Topics

bitx40 on 80

terry hughes
 

hi

i am still waiting for the delivery of my bitx40 but while waiting i am pondering
i have 40 and 20 using my trio ft520 and dipoles.
but i do not have enough room for an 80 m dipole so i have built a qrp atu and erected an end fed long wire for 80.
there is no way to reduce the 200w from the trio to use a qrp atu so the answer is the bitx40. 200 wats would be like a pan galactic gargle blaster to my atu !!
but i need to hack the bitx40 for 80
nd6t has published a hack for 60 m which involves adding parallel caps to c2, c4, c6 and across l7
so i modeled the bpf and lpf using aade program with 560 pf across c2,c4,c6 and 390 across l7 and the plots look good for 80 m . the sketch also has to be hacked but that is not a problem as i am a retired computer programmer.
What do people think about the  thoughts of an idle fellow.
73 de terry gm4dso


Jerry Gaffke
 

Terry,

You have it figured out.

Here's an old thread on moving the Bitx40 to 80m:
    https://groups.io/g/BITX20/topic/4655334
And a search for other such threads:
    https://groups.io/g/BITX20/search?p=Created,,bitx40+80+meters,20,2,20,0
 

Jerry


On Wed, Sep 12, 2018 at 10:50 AM, <terryhugheskirkcudbright@...> wrote:
hi

i am still waiting for the delivery of my bitx40 but while waiting i am pondering
i have 40 and 20 using my trio ft520 and dipoles.
but i do not have enough room for an 80 m dipole so i have built a qrp atu and erected an end fed long wire for 80.
there is no way to reduce the 200w from the trio to use a qrp atu so the answer is the bitx40. 200 wats would be like a pan galactic gargle blaster to my atu !!
but i need to hack the bitx40 for 80
nd6t has published a hack for 60 m which involves adding parallel caps to c2, c4, c6 and across l7
so i modeled the bpf and lpf using aade program with 560 pf across c2,c4,c6 and 390 across l7 and the plots look good for 80 m . the sketch also has to be hacked but that is not a problem as i am a retired computer programmer.
What do people think about the  thoughts of an idle fellow.
73 de terry gm4dso

Timothy Fidler
 

I just checked https://github.com/gcallipo/Raduino_Multi/blob/master/src/raduino_multi_v1_0_1.ino   

covers 80 40 20 15 10  so in fact the code is already there and supposedly tested and contains all the ALLARD Brillig enhancements too.. which is a bonus. CW etc etc.

but  how you do the band switch in ferrite and copper  is up to you - nb a couple of LPF boards are in  the works.  Because the Raduino is already packed,  a rotary switch for band select is the/a  sensible and crude option.  It makes sense to try to retain 40 as well as 80mtrs in  a switchable form.

Allard PE1NWL
 

As far as the firmware is concerned, for monoband operation you could use the latest Raduino sketch v1.28.1.
This includes the latest enhancements such as spurious prevention, CW keyer, capacitive touch keyer, improved calibration, etc.
https://github.com/amunters/bitx40

To modify it for 80m, just change the defines for MIN_FREQ and MAX_FREQ at lines 36 and 37.
And set Region to 0 at line 47.

73 Allard PE1NWL

Henning Weddig
 

Allard,

in addition the "high side" injection must be used and chosen, because fin = fLO - Fif; e.g. fin = 3.5 MHz Fif = 12 MHz then fLO = 15.5 MHz.

The "low side injection" as used in the BITX40 does not work (fin = 7 MHz, flo = 5 MHz then fif = 12 MHz).

Henning Weddig

DK5LV

Am 13.09.2018 um 00:27 schrieb Allard PE1NWL:

As far as the firmware is concerned, for monoband operation you could use the latest Raduino sketch v1.28.1.
This includes the latest enhancements such as spurious prevention, CW keyer, capacitive touch keyer, improved calibration, etc.
https://github.com/amunters/bitx40

To modify it for 80m, just change the defines for MIN_FREQ and MAX_FREQ at lines 36 and 37.
And set Region to 0 at line 47.

73 Allard PE1NWL

Allard PE1NWL
 

Hi Henning,

No, for 80m it works just the same way as for 40m.
For LSB we use low side injection, for USB we use the high side.

on 40m (e.g. 7MHz):
in LSB mode: fLO = 12 - 7 = 5 MHz (= "low side")
in USB mode: fLO = 12 + 7 = 19 MHz (= "high side")

Likewise, on 80m (e.g. 3.5MHz):
in LSB mode: fLO = 12 - 3.5 = 8.5 MHz (= "low side")
in USB mode: fLO = 12 + 3.5 = 15.5 MHz (= "high side")

So the firmware would theoretically work OK as long as we are below 12 MHz (30m, 40m, 60m, 160m, etc.)
If we use it for bands above 12 MHz (20m and up), then it should (theoretically) still work but then the side bands will be flipped.

73, Allard PE1NWL

terry hughes
 

hi all

bitx40 has arrived so watch this space
first job is get it going as delivered
next see if i can get it onto 80
thanks Allard for info on sketch

terry

Timothy Fidler
 

re prev message , PM,  on suggestion of diode switch of BPF element. Using a   BAT 592 PIN diode is better than trying to press a small sig diode into duty.  If you cannot source this part then look at parts anchor-electronics of Santa Clara (mail order)  has for sale. Look at diodes on his PDF  and look for one he calls antenna switching diode. I am assuming you are in the US.

terry hughes
 

hi allard

i have changed lines 36, 37 and 47 as suggested but the scan still goes from 7.0 to 7.3
using the f button does not seem to work i also added my callsign

i confirm that 1.28.1 has loaded because my callsign appears on the display and 1.28.1 appears on start up

terry gm4dso

terry hughes
 

hi timothy

i am planning to make it mono band on 80 so no diode switch need thanks for info

i am in scotland

terry gm4dso

Timothy Fidler
 

Argh.. if I get one and want to make it 40/20 then I will be the guinea pig.... Never mind.

you could of course have gone  for a Mkars 80 in that case which is still a good rig and I think still made as a kit down from the gorse and tartin  in the home counties of the English Dogs .  It uses a huff and puff VFO stabiliser controlled by a PIC micro.

However you have to scratch build it and it costs slightly more however it is all through hole so it is easier to hack about.  Digital display of course.

Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 CB #2885, 
Telephone Whangarei   022  691 8405
e: Engstr@...



----- Original Message -----
From:
BITX20@groups.io

To:
<BITX20@groups.io>
Cc:

Sent:
Sat, 15 Sep 2018 05:48:32 -0700
Subject:
Re: [BITX20] bitx40 on 80


hi timothy

i am planning to make it mono band on 80 so no diode switch need thanks for info

i am in scotland

terry gm4dso

Allard PE1NWL
 

Hi Terry

The scan mode's lower and upper frequency limits are hard coded at lines 71 and 72.
You could modify these values as well for 80m band.
(Note that these values are kHz)
So  for example you could use
71    SCAN_START 3500
72    SCAN_STOP 3600

73 Allard PE1NWL

Allard PE1NWL
 

Terry,
while looking at it again, I realised that you'd also need to change lines 93 and 94.
These are the initial frequencies of VFO A and B. I suggest to set these to a frequency somewhere in the 80m band.
For example to 3600 kHz:

93    unsigned long vfoA = 3600000UL;                  // frequency of VFO A
94    unsigned long vfoB = 3600000UL;                  // frequency of VFO B

Also you need to change line 1734:
1734     u.scan_start_freq = constrain(knob / 2 + 3500 + shift, u.LOWEST_FREQ / 1000, u.HIGHEST_FREQ / 1000);
This will allow you to set the upper and lower scan limits in the 80m band via the Function Button (SETTINGS menu).

After making these changes, remember to reload the default settings (keep Function Button pressed during power on).

73 Allard PE1NWL

Allard PE1NWL
 

Hi Terry,

I quickly tried the modifications to the sketch as I suggested earlier
today, and they seem to work OK.

I tested this on my own BitX40 and I could tune through the entire
80m band. Also the scan mode worked OK, and I could set the upper and
lower scan limits via the Function Button.

Of course, my BitX40 does not have the 80m filters, so I could'nt hear
much. But when I transmit a strong signal on 80m using a nearby
transceiver I can receive it on the BitX.

Good luck on 80m!

73 Allard PE1NWL