Q.
Can I substitute BAT14-099R diode with
HP 5082-2831 ?
A.
HP 5082-2831 diodes are a low forward voltage,
they are for low frequency and they are high capacitance diode (0.5pF), these
diodes are not ok in my RTX. You can substitute BAT14-099R diode with 5082-2292
or 5082-2294.
Q.
Where do I find BAT14-099R diode? Can I
substitute them with BAT15-099R type?
A.
You can find BAT14-099R diodes in Lubljana in
some electronic component shop. For the substitution important are the diode
capacitance (about 0.3pF) and high forward voltage (the schottky diodes are
made with high, average and low forward voltage, the BAT15-099R diodes for
example are at low forward voltage and they are not ok for my RTX).
Q.
On CLY2 gate (RTX 2.4GHz) I have a positive
voltage, why?
A.
The CLY2 gate will never reach a positive
voltage. A positive voltage means a bad connection of the CLY2, this is because
you have exchanged Gate with Drain. It
isn’t important, because in my circuit the CLY2 doesn’t dead ... before to
remove it, disconnect the power supply of the final amplifier transistor and
check it with a ohm meter.
Q.
Can I use a CLY2 with a broken pin?
A.
The CLY2 in this case gives some less
milliwatt, but it is ok.
Q.
I have in my shack antistatic foam already,
like do I know if it is ok?
A.
You must check how many ohm you have at
about 2-3cm. distance in the antistatic
foam. If you check 10-30Kohm, the antistatic foam isn’t good. If you check some
Megaohm it is ok.
Q.
In the
2.4GHz rtx is critical the lenght of the cable from TX Mixer and
front-end?
A.
In the 13cm RTX the cables don’t have a
critical lenght. I never had problems , but I’m not sure at 100%.
Q.
Are the HEMT very difficult to solder?
A.
I have soldered many hundred of HEMT (not for amateur radio) and I never
broke HEMT. In any case before to solder you must disconnect the power supply
and other connections in your circuit.
Q.
The 2.4GHz RTX is not ok in rx, I don’t have
noise in loudspeaker and I don’t have the CW tone when I switch in tx mode. I
have checked the front-end and I have substitued the components: I don’t know
what to do.
A.
I think that you have exchanged base and
collector of two BF199 transistors on the quadrature receive mixer.
Q.
When I power on the RTX in my shack, I listen
an alternate noise in the loudspeaker, this don’t occur when I am in portable
(outside of my shack).
A.
The alternate noise problem is caused by a
transformer near to rtx. You have to move your rtx from trasformer at about 1
meter distance.
Q.
I am checking the multiplier for 5184MHz (RTX
10GHz). I have power supplied only this module. I made these measures (at 12.6V
and at 12V):
power supply module 12.6V 12V
V beetween led anode and gnd 1.72V 1.65V
V beetween
HEMT drain and gnd 1.44V 1.36V
led status much light little light
What is the right voltage on the leds anodes?
My tensions are ok or not? The current drain of this module is about 165mA, is
it ok? The 33 ohm resistor is very hot, can I install it outside the module?
A.
Your tensions are low, but they are ok the same. The red LEDs are made in two versions:
the GaAsP leds give a voltage of 1.6V,
the GaP leds (the new type...) give a voltage of 2V. Ok for 33 ohm resistor: it is very hot .... ! Maybe your
transistors have an higher Idss of the ATF35376 type, did you use ATF35176 or ATF35076?
Q.
I have used the ATF35376 transistors. My red
leds are the old type. I thought to connect 33 ohm resistor outside the module
because the entire module is hot!
A.
Ok, you can connect 33 ohm resistor outside the
module .
Q.
Can I connect the two 10Kohm trimmers on the tx
mixer of the 10GHz rtx outside of the module?
A.
Ok, you can connect the trimmers outside of the
module.
Q.
I completed the construction of all RTX. On the
small meter the output power response of the 2.4GHz rtx is very low, for the
other rtx the output power response is fast. Why ?
A.
Your 13cm RTX is ok. So 23cm RTX should be the
same, but the INA10386 don’t have enough power to drive the CLY5 final
amplifier. The two 5.7 and 10GHz RTX have a different project, without
electrolitic in the gate, in this case the small meter responds more quickly ….
Q.
The 10GHz rtx has a problem on rx mode: it is
very difficult to center the correspondent’s modulation. When I tuned the
correspondent and the modulation is good, if
I switch lsb or usb mode I always listen good modulation. As I
exchange lsb/usb doesn’t work. I
checked the circuit with the 4029 and
4051 and it is OK. Why?
A.
In your 10GHz rtx you have I or Q channel
broken. Disconnect one or the other and you will find the problem.