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Quadruple Watch!

by Marco, IW0FFK.

 

Last week I’ve bought a Kenwood TS-590S, a modern rig with 32bit DSP IF filtering features.
I was especially interested in the NB2 function that seems to be effective in reducing the impulsive noise with variable frequency, like the noise produced by many poorly filtered devices that surround the antenna if you live in a city.

 


The Icom 756p3, that I use on 6m band, has a NB filter that can not handle completely this kind of noise.
In the first video the classic spike noise, maybe some CFL, is well reduced by the NB filter.

 

 

 

In the second video the NB is ineffective against this type of noise.

 

 

 

I have no idea what devilish generates this one, I’d pay to know that. Fortunately this mess is received for “short” periods, randomly. It’s not produced by my home devices: without mains and with the rig powered by a battery, the noise is still in.
It can last minutes or hours, listened to on any day of the week. I think it can be generated by a cordless phone of some of my neighbors..or something similar.

The TS-590S can handle sufficiently this type of noise, reducing it over 2 S-points, but, when the band is clear, I still prefere the sound and the clarity of IC756p3 especially on CW.

So i’ve managed to use both rigs at the same time, choosing each time where connect the headphones.

 

 

In the TS590 the signal from the antenna is tapped with a 4.7 pF just after the relay of RX-ANT producing an attenuation of around 0.03 dB. The signal tapped out is about 23dB below the level of the signal in antenna and it can be connected directly to the IC756p3 RX-ANT or eventually can be buffered with some high impedance amplifier.

 

 

 

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I use a LNA of about 20dB gain and 0.5db NF on the mast, the NF worsening of the TS-590S is irrilevant and that of IC756 is about 1dB, acceptable for the 50 MHz band. On the Icom rig I use PRE2 level, for recover the attenuation of the tap.

During the trasmission, only the TS-590S is used, but also the IC756 goes on TX at the same time (with minimal power on a dummy load) to protect the receiver’s circuitry.

I’m quite happy with that configuration, the IC756 can be used as a totally indipendent receiver with his bandscope and “dual watch” function. In addition the IC756 has a dongle panadapter on his IF…so total quadruple watch HI!

 

 

 

 

 

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73' Marco, IW0FFK.

 
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