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1. [Amps] Checking for IMD (score: 1): Author: Bill Turner <dezrat@copper.net>; Date: Fri, 11 Aug 2006 07:23:45 -0700; Is there a simple procedure one can use for checking the IMD of an amplifier? Frankly, it's something I have never tested myself, instead just keeping the amp tuned correctly and underdriving when us; /archives//html/Amps/2006-08/msg00395.html (7,165 bytes)
2. Re: [Amps] Checking for IMD (score: 1): Author: Martin AA6E <aa6e@ewing.homedns.org>; Date: Fri, 11 Aug 2006 10:43:04 -0400; Bill, I've wondered about this, too. The lab method is to use a high-priced spectrum analyzer, but couldn't you do something useful with a soundcard based spectrum analyzer? You would need to have a; /archives//html/Amps/2006-08/msg00396.html (7,729 bytes)
3. Re: [Amps] Checking for IMD (score: 1): Author: Bill Fuqua <wlfuqu00@uky.edu>; Date: Fri, 11 Aug 2006 10:59:17 -0400; An oscillator, good mixer and a sound card running FFT should work. You want to mix the RF down to around 10 kHz ( center of the sound card frequency range) and observe sidebands around it. You can u; /archives//html/Amps/2006-08/msg00397.html (9,514 bytes)
4. Re: [Amps] Checking for IMD (score: 1): Author: "Joe Subich, W4TV" <w4tv@subich.com>; Date: Fri, 11 Aug 2006 11:23:10 -0400; There are a couple of issues in a "poor man's spectrum analyzer" using sound card. 1) the mixer needs to be clean and handle a 60+ dB dynamic range. If it is overloaded it can generate IMD itself. 2); /archives//html/Amps/2006-08/msg00398.html (8,598 bytes)
5. Re: [Amps] Checking for IMD (score: 1): Author: "m.ford" <k1ern@pioneerwireless.net>; Date: Fri, 11 Aug 2006 11:36:53 -0400; Is anyone using the SDR-14 for IMD measurements? I bought one last year for just that purpose but ended up using it as a receiver instead. I want to buy another one to use for bench work. Unfortunate; /archives//html/Amps/2006-08/msg00399.html (8,796 bytes)
6. Re: [Amps] Checking for IMD (score: 1): Author: "Hsu" <Jbenson@sohu.com>; Date: Sat, 12 Aug 2006 00:02:00 +0800; There is another way, homebrew a inexpensive measure receiver ( please view W7ZOI Wes Hayward's EMRF), it shoud be do this job. I have a question too, we test IMD using a two tone generator and a SSB; /archives//html/Amps/2006-08/msg00400.html (8,216 bytes)
7. Re: [Amps] Checking for IMD (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 11 Aug 2006 17:25:28 +0100; Single Sideband Principles and Circuits includes a section on calculating IMD from measurements of input vs output voltage. I reckon this will include any effects from power supply sag. For amplifier; /archives//html/Amps/2006-08/msg00401.html (8,745 bytes)
8. Re: [Amps] Checking for IMD (score: 1): Author: Martin AA6E <aa6e@ewing.homedns.org>; Date: Fri, 11 Aug 2006 12:27:27 -0400; Why not directly detect the output RF with a linear rectifier / filter? Also, why not use closely spaced tones (20-30 Hz) to make things easier on the sound card? This is basically what the PSKmeter; /archives//html/Amps/2006-08/msg00402.html (10,892 bytes)
9. Re: [Amps] Checking for IMD (score: 1): Author: Martin AA6E <aa6e@ewing.homedns.org>; Date: Fri, 11 Aug 2006 12:32:17 -0400; Oops, the PSKmeter does NOT use the sound card -- it has its own simple A/D converter which connects to a serial port. --Martin _______________________________________________ Amps mailing list Amps@; /archives//html/Amps/2006-08/msg00403.html (8,377 bytes)
10. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Fri, 11 Aug 2006 12:27:48 -0500; The Collins 30L1 has such a meter in it. 73 Gary K4FMX _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps; /archives//html/Amps/2006-08/msg00406.html (10,307 bytes)
11. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Fri, 11 Aug 2006 12:40:21 -0500; Simplest is to talk into the mike and use a second receiver and flip to the opposite side band and compare levels. An attenuator of known calibration ahead of the second receiver will get you in the; /archives//html/Amps/2006-08/msg00407.html (10,104 bytes)
12. Re: [Amps] Checking for IMD (score: 1): Author: Mark Hill <g4fph@mjha.co.uk>; Date: Fri, 11 Aug 2006 18:41:09 +0100; Folks, I have been meaning to try such an idea out for a while as a Friday night (less than four hours build time!) project. I have a Racal 100mW drive source that I can set to CW and pad down to dri; /archives//html/Amps/2006-08/msg00408.html (11,961 bytes)
13. Re: [Amps] Checking for IMD (score: 1): Author: Colin Lamb <k7fm@teleport.com>; Date: Fri, 11 Aug 2006 10:43:39 -0700 (GMT-07:00); I have been thinking, the last few days, that I should clear off a spot on the desk and put my spectrum analyzer and amp on a clean desk and make some tests to see what the input circuit does. I have; /archives//html/Amps/2006-08/msg00409.html (8,889 bytes)
14. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 11 Aug 2006 15:46:39 -0400; You either need to run two radios through attenuators into a combiner and through a 50 ohm input class A amplifier into the amp (I use a class A 8877/3CX1500A7), or find a radio that by itself has -; /archives//html/Amps/2006-08/msg00412.html (8,725 bytes)
15. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 11 Aug 2006 16:32:19 -0400; One thing everyone needs to keep in mind is IMD products at one point can even cancel other IMD products produced at another point in the system. You don't necessarily get the worse case condition, y; /archives//html/Amps/2006-08/msg00414.html (10,046 bytes)
16. Re: [Amps] Checking for IMD (score: 1): Author: "Jim Tonne" <tonne@comcast.net>; Date: Fri, 11 Aug 2006 16:43:39 -0400; And Jim is adding: Very true! And if the separation between tones is down below, say, 100 Hz, then the power supply regulation (or lack of same) starts to enter into the picture. To test the RF block; /archives//html/Amps/2006-08/msg00415.html (9,018 bytes)
17. Re: [Amps] Checking for IMD (score: 1): Author: Colin Lamb <k7fm@teleport.com>; Date: Fri, 11 Aug 2006 14:03:45 -0700 (GMT-07:00); Two-tone tests should be ok for testing the difference between tuned and no-tuned cathode input, since we are not testing the power supply dynamic qualities in this particular test. The test is simp; /archives//html/Amps/2006-08/msg00416.html (8,843 bytes)
18. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 11 Aug 2006 17:08:25 -0400; That would require syllabic variations along with two tones. It isn't difficult to do that. Do you mean for hum and noise? 73 Tom _______________________________________________ Amps mailing list Am; /archives//html/Amps/2006-08/msg00417.html (9,422 bytes)
19. Re: [Amps] Checking for IMD (score: 1): Author: Bill Fuqua <wlfuqu00@uky.edu>; Date: Fri, 11 Aug 2006 17:38:47 -0400; I always have a problem when it comes to trying to make perfect measurements when in reality it is the entire system that counts. That is to say if you exciter is good enough to put on the air and yo; /archives//html/Amps/2006-08/msg00418.html (10,890 bytes)
20. Re: [Amps] Checking for IMD (score: 1): Author: "Jim Tonne" <tonne@comcast.net>; Date: Fri, 11 Aug 2006 17:49:40 -0400; My question about "how pure does each tone need to be" . . . How much harmonic distortion can each tone have without affecting measurements? 1% OK? 2%? - JimT ________________________________________; /archives//html/Amps/2006-08/msg00420.html (9,240 bytes)

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