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Author Topic: CTS Knights CW filter  (Read 1635 times)
DU1FV
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Posts: 2




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« on: December 05, 2011, 07:12:41 AM »

Hello All!
I wonder if anyone here  has ever encountered, used or installed a 400Hz 455kHz filter made by CTS Knights. I want to use this filter in my TS-850S. I am particularly interested in the in/out impedance and how to match it it my radio.
TNX 73
Mon DU1FV
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PA0BLAH
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Posts: 0




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« Reply #1 on: December 08, 2011, 08:52:43 AM »

Of course you only can use a 455 kHz filter in a trx with a 455 kHz IF. I am not acquinted with Japanese typenumbers  or ready to use equipment.

When you want to know the output and input impedance of the filter feed it from a signal generator (50 ohm) with a serial resistor and load it with a high impedance millivoltmeter parallel to a load resistor.

You will watch the bandwith by changing the frequency and the pass band attenuation. Change the resisrors (potmeters) in order to get that pass band flat, and you know your source and load impedance. It is not unwise to add amplification to compensate for the attenuation of the filter. Are you sure you want to do that? Modifications degrade the market value of ready to use Japanese equipment, especially when not documented. I can understand that. Its because hams are hams.
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K0OD
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Posts: 2558




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« Reply #2 on: December 08, 2011, 10:22:39 AM »

Didn't all TS-850s come with 500Hz CW filters? Going with an off brand 400 Hz won't help much.

I have both the 500 and 270Hz Kenwood filters in my 850 and the narrower one is quite good. Its the one I used most of the time.

The going rate for used 850s has fallen in the past 2 or 3 years. For one thing, repair is getting costly. I'm paying $300 right now to have my intermittent readout repaired.

850s are fabulous radios. The receivers alone are gold... about the best for low frequency listening (BCB and below). Great audio. But the most beaten up ones are now showing up on the scrap market. Consider buying a used 270Hz stock Kenwood filter.
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DU1FV
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« Reply #3 on: December 08, 2011, 03:54:41 PM »

PA0BLAH
Thank you for the tip! I will do the tests,


K0OD
I just got the TS-850s. It had no filters other than the ssb one. I have been a TS-850s fan for many years. The club station has one.
Great radio!  I will keep an eye out for a kenwood 270HZ filter.     
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