From owner-qrp-l@Lehigh.EDU Sat Dec 21 07:07:41 1996 Received: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id HAA22522 for ; Sat, 21 Dec 1996 07:07:40 -0500 (EST) X-Received-x: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id HAA22522 for ; Sat, 21 Dec 1996 07:07:40 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35040-39781>; Sat, 21 Dec 1996 07:07:27 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34855-39781>; Sat, 21 Dec 1996 07:06:27 -0500 Received: from utkux4.utcc.utk.edu (UTKUX4.UTCC.UTK.EDU [128.169.76.11]) by nss2.CC.Lehigh.EDU (8.8.4/8.8.4) with SMTP id HAA108525 for ; Sat, 21 Dec 1996 07:06:17 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id MAA23561; Sat, 21 Dec 1996 12:03:10 GMT Message-Id: Date: Sat, 21 Dec 1996 07:03:10 -0500 (EST) Reply-To: cebik@utkux.utcc.utk.edu Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: "L. B. Cebik" To: "Low Power Amateur Radio Discussion" Subject: Re: Tuners: PIs In-Reply-To: <96Dec20.113759est.35520-48668+105@fidoii.cc.lehigh.edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: Cecil A Moore X-Cc: Low Power Amateur Radio Discussion X-Sender: cebik@utkux4.utcc.utk.edu X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO Cecil's note on parts availability reminds me that it is possible to build a balanced network tuner. Design is no harder than multiplying and dividing by 2. The standard unbalanced network values give you the total series inductance (for a PI network, let's say) and the total shunt (parallel across the lines) capacitance. To convert to a balanced network, working against a center ground/earth, divide the inductance by 2 and place inductors of this value, one in each line (for a total series inductance equal to the initial design value. Multiply the capacitance by 2 and place one from each line to ground. Each C is in series with its counterpart and hence the total capacitance across the line is the new C divided by 2, which is the original value of the design. Now find capacitors that are split stator or 2-gang jobs--or mechanically gang them. Mechanically gang the inductors--if variable, use shaft coupler; if tapped, use 2-gang switches. The output will be balanced, and so will the input. Here is the place--the input--to install a good 1:1 balun, since this is the spot that will see resistive source and load. This system also permits chassis or case grounding, since the circuit is balanced on either side of ground. With jumpers, you can concert the system to an unbalanced network of the type usually seen in the handbooks for coax. Remember that virtually all the commercial tuners are compromises for cost of production and for features that ham consumers say they want, for example compactness. For field work in a tent or for the apartment dweller, etc., these units are fine, even if not the most efficient. But if you want maximum efficiency and are willing to devote a little room to it, you can roll your own and create a unit superior to the commercials. And you may only need to do it once in a life time if you clean the components periodically. -73- LB, W4RNL From owner-qrp-l@Lehigh.EDU Sat Dec 21 15:35:58 1996 Received: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id PAA01996 for ; Sat, 21 Dec 1996 15:35:57 -0500 (EST) X-Received-x: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id PAA01996 for ; Sat, 21 Dec 1996 15:35:57 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35413-31591>; Sat, 21 Dec 1996 15:35:48 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <34921-39781>; Sat, 21 Dec 1996 15:34:04 -0500 Received: from motgate2.mot.com (motgate2.mot.com [129.188.136.20]) by nss2.CC.Lehigh.EDU (8.8.4/8.8.4) with ESMTP id PAA203316 for ; Sat, 21 Dec 1996 15:33:56 -0500 Received: from pobox.mot.com (pobox.mot.com [129.188.137.100]) by motgate2.mot.com (8.7.6/8.6.10/MOT-3.8) with ESMTP id OAA25950; Sat, 21 Dec 1996 14:28:25 -0600 (CST) Received: from azbx.mot.com (azbx.mot.com [129.188.127.40]) by pobox.mot.com (8.7.6/8.6.10/MOT-3.8) with SMTP id OAA06644; Sat, 21 Dec 1996 14:33:46 -0600 (CST) Received: by azbx.mot.com (1.38.193.5/16.2) id AA22973; Sat, 21 Dec 1996 14:33:15 -0600 Message-Id: Date: Sat, 21 Dec 1996 12:03:00 -0600 Reply-To: Bob_Tellefsen-CNSE97@email.mot.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: "Bob Tellefsen-CNSE97" To: "Low Power Amateur Radio Discussion" Subject: Balanced tuner X-To: w2gum@juno.com, qrp-l@Lehigh.EDU X-Mailer: Worldtalk (4.0.2-p15)/STREAM X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO Tony: I'm coming late to your thread, as I get the digest a bit delayed lately, for some reason. I have been using a balanced tuner for close to 40 years now. Made it during my Army time in Alaska (ex KL7SMC). I have a split stator variable capacitor, about 100pf per section I think. I use the B & W plug in coil set with swinging center link. Instead of the two turn wire link, I wound a single turn Faraday shielded link from a turn of coax to aid in suppressing any harmonic radiation through capacitive coupling between the link and coil. Whole thing is built on a cigar box! This is a superb tuner for any antenna fed with balanced line. I have used it on dipoles, vee beams, delta loops, diamond loops. If you ground the center of the coil and the frame of the capacitor, you can also feed unbalanced antennas, whether long single wires or even coax. As LB mentioned, a trade off is the need to plug and unplug coils. Also changing antenna lead taps. I have seen complete coil sets for sale at flea markets. However, you can build your own easily. I was missing the 40m coil to my set for years, so ran with a home made one. Finally found one at a flea market, and retired the howemade one. I use miniature clips that fit between the coil turns without shorting to the adjacent turns. Also, I use a very limp, flexible wire on each clip, as a stiffer wire will move the position of the clip when you let go, often shorting to the next turn. This kind of tuner does not require a reference to ground, so long as you are feeding a balanced antenna system. If you go to an unbalanced system like a long wire, then it will need a ground. A coax fed dipole with a balun at the feed point would not require a grounded tuner for antenna feeding purposes. You might want one for other reasons, however, such as draining off snow static if you live where this occurs. Anyway, one more ham's observations. 72 and Merry Christmas, Bob N6WG From owner-qrp-l@Lehigh.EDU Sun Dec 22 06:35:40 1996 Received: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id GAA04187 for ; Sun, 22 Dec 1996 06:35:39 -0500 (EST) X-Received-x: from fidoii.CC.Lehigh.EDU (fidoii.CC.Lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.7.6/8.7.1) with ESMTP id GAA04187 for ; Sun, 22 Dec 1996 06:35:39 -0500 (EST) Received: from Lehigh.EDU ([127.0.0.1]) by fidoii.cc.lehigh.edu with SMTP id <35754-50622>; Sun, 22 Dec 1996 06:34:34 -0500 Received: from nss2.CC.Lehigh.EDU ([128.180.1.26]) by fidoii.cc.lehigh.edu with ESMTP id <35625-50622>; Sun, 22 Dec 1996 06:34:08 -0500 Received: from utkux4.utcc.utk.edu (UTKUX4.UTCC.UTK.EDU [128.169.76.11]) by nss2.CC.Lehigh.EDU (8.8.4/8.8.4) with SMTP id GAA229386 for ; Sun, 22 Dec 1996 06:34:05 -0500 Received: from localhost by utkux4.utcc.utk.edu with SMTP (SMI-8.6/2.7c-UTK) id LAA21354; Sun, 22 Dec 1996 11:34:21 GMT Message-Id: Date: Sun, 22 Dec 1996 06:34:21 -0500 (EST) Reply-To: cebik@utkux.utcc.utk.edu Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: "L. B. Cebik" To: "Low Power Amateur Radio Discussion" Subject: Re: Balanced tuner In-Reply-To: <19961221.170028.5119.2.w2gum@juno.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-To: anthony j colaguori X-Cc: Low Power Amateur Radio Discussion X-Sender: cebik@utkux4.utcc.utk.edu X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN Status: RO On Sat, 21 Dec 1996, anthony j colaguori wrote: > Guess this approach goes back to the system we used in the " 30's > ". BUT IT WORKS. Gang, Tony's note above brings up an important point: just because it's new don't mean it's better, and just because it's old don't mean it's worse. It is important to figure out what the basic principles are for any of the divices, circuits, and techniques are. Then figure out why they are being used or not being used. Commercial tuner makers know hams want things cheap, compact, and simple to use. (At least they think they know that.) Hence, the C-L-C tuner is the standard commercial design. Duffey's flipped L circuit is not simple to use because you have to find coil taps and switch the capacitor--not good for the sealed box syndrome. The inductively coupled tuners noted on the list are probably best for parallel feeders, but require plug-in coils, taps, and other "hands inside" operations. Balanced PIs or even a balanced C-L-C requires expensive split-stator capacitors or mechanical tracking. Any of these things can make up a very fine tuner for parallel feedlines, and all are based on principles that were well known in the 1930s. They are not commercially used for reasons other than electronical soundness. On the other hand, the 4:1 balun stuck in the output of the average commercial tuner is likely to be lossy unless the lines present a perfectly resistive load to it. Expecting hams to use it with parallel feeders is a case of comercial tuner-makers expecting hams to be ignorant of their losses. Unless you precompensate for reactance and design your line lengths for the right resistive component, as Cecil has done, modern will be worse in most cases than the classic 1930's inductively coupled designs. Interesting that just when we think we know more, we have to compensate for shortcomings of devices sold as the most modern. The modern array of network tuners available are primarily designed for the station using coax to an antenna that is already supposed to have a feedpoint impedance close to 50 ohms. Any other use takes them out of their primary design scope. Some do well in this outside region; others do not. For field use, where I want something compact (unless I design something into my own rig), I'd rather use a Z-match or an L-match than one of the commercial small networks with limited C-values and only a few coil taps, unless I was using an almost resonant dipole. Even away from measuring equipment, I'd have more confidence that I was minimizing my network losses. However, for coax-fed monoband antennas, I have used numerous networks designed for the band in question, all with good success. So, he said at the bottom line, analyze what you need a tuner for: what kind of antenna, what bands, what operating conditions, etc. THen go back to basic principles, which are ageless, and design the best tuner for that set of purposes. If your design is close to an existing commercial design, you may prefer to use it ready-built. If not, it is time for home brew--even if this means lurking at hamfests and investing in components from surplus dealers. And start collecting. Since toilet paper rolls for coil forms are not as sturdy as they used to be, save all those rolls under the Christmas wrapping paper. Most are junk, but a few have turned out to be pretty sturdy. If you build a tuner with such materials and like the design, you can always go back and build a pretty version later. But save the old one for telling the new generation what it was like in the "old" days. Happy holidays. -73- LB, W4RNL