Topics

Ideas for AM, NB FM Demod and CW filter board

Jens / DH1AKY
 

Ralph, ku4pt wrote:

  the other is to drive some VHF/UHF converters from the Ukrain that are selling for less than $ 100.  
Same as me, but I've not built my V4 until now. So I use a Multus Proficio SDR for driving the transverters. Works as expected, used that setup during Marconi VHF contest, well done.

The Proficio is an excellent QRP rig from 160m to 10m. On outdoor use I would prefer the uBitx.

73s, Jens/DH1AKY

jim
 

Thot about trying this for an AM detector....

On Friday, January 3, 2020, 5:28:42 AM UTC, g8tdu <jomac_uk@...> wrote:


I have also searched for IC's to add AM/FM and narrowed it down to the same TDA1220 IC you have. Ashhar suggested working from the 45Mhz IF frequency and this is one of the very few that will work with AM at 45Mhz

g8tdu
 

I have also searched for IC's to add AM/FM and narrowed it down to the same TDA1220 IC you have. Ashhar suggested working from the 45Mhz IF frequency and this is one of the very few that will work with AM at 45Mhz

g8tdu
 

It would still be a uBITX but with an add on board

g8tdu
 

I have in fact created a FaceBook group to investigate the possibility of adding AM/FM to the uBITX and the older BITX. This group has attracted 120 members in less than 24 hours.!

I have had a few chats with Ashhar on this and he suggested using the IF frequency of 45Mhz. This limited the choice of IC's which would work at 45Mhz AM, the TDA1220 will work at this IF frequency. Kyocera make some nice 12.5Khz 6 pole filters which should work nicely with this IC.

In addition we also want to add CTCSS to the board for repeater use. Most of my VHF/UHF and above equipment is done via transverters, and i wanted FM especially for repeater use.

The new group dedicated to just this can be found here.... https://www.facebook.com/groups/2517941545160596/

Arv Evans
 

And....the modified design would no longer be a BITX.
There are other low power designs out there in kit or homebrewed form that would be much
easier to modify for FM and/or AM. 

http://www.sp5ddj.pl/taurusdziennik.htm

http://www.glcharvat.com/Dr._Gregory_L._Charvat_Projects/6_%26_10m_SSB_CW

It would seem more productive to work toward an LF mod for the BITX and uBITX
designs.  LF might be more of a challenge due to antenna requirements but should be
easier to do the circuit modifications that are required.

Arv K7HKL
_._


On Tue, Jun 5, 2018 at 11:14 AM Tim Gorman <tgorman2@...> wrote:
For AM you would have to derate the power output from the ubitx to
about 2 watts on 80m. 2 watts on 80m would translate to about 250mw on
10m. Is that enough output for what you want?

Even narrow-band FM on the ham bands are incompatible with the 12hz SSB
filter in the ubitx. That affects both receive and transmit. And FM
power output would have to be derated just like AM.

It would be easier to design an am/fm rig from the ground up, perhaps
using the Radiuno.

tim ab0wr


On Tue, 05 Jun 2018 03:44:09 -0700
tutdavid@... wrote:

> Hi, 
>
> Yes I think this would be a great improvement to implement also AM/FM
> to the uBITX. 
>
> Does anyone have some ideas ?
>
> Thanks !




Tim Gorman
 

For AM you would have to derate the power output from the ubitx to
about 2 watts on 80m. 2 watts on 80m would translate to about 250mw on
10m. Is that enough output for what you want?

Even narrow-band FM on the ham bands are incompatible with the 12hz SSB
filter in the ubitx. That affects both receive and transmit. And FM
power output would have to be derated just like AM.

It would be easier to design an am/fm rig from the ground up, perhaps
using the Radiuno.

tim ab0wr


On Tue, 05 Jun 2018 03:44:09 -0700
@dr.David wrote:

Hi, 

Yes I think this would be a great improvement to implement also AM/FM
to the uBITX. 

Does anyone have some ideas ?

Thanks !

F1BFU - Fr - 79
 

Yes that is true but we must not forget that Bitx and uBitx are affordable for a beginner amateur radio and that adding a lot of additional features will confuse more than one if the price was a lot most important.
What makes Bitx interesting is the price that allows a beginner to start and a seasoned enthusiast to experiment with many things. We are still in the QRP traffic domain.
Or we must add these features in the form of additional cards that can be purchased or manufactured later.
I think the most desirable goal would be to make a modular package that everyone can change as they see fit.

That's just my opinion
73 QRO

2018-06-05 13:03 GMT+02:00 Radu <radu.loga@...>:

@Gilles,

Lets not forget that in some countries HF equipment is quite expensive and therefore many of the new radio enthusiasts are starting in CB 27Mhz AM/FM.
In my opinion this modes are also quite useful.
Also on amateur radio level in 10 meter band in the summer when the propagation is open many nice QSOs can be made in FM around 29600Mhz.
So in these case why not to have AM/FM


 

FM is used on 29 Mhz!

Raj


At 05-06-18, you wrote:
Hello

Questions to ask:
Is the AM still used at amateur radio level
Is the FM used in the HAM band, except that the uBitx attacks a 144 or 430mhz transverter?

73

2018-06-05 12:44 GMT+02:00 <tutdavid@...>:
Hi,Â

Yes I think this would be a great improvement to implement also AM/FM to the uBITX.Â

Does anyone have some ideas ?

Thanks !

 

@Gilles,

Lets not forget that in some countries HF equipment is quite expensive and therefore many of the new radio enthusiasts are starting in CB 27Mhz AM/FM.
In my opinion this modes are also quite useful.
Also on amateur radio level in 10 meter band in the summer when the propagation is open many nice QSOs can be made in FM around 29600Mhz.
So in these case why not to have AM/FM

F1BFU - Fr - 79
 

Hello

Questions to ask:
Is the AM still used at amateur radio level
Is the FM used in the HAM band, except that the uBitx attacks a 144 or 430mhz transverter?

73

2018-06-05 12:44 GMT+02:00 <tutdavid@...>:

Hi, 

Yes I think this would be a great improvement to implement also AM/FM to the uBITX. 

Does anyone have some ideas ?

Thanks !


@dr.David
 

Hi, 

Yes I think this would be a great improvement to implement also AM/FM to the uBITX. 

Does anyone have some ideas ?

Thanks !

 

Hello 
Maybe a simple solution with a NE567 as a PLL FM demodulator / synchronus AM detector will be ok in order to keep the cost and the complexity of the circuits down.

http://www.amalgamate2000.com/radio-hobbies/radio/ne567_tone_decoder_as_am_fm___de.htm

Joe Puma
 

You can’t transmit with a rtl-SDR dongle.  But they make great pan adapters for the bitx line. I will use one with my units when I start to build it. 

Joe
KD2NFC



On May 30, 2018, at 12:05 PM, Nelson <ngtdlt@...> wrote:

Although having the ability to xmit AM etc would be nice, perhaps foregoing xmitting and including a simple AM detector circuit so the receive section could also be a general coverage SW receiver.  It seems it would be easy to do a mod for reception, especially since I had to add a high pass filter to keep local AM stations from swamping the bands.  I could get excellent reception of one local AM BC Band station without any alteration to the circuit so it was getting into the audio amp section and getting rectified somewhere...

Nelson, KG7GYS

On Tue, May 29, 2018 at 9:35 AM, Rahul Srivastava via Groups.Io <vu3wjm@...> wrote:
Hi!

I was discussing with Farhan on this topic for an add on demod board to add more versatility to uBitx.  CB radios often used a common chip for AM as well as NBFM receive. I enquired here and TDA1220 is available in mkt for slightly more than a $.

With the parallel XF mod maybe we can have an add on board with this chip and a 6 pole Cohn CW xtal filter. 2nd IF's now being 12MHz SSB, 10.7MHz + 455KHz for AM/FM and possibly 8.xx MHz or some other for CW. 

Guys what to suggest..

73

Rahul VU3WJM 




--
I always thought the Universe was a wonderfully strange place until I studied Particle Physics - I now know the Universe is, in fact, profoundly odd in nature

Nelson
 

Although having the ability to xmit AM etc would be nice, perhaps foregoing xmitting and including a simple AM detector circuit so the receive section could also be a general coverage SW receiver.  It seems it would be easy to do a mod for reception, especially since I had to add a high pass filter to keep local AM stations from swamping the bands.  I could get excellent reception of one local AM BC Band station without any alteration to the circuit so it was getting into the audio amp section and getting rectified somewhere...

Nelson, KG7GYS

On Tue, May 29, 2018 at 9:35 AM, Rahul Srivastava via Groups.Io <vu3wjm@...> wrote:
Hi!

I was discussing with Farhan on this topic for an add on demod board to add more versatility to uBitx.  CB radios often used a common chip for AM as well as NBFM receive. I enquired here and TDA1220 is available in mkt for slightly more than a $.

With the parallel XF mod maybe we can have an add on board with this chip and a 6 pole Cohn CW xtal filter. 2nd IF's now being 12MHz SSB, 10.7MHz + 455KHz for AM/FM and possibly 8.xx MHz or some other for CW. 

Guys what to suggest..

73

Rahul VU3WJM 




--
I always thought the Universe was a wonderfully strange place until I studied Particle Physics - I now know the Universe is, in fact, profoundly odd in nature

Lawrence Macionski <am_fm_radio@...>
 

Exotic demodulation schemes, variable bandwidth and so on...
the RTL-SDR dongles out there can be had for under $20USD and sorry, I do not know the non-USA market; but here laptops can be had for $75USD with reasonable speed and condition. Granted a fancy laptop can cost $500USD plus, likewise HF rigs.. You want a Ferrari or a bicycle? What you get is what you can afford..

As I see- dreamers looking at General Coverage receivers, AM Broadcast band DXing, Aircraft- 2 meters, 6 meters.. I am astounded, no one is looking at the low cost and popular RTL-SDR dongles...or incorporating them into the uBITX.

The uBITX delivered to your door step I agree can use some tweeks, However it will perform with honors (cost VS specs/features) as is out of the box.

I was involved in a project a number of years ago. International team.. The Brit started designing a 5Vdc power supply. Parts alone were over $25. and delivery time weeks away. I simply put it to the group, a 5Vdc power supply could be bought for $10 in the open market, Why design, build one and wait till we have a working supply to test -debug the rest of the project..  Brits don't like me... 

Gentlemen- (are there any ladies out there?) time to realize it's 2018, as soon as you can digitize it, then manipulate it with software.

Can't wait for the - "I want to use a uBITX to drive a pair of 6146's" post...(because I got 4 at a garage sale for 25 cents each)

I'd like to think "Good Engineering Practice" is the standard, and a bit of humor too..

Larry W8LM



Ashhar Farhan
 

I once played with an AOR7030 on AM at Anil's QTH. It blew my mind. Synchronous AM detection is certainly something.
- f

On Wed, 30 May 2018, 07:10 ajparent1/KB1GMX, <kb1gmx@...> wrote:
My favorite AM radio is my Hallicrafters SX100 or the highly modded S120
of for just being odd ball my really old (1953) RCA am potable AC/DC/battery
using tubes.  ;)

I still wish I had the old RBO II shipboard AM RX.   It was heavy enough to
hold down a truck.


Allison

ajparent1/kb1gmx
 

My favorite AM radio is my Hallicrafters SX100 or the highly modded S120
of for just being odd ball my really old (1953) RCA am potable AC/DC/battery
using tubes.  ;)

I still wish I had the old RBO II shipboard AM RX.   It was heavy enough to
hold down a truck.


Allison

ajparent1/kb1gmx
 

Using SSB radio for AM RX is fine I do it all the time.  Using it for TX not so much
as AM nets sort frown on it.

Building AM rx is fun in it self.

Allison 

Tim Gorman
 

I listen to AM stations all the time with the ubitx! It's not high
fidelity but if you zero beat the station on SSB it is good copy, even
on shortwave! Sounds at least as good as the AM stations in my old 1955
Pontiac many years ago!

If you just want to station hunt give it a try!

Transmitting is a different story of course.

tim ab0wr



On Tue, 29 May 2018 12:34:38 -0600
"Arv Evans" <arvid.evans@...> wrote:

Agree with Allison. If what you want is a FM monitor receiver, then
design and build something
specifically for that purpose. If you want an AM General Coverage
receiver, then build one
specifically for that purpose. As it stands now the BITX or uBITX is
not a good choice for
either mode. Lots of modifications would be required and would still
result in a compromise
design for those modes, and could also degrade the excellent design
and performance of your
BITX or uBITX as an SSB and CW transceiver.

There are several ICs that can be used as the back-end of a AM/FM
receiver. They come
in WBFM or NBFM models, and some are suitable for both wide or narrow
FM. It should be
easy to design and build a simple down-converter to go ahead of one of
those chips and
follow it with an audio amplifier stage. For FM you would probably
want AFC, and lots of
gain followed by a limiter ahead of the FM detector. For AM you will
probably want to include
some sort of AGC.

What does seem to be useful for AM and FM and related to the uBITX or
BITX-40 would be to
use a Raduino board as the frequency and mode control for a new
design for AM, FM, or both.
The Si5351a is inexpensive and could be a good source of LO signals
for the down-converter.
Software for the Arduino Nano could be written to specifically
support this layout.

If your goal is VHF or UHF operation on SSB or CW, then a transverter
might be the most
cost effective way to go. Doing this would only require that the
BITX or uBITX output be
attenuated enough to match input level requirements for the
transverter.

My 2-cents worth.

Arv K7HKL
_._


On Tue, May 29, 2018 at 12:10 PM ajparent1/KB1GMX <kb1gmx@...>
wrote:

On Tue, May 29, 2018 at 10:26 am, Ashhar Farhan wrote:

TDA1220

Superregen at 45mhz as AM/FM detector... I can't go there. ;) I
did it 40 years ago at 10.7mhz
I learned a lot. I wanted a RX that could hear Aircraft (118 to
136mhz) and 2M fm (144-148).
Its a great way to go for low power consumption and poor
selectivity, not a no tune design!

Took a bit of digging to find a data sheet.
Yes, but try to buy them from non questionable sources. It went
EOL years ago so the only
parts are NOS (new old stock that have been sitting). However
something like that would
solve the RX problem and needs to work at the 12mhz IF and its upper
frequency for the
TDA1220 is 30 mhz. It was a 1994 part and I even have two of
them. That and two filters
plus three tuneable cans to add fun to ones life. Look for the
TDA-7000 (also EOL) as
that works easily at 45mhz for FM rx.

That type of part goes in and out of fashion rather quickly but
there is always something
new to replace it.

It still leaves generating AM and FM. Double sideband AM is easy,
sum the 45mhz though
a 6DB pad and a DBM and you get perfect low level modulation. Gain
down stream
becomes critical as the carrier has to be 1/4 peak power or it
sounds distorted.

For AM and power do a class E rig. Using switching fets its fairly
easy to do
Monoband AM at 50W or more (with switchmode class D modulator).s

FM in the current scheme means audio to digital and feed that to the
SI5351. I think
a bigger MPU might be needed. The alternate is 12mhz crystal osc
and FM it using
a varicap diode, not a no tune approach. That also requires audio
processor
(preemphasis and clipping/limiting).

Both AM and FM will easily pass through the 45mhz filter and its
wide enough.

I cut my teeth on AM (marine radio pre VHF and aircraft) and FM
(Land mobile
and Marine VHF) commercial stuff must be 50 years ago. It was fun.


Allison