ADDING A
RECEIVE PREAMP TO THE GE DELTA
This is
an overview of the Hamtronics
LNY UHF preamp
installation in a UHF Delta SX.
A preamp does wonders
for the receive sensitivity in the UHF and VHF Delta radios, both narrowband
(NB) and wideband (WB) versions. The original factory preamps work very well.
They are a little hard to come by, however. Here is a list of GE part numbers
for preamp boards, so you know what to ask for when hunting one down.
GE Part Numbers for
the Original Factory Preamps:
| UHF |
NB |
19C850692 |
| VHF |
NB |
19C850696 |
| UHF |
WB |
19C851294 |
| VHF |
WB |
19C851229 |
So, let's say you
can't find the real GE preamp at the right price. All is not lost! I've
installed aftermarket preamps in the Delta S and SX radios with great success.
I've used the Hamtronics
LNY preamps (VERY good
preamp for the price - I highly recommend them), and I've used the inexpensive
kit preamps from Ramsey (which also work fine).
The LNY
preamp board is mounted to the wall with velcro.
The jumpers are from a dead GE Exec II radio.
To install one of
these aftermarket preamps, find a place inside the Delta where you can safely
mount the preamp. Run short jumpers of RG-174 or similar small 50 ohm coax
between the preamp jack and the preamp. I've done this two ways: 1) soldered the
coax to the pins on the jack; or 2) removed the preamp jack and soldered the
coax directly to the circuit board.
The black
coax carries the 9 volts DC and ground. The grey jumpers
carry the RF in and out signals.
This is how I
used a Ramsey UHF preamp board in a UHF Delta SX. It just fit inside the slot
for the
factory preamp board. Short pieces of 50 ohm coax carry the RF in and out. A
short wire provides
9 volts DC to the board. A small piece of double sided foam tape holds the
preamp in place.
The preamp board is wrapped in heat shrink for protection.
If the preamp you
choose can run off 9 volts, use the voltage present on the preamp jack.
Otherwise, just run a power lead from the preamp board over to the red test jack
(J602) located behind the big J601 jack. There is 12 volts available on pin 2
and 9 volts on pin 3.
There is a jumper next
to the preamp jack. This needs to be removed. If you aren't certain about the
identity of the jumper, consult a manual before proceeding. Below is a chart
showing the pin-outs of the preamp jack for each type of Delta radio. As you can
see, they are significantly different from one another. Since the voltage comes
out of a different pin for each version radio, smoke will result if you put the
wrong preamp board in the wrong radio!
Preamp pin-outs for
Delta S (NB) and Delta SX (WB) radios:
| PIN # |
NB |
WB |
| 1 |
GND |
GND |
| 2 |
RF OUT |
RF IN |
| 3 |
GND |
GND |
| 4 |
9 VOLTS |
GND |
| 5 |
GND |
GND |
| 6 |
GND |
GND |
| 7 |
RF IN |
RF OUT |
| 8 |
GND |
9 VOLTS |
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