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K3 with 144MHz XVTR integrated

Meantime i use the old IC706 had some RX IMD issue with very strong local signals
also switching T/R had some TX spike that activated my SWR protection hence de TX is disabled until reset with power cycle.
The Hi-level mixer XVTR  tried also but still blocking on strong local signals
Possible i need to adjust the the level of  116 injection. 

This is how the 144/28 fits into the K3 with 2nd Rx and KXV3
Also with the original  Elecraft  144MHz  you will need to fit an extra Antenna connector  BNC
I drilled an  20mm pass trough hole to lead the  coax  through the PA compartment to the 144 BNC This is a delicate job it needs precautions to avoid damage.
I removed the left side panel and used a trapped small multi hole drill with an extension hexa shaft.
those one's are available at eBay and are very good to have.

An automatic 12V 144 band  power switch must be added.
A P-channel IRF9540 with some logic switches 12V at 144MHz band
The  diagram above shows the 144 bandselect  switch it is made on a smal piece of PCB
2 LEDS  one =  12V   and the 2nd indicates 144MHz band 12V = on
Using the D15 ACC external control signals.
Those signals are convenient also available at the backside 20pole connector J90 of KIO3 shown at top picture.
With the restriction that the D15 ACC  connections have a series 220R protection
The soldered  wire's bypass the protection 220R
I did insert a protective 220R in the +5V .
I use a 6 pole Dupont detachable connector on the Switch 

Overview of connections to 20pole J90   most are also available at the 15p ACC connector

pin20  +5V  yellow                           few mA needed  (5V not avail. at D15 ACC)
pin 6    GND  white                          #  D15 ACC  5
pin18  DIGOUT0     green               #  D15 ACC  6
pin14 Band1    blue.                         #   D15 ACC 3 BAND1 OUT
pin10  ptt key  purple                       #   D15 ACC 10 KEYOUT-LP connected  to  XVTR key in 3

The 13.6V  white-red wire leads to a soldered single header pin at main board  right front as described in the K3 144 XVTR manual.
Control wire's soldered at the back of 20pole KIO3 J90  same lines of ACC 15pole.
Just visible the extra SMD 220R  to be soldered over  C24 lowering the Q factor of L7
This was needed to stop self oscillation with the K3 top plate closed
The XVTR was stable until i closed the top plate (....)
The output then sinks from 10 to 9W no big deal.
Serge UT5JCW of reacted very quick upon my question about this problem.
fb service  incredible value for money  nice build XVTR
As said in previous posts it's performance is real good

The BAND switch function:
DIO0 is active low for a low power band ie a transverter band   and high  for HF and 6m.
It is connected to the inverted input Q1 with pull up 10k. The output of Q1 is high when a XVTR low power band is selected.
BAND1 is connected to Q3 with XVTR 144 XVTR address: trn2 BAND1 =+5
For 144MHz Q1 is off hence Q3 is on   Q2 is on by BAND1 BCD
Both AND inputs are high  the output of Q2 is low making P-channel fet Q4 on
12V is swiched on to the 144 XVTR only when DIO0=low and BAND1=high

Without this auto band switch  I had to switch manualy, the top plate had to be off to remove or plug the 12V into the main board.
I believe the newer series K3 have  extra XVTR 12V terminals.

Using a BCD decoder on the 4  BCD BAND signals and DIGIOUT0 = hi-Z , all hf BANDS and 6m are addressed. The lowpower XVTR band have DIGIOUT0 =low the BCD output then follow trn1 - 9
So  9 low power ie XVTR bands are coded with the same BCD lines.
With one internal XVTR only the 144MHz 12V had to be switched
Or 2 bands with the same XVTR i.e. 2 local oscillators can be selected 144-146  and 146-148

I tested an Arduino for band switching but i prefered to keep it  simple and reliable as possible.

The RD15HVF1 15W VHF FET is high Efficient 13.6V  1.2A  10W rf at 144 measured
compare this to the old classic BLY89 types  2A 13.6V 10W rf or so

Possible this XVTR  does not have the -70 dB image as claimed
But why should I care?
As long as Solar Edge Solar power system   can legally  pollute 0 300MHz with levels to 9+40db Trash. Why should i care about this?



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