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Author Topic: TS-520 CW filter response  (Read 2008 times)
NV1P
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Posts: 73




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« on: July 30, 2012, 10:37:34 AM »

I have a TS-520 that has served me well when I was first getting into ham radio. I've recently taken an interest in CW, and the rig came with the CW filter. I've noticed that the highest signal strength comes through when I have the rig tuned for a beat frequency of about 1KHz, which seems a bit high. Is this an indication that something in the IF stage is tuned wrong (like a BFO), or is the filter response actually centered for that frequency? Or am I just not seeing the obvious.
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AD4U
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Posts: 2157




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« Reply #1 on: July 30, 2012, 11:40:42 AM »

From my personal experience with a TS-520S, a TS-830S, and a Heathkit SB-102, SB-301, and SB-303 (all presently in my boat anchor collection) each with the factory supplied 400-500Hz CW filter, the passband in these rigs was optimized for a CW note around 1000Hz.  

I agree this is a poor tone for CW, but there is little you can do about it without significant changes in the rig.  Just buying an after market CW filter may help with the filter shape factor but it will not lower the CW tone.

You MAY be able to lower the CW tone by using the IF shift control on the Kenwood rigs.  On the Heathkits you just have to live with it.

Dick  AD4U
« Last Edit: July 30, 2012, 12:21:07 PM by AD4U » Logged
KE3WD
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Posts: 5694




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« Reply #2 on: July 30, 2012, 01:18:51 PM »

The IF filters are great if there is really passband interference, or an adjacent transmission, that sort of thing. 

Adding an aftermarket AF filter and speaker, designed for CW work, can make for good armchair CW copy, great for the long ragchew.  DSP, or SCAF filtering in the AF section is nice.  Won't help with the adjacent channel swamping, that's what your IF filtering is for. 

Also -- Learn to use the RF Gain Control to advantage as well.  Once you have found a station that you wish to listen to awhile, try backing off the RF Gain to remove background noise yet preserve the signal.  Often necessary to then turn the AF Gain volume control up a bit to compensate for the lowered RF Gain, but well worth it to obtain that nice clear "FM-like" copy.


73
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WA0ZZG
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Posts: 157




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« Reply #3 on: August 06, 2012, 08:19:30 PM »

The TS-520 uses a seperate BFO oscillator with crystals for lower, upper sideband and CW.  Have you tried shifting the CW BFO crystal frequency?  It may have enough range to move the filter bandpass to what ever you like.
Dave  WA0ZZG
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