[Premium-Rx] Harris RT-1446 / RF-350 used as a RX

[Tisha Hayes]

Quote:
"Greetings,

Just started to get one of these up and running.? Got the RX working fine
but  need the power plug?before I test the TX.? I do not have the PS but
have loads  of 13VDC available and can't bring myself to pay Torronto
Surplus $300 for a
30amp dc supply.? So with that I have a fan question.? Looking at the
manual, it seems like the fan in the PS is vented such that it cools the TX
PA cooling fins.? It would seem that when I'm using it as a RX, there is no
internal fan requirement?? Am I correct there?? In my quick test here,
the?RX?worked very well even with HF in flux due to MR. Sol.? I'm convinced
when I get this solid state beast it?into one of the racks, the R-725,
RA-17, or one of the  Super-Pros?will break down in protest. John Flood
KB1FQG"

You are quite correct. The cooling fan that pulls air in through the front
foam filter, down a duct to the back of the unit blows the air up against
the bottom of the transmitter PA fins. The bottom power supply is just a
glorified DC supply with a gigantic transformer, a step-start circuit to
charge up a 60,000 uFd capacitor, transient filtering and the ability to
switch from 120 to 240 VAC or 12 and 24 VDC. It by far is the heaviest piece
of the radio.

If all of the secondary covers are in place (bottom of the transceiver
(between the power supply and the radio) and you provide some sort of high
capacity fan to push air across the PA heat sink you should be perfectly OK
running the radio with a +30 Amp, filtered, regulated DC supply.

It is not all that great of a receiver, an RF-590 will run circles around it
(as would an SP-600 or R-390 in proper operating condition). If you have the
remote control card there are some decent radio control software apps out
there for the radio. When properly cooled the radio is rated for nearly 100%
transmitter duty cycle, making it a good radio for digital modes like ALE.

I added a few secondary fans to blow air down in through the top of the
chassis as I do not like relying upon one single fan to cool the radio. As
you have found, it is a highly modularized design. Almost every one out
there has three problems that you can work on; 1). The sticky relays for
selecting the low pass filters, these will throw up semi-random BITE errors
on testing. 2) The electro luminescent lights behind the LCD displays are
very dim (can be replaced). 3). The backup battery on the CPU board needs to
be replaced (after opening the front cover the battery is mounted on the top
right corner of the board) A standard computer backup battery will work fine
there.

I have two RF-350K's in full time operation and a third unit that is a
"hangar queen" that I use as a test bench for servicing cards and modules. A
few years ago I purchased a case full of almost every spare module (2-8 of
each) and have been gradually rehabbing the cards. What I have only one
spare of is the CPU card, PA. serial interface and synthesizer.

If you need a particular board let me know. I should never need to use 8
different Low pass filter boards.

BTW, the relays are no longer produced but I see them on eBay from time to
time. If you are skilled, you can open the old relays up and burnish the
contacts to make the intermittent BITE errors go away. (the problem is
caused by too low of current flowing through the relay contacts and it
becomes difficult for a closed contact to break through the oxide layer).
There is also a mod out there to put a small amount of current through the
relays to reduce the incidence of relay failure.

Ms. Tisha Hayes/ AA4HA
----------------
"I'll be a diode, cathode, electrode
Overload, generator, oscillator
Make a circuit with me." -- The Polecats