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Question about power output #ubitx #v5

Anthony F4HUY
 

Hello,
got my ubitx v5 one month ago, almost finished ...

it's sell with "More than 10 watts up to 10 MHz, 7 watts up to 21 MHz, 2 watts on 28 MHz" ,
i get 2w between 21 an 30Mhz, then the power drastically decrease under 2w under 21mhz, around 800mw at 7.1mhz, and close to zero on 3.5mhz

what's happen ? it's should be the opposite.

i have already checked and re*tuned rv2/rv3, my microphone is a baofeng, test with cw give same result

i want to operate mainly on 20meters, hope 5watts, should be nice.

any idea ???
73'

Ted
 


Bonjour,

The proper setting of the BFO is very important for output power as well as for receiving, it seems.

I would suggest setting this to 11,056400 and see how the output power is on the bands.  I have one V5 set for 11,056560 and another V5 set for 11,056210, so my suggestion here is about the middle of those.

After this, if the output has improved, one might find an audio spectrum graph application (or the HF Signals web page tool for the purpose) and find your specific BFO value that performs the very best on TX and RX alike.  



Bon chance,


Ted
K3RTA

Jerry Gaffke
 

F4huy,

My best guess is a broken or shorted wire in one of the transformers: T8,9,10,11

The fact that you get 2 Watts of SSB at 30mhz is good news,
that shows that everything from the mike to the first mixer at D1,D2 is working fine.

When transmitting CW, CLK#2 is a square wave at the operating frequency.
Mixer D1,D2 is unbalanced by CW-KEY to allow that signal right on through to the final amp.
So this is not an issue with the BFO offset as previously suggested,
this would affect only SSB transmissions, and attenuate all bands equally.

If the receiver works at 3.5mhz, then the low pass filter at L1,2,3,4 should be working fine.
The problem is somewhere between Q90 and the antenna jack.

The signal going into Q90 should be around 0.1 volts pk-pk,
and the voltage increases by roughly a factor of four as it passes through each stage.
Since there are four stages of amplification between Q90 and the IRF510's,
the output from the IRF510's should be roughly 0.1*4*4*4*4 = 25.6 volts pk-pk.

If you have access to a good oscilloscope capable of seeing at least 3.5mhz,
probe the collector (or drain) of each of the four amplification stages.
See if the AC voltage increases with each stage when operating at 3.5mhz.
Compare that to what you see when operating at 30mhz.

If you don't have a scope, I suggest you build a diode RF probe.
Use either one of the first two circuits shown here, they should give equivalent results:
    http://www.techlib.com/electronics/detect.htm
The first circuit shown is the one most commonly described elsewhere.
The second circuit is easier for most of us to understand.
Note that the smallest AC voltage either circuit can sense will be around 0.3 volts rms,
so it probably will see no signal if you look at the base of Q90.

Many webpages on diode RF probes recommend using a germanium diode,
but those are getting hard to find.  A schottky diode such as the 1n5711 will do fine.
Many dishonest vendors of 1n34 germanium diodes will actually ship a schottky diode instead.
A true 1n34 will be able to see slightly lower level signals than an 1n5711.

When output varies more than it should between bands, my first suspicion
would be the output low pass filters selected by relays KT1, KT2, KT3.
However, all of those output filters are low pass, so all of them should pass
a 3.5mhz signal unmolested even if they got swapped around somehow.

If you do suspect trouble between the IRF510's and the antenna connector,
a good test would be to cut the trace between transformer T11 pin 5 and relay KT1 pin 12,
Then put your wattmeter directly between T11 pin 5 and ground.
The wattmeter will see the raw power coming out of the IRF510's, harmonics and all.
So readings will be a little high, but 3.5mhz should definitely be stronger than 30mhz
since each of the 4 amplifier stages will have more gain at lower frequencies.

Verify that your BNC antenna connector is working with an ohmmeter, 
perhaps go around it by soldering a wire to the PC board till you find this problem.
There have been reports of some BNC connector center pins not making proper contact.


Best Regards,
Jerry Gaffke, KE7ER




On Tue, Jan 14, 2020 at 01:30 PM, <f4huy.ham@...> wrote:
Hello,
got my ubitx v5 one month ago, almost finished ...

it's sell with "More than 10 watts up to 10 MHz, 7 watts up to 21 MHz, 2 watts on 28 MHz" ,
i get 2w between 21 an 30Mhz, then the power drastically decrease under 2w under 21mhz, around 800mw at 7.1mhz, and close to zero on 3.5mhz

what's happen ? it's should be the opposite.

i have already checked and re*tuned rv2/rv3, my microphone is a baofeng, test with cw give same result

i want to operate mainly on 20meters, hope 5watts, should be nice.

any idea ???
73'

Evan Hand
 

I would also check that there is not an issue with one of the relays/LPFs.  Without power connected to the PA (brown power wire), check each band for continuity from the antenna jack to TP7.  You should have a connection for all of the bands.  

The above reasoning is that all of the relays are de-energized for 10 meters (28 MHz).  Not sure why all of the other bands have low output, however it is worth a try.

Just a thought.
73
Evan
AC9TU

Gary Anderson
 

Simple question:
Are you using the factory V5 firmware?  Confirmed that your board is a V5?

With board changes from V3/4 to V5 the BFO and filter circuits changed.
I haven't gone through the logic mapping of what exactly would happen on the LPF circuits if the wrong version of firmware is used, but it will be problematic.

Jerry Gaffke
 

Firmware for a v3 or v4 board mistakenly installed on a v5 or v6
would seriously attenuate 80 and 40 meters, but 10 and 20 meters should be unaffected.
Operation on 80 and 40 would be as if the antenna was disconnected, might damage the IRF510's.

Firmware for v5 or v6 on a v3 or v4 board would allow harmonics out on 80 and 40 meters
since only the 30m filter would be getting used, but again 20 and 10 meters are unaffected

Here's what the routine setTXFilters() does in the firmware for v3,v4 and v5,v6 boards:
                        30m   20m   40m   80m
ver 3,4:   abc = 000    100    110    111        (a=0 for 30m, else b=0 for 20m,  else c selects 80m not 40m)
ver 5,6:   abc = 000    100    010    001       (1 to engage each filter for 20m,40m,80m,  but 30m is always inline)
 
To get the symptoms reported (particularly an attenuated 20m) would require two different problems
out in the LPF's.   Possible, but seems more likely to be trouble further back in the power amp somewhere.

He reports that CW transmissions are also affected, so not an issue of anything prior to the first mixer at D1,D2.

Jerry, KE7ER


On Wed, Jan 15, 2020 at 06:38 AM, Gary Anderson wrote:
Simple question:
Are you using the factory V5 firmware?  Confirmed that your board is a V5?

With board changes from V3/4 to V5 the BFO and filter circuits changed.
I haven't gone through the logic mapping of what exactly would happen on the LPF circuits if the wrong version of firmware is used, but it will be problematic.

Jerry Gaffke
 

Here's a corrected version of that chart showing how TXA,TXB,TXC get mapped to specific bands.
Corrections are:  30m should read 10m for 30mhz,   and  "else c=0 for 40m, else 80m".

Note that the 10m LPF also handles 12m and 15m, the 20m LPF also handles 17m,
the 40m LPF also handles 30m,  and the 80m LPF also handles 60m, true for all versions.
I've added a third line to show Allison's hacked v3,v4 board, which fixes the LPF harmonics.
The symbols a, b, and c refer to signals TXA, TXB, and TXC from the Nano out to the three LPF relays.


##########################
Here's what the routine setTXFilters() does in the firmware for v3,v4,  and  v5,v6.  Also v3,v4 with Allison's hack:
                        10m   20m   40m   80m
ver 3,4:   abc = 000    100    110    111        # a=0 for 30m, else b=0 for 20m,  else c=0 for 40m, else 80m
ver 5,6:   abc = 000    100    010    001       # 1 to engage each filter for 20m,40m,80m,  but 30m is always inline
allison:    abc = 000    010    001    100       # hack to v3,v4,  now similar to v5,v6 boards except filters ordered differently
##########################


Allison, KB1GMX, gets major kudos for this fix addressing the LPF harmonics, which Farhan then used on v5 and v6:
    https://groups.io/g/BITX20/wiki/uBITX-spur-and-harmonics
Allison kept the physical placement of the v3,v4 filters the same as much as possible to avoid excessive rework, 
Farhan ordered them logically on the new v5,v6 builds. 
Allison's hack can be made firmware compatible with v5,v6 boards by either swapping around the TXA,TXB,TXC
signals via cutting traces and adding wire jumpers, or by stuffing all the LPF L's and C's differently.
Unfortunately, it's a lot of work to do all the mods required for Allison's hack, and difficult to verify without a spectrum analyzer.
Replacing the relays with Axiom parts on v3,v4 boards is easier, adding an outboard LPF filter assembly is easy and thorough.

It is possible to operate the uBitx on 160m.  But for all versions, you must add a low pass filter appropriate for 160m 
in line between the uBitx and your antenna to cut down the harmonics.  Otherwise the 3'rd harmonic will be 
almost as strong as your 160m fundamental.

Jerry, KE7ER



On Wed, Jan 15, 2020 at 08:25 AM, Jerry Gaffke wrote:
Here's what the routine setTXFilters() does in the firmware for v3,v4 and v5,v6 boards:
                        30m   20m   40m   80m
ver 3,4:   abc = 000    100    110    111        (a=0 for 30m, else b=0 for 20m,  else c selects 80m not 40m)
ver 5,6:   abc = 000    100    010    001       (1 to engage each filter for 20m,40m,80m,  but 30m is always inline)
 

Anthony F4HUY
 

Hi Jerry,

thx you, it's a good start to check.
my ubitx run with v5.1 firmware (that i can see on the screen at startup)
my oscilloscope can up to 50mhz,
yesterday, i have cheked the rf connector, i use SO239 instead BNC because my antenna and TOS meter is already PL/SO239

i 'll check this weekend, relay, coils, and test point, and back to you.

73'

Anthony F4HUY
 

Hi Gary,

my ubitx run with v5.1 firmware (that i can see on the screen at startup)

73'