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A month of FT8

Yesterday was when Tom  AB7WT completed his first month of using his uBITx on the air and it’s been 100% FT8.

After one month, Tom has had 252 FT8 contacts!

This has been achieved with a modest random length end-fed 59 ft antenna with one end up in a tree.  He’s worked 80m, 60m, 40m, 30m, 20m, 17m, & 15 meters.

Almost all contacts have been using 4 watts or less. The results have
been great.  It includes 45 of 50 US states confirmed toward Worked All States (WAS).   He is still trying to nail down those last 5 states.  Tom has worked New Zealand, Australia, Russia AS, Samoa, Cuba, Japan,
and Canada.

So, he’s been very happy with FT8.  He’ll be even happier when
the sunspot cycle turns upwards …..:)

Are there other happy op stories out there?

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AE7TO experience with evening up power output

Mark Cantrell (AE7TO) has been having fun getting his uBITx to have more even power out.

All this experimentation was to allow Mark to get enough power out of his µBITx to make up for low efficiency portable antennas.  He didn’t want to carry a separate power amp.  He just needs to build a 24 VDC battery pack now!

His rig can be seen in the photo above.   At the left hand side (with controls incorporated on the rear panel) is an Antenna Tuning Unit and in the middle is a new daughter board.

Step 1

The new daughter board implements the relay-based band output power leveling mod designed by Bill (K9HZ). 

This mod helped quite a bit at 10 and 14 MHz.  Here is a summary of power levels, as observed by Mark, on each band after the mod:

  • 7 MHz and lower frequencies = 11 watts out (no change from before the mod
  • 10 MHz = 8 watts out (twice was I was seeing before the mod)
  • 14 MHz = 8 watts out (also twice what I was getting before the mod)
  • 18 MHz = 6 watts out (never checked that band before the mod)
  • 21-28 MHz = 3-4 watts out (didn’t test that band before the mod)

Mark didn’t bother adding a 4th relay for tuning as he usually uses an antenna analyzer and manual tuner anyway.

A 3D model file is available for the plastic bridge built to hold the daughter-card above the main uBITX circuit board.  Someone else may find that file useful.    

Step 2

Mark split off the PA power line and fed it 25 VDC (two small lead acid batteries in series).  A buck converter was used to reduce the 25 volt main supply to 13.5 VDC for the rest of the uBITX main board.
That gave 25W at 3.5 to 7 MHz, 12W at 10 MHz, 14W at 14 MHz, 5W at 21 MHz, and 4.5W at 28 MHz.

Then he added a 33 uH inductor in series with R86, and 220 pF caps in parallel with R87 and R88, as suggested by Howard WB2VXW.

Here is a summary of power levels after the above changes (plus replacement of RV1 with the 3-relay/4-pot mod discussed below):

Freq / Power Out / Current Draw
  • 3.5 MHz / 28 W / 2.3 A
  • 7 MHz / 28 W / 2.2 A
  • 10 MHz / 16 W / 1.4 A
  • 14 MHz / 20 W / 1.5 A
  • 18 MHz / 11 W / 1.1 A
  • 21 MHz / 7 W / 0.7 A
  • 28 MHz / 7 W / 0.7 A

These numbers are good enough that Mark no longer feels the need to fiddle any more.  In particular, he is not going to change the bias settings on the finals as they seem well adjusted from the factory.   Mark has turned back the power output on the low bands to give no more than 20w out to protect his finals.

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VU2ESE power mod for 10m operation


Ashhar Farhan VU2ESE notes that 28 Mhz has, unusually, been open for the last week.  As a result, he realised that the ubitx output was woefully low on 10m.  Hence the experiment below:

Ashhar suggests the following final fix, and asks for others to try it out and see if it is replicable:

Replace C81 from 0.1uf to 470pf
Replace R83 from 10 ohms to 2.2 ohm
(you can short R83 as well)
Replace 97, R98 from 47 ohms to 220 ohms
Remove C261, C262.
So, what happens is that removing the C261 and C262 increases the gain of the finals. They are run open. Hence greater gain at 28 mhz.
However, the gain is very high at lower frequencies. So, in order to reduce the gain at the lower frequencies, the 0.1 uf cap is replaced by the 470 pf. As the frequency of the signal drops, less and less RF flows through the 470 pf, decreasing the gain of the predriver. 470 pf is not a magical value, 220 pf works almost as well.

Step #1 Increase the predriver gain towards the higher frequencies

The predriver Q90 has a emitter degeneration capacitor C81 (0.1uf) and and R83 (10 ohms). Replace C81 with a 470 pf and R83 with 2.2 ohms. Altenatively, short R83.

With this, the emitter reactance decreases with increasing frequency, yielding higher gain beyond 14 MHz.

Step #2 Take off the feedback from the IRF510s.

a) Replace the existing  R97 and R98 with a value of 47 ohms  with 220 ohm resistors.
b) Remove C261, C262.
Reference #1
Reference #2
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VU2SPF/VE1BWV new firmware release v2.9u

SP VU2SPF and Joe VE1BWV have just released the latest version of the TFT Colour Touch Control software.

Highlights

This software/hardware combination is low cost, uses standard easy to get parts and provides a colour, touch control and physical buttons if you want them.

You will require a TFT (Touch) Display module, an At Mega 2650 arduino board, Si5351 DDS module, a µBITx and a few wires

The result is an all-band rig with a computer controlled Radio Touch Control Colour Display.

Some new features

Automatic Scanning – up to band edges in both the directions is now added in V2.9bU of software. Scanning finds signals of interest across the band. Two small buttons labeled ‘U’ and ‘D’ scan in up and down from the currently set frequency.  Scanning can be stopped by touching the display panel.

CAT Control  – the software now has new code to emulate FT817 CAT commands. This provides radio and computer control for digital modes.

User Manual –  A new comprehensive user manual has also been added. Constructors have been looking for this for quite a while.

The new version is available on Github at : https://github.com/sprakashb/TFT_TouchScreen_for_uBitx

Information is also available at:
http://vu2spf.blogspot.ca

and

https://www.youtube.com/watch?v=zkg-IrjV2h4&t=375s

(UBITX ver2.9bu Installation Results)

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K5BCQ boards very popular

The list of potential orders for Keys K5BCQ on 3 May is surprisingly high (250+).   Email Keys  K5BCQ(at)ARRL.net (to keep from overloading this “topic”) and he’ll update the spreadsheet to include or amend your order.

Reference
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VA7AT Audio Pop and ND6T AGC Fixes: PCBs

 

Would you would like to have fixes in your µBITx for the audio pop and the missing AGC issues?

There are now two proven designs to the audio pop and AGC issues from:

  • VA7AT for the audio pop problem
  • ND6T for an effective AGC

Kees K5BCQ is taking orders now for two small PCBs to make it easier for constructors to complete these fixes.  The PCBs require the use of surface mount components.    They are tiny (about 1″ square) and can easily be mounted in any case.  They will be very cheap and available both in the US and DX.

Reference
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uBITx panels for EF01 Excellway case

Bought the Banggood case?   Want some 3D printed drop in front and back panels so you don’t need to cut out the hole for the display and controls?

https://www.ebay.com/itm/3D-printed-Front-Back-panel-for-EF01-case-for-uBITX-HF-Transceiver/362218558429

Gary AG5TX says:

“I bet some find it hard to stomach buying $27 plastic panels for a $10 plastic case when debating a few bucks differences in micro-controllers.
That said, my building brother, I too get anxious on cutting holes.  We don’t know what tools you have, and given the question, assume not a mill or a drill press.

“What I would do is cover the front side of the plastic panel with blue 3M painters tape. Scribe the centerline for the holes directly on the ‘inside the box’ portion of the plastic where it won’t be seen. I use center drills to start the holes (they are cheap), if you don’t have center drills, use a small drill bit.  Once the initial undersized holes are cut, flip the piece over and drill from the ‘outside the box’ side so if you get a chip out it won’t be seen. Best to start small and step up to one drill bit less than size. When drilling, secure the plastic panel over a scrap piece of softwood, and make this a “pine board project.”  With thin plastic and drilling with hand tools, I find that the final drill bit size is best done by hand. I have an old pcb hand nibbler tool ($10?)  for cutting somewhat square holes with patience.    Just slightly undercut the rectangle for the LCD with the nibbler, remove the tape and finish out with a bastard file and sand paper.  If all goes wrong, you can still try 2 more cases or spend the $27.  Also search this forum for good ideas on printing a full face ‘label’ which might cover up the sins of a nonperfect cut. Stain grade or paint grade? My wood working Grandfather taught me very early in life that a coat of paint covers a multitude of sins. Nothing ventured, nothing learned. Maybe someone else has some tips.”

Michael VE3WMB comments:

“I have now used three of the Excelway EF01 cases for rigs with 16 X 2 displays with good success.   The ABS enclosure panels are quite easy to work with.

“Just to add a couple of comments to Gary’s suggestions. I have found that drilling corner holes and using a coping saw to cut out the “window” for the display works quite well. As Gary suggests you want to make it undersized by a couple of millimetres.   With patience and a nibbler or even an exacto knife and a file you can make a decent looking opening. In all three cases I made
the “window” just large enough to friction fit the display without resorting to using screws to hold it in place and this works fine.

“One other point; I suggest that you mark the position of where you are going to drill holes and then make a small divot (a nail and hammer works fine for this) so that the drill doesn’t wander. Also starting with a small sized drill bit first helps. For larger holes (i.e. for BNC etc) I swear by a stepped drill bit to get the hole  to the proper size.

“The key to getting a good result is to plan and carefully mark everything in advance on the back of the panels and then take your time. Remember if an opening is too small you can enlarge it, if it is too big there is not a lot you can do so, measure twice and cut once.”

MVS Sarma says, “For cutting rectangular windows in plastic, I resort to a lamination cutter sold in India at just fraction of a $. I keep the tool drawing across the 4 lines of the rectangle (the lcd mounting window in this case on the µBITx).  After a while you can push out the small window from the plastic.

This is what a laminate cutter looks like.

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uBITx at FDIM and Dayton Hamvention?

W8TEE will be talking about his µBITx at QRP Club Night at FDIM  (Friday 17 May.  Hans G0UPL from QRP Labs has a table at the vendor evening at FDIM (Thursday 17-May-2018).  It is understood that the µBITx designer from HFSignals.com (Ashhar Farhan) will also be at FDIM.
Hans G0UPL also has a booth at the Dayton Hamvention, #6414. He plans to have a good selection of QRP Labs kits on show and for sale.
There will undoubtedly be a number of µBITx constructors at Hamvention.  Any suggestions for a hang-out spot to share your µBITx tips?
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