SWR (not sure I knew about SWR back then) but it was fed by coax and worked 80 meters. No one made fun of  my trap doublet, after all it was being advertised in QST!

Someday I will relate further adventures with my antennas, starting with that Fantastic Gotham vertical I also bought......   Cheesy
http://www.w8ji.com/gotham.htm

Stan K9IUQ
« Last Edit: August 04, 2012, 11:30:32 AM by K9IUQ » Logged
K9IUQ
Member

Posts: 1626




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« Reply #11 on: August 04, 2012, 11:47:29 AM »

George worked all over the world with that antenna, even though an SWR meter, if he'd had one, would have told him he couldn't possibly do it!

That antenna is called a Hamstick today. George should have gotten a patent on that wired broomstick.  Cheesy

Antenna lore is rampant on the hambands. Antenna facts are also dispensed. Most of it is wrong...

Stan K9IUQ
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K0ZN
Member

Posts: 1533




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« Reply #12 on: August 04, 2012, 10:10:24 PM »

To K9IUQ:

I also had an Eico 720 for my first rig which I built from the kit as yours was. The 720 was a good rig; never had any problems with it. I also thought it was one of the better
looking rigs out there at that time.  Like you I worked a TON of stations with it.  NO swr meter in shack....too expensive.... I was in high school and I could work about anybody I could hear, so why would an SWR meter be of any value?? The antenna was a 40 M folded dipole fed with that "cheap" 300 ohm TV twin lead to a Heathkit air wound balun. That set up worked very well on 40 and 15 M. What I learned from was that SWR is NOT very important..... I found that the best measure of how well an antenna works is QSL cards received !! I also felt my success was partly because I could "move all over the band" because I had 7 crystals !  Looking back on it, I think there was probably more FUN for the buck with those stations that what we have now.  ....although it is nice not to have to worry about bumping the operating table and have the receiver move 25 Khz !     ...it is all relative......

73,  K0ZN
« Last Edit: August 04, 2012, 10:13:02 PM by K0ZN » Logged
KG4NEL
Member

Posts: 373




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« Reply #13 on: August 04, 2012, 11:38:47 PM »

George worked all over the world with that antenna, even though an SWR meter, if he'd had one, would have told him he couldn't possibly do it!

If anything, I get scared if the SWR is too good the first time I try an antenna  Grin

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K9IUQ
Member

Posts: 1626




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« Reply #14 on: August 05, 2012, 02:50:03 AM »

I also felt my success was partly because I could "move all over the band" because I had 7 crystals !  

At the time, my ham activitys were funded by a newspaper route that payed about $15 a week. I could only afford 2 crystals, one for 40mtrs and one for 15 mtrs. I was only a Novice for 4 months. When I got my General license I borrowed some $$ from Mother to get a Heathkit HG-10 VFO. WOW, what an improvement over crystals....   Wink

I also got a Eico 730 modulator for AM operations. Couldn't afford SSB equipment.   Cheesy

Stan K9IUQ
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