has anybody hacked the bitx40 for 20 meter. i have not yet purchased a bitx40 . i only want one band, so ubitx is a bit ottp. But i prefer 20 m to 40 m what coils need rewinding and how many turns. What change to the raduino sketch.

terry gm4dso

开云体育

Fairly healthy rebuild wouldn’t you say?

I'm sure others will chime in but I remember Ryan Flowers doing a lot of experimenting with different bands on the BITX40 on his blog.? Search his site for 20M.? I think Don did a band conversion too.
--

Very reasonable if your using Raduino or other digital signal source for VFO and BFO.

The very original BITX was the BITX20.? So ther eiss a schematic for that and you can
get the bandpass filter and low pass filter from that.

The two big things are the band pass filters and replacing the low pass filter.
Of course the Raduino sketch has a few changes as well (set up the correct frequencies.).

Allison

On Sun, Jul 29, 2018 at 04:38 AM, <terryhugheskirkcudbright@...> wrote:

tHacking bitx40 for 20 metre

Terry GM4DSO

Way back in the early BITX? days there were several band conversion projects, and even some
band conversion kits.? Methodology was to determine the impedance of LC networks at the
original frequency and then determine the L and C values to obtain the same impedance at the
new frequency.? This usually involved using the calculator at https://toroids.info and then changing?
LO frequencies for the new band.? If the IF frequency is also changed the BFO will also need to be
changed.?

Arv K7HKL
_._

Go to QRPKITS.COM and you can find manuals for both BitX20 & 17.?

On top of changing the BPF and the LO, you may have to change the BFO frequency (depending on which new VFO range you pick) and move it to the other edge of the IF pass band filter since 20m ham SSB uses USB.

Thang AA6SV

just a bit more about my hacking requirements
what i would really like is a general coverage receiver (like the ubitx) but leave the tx to 40 m only
presumably this means a hack to the rx input filter and a hack to the sketch

any ideas

Terry,
The latest Raduino sketch v1.28 provides this feature:

Prevention of out-of-band transmissions

The software restricts transmission to the 40m ham band allocation. By default this is ITU region 2 (Americas: 7000-7300 kHz). If you are located in a different ITU region, uncomment ONE of the lines 44-47 depending on your location, and recompile.

If the is installed, out-of-band TX will be disabled, but RX is still possible outside the band. If the is NOT installed, both TX as well as RX will be disabled outside the band.

Download it from

73 Allard PE1NWL

hi

do i need to hack the receiver input filter

terry

Terry, I did this. I also changed the PA FET for a RD15HVF1 because it worked a lot better on 20m than the IRF510. Info on both here:





--
Ryan Flowers - W7RLF

IRF510 at 20M is not an issue or even working hard.?

I have several radios that really work on that band using that critter.
Bitx20 (V0) from the early years, uBitxV3,? Slopbucket 20 a Kd1JV design.? Never
minding a 10M radio that just got an upgrade from 2sc1307 to IRF510 (went from
5W to 12), a 160 to 10M amp using them (WA2EBY).? ?

Makes me ask what's wrong??

Allison

?

Terry,

You need a separate band pass filter for each band if you want to use the single conversion BitX40. The UbitX uses double conversion that eliminates that requirement. You could use a multiple band pass filter, (QRP Labs has them) but then the cost is getting closer to a UbitX once you do that.?