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#51
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4NEC2?
On Sun, 14 Oct 2018 11:12:14 -0700, Jeff Liebermann
wrote: (...) However, if you plan to do more than that, some test equipment might be useful. Since you prefer a minimalist approach to test equipment, as an alternative to your light bulb, may I suggest a return loss bridge: https://www.google.com/search?q=return+loss+bridge&tbm=isch Note that there are several basic designs and configurations but all are fairly simple and easy to construct. Note that these are NOT the same as directional couplers. You can purchase them on eBay: https://www.ebay.com/sch/i.html?_nkw=return+loss+bridge There are tutorials on YouTube: https://www.youtube.com/results?search_query=return+loss+bridge I have three of these made by Texscan: https://www.qsl.net/n9zia/wireless/rtrn_loss-pics.html https://www.qsl.net/n9zia/rlb/texscan.png and a few that I've built for microwave frequencies: http://pe2er.nl/wifiswr/ and one for HF: http://www.dicks-website.eu/return%20loss%20bridge_part1/part1.html http://www.dicks-website.eu/return%20loss%20bridge_part2/part2.html http://www.dicks-website.eu/return%20loss%20bridge_part2/part3.html http://www.dicks-website.eu/return%20loss%20bridge_part2/part4.html http://www.dicks-website.eu/return%20loss%20bridge_part5/part5.html A return loss bridge is similar to a VNA except that it does not produce numbers for the real (resistive) and imaginary (reactive) components of the antenna impedance. It just produces the return loss compared to a reference termination resistor, which can then be translated into the VSWR. To use it, you need a minimum of an RF signal generator and a voltmeter or oscilloscope. I prefer to sweep the frequency range of interest, so I use an RF sweep generator, and display the result on an oscilloscope. With this arrangement, you can tune your antenna without requiring a light bulb. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#52
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4NEC2?
In message , Gareth's Downstairs Computer
writes On 14/10/2018 20:30, brian wrote: In message , Gareth's Downstairs Computer writes Whereas such antenna predictors seem to feature in amateur usage, does anyone, anywhere, in the world of amateur radio have an understanding of the underlying principles involved in predicting the performance of antennae, or have we all, regrettably, become indistinguishable from consumerist CBers or beginner licensees? 4NEC2 and EZNEC are* just a fancy front and back ends for NEC2 (and NEC4) Engines. Program description is here :- https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA956129. xhtml. Thanks for the heads up, Brian, but a quick glance suggests that some revision might be necessary of my 3rd year uni textbook, "Fields and Waves in Communications Electronics" by Ramo, Whinnery and Van Duzer. ISTR it to be an excellent book explaining complicated things in words of one syllable, but 46 years down the line, I might have a more romantic memory of it in reality :-) I've got mine here. We used to call it Ramo Whinnery and Bamboozle. From the inscription in the fly leaf, it looks like I used it in 3rd year too. Mine has one of the equations printed upside down, which threw me a bit. Brian -- Brian Howie |
#53
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4NEC2?
On 14/10/2018 23:14, Ralph Mowery wrote:
I think the tests have gotten away from the technical part of ham radio and are now geared more to the operating practices. It is never too late to correct such an egregious mistake, for operating as such is CB Radio whereas Amateur / Ham Radio is a whole-life technical pursuit. |
#54
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4NEC2?
On 15/10/2018 04:49, brian wrote:
In message , Gareth's Downstairs Computer writes On 14/10/2018 20:30, brian wrote: In message , Gareth's Downstairs Computer writes Whereas such antenna predictors seem to feature in amateur usage, does anyone, anywhere, in the world of amateur radio have an understanding of the underlying principles involved in predicting the performance of antennae, or have we all, regrettably, become indistinguishable from consumerist CBers or beginner licensees? Â*4NEC2 and EZNEC areÂ* just a fancy front and back ends for NEC2 (and NEC4) Engines. Â*Program description is here :- https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA956129. xhtml. Thanks for the heads up, Brian, but a quick glance suggests that some revision might be necessary of my 3rd year uni textbook, "Fields and Waves in Communications Electronics" by Ramo, Whinnery and Van Duzer. ISTR it to be an excellent book explaining complicated things in words of one syllable, but 46 years down the line, I might have a more romantic memory of it in realityÂ* :-) I've got mine here. We used to call it Ramo Whinnery and Bamboozle. From the inscription in the fly leaf, it looks like I used it in 3rd year too. Mine has one of the equations printed upside down, which threw me a bit. Simon Ramo is an undoubted expert in that "field", but probably deals only in that area. Much more difficult for we polymaths who must have a working knowledge of so many more subjects, eg, the low level programming of computers. |
#55
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4NEC2?
"Jeff" wrote in message news I wired up a neg ground rev counter to my pos earth 1963 mini in 1969 by insulating the live case of the rev counter and earthing the live terminal...worked well ..... Most of us just reversed the battery etc. and flashed the dynamo. Jeff I didn't .... |
#56
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4NEC2?
"Gareth's Downstairs Computer" wrote in message news On 14/10/2018 23:14, Ralph Mowery wrote: I think the tests have gotten away from the technical part of ham radio and are now geared more to the operating practices. It is never too late to correct such an egregious mistake, for operating as such is CB Radio whereas Amateur / Ham Radio is a whole-life technical pursuit. I have been persuing an HRO500 since the 60's .......... |
#58
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4NEC2?
On 14/10/2018 20:59, Bernie wrote:
On Sun, 14 Oct 2018 20:25:28 +0100 Brian Howie wrote: In message , Bernie writes On Sun, 14 Oct 2018 05:59:35 -0700 (PDT) Jeefaw K Effkay wrote: On Sunday, October 14, 2018 at 12:57:21 PM UTC+1, Geoff wrote: On Sun, 14 Oct 2018 11:55:13 +0000 Spite sent a message from the other side: On 14/10/2018 11:44, Geoff wrote: On Sun, 14 Oct 2018 11:39:58 +0000 Spite sent a message from the other side: On 14/10/2018 11:04, Geoff wrote: On Sun, 14 Oct 2018 08:50:13 +0000 Spike lied: On 14/10/2018 01:32, Jeff Liebermann wrote: wrote: Gareth once complained about a mobile CB set-up he installed in a 4x4 couldn’t reach further than a quarter mile. That’s all you need to know about Gareth and radio. He probably didn't need any antenna at 1/4 mile (400 meters). snip interesting detection story Stephen Thomas Cole, the PP, just after gaining his UK Full licence by 'acing' all three exams, appeared on a UK Amateur group asking which sideband he should use on 40m. That's all you need to know about him and and his ability with radio. That sounds interesting - can you provide a link to that post? No. For some reason it's been deleted. Then we only have your word that it ever exsisted. I choose not to believe a word of it. 'It's been deleted' means it did exsist. You can't delete was was never posted. You might ask yourself why it was deleted. That's all you need to know about his ego and and his ability with radio. We only have your word for any of that. I choose not to believe a word of it. What STC actually asked was which sideband he should use for RTTY on 40m. Which is, of course, an interesting question as it's not something that was covered in any exam, current or previous. My $0.02 worth is that it doesn't matter, since an RTTY operator will know that he needs to invert the received tones if he sees a string of "46464646" instead of "RYRYRYRY" Here's what was asked, and it wasn't posted no archive, or deleted, or any of the other weak bull**** that Burt has bean spraying around: "Was pottering at my radio last night, heard the scream of data being sent and was triggered to revisit a long parked project; getting going on RTTY! Here's the hardware I'm using: Yaesu FT757-GXii Serial/USB cable interface thing PowerMac G4 running CocoaModem I've got everything hooked up, have CocoaModem configured and displaying a waterfall but when set to RTTY mode it's just decoding gibberish... Other than a couple of short spells at club days, this is my first go at this and I have no idea what I'm doing... Any tips?" https://groups.google.com/forum/#!or...-radio/MjriIIU zuHA/_ityI76x0IMJ Good old Burt. For the record all the data modes including RTTY use upper sideband all the way up from 136KHz . CW A1A is also upper sideband but there can be advantages to be had by swapping to LSB to avoid interference. F1A beacons seem to be a law unto themselves. You can get quite good at reading inverted morse. Amateur RTTY uses inverted tones and a different narrower shift compared with commercial RTTY. I don't know why your getting onto Steve about this as none of it is the radio amateur courses or even online anywhere, unless some smarty pants comes along and tells me it is. Ok it's in here for WSJT It was Burt who was doing the 'getting onto' and when it wasn't going well for him he introduced a new plotline about mysterious disappearing posts and the character defects that could be at the root of the disappearing posts. I joined it to point out that the posts are still there and that Burt is a liar and a ****ing idiot. But Burt is an excellent troller. Of course none of us would **** on Burt if he were on fire. Apart from Dicky 'Rimjob' Brown. But that's because he's trying to hide the fact he lied about his licence level. |
#59
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4NEC2?
On 15/10/2018 01:20, Jeff Liebermann wrote:
On Sun, 14 Oct 2018 11:12:14 -0700, Jeff Liebermann wrote: Since you prefer a minimalist approach to test equipment, as an alternative to your light bulb, may I suggest a return loss bridge: https://www.google.com/search?q=return+loss+bridge&tbm=isch Note that there are several basic designs and configurations but all are fairly simple and easy to construct. Note that these are NOT the same as directional couplers. To use it, you need a minimum of an RF signal generator and a voltmeter or oscilloscope. I prefer to sweep the frequency range of interest, so I use an RF sweep generator, and display the result on an oscilloscope. With this arrangement, you can tune your antenna without requiring a light bulb. So, let me get this right. By employing a return-loss bridge, an RF signal generator, and either a voltmeter or an oscilloscope, you can get results that a distant station can't distinguish from those obtained by using a torch bulb? Given your ability to estimate the performance of an antenna by looking at it rather than employ modelling methods, I would have though you would be sympathetic to the merits of the torch bulb approach. -- Spike "Nearly all men can stand adversity, but if you want to test a man's character, give him an internet group to manage" |
#60
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4NEC2?
On 14/10/2018 22:01, Ralph Mowery wrote:
In article , lid says... On Sun, 14 Oct 2018 12:04:52 -0700 (PDT) Jeefaw K Effkay wrote: On Sunday, October 14, 2018 at 7:33:10 PM UTC+1, Jeff Liebermann wrote: It might help to understand why some bands use LSB while others USB. In the early daze of sideband radio, the common IF frequency was 9MHz. The radios had only one sideband filter. With one filter, it was cheaper and easier to mix and up convert in the transmitter. So, to save the cost of adding a second filter, the bands below 9MHz were designated as LSB and the band above 9MHz became USB. Eventually, radios were built with two sideband filters, and this was no longer important. As usual, the legacy technology remained in place to haunt the survivors to this day. I've seen this explanation before, but it doesn't make sense. A 9MHz USB signal mixed with a 5.0 to 5.5MHz VFO will produce mixing products in the 80m and 20m bands - but both will be upper sideband. When the 9 MHz is mixed with the 5 mhz the 20 meter signal is upper sideband. The 80 meter signal is inverted and becomes the lower sideband NOT usb. Years ago when ssb was just starting out on the ham bands this made 80 meters and 20 meters easy and inexpensive compaired to other methods. So it was decided on by hams to use 40 metes and lower frequencies as LSB and 20 meters and above as USB. Then the government stepped in for the 5 and 10 MHz bands and dictated what to use. For other reasons most digital is in the USB mode for all bands except for RTTY. RTTY is usually used in the LSB mode for all ham bands, but can be used in the USB mode if the tones are inverted. The commercial RTTY was usually inverted from the normal ham RTTY. "Geoff" has long had a 'difficult' relationship with HF. -- Spike "Nearly all men can stand adversity, but if you want to test a man's character, give him an internet group to manage" |
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