|
Bird wattmeter
I have never seen a reason to spend big money on
a Bird wattmeter but I do have a question. What exactly is inside the various slugs that one must use with this meter ? Art |
|
"Richard Clark" wrote in message ... On 14 Sep 2003 12:35:05 -0700, (Art Unwin KB9MZ) wrote: I have never seen a reason to spend big money on a Bird wattmeter but I do have a question. What exactly is inside the various slugs that one must use with this meter ? Art Hi Art, A loop, at least one cap, a diode, at least one resistor. 73's Richard Clark, KB7QHC The little network, along with the section of coax line inside the main housing, forms a directional coupler. A Bird 43 (or similar, but the 43's are readily available, used, on eBay) is about the cheapest way to get answers about the design and performance of your antenna and transmitter system. And if you think a Bird 43 is big money, you ain't seen nothing yet! Ed WB6WSN |
In article , Art Unwin
KB9MZ wrote: I have never seen a reason to spend big money on a Bird wattmeter but I do have a question. What exactly is inside the various slugs that one must use with this meter ? Art A coupling network and a diode are inside the slug. Slugs are calibrated by twiddling (literally) components inside the slug, and then putting the label on the front of the slug. You can find the meters on eBay, but you need to be careful buying the slugs sight unseen -- some of the lower-power slugs can be thrown out of cal by being dropped (on a hard surface). An easy way to check a slug is to put two high quality 50 ohm loads in parallel (use a "T") on the output of the meter. Bird loads are also easy to find on eBay and swap meets -- I have one that's probably 40 years old, and a newer one, only 20 years old. Try and keep your readings midscale for best accuracy. Put the shorting slug in the meter when the meter isn't in use, or turn the slug so the arrow points up at the meter to protect the movement. The Bird is a wonderful, stable design that's simple and well understood. You can get fancier (from Bird, among others), you can get more accurate (my old HP), but it's hard to get simpler. |
On Sun, 14 Sep 2003 14:31:08 -0700, "Ed Price"
wrote: The little network, along with the section of coax line inside the main housing, forms a directional coupler. A Bird 43 (or similar, but the 43's are readily available, used, on eBay) is about the cheapest way to get answers about the design and performance of your antenna and transmitter system. And if you think a Bird 43 is big money, you ain't seen nothing yet! Ed WB6WSN Hi Ed, I am quite familiar with the Bird 43. A useful instrument on the bench, more appropriate in the field. The URM-120 by Sierra is far more robust and always keeps its calibration. I have used instrumentation that is far more expensive and I have used instrumentation that was far cheaper. I have calibrated them all. For the amateur, a cheap Radio Shack CB SWR meter is more than adequate, and if it is not perceived to be, is easily tailored to fill that shortfall of perception. It shouldn't cost anyone more than $20 (mostly for the meter) to build a very good one. There are scads of designs available, and all revolve around the same assembly of simple components I described for Art. If any trick is involved, it is close attention to dimension and wavelength. Choice in SWR meters is almost akin to preference in tie color, a personal matter. 73's Richard Clark, KB7QHC |
artie wrote:
The Bird is a wonderful, stable design that's simple and well understood. You can get fancier (from Bird, among others), you can get more accurate (my old HP), but it's hard to get simpler. I use a homebrew directional coupler (see QEX for March 1995) for everyday use, and a brand new, well preserved (in a closet) Bird 43 as a reference instrument. At full scale it is specifed as accurate within +/- 0.5 db, which is plenty good enough for me. Bill W0IYH |
Art Unwin wrote:
"What exactly is inside the various slugs that one must use with this meter?" 73 Amateur Radio had an article, "Calibration and Repair for Bird Wattmeter Elements" in its April 1989 issue by Francis Kelson, K2KSY. K2KSY`s plug-in element diagram is more complete than that given by Bird under the topic, "Thruline Principle" in my Bird catalog. Bird may have been guarding proprietary information in 1989 when my catalog was issued. The Bird Model 43 accuracy is specified as + or - 5% of full scale in the catalog. So, a "slug" which would cause nearly full scale deflection should probably be used for accuracy. Accuracy results from the careful, rugged construction and calibration of the Bird. Bird says: "Broadcasters may want to order two identical Elements at the same time and keep one in a safe place after recording the meter readings obtained by each. If a question arises about recalibration (e.g. in case an Element has been dropped on a cement floor), a quick comparison with the original twin could save time, effort and inconvenience of shipping the whole wattmeter back for a checkup. For better resolution of low reflected power levels, we recommend a second Element 1/10 the power of the forward Element." From the above, Bird seems to advise broadcasters initially buy 4 Elements. Richard Clark, a metrologist, occasionally disparages Bird`s accuracy on this newsgroup. I`m no metrologist, but have experience with many Bird 43`s and have seen them to be highly repeatable and exchangeable. They usually read what you would expect and they read what you determine the power to be by other means. I doubt that cheap meters come close to the Bird`s reliability. I think the Bird Model 43 is a good value. Best regards, Richard Harrison, KB5WZI |
"William E. Sabin" sabinw@mwci-news wrote in message ...
artie wrote: The Bird is a wonderful, stable design that's simple and well understood. You can get fancier (from Bird, among others), you can get more accurate (my old HP), but it's hard to get simpler. I use a homebrew directional coupler (see QEX for March 1995) for everyday use, and a brand new, well preserved (in a closet) Bird 43 as a reference instrument. At full scale it is specifed as accurate within +/- 0.5 db, which is plenty good enough for me. Bill W0IYH Why would a ham operator have a need for such accuracy ? Isn't consistency enough ? For ensurance of not exceeding the power output for those who want to equal the max then a scope would be the way to go. For those that build then there is a need for accuracy and bragging rights are fully earned. Seems like this falls into the same catagory of 'I have six elements where you have only five' Art |
Why would a ham operator have a need for such accuracy ? Isn't consistency enough ? For ensurance of not exceeding the power output for those who want to equal the max then a scope would be the way to go. For those that build then there is a need for accuracy and bragging rights are fully earned. Seems like this falls into the same catagory of 'I have six elements where you have only five' Art 'need' is maybe too strong a word, but in general, i'll buy a more precise meter if i can afford it, rather than a less precise one. your tools are your eyes. if you can't measure it, you can't improve it. bird owner |
isn't the power rule about input?
sam -- toys: diesel BMW motorcycle, homebuilt electric motorcycle, gold wing trike, honda gyros, dodge diesel dualie, fiat osca 1500 cabriolet, W3CYO/R, 145.49, 224.40, 443.300 mhz. repeaters. "Art Unwin KB9MZ" wrote in message m... "William E. Sabin" sabinw@mwci-news wrote in message ... artie wrote: The Bird is a wonderful, stable design that's simple and well understood. You can get fancier (from Bird, among others), you can get more accurate (my old HP), but it's hard to get simpler. I use a homebrew directional coupler (see QEX for March 1995) for everyday use, and a brand new, well preserved (in a closet) Bird 43 as a reference instrument. At full scale it is specifed as accurate within +/- 0.5 db, which is plenty good enough for me. Bill W0IYH Why would a ham operator have a need for such accuracy ? Isn't consistency enough ? For ensurance of not exceeding the power output for those who want to equal the max then a scope would be the way to go. For those that build then there is a need for accuracy and bragging rights are fully earned. Seems like this falls into the same catagory of 'I have six elements where you have only five' Art |
Bill:
Your March 1995 QEX article says that you prepared an accompanying construction article for QST. I haven't been able to find it in '95, 96 or '97 QST editions. Was it published? If so, when? Jack K8ZOA |
I have two good reasons. My homebrew 100 watt
solid state MOSFET PA, 160 M to 10 M, provides the signal cleanliness that I designed it for when the power output on SSB is 100 W PEP Hmmmm...plans available for this? QUITE interested! Tnx de kilo golf 4 golf sierra charlie!! mycall@arrl dot net |
Main reason is that the diode detector types of VSWR Meters are very
inaccurate when any VSWR is present Also I have found that running PA's at 90% gives a much cleaner output (Usually) so I need a meter that will give reasonable accuracy when making these adjustments. Some cheapo VHF VSWR meters are so inaccurate as to be useless. For Bird -- buy the appropriate slug -- slugs are very inexpensive on the used market. Not E-BAy -- hi hi And Mil Surplus thru line meters are very cheap on the surplus market, Less than new diode detector types. -- 73 From The Signal In The Noise Caveat Lector Ya All Why would a ham operator have a need for such accuracy ? Isn't consistency enough ? For ensurance of not exceeding the power output for those who want to equal the max then a scope would be the way to go. For those that build then there is a need for accuracy and bragging rights are fully earned. Seems like this falls into the same catagory of 'I have six elements where you have only five' Art |
On Mon, 15 Sep 2003 15:50:26 -0700, "Caveat Lector"
wrote: Main reason is that the diode detector types of VSWR Meters are very inaccurate when any VSWR is present Also I have found that running PA's at 90% gives a much cleaner output (Usually) so I need a meter that will give reasonable accuracy when making these adjustments. Some cheapo VHF VSWR meters are so inaccurate as to be useless. For Bird -- buy the appropriate slug -- slugs are very inexpensive on the used market. Not E-BAy -- hi hi And Mil Surplus thru line meters are very cheap on the surplus market, Less than new diode detector types. Hi OM, Art says why buy expensive equipment, and then extols a scope (easily three to ten times expensive as a new Bird 43). He probably intends to only measure flat power with perfect sine shape applied to perfect designs. A CB SWR meter works better with even the slightest hint of imperfection and just as well when every thing is hunky-dory. If you want to watch a phosphor glow, get TV or build your meter with a Magic Eye tube (more range than LEDs suggested elsewhere). You say diode detector types of VSWR Meters are very inaccurate when any VSWR is present and then extol the Bird or Mil Surplus - which are diode detector types (what aren't - scopes? WHOOPZ back into that yarn). Has anyone here actually measured SWR without using a diode? Form a que here and tell your story. I want to hear the one about your single device non-linear detector (a way of not saying diode while still being a diode). Caveat Reader, Richard Clark, KB7QHC |
Ah at URL:
http://www.hamradiomarket.com/articles/Wattmeters.htm The cheapos are called "inexpensive cross needle, putt-putt SWR/wattmeters" Interesting article -- 73 From The Signal In The Noise Caveat Lector Ya All "Caveat Lector" wrote in message news:33t9b.134831$kP.127157@fed1read03... Perhaps poor choice of words Bird meters and monimatch type meters use the capacitive coupling of the coupled line to couple voltage and magnetic coupling to the coupled line to couple current. THEN the diode sees the vector sum of the two couplings. The cheaper ones - like Radio Shack had just diodes to detect peak V or I and -- I always called em diode detector types -- what wud u call em Any way I am sure you know the difference -- 73 From The Signal In The Noise Caveat Lector Ya All "Richard Clark" wrote in message ... On Mon, 15 Sep 2003 15:50:26 -0700, "Caveat Lector" wrote: Main reason is that the diode detector types of VSWR Meters are very inaccurate when any VSWR is present Also I have found that running PA's at 90% gives a much cleaner output (Usually) so I need a meter that will give reasonable accuracy when making these adjustments. Some cheapo VHF VSWR meters are so inaccurate as to be useless. For Bird -- buy the appropriate slug -- slugs are very inexpensive on the used market. Not E-BAy -- hi hi And Mil Surplus thru line meters are very cheap on the surplus market, Less than new diode detector types. Hi OM, Art says why buy expensive equipment, and then extols a scope (easily three to ten times expensive as a new Bird 43). He probably intends to only measure flat power with perfect sine shape applied to perfect designs. A CB SWR meter works better with even the slightest hint of imperfection and just as well when every thing is hunky-dory. If you want to watch a phosphor glow, get TV or build your meter with a Magic Eye tube (more range than LEDs suggested elsewhere). You say diode detector types of VSWR Meters are very inaccurate when any VSWR is present and then extol the Bird or Mil Surplus - which are diode detector types (what aren't - scopes? WHOOPZ back into that yarn). Has anyone here actually measured SWR without using a diode? Form a que here and tell your story. I want to hear the one about your single device non-linear detector (a way of not saying diode while still being a diode). Caveat Reader, Richard Clark, KB7QHC |
On Mon, 15 Sep 2003 17:45:52 -0700, "Caveat Lector"
wrote: Perhaps poor choice of words Bird meters and monimatch type meters use the capacitive coupling of the coupled line to couple voltage and magnetic coupling to the coupled line to couple current. THEN the diode sees the vector sum of the two couplings. The cheaper ones - like Radio Shack had just diodes to detect peak V or I and -- I always called em diode detector types -- what wud u call em Any way I am sure you know the difference Hi OM, Not when you incorrectly describe them. They all use two diodes, or in the case of the Bird, the single diode is used twice, once in each direction. There is every chance someone tried to reduce the bottom line (boost profits) by using one diode to read both - give us an example. Peak, Average, PEP, call it what you will is only a matter of meter scaling (and in the case of SWR no different at all) and what the Time Constant is with any particular resistor-capacitor pair used as the meter load. What is really sadistic, are digital numeric displays when SWR/Power is swinging. Reading 8.88 because the numbers' segments blur is pitiful in the extreme. 73's Richard Clark, KB7QHC |
Ok you win -- I retract all
Now where did I put the Bird -- 73 From The Signal In The Noise Caveat Lector Ya All "Richard Clark" wrote in message ... On Mon, 15 Sep 2003 17:45:52 -0700, "Caveat Lector" wrote: Perhaps poor choice of words Bird meters and monimatch type meters use the capacitive coupling of the coupled line to couple voltage and magnetic coupling to the coupled line to couple current. THEN the diode sees the vector sum of the two couplings. The cheaper ones - like Radio Shack had just diodes to detect peak V or I and -- I always called em diode detector types -- what wud u call em Any way I am sure you know the difference Hi OM, Not when you incorrectly describe them. They all use two diodes, or in the case of the Bird, the single diode is used twice, once in each direction. There is every chance someone tried to reduce the bottom line (boost profits) by using one diode to read both - give us an example. Peak, Average, PEP, call it what you will is only a matter of meter scaling (and in the case of SWR no different at all) and what the Time Constant is with any particular resistor-capacitor pair used as the meter load. What is really sadistic, are digital numeric displays when SWR/Power is swinging. Reading 8.88 because the numbers' segments blur is pitiful in the extreme. 73's Richard Clark, KB7QHC |
Caveat Lector wrote:
Main reason is that the diode detector types of VSWR Meters are very inaccurate when any VSWR is present Why can't the diode be biased to improve the accuracy? Or a class-B amp be used? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
"Richard Clark" wrote in message ... On Sun, 14 Sep 2003 14:31:08 -0700, "Ed Price" wrote: The little network, along with the section of coax line inside the main housing, forms a directional coupler. A Bird 43 (or similar, but the 43's are readily available, used, on eBay) is about the cheapest way to get answers about the design and performance of your antenna and transmitter system. And if you think a Bird 43 is big money, you ain't seen nothing yet! Ed WB6WSN .. 73's Richard Clark, KB7QHC Bu, bu, bu, Richard it has to be expensive for a CBer. How else is he to get them "bird" watts thar? (snicker) :) Jerry |
AA wrote:
I have two good reasons. My homebrew 100 watt solid state MOSFET PA, 160 M to 10 M, provides the signal cleanliness that I designed it for when the power output on SSB is 100 W PEP Hmmmm...plans available for this? QUITE interested! Tnx de kilo golf 4 golf sierra charlie!! mycall@arrl dot net See QEX for Nov/Dec 1999. Bill W0IYH |
Jack Smith wrote:
Bill: Your March 1995 QEX article says that you prepared an accompanying construction article for QST. I haven't been able to find it in '95, 96 or '97 QST editions. Was it published? If so, when? Jack K8ZOA I did not write a construction article, but QEX for May 1995 has an article on the design of the transformers for the directional coupler. Actual construction articles have been described in ARRL Handbook and Antenna Book editions. Bill W0IYH |
On Tue, 16 Sep 2003 06:38:21 -0500, "William E. Sabin"
sabinw@mwci-news wrote: Jack Smith wrote: Bill: Your March 1995 QEX article says that you prepared an accompanying construction article for QST. I haven't been able to find it in '95, 96 or '97 QST editions. Was it published? If so, when? Jack K8ZOA I did not write a construction article, but QEX for May 1995 has an article on the design of the transformers for the directional coupler. Actual construction articles have been described in ARRL Handbook and Antenna Book editions. Bill W0IYH Found it. As usual, an excellent piece of work! Jack K8ZOA |
Richard Clark wrote:
"Has anyone here actually measured SWR without using a diode?" I did something similar and could have used the same rig to measure SWR in a feedline. I used a wire loop which included a thermoammeter suspended from a horizontal antenna element. I pulled this along the element to measure its current distribution using a long tow rope and a telescope. Pulled along a transmission line wire, this would have produced the currents at the minima and maxima along the wire. From these we could calculate SWR. Best regards, Richard Harrison, KB5WZI |
|
In message ,
Richard Harrison writes Richard Clark wrote: "Has anyone here actually measured SWR without using a diode?" I did something similar and could have used the same rig to measure SWR in a feedline. I used a wire loop which included a thermoammeter suspended from a horizontal antenna element. I pulled this along the element to measure its current distribution using a long tow rope and a telescope. Pulled along a transmission line wire, this would have produced the currents at the minima and maxima along the wire. From these we could calculate SWR. This was a common task for the students at Marconi College in the 50's. The meter was read with binoculars. Mike -- M.J.Powell |
Mike Powell wrote:
"This was a common task fot the students at Marconi College in the `50`s." The student practice had a commercial application. It was in the same decade but at a different locale. It was during the tune-up of a SW broadcast curtain array near Lisbon, Portugal. Best regards, Richard Harrison, KB5WZI |
| All times are GMT +1. The time now is 09:12 AM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
RadioBanter.com