Difference between revisions of "ΜBITX"
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== Antenna setup == | == Antenna setup == | ||
| + | |||
| + | === 20m dipole === | ||
Inverted V dipole made with Amateur Radio Supplies [https://www.amateurradiosupplies.com/product-p/20405.htm 20m dipole antenna wire] (two 18' strands, trimmed, wrapped around insulators, strung up in attic) and 450Ω window line. | Inverted V dipole made with Amateur Radio Supplies [https://www.amateurradiosupplies.com/product-p/20405.htm 20m dipole antenna wire] (two 18' strands, trimmed, wrapped around insulators, strung up in attic) and 450Ω window line. | ||
| Line 17: | Line 19: | ||
QRPGuys [https://qrpguys.com/12w-dummy-load-power-meter 12W dummy load] | QRPGuys [https://qrpguys.com/12w-dummy-load-power-meter 12W dummy load] | ||
* Still no luck getting power measurements working. | * Still no luck getting power measurements working. | ||
| + | * dummy load works when diode is removed (??) | ||
Items from QRPGuys took about 2 weeks from date of order to arrive. | Items from QRPGuys took about 2 weeks from date of order to arrive. | ||
| + | |||
| + | === 7-band OCF dipole === | ||
| + | |||
| + | Ordered [[7-band OCF dipole]] from gniklat1 on eBay. | ||
== Mods perfomed == | == Mods perfomed == | ||
| Line 32: | Line 39: | ||
I started by adding a small 5V switching power supply before LM7805. This created a ton of noise on RX, so I took it out. | I started by adding a small 5V switching power supply before LM7805. This created a ton of noise on RX, so I took it out. | ||
| − | Instead, I relocated LM7805 to case (up against case and screwed to it). The first time I got the leads switched, though, and smoked the nano. | + | Instead, I relocated LM7805 to case (up against case and screwed to it). The first time I got the leads switched, though, and smoked the nano, so had to replace that. |
| + | |||
| + | This arrangement seems to dissipate heat nicely. | ||
| − | I also have a heatsink in | + | I also have a heatsink in some old electronics that I've been meaning to try out too. |
=== Dim the LCD === | === Dim the LCD === | ||
| + | [https://ubitx.net/2018/02/10/reducing-display-brightness/ As documented here]. | ||
At first it had no effect, but then found I hadn't cut the trace between the two leads first, which I did 2018-09-06. | At first it had no effect, but then found I hadn't cut the trace between the two leads first, which I did 2018-09-06. | ||
| Line 45: | Line 55: | ||
Soldered up red LED per [https://groups.io/g/BITX20/message/46853 BITX20 message 46853] on 2018-09-06. Works great! | Soldered up red LED per [https://groups.io/g/BITX20/message/46853 BITX20 message 46853] on 2018-09-06. Works great! | ||
| − | == | + | === Leveling out power === |
| + | Replaced some of the transistors (etc.) per [http://ubitx.net/fix-fix-uneven-tx-output-across-bands/ this solution]: | ||
| − | + | * Replace the 2N3904 transistors in driver stages (Q911, Q912, Q92, Q93, Q96, Q97) with 2n2222 transistors (in TO18 metal can), | |
| − | + | * Parallel up R941, R911, R96, and R942 to get 11 ohms each by placing a 22 ohm resistor across each existing resistor (stacked 1206), | |
| + | * Replace Q90 with a BFR106 transistor, | ||
| + | * Increase R81 to 2.7K, | ||
| + | * Change C81 to 470 pF. | ||
=== Reducing spurs === | === Reducing spurs === | ||
| − | * [http://ubitx.net/2018/10/10/rajs-second-spurs-mod-simpler-again/ | + | * [http://ubitx.net/2018/10/10/rajs-second-spurs-mod-simpler-again/ Replaced L5 and L7] |
=== Reducing harmonics === | === Reducing harmonics === | ||
| − | * [http://ubitx.net/spectral-purity/ | + | * [http://ubitx.net/spectral-purity/ Replaced relays with Axicom D2n 12v relays (model V23105-A5403-A201)] |
| − | === | + | === Power measurements === |
| − | * SWR meter | + | * Before and after the 3 mods above (levelling out power, reducing spurs, reducing harmonics) |
| − | + | ||
| + | [[Image:µBitX mods power readings 2021-07.png]] | ||
| + | |||
| + | == Mods planned == | ||
| + | * SWR meter (rx) | ||
* Red-on-black or amber-on-black display (for night-time operation) | * Red-on-black or amber-on-black display (for night-time operation) | ||
** And/or a 6-8 digit LED display | ** And/or a 6-8 digit LED display | ||
| − | * More buttons - I like [https://www.bolkesteijn.nl/blog/index.php?page=ubitx-mods#ubitx-mod5 PH2LB's approach]! | + | * More buttons - I like [https://www.bolkesteijn.nl/blog/index.php?page=ubitx-mods#ubitx-mod5 PH2LB's approach] ([https://www.bolkesteijn.nl/blog/index.php?page=ubitx-mods3#ubitx-mod16 part 2])! |
** band up, band down, left/right digit selection for tuning, ...? | ** band up, band down, left/right digit selection for tuning, ...? | ||
* Foot-pedal controlled TX | * Foot-pedal controlled TX | ||
| − | ** Have obtained an old (working) foot pedal switch for this purpose | + | ** Have obtained an old (working) foot pedal switch for this purpose (edit: now have two somehow?) |
* Some sort of audio pre-processing? | * Some sort of audio pre-processing? | ||
* Fix filters?? | * Fix filters?? | ||
| + | * line out | ||
| + | ** Again, [https://www.bolkesteijn.nl/blog/index.php?page=ubitx-mods3#ubitx-mod13 PH2LB's approach is great]. | ||
| + | |||
| + | === Other things on wish list === | ||
| + | * <s>external SWR + power meter</s> | ||
| + | ** YL got me a DAIWA CN-501H for my birthday, 2021-03 | ||
| + | * Antenna analyser / antuino | ||
[[Category:Amateur radio]] | [[Category:Amateur radio]] | ||
Latest revision as of 21:15, 14 September 2023
Notes on µBITX assembly and use.
Assembly
Parts that took some time to decide on approach to:
- Case: used a cookie tin from Goodwill for $3 as a case.
- Mic assembly: TODO
Antenna setup
20m dipole
Inverted V dipole made with Amateur Radio Supplies 20m dipole antenna wire (two 18' strands, trimmed, wrapped around insulators, strung up in attic) and 450Ω window line.
- Originally was sent two 16ft strands, which is really too short. Customer service was great and sent me the 18ft strands and a prepaid return envelope for the 16ft strands.
QRPGuys Multi Z Tuner
QRPGuys 12W dummy load
- Still no luck getting power measurements working.
- dummy load works when diode is removed (??)
Items from QRPGuys took about 2 weeks from date of order to arrive.
7-band OCF dipole
Ordered 7-band OCF dipole from gniklat1 on eBay.
Mods perfomed
Fuse before diode
Applied this fix during initial assembly.
The diagram there appears to be labelled incorrectly, though.
Have blown the fuse twice (first time forget, second time transmitting on 40m with untuned antenna) quite a few times, so it seems to work.
Mitigating heat on LM7805
I started by adding a small 5V switching power supply before LM7805. This created a ton of noise on RX, so I took it out.
Instead, I relocated LM7805 to case (up against case and screwed to it). The first time I got the leads switched, though, and smoked the nano, so had to replace that.
This arrangement seems to dissipate heat nicely.
I also have a heatsink in some old electronics that I've been meaning to try out too.
Dim the LCD
As documented here. At first it had no effect, but then found I hadn't cut the trace between the two leads first, which I did 2018-09-06.
CEC firmware
After getting some extra nanos, I flashed one with CEC firmware. Works great!
TX LED
Soldered up red LED per BITX20 message 46853 on 2018-09-06. Works great!
Leveling out power
Replaced some of the transistors (etc.) per this solution:
- Replace the 2N3904 transistors in driver stages (Q911, Q912, Q92, Q93, Q96, Q97) with 2n2222 transistors (in TO18 metal can),
- Parallel up R941, R911, R96, and R942 to get 11 ohms each by placing a 22 ohm resistor across each existing resistor (stacked 1206),
- Replace Q90 with a BFR106 transistor,
- Increase R81 to 2.7K,
- Change C81 to 470 pF.
Reducing spurs
Reducing harmonics
Power measurements
- Before and after the 3 mods above (levelling out power, reducing spurs, reducing harmonics)
Mods planned
- SWR meter (rx)
- Red-on-black or amber-on-black display (for night-time operation)
- And/or a 6-8 digit LED display
- More buttons - I like PH2LB's approach (part 2)!
- band up, band down, left/right digit selection for tuning, ...?
- Foot-pedal controlled TX
- Have obtained an old (working) foot pedal switch for this purpose (edit: now have two somehow?)
- Some sort of audio pre-processing?
- Fix filters??
- line out
- Again, PH2LB's approach is great.
Other things on wish list
external SWR + power meter- YL got me a DAIWA CN-501H for my birthday, 2021-03
- Antenna analyser / antuino
