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antenna tuner balun question
Having never wound a balun before, pardon if this is an elementary
question, but... I recently got a Murch 2000B antenna tuner off eBay. It's a commercial version of the so-called ultimate transmatch. A T-network design. For balanced line, it has a "broadband toroidal transformer" according to the review in a 1980 QST. When I place a VOM multi-meter across the two balanced line terminals, it shows continuity. Is that normal, or is the balun cooked or shorted? Thanks for any info. Bob k5qwg |
Bob Miller wrote:
For balanced line, it has a "broadband toroidal transformer" according to the review in a 1980 QST. When I place a VOM multi-meter across the two balanced line terminals, it shows continuity. Is that normal, or is the balun cooked or shorted? It's probably a 4:1 voltage balun which does exhibit a DC short. That's actually good for cutting down on static electricity. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Bob:
Totally normal, in fact, if you check secondary to primary--will also show continuity--it is normal too...look at a schematic of a torrid balun on the net, all windings have some sort of connection to all others... in a "rf transformer" with seperate primary/secondary there will be electrical isolation between windings... Warmest regards, John "Bob Miller" wrote in message ... Having never wound a balun before, pardon if this is an elementary question, but... I recently got a Murch 2000B antenna tuner off eBay. It's a commercial version of the so-called ultimate transmatch. A T-network design. For balanced line, it has a "broadband toroidal transformer" according to the review in a 1980 QST. When I place a VOM multi-meter across the two balanced line terminals, it shows continuity. Is that normal, or is the balun cooked or shorted? Thanks for any info. Bob k5qwg |
In article ,
Bob Miller wrote: For balanced line, it has a "broadband toroidal transformer" according to the review in a 1980 QST. When I place a VOM multi-meter across the two balanced line terminals, it shows continuity. Is that normal, or is the balun cooked or shorted? Very probably normal... or, at least, to be expected of many types of balun and thus not diagnostic of a failure. You're probably reading the DC resistance one or more of the windings, which would be rather less than an ohm. Based on what I see in Sevick's book on baluns and ununs, both the Guanella 4:1 current balun and the various Ruthroff voltage balun configurations would exhibit this behavior. A Guanella 1:1 with the center of the load un-grounded would not, nor would a Reisert or W2DU 1:1 balun. Now, for something completely different. If you want to revisit an old controversy, and if you're not adverse to modifying a classic piece of equipment, you might want to review the various debates about the pros and cons of the Ultimate Transmatch vs. the SPC configuration. See if you can locate a copy of the August 1981 QST, and review the Technical Correspondence column on pages 42-43. As I understand it, the SPC configuration can be shown to have some significant technical advantages over the Ultimate Transmatch, in terms of matching range and harmonic attenuation, when the same component values are used in each. It is reportedly possible to re-wire an Ultimate into an SPC configuration little or no cost, as both use a split-stator capacitor (just in different places in the circuit). -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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On Sat, 04 Jun 2005 14:58:33 -0500, Cecil Moore
wrote: Bob Miller wrote: For balanced line, it has a "broadband toroidal transformer" according to the review in a 1980 QST. When I place a VOM multi-meter across the two balanced line terminals, it shows continuity. Is that normal, or is the balun cooked or shorted? It's probably a 4:1 voltage balun which does exhibit a DC short. That's actually good for cutting down on static electricity. Thanks, Cecil, I noticed a more up-to-date MFJ tuner doesn't show continuity across the balanced line terminals; just wanted to make sure the Murch balun wasn't whacked out. Bob k5qwg |
On Sat, 04 Jun 2005 14:58:33 -0500, Cecil Moore
wrote: Bob Miller wrote: For balanced line, it has a "broadband toroidal transformer" according to the review in a 1980 QST. When I place a VOM multi-meter across the two balanced line terminals, it shows continuity. Is that normal, or is the balun cooked or shorted? It's probably a 4:1 voltage balun which does exhibit a DC short. That's actually good for cutting down on static electricity. Okay, Cecil, Dave, one more elementary question. My copy of the instructions for the Murch 2000B says the following: "Connect balanced line to connection marked Balance Line with Jumper as indicated on back panel." On the back panel, there's a painted line between the two balanced line connections. Surely, they don't mean to run a jumper wire between the two connections *while* a balanced line is attached? It seems to tune fine without the jumper -- I'm afraid I'd blow something up with the jumper. Bob k5qwg |
On Sat, 4 Jun 2005 14:01:25 -0700, "John Smith"
wrote: Bob: If you don't mind me asking--how much did you pay for it, I have one in the barn here I bought as lot with other gear from an estate sale--just wondering... John The eBay bidding started at $100. There were 20 bids, and it finally ended up at $171, plus $20 for shipping. The case is a little scratched up, but the front panel and inside components look good. Bob k5qwg |
WOW, that makes me smile... I am going to dig it out!
Warmest regards, John "Bob Miller" wrote in message ... On Sat, 4 Jun 2005 14:01:25 -0700, "John Smith" wrote: Bob: If you don't mind me asking--how much did you pay for it, I have one in the barn here I bought as lot with other gear from an estate sale--just wondering... John The eBay bidding started at $100. There were 20 bids, and it finally ended up at $171, plus $20 for shipping. The case is a little scratched up, but the front panel and inside components look good. Bob k5qwg |
In article ,
Bob Miller wrote: It's probably a 4:1 voltage balun which does exhibit a DC short. That's actually good for cutting down on static electricity. Okay, Cecil, Dave, one more elementary question. My copy of the instructions for the Murch 2000B says the following: "Connect balanced line to connection marked Balance Line with Jumper as indicated on back panel." On the back panel, there's a painted line between the two balanced line connections. Surely, they don't mean to run a jumper wire between the two connections *while* a balanced line is attached? No, I think the painted line is meant to indicate "the line is connected to/between these two points." The "jumper" they refer to probably refers to a short section of balanced line, to be connected between the transmatch and whatever terminals you use to terminate the ladder-line or open-wire line when it comes into your shack. It seems to tune fine without the jumper -- I'm afraid I'd blow something up with the jumper. Yeah, you'd be trying to tune a near-short-circuit... often difficult and the results are less than productive :-) There are some transmatches in which the balun is normally out of circuit, and has to be jumpered to the hot side of the unbalanced output when you want to use it. That *might* be what they're referring to? -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Bob Miller wrote:
Okay, Cecil, Dave, one more elementary question. My copy of the instructions for the Murch 2000B says the following: "Connect balanced line to connection marked Balance Line with Jumper as indicated on back panel." On the back panel, there's a painted line between the two balanced line connections. Surely, they don't mean to run a jumper wire between the two connections *while* a balanced line is attached? It seems to tune fine without the jumper -- I'm afraid I'd blow something up with the jumper. If it's like my MFJ-949E, the balun is completely out of the circuit until the jumper is installed. Without the jumper on the MFJ, there would be no output at the balanced line output terminals. Do you have a schematic? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On Sat, 04 Jun 2005 19:24:15 -0500, Cecil Moore
wrote: Bob Miller wrote: Okay, Cecil, Dave, one more elementary question. My copy of the instructions for the Murch 2000B says the following: "Connect balanced line to connection marked Balance Line with Jumper as indicated on back panel." On the back panel, there's a painted line between the two balanced line connections. Surely, they don't mean to run a jumper wire between the two connections *while* a balanced line is attached? It seems to tune fine without the jumper -- I'm afraid I'd blow something up with the jumper. If it's like my MFJ-949E, the balun is completely out of the circuit until the jumper is installed. Without the jumper on the MFJ, there would be no output at the balanced line output terminals. Do you have a schematic? Sorry, I don't have a schematic. On my MFJ 989c, I have two balanced line connectors. I also have a 3rd connector for Random Wire, and a 4th odd connector. For balanced line operation, I install a jumper between the Random Wire and 4th connectors. On the Murch 2000B, there are two connectors for balanced line. And a 3rd connector for Random Wire. The directions seem to be saying put a jumper on the balanced line connectors for balanced line operation. "Connect any antenna with single wire feed to connection marked Random Wire. Connect balanced line to connection marked Balanced Line with Jumper as indicated on back panel." (and there's a painted line between the Balanced Line connectors.) If it's helpful, there are pictures, inside & out, of the Murch tuner at http://cgi.ebay.com/ws/eBayISAPI.dll...m=5757714 402 Bob k5qwg |
Bob Miller wrote:
"Connect any antenna with single wire feed to connection marked Random Wire. Connect balanced line to connection marked Balanced Line with Jumper as indicated on back panel." (and there's a painted line between the Balanced Line connectors.) If it's helpful, there are pictures, inside & out, of the Murch tuner at http://cgi.ebay.com/ws/eBayISAPI.dll...m=5757714 402 I suspect the jumper wire needs to go between the random wire terminal and one of the balanced line terminals. That's the way it is on my MFJ. On the inside, do the balanced line terminals go anywhere besides the balun? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
"Connect any antenna with single wire feed to connection marked Random
Wire. Connect balanced line to connection marked Balanced Line with Jumper as indicated on back panel." (and there's a painted line between the Balanced Line connectors.) If it's helpful, there are pictures, inside & out, of the Murch tuner at http://cgi.ebay.com/ws/eBayISAPI.dll...m=5757714 402 I suspect the jumper wire needs to go between the random wire terminal and one of the balanced line terminals. That's the way it is on my MFJ. On the inside, do the balanced line terminals go anywhere besides the balun? According to one note I saw on the net, many of the Ultimate Transmatch designs had an internal strap/jumper to connect the unbalanced tuner circuitry to the balun, when necessary. I rather strongly suspect that this is the case for the Murch. The photos show that it has internal switching of the tuner output. The switch has five positions - 1 2 3 (which I assume correspond to the three unbalanced jacks) and two I can't really read clearly in the photo - perhaps the random-wire output, and the balun for the balanced output? Sounds to me as if no external hot-to-balun jumper is requires, especially as the OP reports that it tunes a balanced antenna just fine without one. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
On Sat, 04 Jun 2005 21:49:25 -0500, Cecil Moore
wrote: Bob Miller wrote: "Connect any antenna with single wire feed to connection marked Random Wire. Connect balanced line to connection marked Balanced Line with Jumper as indicated on back panel." (and there's a painted line between the Balanced Line connectors.) If it's helpful, there are pictures, inside & out, of the Murch tuner at http://cgi.ebay.com/ws/eBayISAPI.dll...m=5757714 402 I suspect the jumper wire needs to go between the random wire terminal and one of the balanced line terminals. That's the way it is on my MFJ. On the inside, do the balanced line terminals go anywhere besides the balun? One Balanced Line terminal goes to a balun winding wire. The second Balanced Line terminal goes to another balun winding wire; the second terminal also has a wire going to the Antenna Selector Switch, which selects the balanced antenna. The Random Wire terminal has a wire going to the same Antenna Selector Switch, which also selects the random wire antenna. Those are the only wires on these three terminals. bob k5qwg |
On Sun, 05 Jun 2005 03:21:08 -0000, (Dave Platt)
wrote: "Connect any antenna with single wire feed to connection marked Random Wire. Connect balanced line to connection marked Balanced Line with Jumper as indicated on back panel." (and there's a painted line between the Balanced Line connectors.) If it's helpful, there are pictures, inside & out, of the Murch tuner at http://cgi.ebay.com/ws/eBayISAPI.dll...m=5757714 402 I suspect the jumper wire needs to go between the random wire terminal and one of the balanced line terminals. That's the way it is on my MFJ. On the inside, do the balanced line terminals go anywhere besides the balun? According to one note I saw on the net, many of the Ultimate Transmatch designs had an internal strap/jumper to connect the unbalanced tuner circuitry to the balun, when necessary. I rather strongly suspect that this is the case for the Murch. The photos show that it has internal switching of the tuner output. The switch has five positions - 1 2 3 (which I assume correspond to the three unbalanced jacks) and two I can't really read clearly in the photo - perhaps the random-wire output, and the balun for the balanced output? That's right, the 5-position Antenna switch selects coax 1, 2 and 3, and R for Random Wire, and BL for balanced line. bob k5qwg Sounds to me as if no external hot-to-balun jumper is requires, especially as the OP reports that it tunes a balanced antenna just fine without one. |
Bob Miller wrote:
One Balanced Line terminal goes to a balun winding wire. The second Balanced Line terminal goes to another balun winding wire; the second terminal also has a wire going to the Antenna Selector Switch, which selects the balanced antenna. That's different from the MFJ which has wires from the balanced output terminals going only to the balun. The Random Wire terminal has a wire going to the same Antenna Selector Switch, which also selects the random wire antenna. MFJ saved money on the switch by combining the balanced and random wire functions. Sounds like your tuner has separate switch settings for balanced and random wire. So I don't know what that jumper statement is all about. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
The line he is refering to simply indicates which of the three terminals to
connect a balanced line to. It has nothing to do with a jumper. "Cecil Moore" wrote in message ... Bob Miller wrote: One Balanced Line terminal goes to a balun winding wire. The second Balanced Line terminal goes to another balun winding wire; the second terminal also has a wire going to the Antenna Selector Switch, which selects the balanced antenna. That's different from the MFJ which has wires from the balanced output terminals going only to the balun. The Random Wire terminal has a wire going to the same Antenna Selector Switch, which also selects the random wire antenna. MFJ saved money on the switch by combining the balanced and random wire functions. Sounds like your tuner has separate switch settings for balanced and random wire. So I don't know what that jumper statement is all about. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On Sun, 5 Jun 2005 10:50:17 -0400, "Fred W4JLE"
wrote: The line he is refering to simply indicates which of the three terminals to connect a balanced line to. It has nothing to do with a jumper. Thank you, that's what I finally have figured out -- Murch made several versions of their tuner; perhaps my copy of the instruction manual refers to some other version, or maybe they just weren't clear in what they were trying to say. Thanks to all... bob k5qwg |
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