[Elecraft] K3 FM Operation ???

[Brian Lloyd]

On May 25, 2008, at 7:57 AM, Charles Harpole wrote:

>
> So many msg abt K3 and FM..... I sit puzzled.... why in the world  
> would one bother to wait and
>
> buy a K3 JUST TO RUN FM???   The K3 is a CW radio..... pure and  
> simple, and the other modes
>
> are just thrown in....  My point is why waste a great K3 on  
> something virtually any radio today
>
> can do well....FM !!??!!   That is, no use for vy narrow filtering  
> in K3 on FM, nor many of its other
>
> features... and there are rcvrs more sensitive if u must have  
> that..... Sign me puzzled.... 73

The K3 is a great receiver for whatever mode. One problem I have  
always had to contend with in FM is desense from a strong in-band  
signal. I would hope that would not be a problem with the K3 as it is  
with most purpose-built 'FM' receivers.

If you think about it, the receiver is a linear translator. It takes a  
signal at a high frequency and it translates it to a very low  
frequency while preserving the time, amplitude, and frequency  
relationship between spectral lines in the passband. In the case of  
SSB it translates it to baseband where the ear detects it. In the case  
of CW it translates it to a very low (AF) frequency where the ear  
again acts as a detector. In the case of digital modes like FM, PSK,  
MFSK, RTTY, PACTOR, etc., it translates the signal to a very low IF  
(about 1.5KHz) where it is detected by hardware operating there. The  
point is that, while the end-function is different, the mode of  
operation is similar. The receiver is a linear translator to either  
baseband or very low IF.

--

73 de Brian, WB6RQN
Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com