Topband: [Fwd: Re: Question for the EXPERTS and Heavy Transceiver users and testers]

[GEORGE WALLNER]

On Wed, 31 Mar 2010 12:33:41 -0400
  Herb Schoenbohm <herbs at surfvi.com> wrote:
> I replaced my aging Icom 765 with a 746 pro> 
>I would like to 
>see a side by side test on RX with the K3.  

Herb,

While I have not done a formal side-by-side test of the 
two rigs, and I don't claim to be an expert, both HA7RY 
(Tomi) and I have used both rigs, side-by-side, on the 
5K0T and VK9GMW DXpeditions. On VK9WWI we only had the 
746. During these operations we made a combined 6000 QSO-s 
on TB -- most of them DX. I also use both rigs at my home 
QTH.

Both Tomi and I were impressed by the 746. As you point 
out, RX sensitivity is excellent and the DSP filter is 
very handy. Indeed, in a weak signal environment it is 
hard to tell which RX is better. Although I like the K3 a 
lot, I feel that its DSP, when set to narrow, tends to 
"mangle" weak signals in the presence of high noise. What 
I mean by that is that when you set the DSP to a bandwidth 
narrower than 200 Hz, weak signals seem to become 
"modulated" by the noise and they become harder to read. 
Again, this is just an impression that both Tomi and I 
shared. I don't remember having this issue with the 746. 
During those DXpedtions, and more recently on TX3A, we 
almost always had the K3 DSP set to 300 Hz on TB, even 
when we had some dense pile-ups.

On the other hand, I believe that the 746 has a weaker 
front-end than the K3. There is a 50 kW BC station on 1500 
kHz about 3 miles from my home QTH. That station puts on 
my 30 meter tall vertical about 20 mW of power (+13 dBm). 
The 746 front-end overloads while the K3 is not effected. 
(The problem is easily overcome by turning on the 746's 
Antenna Tuner, which effectively acts as a high-pass 
filter.)

During the past three years I have used both radios 
extensively. There were two failures on the K3 and none on 
the 746. I believe that both radios are good. I prefer the 
K3 but that may be entirely due to the fact that I paid 
more for it. ;-)

I hope this helps,

73, George, AA7JV