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Post by vanlifeson on Apr 25, 2022 10:20:44 GMT -5
Can anyone tell me what frequency crystal would be needed to put this radio on channel 30? Thanks!
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Post by bobcat4109 on Apr 26, 2022 17:29:38 GMT -5
I just looked in the SAMS on that radio. It has a 6.2 Mhz first IF.
You currently have 6 crystals in the 40 MHz range and 4 crystals in the 7.7 Mhz Range.
An example of how it works is....
Channel 1 is made up of the 40.900 Mhz and 7.735 Mhz combination.
40.900 - 7.735 - 6.2 (for the IF) = 26.965 Mhz ... which is channel 1.
So.... to get channel 30... which is 27.305....
You would need to add a 41.200 Mhz Crystal. Either replace one of the others and lose 4 normal channels... or put one of the originals and the 41.200 Mhz on a switch..
That will give you
41.2 7.735 27.265 26
7.725 27.275 27
7.715 27.285 28
7.695 27.305 30
Since this was a 23 channel radio it has the skips built in to the switch so you would miss channel 29 but get Channel 30.
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Post by bobcat4109 on Apr 26, 2022 17:42:00 GMT -5
I took a look on Ken's Electronics...and found this..... *More Synthesis ($12), Special & PLL* (* =$15) crystals: [1]33.550, [1]33.600, [1]33.766, [2]33.900-HC18w, [5]33.971, [2]*34.766, [6]*34.771, [3]34.806, [7]*34.821, [8]*34.871, [14]*34.921, [18]34.971, [9]35.021, [3]35.071, [6]35.121, [6]35.171, [10]35.221, 35.241, *35.271, [1]*35.300, *35.321, 35.331, [4]*35.371, 35.421-pt, *35.4875, *35.740, 35.775-pt, 35.910, 35.915, *35.930, 35.951, 35.970, 36.000, 36.015, [1]36.030, 36.035, 36.060, 36.105, 36.115, [3]36.170, *36.180, [5]*36.190, 36.230, *36.380, [3]*36.570 , [3]*36.630, [9]36.750, *36.820, [1]*37.010, [2]*37.020, *37.200, *37.250, *37.300, *37.340, *37.345, *37.350, *37.395, *37.400, *37.445, *37.450, *37.495, *37.500, *37.550, 37.600, 37.650, 37.700, 37.750, 37.795, 37.800, 37.850, *37.870, *37.900, *37.930, *37.950, *37.960, *37.990, *38.000, 38.025, *38.050, *38.100, *38.150, *38.165, *38.195, *38.200, *38.215, *38.265, *38.275&PB, *38.285&PB, *38.295&PB, *38.315&PB, *38.350, *38.385&PB, *38.395&PB, *38.400, *38.415&PB, *38.475, *38.485, *38.515&PB, *38.565, *38.615, *38.665, *38.970, 39.070, *39.130, 39.160, 39.175, 39.190, 39.230, 39.270, 39.290, *39.570, 40.000, *40.010, 40.500, 40.850, 41.200, 41.250, 41.300, <------------------------------------- first on this row..... 46.415, 49.405, 49.475, 49.515, --------------------------------------------------------------- I notice that there is a 41.200 on the list so Ken may be able to help you if you want to do this.... assuming that this means he actually has this crystal. WebSite for the crystals page: www.kenselectronics.com/lists/cbxtal.htmKens website home: www.kenselectronics.com |
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Apr 26, 2022 19:27:12 GMT -5
I just looked in the SAMS on that radio. It has a 6.2 Mhz first IF. You currently have 6 crystals in the 40 MHz range and 4 crystals in the 7.7 Mhz Range. An example of how it works is.... Channel 1 is made up of the 40.900 Mhz and 7.735 Mhz combination. 40.900 - 7.735 - 6.2 (for the IF) = 26.965 Mhz ... which is channel 1. So.... to get channel 30... which is 27.305.... You would need to add a 41.200 Mhz Crystal. Either replace one of the others and lose 4 normal channels... or put one of the originals and the 41.200 Mhz on a switch.. That will give you 41.2 7.735 27.265 26 7.725 27.275 27 7.715 27.285 28 7.695 27.305 30 Since this was a 23 channel radio it has the skips built in to the switch so you would miss channel 29 but get Channel 30. If you sub out the crystal that gives you channels 21 through 23 *and including the "A" and "B" channel (24 and 25), you would get channel 29in the "B" position. These are the same crystal freqs that the Comstat 25 uses. I remember adding the 41.2 Mhz crystal back when the 40 channels first became legal in 1977. |
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Post by vanlifeson on Apr 27, 2022 9:58:23 GMT -5
I just looked in the SAMS on that radio. It has a 6.2 Mhz first IF. You currently have 6 crystals in the 40 MHz range and 4 crystals in the 7.7 Mhz Range. An example of how it works is.... Channel 1 is made up of the 40.900 Mhz and 7.735 Mhz combination. 40.900 - 7.735 - 6.2 (for the IF) = 26.965 Mhz ... which is channel 1. So.... to get channel 30... which is 27.305.... You would need to add a 41.200 Mhz Crystal. Either replace one of the others and lose 4 normal channels... or put one of the originals and the 41.200 Mhz on a switch.. That will give you 41.2 7.735 27.265 26 7.725 27.275 27 7.715 27.285 28 7.695 27.305 30 Since this was a 23 channel radio it has the skips built in to the switch so you would miss channel 29 but get Channel 30. If you sub out the crystal that gives you channels 21 through 23 *and including the "A" and "B" channel (24 and 25), you would get channel 29in the "B" position. These are the same crystal freqs that the Comstat 25 uses. I remember adding the 41.2 Mhz crystal back when the 40 channels first became legal in 1977. Awesome, thank you! You wouldn’t happen to have a Sam’s book on a heathkit GW42 to be able to figure out channel 30 for that radio also would you? Any info greatly appreciated thank you again sir! |
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Post by bobcat4109 on Apr 27, 2022 18:31:02 GMT -5
I am very sorry to say I can not find it. And I have checked several resources...... just can't come up with it.
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Post by 2600 on Apr 27, 2022 23:35:26 GMT -5
In the "more synthesis" section of this web page, most of the way down you'll find 41.200 listed. Don't know if he really has it, but it's the only reference to it I have found. www.kenselectronics.com/lists/cbxtal.htm73 |
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Post by vanlifeson on Oct 11, 2023 17:33:51 GMT -5
Ken doesn’t have a 41.200 crystal. Could one of the 7mhz crystals be swapped to get the radio to channel 30.
If so what frequency in the 7mhz crystal would I need? Thanks for any info.
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