[1000mp] MP vs MkV vs K2

[Tom Rauch]

> Thanks, Tom (W8JI) , for the detailed response.  I think you have
> confirmed what I suspected...that the MP IM problems are generated
> prior to the IF filters.  Almost tempts me to put a little disconnect
> switch on the noise blanker FET.  I  don't use it often, and when it's
> off, it would be nice if it didn't serve as an unintentional limiter!

I've had success clamping G2 (it is a dual-gate FET) to ground, to 
turn the device off. I have to admit I have never tried disconnecting 
it, mostly because I am leary of adding cables to the 70MHz system. I 
doubt it is a 50 ohm or 75 ohm system at that point, and even a short 
shielded lead would affect the system. 

You can take a FT1000MP and inject two moderately close-spaced clean 
signals into the front end, tune to 2F2-F1 or 2F1-F2, and watch the 
IM product go from almost inaudible with the blanker gain control off 
in the MP to over S-9.

I've never spent a lot of time with the MP, but Dean Straw and others 
have reported additional clamping of G2 reduces IM3 even further. 

In the FT1000(D), the NB gain has no effect on G2 voltage, and so IM 
is poor unless you add a dc switch to clamp G2 to ground when the 
blanker is off.

While some people report not noticing this effect, others clearly do. 
K3LR and other contestors notice it, and make sure operators keep the 
NB gain off in MP's. I noticed my FT1000 in just seconds of operating 
in the Stew Perry 160 contest, not a particularly QRO or crowded 
contest.

Part of the reason some notice such things when others don't is  
noise level. With low noise, flaws stand out more. The better the 
location and antennas, the more noticeable flaws are in transmitters 
and receivers.

It's ironic that most popular deluxe expensive rigs, radio's most 
likely used in tough situations, have the biggest performance flaws 
while the cheap little K2's targeted to be inexpensive QRP rigs used 
with small antennas have fewer performance flaws.   
   
> As an aside, and lest we don't get too upset at our MPs...   I worked
> a lot of CW on field day last weekend.  Due to little equipment 
> problems, we ended up using an IC706, with 500 Hz. CW filter, for our
> CW rig.  Boy was it nice to get back home to my MP after that. 

You probably would not say that had you used a K2.

73, Tom W8JI
W8JI@contesting.com