general coverage receive on X3

[webrehm]

wiil the KX3 receive at ~8.5 MHz or ~12 MHz without diminished sensitivity? If the sensitivity is diminished, by how much?

tks

Dennis

[Johnny Siu]

To my understanding, KX3 is a direct conversation SDR radio.  There is no such 8Mhz IF, so no need to reduce sensitivity in 8Mhz.


TNX & 73,


Johnny VR2XMC

寄件人︰ webrehm <[hidden email]>
收件人︰ [hidden email]
傳送日期︰ 2012年07月14日 (週六) 2:44 PM
主題︰ [Elecraft] general coverage receive on X3

wiil the KX3 receive at ~8.5 MHz or ~12 MHz without diminished sensitivity?
If the sensitivity is diminished, by how much?

tks

Dennis



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[webrehm]

I am not talking about the need to desense because of an IF frequency but that the front end ham band filters may still be active when doing SWL.   It is my understanding that the K2 can receive SWL but its front end filters are ham band only so if you are between any ham bands the sensitivity falls off, perhaps quite a bit due to the ham band filtering.  so I am really asking if the front end filters of the KX3 can change/switch to accomodate SWL across the most common range of 3-16 MHz.

tks

Dennis

[webrehm]

the kx3 manual describes these front end filters as follows

The relay-switched low pass filters are used during both transmit and receive. A few of the filters are dedicated to one band but most cover two bands. The signal on the antenna side of the filters pass through a forward/reflected power and SWR bridge to the HF-6 meter antenna jack (BNC), or to the optional KXAT3 automatic antenna tuner. Latching relays are used to minimize power consumption.

The RF band-pass filters are used for both transmit and receive. Filters are selected with low-loss CMOS RF switches. The band pass filters significantly attenuate receive signals at harmonics of the RX frequency, particularly the odd harmonics.

These filters can seriously degrade SWL sensitivity at non-ham band regions.
Wayne or another designer will be able to answer this question if they are watching this.

Dennis

[wayne burdick]

webrehm wrote:

> The RF band-pass filters are used for both transmit and receive.  
> Filters are
> selected with low-loss CMOS RF switches. The band pass filters  
> significantly
> attenuate receive signals at harmonics of the RX frequency,  
> particularly the
> odd harmonics.

This is true.


> These filters can seriously degrade SWL sensitivity at non-ham band  
> regions.

Not true. The band-pass filters overlap, so sensitivity is good on  
virtually all SWL bands. It may be a few dB worse in isolated cases.

73,
Wayne
N6KR



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