[HCARC] HCARC Digest, Vol 16, Issue 38
Michael R Perez
mikerey.perez at me.com
Wed Aug 29 23:48:25 EDT 2012
Gary:
I'm right there with you learning along the way, but of course I'm not into HF since I am still on my Technician level for the moment.
I'm basically on 2meters and 70cm with all of my stuff and group activities that our groups volunteers for (parades, escorting, bike rides, etc).
But I want to learn more and I am looking and hearing 'over your shoulder' as your questions surface.
I'd heard of baluns, a friend of mine made one, but I really had no idea of how they are being used and their purpose.
Keep asking. I'm soaking up all everybody has to contribute.
It'll soak in.
Best to get antenna, a nice radio, and start talking and building from there.
One day I hope to build an antenna from scratch; for now, I'll buy one and then learn the mechanics for next time.
Keep on.
'73
Thanks,
Michael Pérez
Sent from my iPhone
On Aug 25, 2012, at 9:24 PM, hcarc-request at mailman.qth.net wrote:
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> Today's Topics:
>
> 1. Baluns - Lots of Questions (Gary and Arlene Johnson)
> 2. Re: Baluns - Lots of Questions (Kerry Sandstrom)
> 3. Re: Baluns - Lots of Questions (Gary and Arlene Johnson)
> 4. Re: Baluns - Lots of Questions (Kerry Sandstrom)
> 5. Best Info On Balun's I have seen (Gary and Arlene Johnson)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 25 Aug 2012 11:07:42 -0500
> From: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
> Subject: [HCARC] Baluns - Lots of Questions
> To: <hcarc at mailman.qth.net>
> Message-ID: <94087E69F796452CBCD193CCE22E886B at Minnie>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Try as I might, I get confused with the use of Baluns, when to use Baluns, and the types of Baluns that there are. I have seen 1:1, 4:1, 6:1 Baluns. I have seen voltage Baluns, Current Baluns, Choke Baluns, and probably a few more that I can't remember. I have seen Baluns advertised as ones that won't get overloaded by RF (RF saturated). What is the difference between them and when do you need to use them, where is the best place to get them?? Can you make them?? BTW, discussions like this would make great classes for either before the meetings or as the presentation during the meetings. Remember, as more and more newbies join the club, more and more of this technical stuff that everyone assumes everyone knows about is not known.
>
> Gary Johnson
> N5"BAA"
>
> ------------------------------
>
> Message: 2
> Date: Sat, 25 Aug 2012 14:51:51 -0500
> From: "Kerry Sandstrom" <kerryk5ks at hughes.net>
> Subject: Re: [HCARC] Baluns - Lots of Questions
> To: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>,
> <hcarc at mailman.qth.net>
> Message-ID: <13847F35FEAA4124B381BCA0E2C8B06D at NumberCruncher>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> Hi Gary,
>
> Several years ago the ARRL published a book called "Transmission Line
> Transformers" by Jerry Sevick. I think it was published in 1987 since that
> is the copyright date on mine. The ARRL Antenna Book, any edition, also
> talks about baluns and transmission line transformers.
>
> They are called transmission line transformers because that is what they
> are: transformers made from lengths of transmission line that are coupled
> together. A 1:1 balun is basically a 1:1 transformer that is unbalanced on
> one end and balanced on the other. A 1:1 balun can be made from two quarter
> wave sections of coaxial cable. Chapter 18, figure 6 of the 18th edition of
> the ARRL Antenna Book shows this kind of a 1:1 balun. Figure 5 of the same
> chapter shows a 4:1 balun made with a half wavelength section of coax. VHF
> guys have been using these baluns for decades.
>
> HF baluns and transformers haven't been as popular. You can imagine
> some of the reasons, quarter and half wave sections of coax for 80 meters
> aren't exactly small and light! Many years ago, the 1950's, Heathkit sold
> an HF balun that was reasonably broadband that consisted of a two large air
> wound bifalar coils. The ARRL Antenna Book 9th edition, Figure 3-41 shows
> this kind of a balun and how to connect it either for 1:1 or 4:1 operation.
> It worked from 80 through 10 meters. They solved the 'you need a different
> one for each band' problem but they still weren't small.
>
> Several years ago ferrite material became available at reasonable prices
> with good RF performance. Ferrite is a non-linear material. I don't
> believe there is any linear ferrite! When you apply one or more RF signals
> to a nonlinear device, the device wiil generate harmonics and
> intermodulation products from the applied RF signals. Ferrites also have
> some losses. When you wind a coil on a ferrite, you will get both harmonics
> and intermodulation products. There is no way of avoiding it. By the way,
> even air is nonlinear if you are running enough power. I think the power
> density is Megawatts per centimeter squared. I only wish I could run power
> like that.
>
> "Ham Radio", an old ham magazine that has not been published for ten
> plus years and was fondly (and not so fondly) called the Proceedings of
> Amateur Radio because of its technical content, had an article about
> saturation in ferrites. I'll see if I can find it. I think the article was
> primarily concerned with ferrites in a receiver front end limiting the
> intermodulation performance of the receiver. That should give you an idea
> of the problem. Several years ago one of the ferrite balun manufacturers
> had a lot of trouble with their transmitting baluns generating harmonics and
> causing TVI. It is a real problem.
>
> There are some ferrites that will operate at a higher power before they
> cause a problem. They are still generating harmonics, they are just below
> the problem level at moderate power levels. Baluns with more ferrite
> material, larger and heavier, will handle more power generally before they
> cause a problem. I believe ferrite baluns that are used in high SWR
> situations have more of a problem. Ferrite really came into their own in
> wideband solid state amplifiers. Interestingly, they were running at
> impedance levels below 50 Ohm. The input impedance of high power
> transistors used in wideband power amplifiers, your 100 W 160 to 10 meter
> XCVR for instance, is very low, often as low as 5-10 Ohm. A couple 4:1 RF
> transformers to go from 50 Ohm to 12.5 Ohm and then to 3 Ohm were ideal.
> 4:1 transformers to go from 75 Ohm to 300 Ohm are about the highest
> practical impedance levels. You can build transmission line transformers
> that are 1:1, 4:1, 9:1, 16:1, etc. I don't believe that there is a 6:1
> possibility. You can build RF transformers for any ratio you want, but they
> aren't transmission line transformers.
>
> You will have to find someone else to tell you aboput voltage baluns and
> current baluns and choke baluns. I personally think they are just a lot of
> mumbo jumbo. I don't use ferrite baluns much myself. I have an old Hy-Gain
> 15 meter yagi that uses a balun and hairpin match. I laso have a Heathkit
> antenna tuner that has a balun for balanced output, but I've never used it.
> I have built some solid state transmitters that use ferrite transmission
> line transformers to match the driver to the final stage.
>
> I'm sure thast this is more than you wanted to hear, but I don't believe
> you can understand the issues with any less.
>
> Kerry
>
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 25 Aug 2012 19:10:20 -0500
> From: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
> Subject: Re: [HCARC] Baluns - Lots of Questions
> To: "Kerry Sandstrom" <kerryk5ks at hughes.net>
> Cc: hcarc at mailman.qth.net
> Message-ID: <8B256C266181444792E85BAC78EDE1C3 at Minnie>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
> I guess I need to do some more research beacuase I am more confused than
> before. Am I the only one in the club who is confused on this kind of
> thing?? I surely hope not, and I don't think so. I guess the other
> question is how many books am I going to have to buy and read. My library
> already has well over a thousand pages, probably working on 2000 and I still
> seem to have BASIC questions. Maybe the secret is just to go out and buy
> some antennas or look in the book and build them exactly as specified.
> Isn't a balun that has windings the same on both sides an UNUN - whatever
> that is and whatever that is for. It's like I found a third of a spool of
> RJ6 coax the other day that the Dish Network or whomever must have left
> here. It's 75 ohm coax. Not sure what to do with it, or when I could use
> it on what antenna. How do I tell if 75 ohm coax can or should be used or
> ladder line, or TV twinlead or?????
>
> Feeling dumb or lost in Center Point.
>
> Gary J
> N5"BAA"
>
>
> ----- Original Message -----
> From: "Kerry Sandstrom" <kerryk5ks at hughes.net>
> To: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>;
> <hcarc at mailman.qth.net>
> Sent: Saturday, August 25, 2012 2:51 PM
> Subject: Re: [HCARC] Baluns - Lots of Questions
>
>
>> Hi Gary,
>>
>> Several years ago the ARRL published a book called "Transmission
>> Line Transformers" by Jerry Sevick. I think it was published in 1987
>> since that is the copyright date on mine. The ARRL Antenna Book, any
>> edition, also talks about baluns and transmission line transformers.
>>
>> They are called transmission line transformers because that is what
>> they are: transformers made from lengths of transmission line that are
>> coupled together. A 1:1 balun is basically a 1:1 transformer that is
>> unbalanced on one end and balanced on the other. A 1:1 balun can be made
>> from two quarter wave sections of coaxial cable. Chapter 18, figure 6 of
>> the 18th edition of the ARRL Antenna Book shows this kind of a 1:1 balun.
>> Figure 5 of the same chapter shows a 4:1 balun made with a half wavelength
>> section of coax. VHF guys have been using these baluns for decades.
>>
>> HF baluns and transformers haven't been as popular. You can imagine
>> some of the reasons, quarter and half wave sections of coax for 80 meters
>> aren't exactly small and light! Many years ago, the 1950's, Heathkit sold
>> an HF balun that was reasonably broadband that consisted of a two large
>> air wound bifalar coils. The ARRL Antenna Book 9th edition, Figure 3-41
>> shows this kind of a balun and how to connect it either for 1:1 or 4:1
>> operation. It worked from 80 through 10 meters. They solved the 'you need
>> a different one for each band' problem but they still weren't small.
>>
>> Several years ago ferrite material became available at reasonable
>> prices with good RF performance. Ferrite is a non-linear material. I
>> don't believe there is any linear ferrite! When you apply one or more RF
>> signals to a nonlinear device, the device wiil generate harmonics and
>> intermodulation products from the applied RF signals. Ferrites also have
>> some losses. When you wind a coil on a ferrite, you will get both
>> harmonics and intermodulation products. There is no way of avoiding it.
>> By the way, even air is nonlinear if you are running enough power. I
>> think the power density is Megawatts per centimeter squared. I only wish
>> I could run power like that.
>>
>> "Ham Radio", an old ham magazine that has not been published for ten
>> plus years and was fondly (and not so fondly) called the Proceedings of
>> Amateur Radio because of its technical content, had an article about
>> saturation in ferrites. I'll see if I can find it. I think the article
>> was primarily concerned with ferrites in a receiver front end limiting the
>> intermodulation performance of the receiver. That should give you an idea
>> of the problem. Several years ago one of the ferrite balun manufacturers
>> had a lot of trouble with their transmitting baluns generating harmonics
>> and causing TVI. It is a real problem.
>>
>> There are some ferrites that will operate at a higher power before they
>> cause a problem. They are still generating harmonics, they are just below
>> the problem level at moderate power levels. Baluns with more ferrite
>> material, larger and heavier, will handle more power generally before they
>> cause a problem. I believe ferrite baluns that are used in high SWR
>> situations have more of a problem. Ferrite really came into their own in
>> wideband solid state amplifiers. Interestingly, they were running at
>> impedance levels below 50 Ohm. The input impedance of high power
>> transistors used in wideband power amplifiers, your 100 W 160 to 10 meter
>> XCVR for instance, is very low, often as low as 5-10 Ohm. A couple 4:1 RF
>> transformers to go from 50 Ohm to 12.5 Ohm and then to 3 Ohm were ideal.
>> 4:1 transformers to go from 75 Ohm to 300 Ohm are about the highest
>> practical impedance levels. You can build transmission line transformers
>> that are 1:1, 4:1, 9:1, 16:1, etc. I don't believe that there is a 6:1
>> possibility. You can build RF transformers for any ratio you want, but
>> they aren't transmission line transformers.
>>
>> You will have to find someone else to tell you aboput voltage baluns
>> and current baluns and choke baluns. I personally think they are just a
>> lot of mumbo jumbo. I don't use ferrite baluns much myself. I have an
>> old Hy-Gain 15 meter yagi that uses a balun and hairpin match. I laso
>> have a Heathkit antenna tuner that has a balun for balanced output, but
>> I've never used it. I have built some solid state transmitters that use
>> ferrite transmission line transformers to match the driver to the final
>> stage.
>>
>> I'm sure thast this is more than you wanted to hear, but I don't
>> believe you can understand the issues with any less.
>>
>> Kerry
>>
>>
>>
>>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 25 Aug 2012 20:12:20 -0500
> From: "Kerry Sandstrom" <kerryk5ks at hughes.net>
> Subject: Re: [HCARC] Baluns - Lots of Questions
> To: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
> Cc: hcarc at mailman.qth.net
> Message-ID: <8CC80974E3F041AC8F2B61A8E4EF560B at NumberCruncher>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
> Gary,
>
> You don't have to have all the answers at the beginning-nobody does. In my
> opinion the best thing to do is get on the air with a simple antenna and a
> simple rig. Don't worry about the best way. The best way is different for
> different people. Until you know what you really want to do, don't worry,
> just get on the air. As I've said earlier, just get a simple entry level
> rig, hopefully used, get a simple manual external antenna cable and put up a
> simple wire antenna fed with plain old coax. As time goes on you will find
> things that need improvement. When you find things to improve, study them
> and make your choice and see if things work better. Then when you
> study/learn it will have an immediate application and it will mean a lot
> more to you.
>
> The question about TV cable is easy. Your rig will not know the difference
> between 75 Ohm and 50 Ohm coax. RG-6 is compatible with a PL-259 plug with
> the insert for RG-59/U. The two main problems with RG-6 is all that I've
> seen has an aluminum foil outer conductor which is impossible to soldew.
> You probably have to use crimp style connectors. The military has gone
> completely to crimp connectors. They seem plenty rugged when properly
> installed. You can even use the F-type connectors. They will handle 100 W
> at HF with no problem. Besides the aluminum foil, the other problem is most
> of the cable I've seen has foam dielectric. I don't think foam is as rugged
> and weather tolerant as the old solid dielectric cables and you sure don't
> need its low loss at HF but if you've got free cable, it doesn't matter.
>
> Did you ever get the answer on what cable to use to extend your internet
> connection to your shack?
>
> By the way, I'm working on an article for the Static (October issue, think)
> that talks about different types of cable and the advantages/disadvantages
> of each.
>
> Remember, priority 1 is to get on the air with something simple and have
> fun and stop worrying about everything. The only guy I know who spent
> literally years figuring outple and how to put the perfect station together
> is K5XA.
>
> Kerry
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Sat, 25 Aug 2012 21:23:01 -0500
> From: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
> Subject: [HCARC] Best Info On Balun's I have seen
> To: <hcarc at mailman.qth.net>
> Message-ID: <57F9F619985E49D5AF4AE2E45ABECD9B at Minnie>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Unless this wrong, this is the best info in the simplest terms I have seen yet.
>
> "
> Why a Balun?
> Why a Balun? - by Kurt N. Sterba, originally published in the February 2010 issue of World Radio Online.
>
> While listening to a conversation on 75 meters, Kurt heard more incorrect information on baluns than he thought existed. Such a simple thing should not be made so complicated. It just adds to the hot air already on that band. Here is Krusty Olde Kurt's simplification.
>
> The most popular, simple and effective antenna is the horizontal dipole. It is a balanced antenna, that is, the wires on both sides of the center insulator are of equal length. In the early days of radio it was fed with ladder-line, two wires in parallel spaced by insulators. It, too, is balanced. Feeding a balanced antenna with a balanced feeder works well. Many amateurs still use this method because of the very low loss of ladder-line.
>
> But back around the time of World War II, coaxial cable was introduced. It has certain advantages over ladder-line. It is self-shielded and does not radiate. It can be routed next to metal objects or even buried in the ground with no effect on its operation. But it has a major defect in that it is unbalanced.
>
> The coaxial cable has a center conductor and a surrounding metal shield. The center conductor connects to one side of the dipole and the shield to the other. There are equal currents in the center conductor and in the shield, so we expect equal currents in the two sides of the dipole. This looks simple and straightforward, but there is a problem.
>
> The problem is caused by something called "skin effect." This tells us that, at radio frequencies, the current in a conductor flows just in the "skin" of the conductor and does not penetrate further into the conductor. This means that the current in the shield of the coaxial cable is confined to the inside of the shield. No current reaches the outside of the shield. Therefore, the outside of the shield is just like a third conductor. But this third conductor is connected to one side of the antenna, the same side the inner surface of the shield is connected to.
>
> Now it is possible that not all of the current from the inside of the shield goes into one side of the dipole. Some may go down the outside of the shield. This can cause problems. With less current in the antenna, its radiated signal will be less. The radiation from the outside of the shield brings radiation closer to the house and may cause TVI. When the antenna is used for reception, there will be pickup from the dipole and from the coax shield. Most man-made noise is vertically polarized, so the horizontal dipole discriminates against it. The vertical shield, on the other hand, readily picks up the noise, so your antenna becomes noisier and reception is poorer.
>
> Balun To The Rescue
>
> The current flow down the outside of the shield can be eliminated by use of a balun, a balanced to unbalanced device. There are several ways to make a balun, but all of them place high impedance between the antenna and the outer shield. This prevents any current flow down the shield.
>
> To make a very simple balun, you wind the top portion of the cable into a coil. This does not affect the currents flowing inside the cable but now the outside of the shield is a coil and just like any coil it has inductive reactant that presents an impedance to any flow of RF. At low frequencies it is difficult to get enough inductance to be effective and the coil tends to whip in the wind and is physically unwieldy. But it works.
>
> The "transmission-line" balun is much better. This is a short section of two-conductor transmission line wrapped around a ferrite toroid and connected between the coax and the antenna. The ferrite gives the coil high impedance so no current will flow through it to the coax shield and the antenna sees a balanced line.
>
> Then there is the ferrite bead balun. Enough ferrite beads are placed over the coax to provide a high impedance to RF. This prevents any current flowing down the shield. This is a simple and effective balun and is in widespread use today following its initial introduction to radio amateurs in an article by Walt Maxwell, W2DU, published in 1982.
>
> Matching Transformers
>
> The baluns described above are 1:1 baluns, that is, their input and output impedances are the same. They are useful for connecting 50-ohm coaxial cable to dipoles or other antennas that have impedances close to 50 ohms. But some antennas have higher or lower impedances where an impedance change in the balun can provide a better match.
>
> The transmission line balun adapts itself easily to 4:1, 9:1, 16:1 ratio step-up and step-down transformers. Other ratios are also available. Thus the impedance matching function can be built right into the balun.
>
> At The Transmitter
>
> We have been talking about the use of baluns at the antenna feedpoint. Another common use of baluns is at or near the transmitter. Quite often, ladder-line is used to feed the antenna. But it is difficult to run the ladder-line into the radio shack. So, a short length of coaxial cable is run from the transmitter or antenna tuner out to the ladder-line. At this connection, we have the same problem as before - connecting unbalanced coax to a balanced feedline. Again, a balun is required.
>
> The ladder-line usually has 450-ohm impedance. Since we are connecting a 50-ohm coax to 450-ohm line, it would seem that we need a balun with a 9:1 step-up to get a good match. No, no, no! Remember that the 450-ohm line is connected to a 75-ohm antenna. If the line is a half-wave long we'll see 75 ohms at the bottom, not 450. At other cable lengths we'll see impedance's from less than 75 ohms, up to much higher than 450 ohms. So we are not at all likely to get a match. It is helpful, however, to have a step-up transformer and a 4:1 step-up is a good compromise value to use.
>
> So what I learned..
>
> a.. Use a 1:1 balun for balanced dipole antenna where both sides of the center insulator are of equal length.
> b.. Use a 4:1 (or higher if needed) balun for antennas that have a higher or lower impedance change between the actual antenna and the feed line.
> Gary J
> N5"BAA"
>
> ------------------------------
>
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> End of HCARC Digest, Vol 16, Issue 38
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