High power amplifier for 1296
1 KW SSPA for 1.8-54 MHz
A 1.5 KW LPF for 160-6m
1.8 to 54 MHz Dual Directional Detector
1.8 to 54 MHz combiner set
Automatic Transverter Interface
1 KW 6 Meter LDMOS Amplifier
2 Meter 80W All Mode Amplifier
1 KW 2M LDMOS Amplifier
1 KW 222 MHz LDMOS Amplifier
500w 70cm Amplifier
1KW 70cm LDMOS Amplifier
A Big Power Supply for SSPAs
Low Pass Filter/Dual Directional Detector
Sampling RF Power
LED Bar Graph Meter
Amplifier Control Board
LNAs (preamps) and MMICs
LNA Sequencing and Protection
Building UHF Antennas
Crystal Oven Controller
Latching Relay Driver
12 to 28v
High Current DC Switch
L & S Band LNA
Microwave L.O. Filters
PC Board Filters
Using Inexpensive Relays
600w 23cm LDMOS Amplifier
XRF-286 Amplifiers for 23cm
150W 23CM Turn-Key Amplifier
300w 23cm Amplifier
200w 23cm Amplifier
100w 23cm "brick"
100w 23cm Transverter
60w 23 cm Amplifier
23 CM Beacon
23cm Signal Generator
23cm Double Quad
13cm Signal Generator
120w 13 cm Amplifier
300w 33cm Amplifier
33 cm Crystal Source
33cm Signal Generator
12 AND 28 volts
Parts I Can Supply
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For those of you using this radio on SSB or CW in the weak-signal part of the
bands, you probably already noticed that the receiver needs some help. The
overall sensitivity is too low, making the need for preamplifiers obvious.
Actually, the radio has enough sensitivity built into it already; there are
modern GaAsFETs ahead of the mixers on every band, including 23 CM. The factory
alignment of the radio does not exploit it's full capabilities. This is
a common phenomenon of almost all multimode VHF/UHF radios, including those made
by Kenwood, Yaesu and others. One might think this may be part of the way they
market their preamplifiers, but that is only my own speculation.
The adjustments described below will bring the overall sensitivity of the
radio up to par, and will eliminate the need for external preamplifiers. An
external preamplifier may still help if your feedline is lossy; in this case,
you may still benefit from a mast-mounted one. After I made these adjustments, I
found that my limitation was external noise and not the sensitivity of the
radio. This was even the case on 23cm; in fact, it now hears almost as well as
the transverter I usually use on this band, which has an excellent front-end.
No magic here; all you will be doing is turning up the I.F. gain on each
band, which is set lower at the factory. The service manual contains pictures
and descriptions of the trimmer resistors to adjust, and can be downloaded here:
It's big (over 12mb), so it will take a little while to download. If you don't
want the entire manual, the 4 pictures you need to see are here: 144-R547,
Note: use a small insulated alignment stick to make these adjustments.
The controls are tiny, and if shorted to ground or to another component, will
damage the circuit. The first control is especially susceptible, as it is very
close to a coil shield.
Turn off the radio and remove the top and
bottom covers. If you have the UX-910 module installed, remove it in order
to make the 144 and 430 band adjustments possible. It's easy, there are just
4 screws holding it in place, and 3 connectors to unplug. Set it aside until
you are ready to make the 23cm adjustments.
Turn the radio on.
Refer to page 5-5 of the service manual, and
find R547 and R360. Adjust these controls for max receiver gain on 144 (main
band). Then switch 144 to the sub band and adjust R857 for max receiver gain
on the sub band.
Switch 430 to the main band and refer to page
5-7. Adjust R61 for max receiver gain on 430.
Turn the radio off.
Reinstall the UX-910 23cm module. Remove the
cover plate on the UX-910 and set it aside.
Turn the radio on.
Set the main band to 1296.1 Mhz USB, and
connect a proper dummy load to the antenna terminal. Refer to page 5-19 and
adjust R224 for max gain. On my unit, I was actually able to adjust the gain
too high, as the s-meter was reading about s3 on background noise. I backed
off the gain until the meter dropped just below s1, you may have to do the
This last adjustment is for the overall
transmitter gain on 1296, and I adjusted this because I found that I did not
have sufficient ALC action when on SSB, even with the mic gain all the way
up. I turned up R83 to correct this...you may or may not need to do the
Turn off the radio, reinstall the UX-910 cover
and the top and bottom covers of the radio. All done!