Re: UHF FM Transmit Power


Steve W3AHL
 

I disagree that the basic adjustments are not needed.  The RD60HUF1-101 parts being shipped now have different characterisics from those produced 12 years ago.  The bias (Idle current) certainly needs to be verified, as a minimum to maintain linearity of the PA.  If power output in FM is about 17 watts at 50% TX PO setting and 35 watts at 100%, then the other settings may be OK.  I find that the new parts have more gain and cause the ALC to excessively limit the IF stage gain in SSB, resulting more distortion products seen on the analyzer.  But to each their own....

Steve, W3AHL


On Sat, Mar 24, 2018 at 08:37 am, Helmut Wabnig wrote:
On Sat, 24 Mar 2018 08:05:37 -0700, you wrote:


Replacing the UHF PA is relatively simple.  But getting to it takes a little work.  The driver board is soldered to the PA board, so it has to be unsoldered. 

No, you do NOT remove the PA board to replace the UHF transistor.
You have to remove the PA only for the driver.

Just remove two screws, unsolder the cover which is over the UHF
transistor, plug in the new one, screw&resolder the cover shield
and that's it. Takes 30 minutes.
No adjustments necessary, although it is ok to do with older IC7000
units because electrical parameters shift over time.
The adjustments are tricky and complicated,
better leave as is.
The main difficulty is to get exactly 3, 20 and 30 mVolt 1500 Hz
at the microphone input. Everything else is straightforward.
And you must provide exactly 13,8 Volt at the transceiver DC input
during transmit!

OE8UWW

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