+++++++++++++++++ Reply-To: From: DL2FI at t-online.de (Peter Zenker) To: Date: Wed, 21 Aug 2002 09:27:17 +0200 Organization: QRPproject Subject: [Elecraft] PlugIn Balun for K2/Kat1 ATU Inspired by the article in QRP Homebrewer of W1CQ and after doing some experiments, we designed a PlugInBalun for the K2/K1 ATU. It is housed in a small 50mm x 30mm x 25mm box and fits direct on one of the BNC jacks of the Tuner. Its an 1:4 Balun, the VSVR between 1 MHz and 30 MHz is less the 1,1. As usually from QRPproject you can get either the description to make it complete on your own, or a kit. In the special case we added a ready mad PlugInBalun which is shipped including its individual chart measured from 1 to 30 MHz. Pictures of the PlugInBalun can be found at .. See below .. dwn 73 de Peter,=A0 DL2FI ********************************************************************** DV Berlin DARC e.V. German QRP Group DL-QRP-AG http://www.dl-qrp-ag.de QRPproject QRP and homebrew international http://www.qrpproject.de +++++++++++++++++++ Reply-To: From: DL2FI at t-online.de (Peter Zenker) To: Date: Wed, 21 Aug 2002 13:32:52 +0200 Organization: QRPproject Subject: [Elecraft] Adress correction PlugInBalun Sorry OM,=20 The addresses do not work for direct page access, The ral address is www.werdau.net/qrpproject/k2_k1_balun.htm (English) or (corrected from entry below) www.werdau.net/qrpproject/qrppbaluns.de (German) 73 de Peter,=A0 DL2FI ********************************************************************** DV Berlin DARC e.V. German QRP Group DL-QRP-AG http://www.dl-qrp-ag.de QRPproject QRP and homebrew international http://www.qrpproject.de ++++++++++++++ Date: Wed, 21 Aug 2002 05:36:27 -0700 From: Phil Wheeler Organization: Outstanding To: DL2FI at t-online.de Cc: Elecraft at mailman.qth.net Subject: Re: [Elecraft] Adress correction PlugInBalun For English I just went to the qrpproject site and found my way here: http://www.werdau.net/qrpproject/k2_k1_balun.htm Maybe case (k1 vs K1) matters. Phil ++++++++++++++++ Date: Wed, 21 Aug 2002 14:17:59 -0500 From: "George, W5YR" Organization: AT&T WorldNet Service To: DL2FI at t-online.de Cc: Elecraft at mailman.qth.net Subject: Re: AW: [Elecraft] PlugIn Balun for K2/Kat1 ATU Thanks, Peter. My experience has been just the opposite using non-resonant 20-meter EDZ antennas on 80-10 and a large non-resonant loop on 80 - 10, all fed with ladderline, and using 1:1 current baluns for the transition to unbalanced tuners. The calculated and measured impedance at the tuners is under 10 ohms on some bands with all three antennas so 4:1 baluns would lead to an intolerable situation. Hence my use of 1:1 current baluns. Apart from just matching the antenna and line, tuner losses go up significantly when the real part of the line impedance falls below about 10-15 ohms. I suspect that the Elecraft tuners are suffering the most loss when operated with such low impedance loads. In that event, using the balun as a 1:4 might be better - except . . . A balun is NOT a transformer. It is, in the words of Jerry Sevick, W2FMI, a *transmission line transformer* and so its properties are those of a transmission line and not those of a simple transformer. The actual "transformation" ratio of the balun can be 4:1 at some frequencies and with some loads and be far from that under other conditions. So, we cannot remedy a difficult match situation by merely reversing the balun connection using the appropriate connectors, as if it were indeed only a transformer. This is an advantage of the 1:1 current balun: its performance is independent of the load impedance. Although W1CG disagrees with that statement, and thus designed his balun to be a 4:1 unit, Lewallen, Maxwell, Sevick and others do not and are strong proponents of 1:1 current baluns for line isolation situations. I really do think that having the 4:1/1:1 switchable capability would make the unit usable under a wider range of conditions. For QRP, the switch can be correspondingly "tiny" - perhaps a miniature slide switch could be worked into the case design. Again, thank you for sharing your thoughts about this new product. 73/72/oo, George W5YR - the Yellow Rose of Texas Fairview, TX 30 mi NE of Dallas in Collin county EM13qe Amateur Radio W5YR, in the 56th year and it just keeps getting better! QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735 Icom IC-756PRO #02121 Kachina 505 DSP #91900556 Icom IC-765 #02437 Peter Zenker wrote: > > George, > the KAT 2 handles abt 8 to 800 Ohm as far as I know. The feed point > Impedance of a Lambda 1/2 Dipole is abt 72 Ohm, used on the next > harmonic I assume its higher then 800 Ohm. That’s the reason for me to > use a step up balun. The impedance transformed to the ATU depends on > length of the feed line, and frequency. You can bring it up to either > higher or lower impedances. In my experience, it was very seldom, that > the impedance at the ATU side was less then 30 Ohm, this happened only > with extreme short antennas. ( With my ZM-2 I never ever needed the > extra capacitor at the input side which is needed, if you have extra low > impedance.) > > BTW, > If I am outdoor with a twin wire feeder (my normal Antennas :-) I carry > with me an extra length of 3 Meter feeder line with 2 Banana jacks at > one side and 2 Banana plugs at the other side. If a given Antenna has a > "bad" impedance at the ATU end, I add this extra line and, bingo, its > easy to tune now. > > I will think about adding a switch and will test it. Actually there is > definitely no place for such a swich, I have to use a bigger enclosure, > and I am not sure if I get the same excellent results if I use the > switch. > But I will try it. +++++++++++++++++ From: "Stuart Rohre" To: "Mario Lorenz" , Subject: Re: [Elecraft] PlugIn Balun for K2/Kat1 ATU Date: Wed, 21 Aug 2002 19:23:09 -0500 Use of a 1:1 balun or cable choke on the input side of a floating transmatch would seem to be the better thing to implement in tight spaces of a K2. The advantages of input side balance device such as the cable coax choke, is that both sides see 50 ohms at all times when the transmatch is in adjustment. Voltages are lower than output baluns of the 4:1 type. With high current, low impedance, you might not couple into the case or nearby conductors as much as a high step up balun. Losses of a 1:1 device are purported to be lower, and certainly minimal using a cable choke. Most autotuners are unbalanced circuits I believe, what effective unbalance amount this would be to balanced feeders and antennas has not been covered in the literature to any well known degree. I think there are some web postings on antenna web sites about percentage imbalance seen when feeding parallel line to such antennas as the end feed Zepp, but effects of L net or pi net auto tuners have not been covered that I could find. Anyone have any data on that balancing means? 72, Stuart K5KVH ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] PlugIn Balun for K2/Kat1 ATU Date: Wed, 21 Aug 2002 17:27:40 -0700 Is there a reason a male BNC was chosen? It just seems a little umm... 'fragile' having to connect the balun to the K2 via a female/female BNC adapter. I'd hate to think what might happen if it inadvertently took a smack.... Thanks & 73 Mike - AD5IU I built a dummy load one time that used a male BNC that plugged directly into the female connector on my rig. Problem was, I couldn't get my fingers into the narrow space to attach the connector! It took a pair of needle-nose pliers. So much for planning ahead... I would use the device with a short coaxial cable jumper rather than subject the BNC's to the side stresses too. The part that is most likely to break is the connection to the PCB in the K2 of course... Ron AC7AC K2 # 1289 ++++++++++++++++