[Lowfer] Bypassing the BCB attenuator in the Kenwood TS450S and TS-850S

[Jordan]

Having had performed the this mod on my 450S years ago, I thought it was 
well-known, seeing as Kenwood attenuates the BCB on all their transceivers, 
and also on the R-5000 receiver.

In the 450S the series resistors are R-6 and R-7 ( 39 ohms each ), with R-8 
( 10 Ohms ) being the shunt section of the attenuator.

In the 850S the series resistors are R-7 and R-8 ( 150 ohms each ), and R-9 
is the shunt resistor.

Aside from being part of the attenuator, the shunt resistors also set the 
bias level on the switching diodes, as well as keeping the RF signal a 
certain level above ground, so jumpering this resistor will lead to an even 
deafer receiver than you started with.

If you look at the other bandpass filters, you'll see they all use a 120 ohm 
resistor in the active low SELECT line for each filter.
In my radios, I removed the actual series pairs of resistors, and jumpered 
the pads.
In the 450S I replaced R-8 with a 50 ohm 1206 size SMD resistor, which 
increased the sensitivity dramatically, although it is still less than on 
the other bands, and yet I have no signs of IMD or other 'junk' showing up 
across the band.

In the 850S, I am currently using a 56 ohm resistor in the SELECT line , and 
it does show some IMD and mixing 'junk' on the BCB.

Since I'd rather not have to use the 850Ss 6 and 12 dB attenuators, next 
time I go back inside, I'll change out that resistor to have a little lower 
gain.

I use a 130 foot Windom fed wire, and live in the middle of the city of 
Calgary, so your mileage may vary.......73...Jordan.....