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41. Re: [Amps] Checking for IMD (score: 1): Author: R L Measures <r@somis.org>; Date: Sun, 13 Aug 2006 03:38:57 -0700; Indeed, Tony, indeed. R L MEASURES, AG6K. 805-386-3734 r@somis.org _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/a; /archives//html/Amps/2006-08/msg00459.html (10,376 bytes)
42. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Sun, 13 Aug 2006 14:10:36 -0400; We are looking for an easy method here. Swapping side bands does just that. 4.5 KHz doesn't get you out far enough to get all products for all voice frequencies either, but again we are looking for a; /archives//html/Amps/2006-08/msg00461.html (15,724 bytes)
43. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 13 Aug 2006 15:02:30 -0400; It's certainly easy. Let's see. The frequency spread of IM is the difference of the two frequencies. So if we have speech (an ahhh won't work well to replicate real speech) we can consider the frequ; /archives//html/Amps/2006-08/msg00462.html (10,537 bytes)
44. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Sun, 13 Aug 2006 21:57:17 -0400; See below: To be a little more precise; the IM is the difference of the two frequencies PLUS the high frequency and MINUS the low frequency for 3rd order products. For 5th order it is 2 times the dif; /archives//html/Amps/2006-08/msg00463.html (14,806 bytes)
45. Re: [Amps] Checking for IMD (score: 1): Author: Martin AA6E <aa6e@ewing.homedns.org>; Date: Sun, 13 Aug 2006 23:02:58 -0400; Thinking a little more about the dynamic IMD with syllabic fluctuations, etc., I wonder if a narrow spaced two-tone test (10 to 30 Hz, ala PSK31) would be a useful proxy. The low-frequency beat would; /archives//html/Amps/2006-08/msg00464.html (9,781 bytes)
46. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Sun, 13 Aug 2006 23:16:49 -0400; The extremes of IM3 product are the *highest frequency transmitted* plus 2.7 kHz and the *lowest frequency transmitted* minus 2.7kHz. Consider a 7 MHz USB signal . The upper IM3 would be 7.003 plus; /archives//html/Amps/2006-08/msg00465.html (11,609 bytes)
47. Re: [Amps] Checking for IMD (score: 1): Author: Tony King - W4ZT <amps080906@w4zt.com>; Date: Mon, 14 Aug 2006 09:43:29 -0400; <snip> Gary, I think if you re-examine this, you will find that the products you computed fall on both sides of the carrier frequency. Switching sidebands does not move you to the very next channel.; /archives//html/Amps/2006-08/msg00468.html (10,871 bytes)
48. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Mon, 14 Aug 2006 10:55:48 -0400; See below. Hi Tony, Switching side bands IS the same as tuning your receiver the width of your filter. If you have a 3 KHz wide filter and listening to the upper side band and you tune down 3 KHz wit; /archives//html/Amps/2006-08/msg00469.html (13,418 bytes)
49. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 14 Aug 2006 11:13:55 -0400; It looks to me like one group of IM3 products will be mostly OK, except carrier offset causes a gap. That group will miss close-spaced mixing of IM3 products however, so it is incomplete. One group; /archives//html/Amps/2006-08/msg00470.html (10,185 bytes)
50. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Mon, 14 Aug 2006 11:27:09 -0400; See below: Yes tom, you come up with the same numbers that I do. Plus 5.7 KHz and minus 2.4 KHz from the carrier frequency. We really don't care with this kind of test if they all fall in the pass ba; /archives//html/Amps/2006-08/msg00471.html (14,460 bytes)
51. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 14 Aug 2006 11:33:50 -0400; No. It is not the same. The filter is offset from the carrier in both the transmitter and the receiver, and you will miss the close-spaced high audio frequency tones that would be in the clear if yo; /archives//html/Amps/2006-08/msg00472.html (9,748 bytes)
52. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Mon, 14 Aug 2006 11:47:03 -0400; Think about that again. If you are listening to upper side band with a 3 KHz filter and you tune down 3 KHz in frequency with the dial you have moved the band pass the same amount lower in frequency; /archives//html/Amps/2006-08/msg00474.html (11,132 bytes)
53. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 14 Aug 2006 12:09:00 -0400; 1.) The passband of the filter is 3000Hz. 2.) The offset is 300Hz from the carrier. 3.) The sideband switch now moves the start of the receiver filter 600Hz lower than the start of the transmitter f; /archives//html/Amps/2006-08/msg00475.html (9,287 bytes)
54. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Mon, 14 Aug 2006 13:00:49 -0400; Yes you are right Tom, my apologies. I forgot to add the offsets in when tuning. An equivalent to changing side bands would be to tune down 3.6 KHz rather than 3 KHz. The transmitter doesn't really; /archives//html/Amps/2006-08/msg00477.html (11,939 bytes)
55. Re: [Amps] Checking for IMD (score: 1): Author: Tony King - W4ZT <amps080906@w4zt.com>; Date: Mon, 14 Aug 2006 14:02:47 -0400; Gary, Perhaps that is where the confusion is/was all along. My point was that, as you pointed out, there is a very large portion of the IM that will yield mix frequencies outside the normal listening; /archives//html/Amps/2006-08/msg00481.html (10,748 bytes)
56. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 14 Aug 2006 14:10:13 -0400; Hi Gary, Why worry about precise repeatability with a rough test? We know now the test initially claimed to measure IM average power ratios measures something near peak power, misses some of the thir; /archives//html/Amps/2006-08/msg00483.html (9,180 bytes)
57. Re: [Amps] Checking for IMD (score: 1): Author: Tony King - W4ZT <amps080906@w4zt.com>; Date: Mon, 14 Aug 2006 14:24:38 -0400; My use of the words "average IMD" was out of place and I apologize. Please do not let this cloud the discussion. 73, Tony W4ZT _______________________________________________ Amps mailing list Amps@c; /archives//html/Amps/2006-08/msg00484.html (9,403 bytes)
58. Re: [Amps] Checking for IMD (score: 1): Author: "Gary Schafer" <garyschafer@comcast.net>; Date: Mon, 14 Aug 2006 14:37:01 -0400; I don't think I used the word "precise" there. How far should we then tune away from the wanted signal for any kind of repeatability? In which direction? Do we tune to several different frequencies; /archives//html/Amps/2006-08/msg00485.html (10,531 bytes)
59. Re: [Amps] Checking for IMD (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Mon, 14 Aug 2006 14:48:52 -0400; To try and help everyone understand what it does and what it cannot do and how it works. Who's going measure the dynamic range of various radios using S meter movement? 73 Tom ______________________; /archives//html/Amps/2006-08/msg00486.html (7,931 bytes)
60. Re: [Amps] Checking for IMD (score: 1): Author: "Joe Subich, W4TV" <w4tv@subich.com>; Date: Mon, 14 Aug 2006 14:55:05 -0400; Gary, there is one problem with your analysis. Most modern rigs have an 8 to 15 KHz wide filter in the front end (first IF). This filter is symmetric around the "carrier." When switching to the oppos; /archives//html/Amps/2006-08/msg00487.html (9,077 bytes)

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