Topics

Ideas for AM, NB FM Demod and CW filter board

Rahul Srivastava
 

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 

Ralph Mowery
 

Mr Farhan did a great job of designing the uBITX and keeping the price as low as it is.  I doubt it could be done, but I would like to see something along the same line that has NBFM  and maybe AM and a CW filter in it for less than $ 200 USD shipped.  Just wish that I had the skills to do things like this.

I had two reasons to get this rig.  One was to play and modify it, the other is to drive some VHF/UHF converters from the Ukrain that are selling for less than $ 100.  

de ku4pt

On Tue, May 29, 2018 at 12:35 PM, 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 

ajparent1/kb1gmx
 

if the board does 10W SSB then am will be about 2.5W, not so much on that.
The bands I see AM on or are 160, 75 and 40M and rarely on 10M but 2.5w
will not cut it.  Generating  AM in a SSB system requires doing low level
AM adding parts.

For FM you need to cut back on power as it 100% duty cycle.  The only place I see any 
HF FM activity is 10M, the rest is VHF and up.  That and a way to modulate one of
the oscillators.  

Adding AM and FM to a ubitx is a bad way to go.  For AM RX you could use a chip but
then you need agc. Listening to AM without AGC is really poor.   Some AM/FM RX chips
exist but they must be upstream of the 12mhz filter (too narrow for both am and
FM as you need a 6-8khz wide filter for that.

The uBitx is well developed for SSB and CW why make for costly and complex for modes
not often used and might make for a better separate low cost radio. 

Now using it with a transverter to get SSB on VHF and UHF is simple and a good match.
For FM work on those bands (2m and UHF) there are so many cheap radios that do that
well enough so don't bother.  Here a BaoFeng is under 30$ and does everything I can
want at 5W and it fits in my bag.

Can it be done, yes the FT817 and IC703 prove it can.  Inexpensively not so much.
I'd expect doing that would turn the board form a 110$ to a 200++ very quickly.
Also with used FT817s out there for about 400$ (they do 6,2 and 432 as well)
as all mode cost and compliance with regulator agencies becomes an issue.


Allison

Ashhar Farhan
 

Trust Rahul to discover these chips! The TDA1220 appears to be a winner. The simple alternative is a super regen at 45 mhz...
- f

On Tue, 29 May 2018, 22:49 ajparent1/KB1GMX, <kb1gmx@...> wrote:
if the board does 10W SSB then am will be about 2.5W, not so much on that.
The bands I see AM on or are 160, 75 and 40M and rarely on 10M but 2.5w
will not cut it.  Generating  AM in a SSB system requires doing low level
AM adding parts.

For FM you need to cut back on power as it 100% duty cycle.  The only place I see any 
HF FM activity is 10M, the rest is VHF and up.  That and a way to modulate one of
the oscillators.  

Adding AM and FM to a ubitx is a bad way to go.  For AM RX you could use a chip but
then you need agc. Listening to AM without AGC is really poor.   Some AM/FM RX chips
exist but they must be upstream of the 12mhz filter (too narrow for both am and
FM as you need a 6-8khz wide filter for that.

The uBitx is well developed for SSB and CW why make for costly and complex for modes
not often used and might make for a better separate low cost radio. 

Now using it with a transverter to get SSB on VHF and UHF is simple and a good match.
For FM work on those bands (2m and UHF) there are so many cheap radios that do that
well enough so don't bother.  Here a BaoFeng is under 30$ and does everything I can
want at 5W and it fits in my bag.

Can it be done, yes the FT817 and IC703 prove it can.  Inexpensively not so much.
I'd expect doing that would turn the board form a 110$ to a 200++ very quickly.
Also with used FT817s out there for about 400$ (they do 6,2 and 432 as well)
as all mode cost and compliance with regulator agencies becomes an issue.


Allison

lkorahul
 

Alison,

My main interest was in demodulation. With its full HF coverage lack of proper AM detector seems a major feature lacking in the rig. NBFM comes as bonus with this chip. TDA1220 has an internal  AGC for AM. I feel simple addition of this add on board will  make uBitx a very fine Gen coverage Rx. 

FM can be done possibly shift the BFO to 15MHz  phase modulate and triple it for decent deviation and modulation index and pass the signal thru 45MHz filter up reverse. As you rightly say cost and complexity will go up and we still wont be able to beat a Baofeng and a 2nd hand 817 will be a better option.

With the new Ver 4 boards and connectors across the 12MHz filter I foresee people trying out parallel CW xtal filter mod soon hence thought about a plug in board.

73

Rahul VU3WJM

Ashhar Farhan
 

We can probably use the AGC for SSB as welll.

- f

On Tue, May 29, 2018 at 11:16 PM, lkorahul via Groups.Io <lkorahul@...> wrote:
Alison,

My main interest was in demodulation. With its full HF coverage lack of proper AM detector seems a major feature lacking in the rig. NBFM comes as bonus with this chip. TDA1220 has an internal  AGC for AM. I feel simple addition of this add on board will  make uBitx a very fine Gen coverage Rx. 

FM can be done possibly shift the BFO to 15MHz  phase modulate and triple it for decent deviation and modulation index and pass the signal thru 45MHz filter up reverse. As you rightly say cost and complexity will go up and we still wont be able to beat a Baofeng and a 2nd hand 817 will be a better option.

With the new Ver 4 boards and connectors across the 12MHz filter I foresee people trying out parallel CW xtal filter mod soon hence thought about a plug in board.

73

Rahul VU3WJM


ajparent1/kb1gmx
 

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

lkorahul
 

Alison !

Your reference to TDA7000 got me thinking how about a filter and ZN414 clone MK484 available from China. Appears nice simple a typical uBitx like solution.

I still have some marine radios with me  namely Eddystone, SEA, ITT etc. Amazing how much performance they were able to squeeze out with MC1496, ring mixers, TBA810 AF amps etc in those days...

Rahul VU3WJM

Arv Evans
 

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

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

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 

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

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

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



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

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

 

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

@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 !

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 !


 

@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