Mike,
I spent all afternoon with my spectrum analyzer, a two-tone generator,
and my ubitx and came up with 10watts on 80m at 1.4amp total current
draw being the cleanest signal I could get.
I didn't chk 40m but on 20m I could only get 2 watts out.
I tried every combination of PA bias and drive to mimimize 3rd order
IMD products. I could crank the power output up further but 10watt out
on 80m seemed to be the cleanest.
I wonder if running higher voltage on the IRF510's would help with the
3rd order IMD so you could be more clean power out? Or will you wind up
saturating the driver stages trying to drive the PA to get more power
out and thus make the 3rd order IMD worse?
tim ab0wr
On Sat, 24 Mar 2018 13:53:09 -0700
"Mike R." <ubitx@...> wrote:
Finally got around to working on the ubitx again.
I traced the logic for each of the three lines (TXA,TXB, and TXC) to
ensure the logic was operating as it should. They were. I then traced
through each of the relays and filters to see if and where the signal
might be getting attenuated. KT1 looked somewhat strange on the scope
when going into transmit - the signal started out strong but soon
went very low. Hmmm. I then went and re-heated the pins of each of
the three relays (KT1, 2, and3). I also re-heated some of the leads
on some of the components in the 4 filters that looked dull to me. I
then went back and had another look at the bias to the 510's. Both
were set to 100ma each. Here are the results: Band ?? Current
Wattage 80 ? ? ? ?? 1.84A ? ?? 9W 60 ? ? ? ?? 1.46A ? ?? 6W 40
?? 1.26A ? ?? 7.8W 30 ? ? ? ?? 1.26A ? ?? 4.2W 20 ? ? ? ?? 1.61A
5.5W 17 ? ? ? ?? 1.25A ? ?? 3W 15 ? ? ? ?? 1.07A ? ?? 2W 12
1.3A ? ? ?? 2W 10 ? ? ? ?? 1.0A ? ? ?? 1.5W Judging by others
results, it doesn't look like I can get much more out of the rig as
it stands without replacing finals, etc. It looks like my rig is now
"normal" for the ubitx. That seem like a fair conclusion? Thanks to
all for the help, now to start playing with larger displays, new
finals, new software, etc. It never ends! 73, Mike W1USN
