Date   
Re: Altoids tin? go small???

Hans Summers <Hans.Summers@...>
 

I like that kind of challenge too, though I have yet to even finish my
conventionally sized BITX :-(

If you look in your component catalogues you will find very small
alternatives to large conventional items such as potentiometers. One example
is a kind of preset trimmer which has an 11 x 11mm footprint nd is 10mm
high. See Farnell part number 452853 or this link:
http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=452853 (I hope the
link works for you). Despite only being a trimmer potentiometer, is actually
has a tiny knob instead of just a screwdriver hole. The little knob can be
turned between thumb and finger, though obviously not as easily as a real
full size knob.

Other ideas:

The VFO course and fine tune could be replaced by a single multiturn
ultraminiature preset potentiometer, these come with a small protruding
metal shaft to take a flat-headed screwdriver. You can glue a small PCB disk
onto the shaft in order to turn it. This idea replaces the two separate
controls for course and fine tuning, but it does mean that you won't have
any idea where on the band you are tuned to. Unless you 1) count turns, 2)
miniature frequency counter such as
http://www.hanssummers.com/radio/sfreq/index.htm (could be made even smaller
using Surface Mount Devices) 3) meter the tuning voltage somehow.

You can get very tiny switches too, as well as other miniature components
for things like headphone sockets etc.

PCB: you can get board which has half the thickness of the usual stuff.
Might not sound like much difference, but volume consumed by the PCB is
wasted volume!

With "ugly" construction you can be VERY compact, provided you don't mind
double- or tripple-deckering your components!

73 Hans G0UPL

-----Original Message-----
From: Allison Parent [mailto:kb1gmx@...]
Sent: 11 September 2005 04:34
To: BITX20@...
Subject: [BITX20] Re: Altoids tin? go small???


Go for it, thats a real challenge.

I've put what amounts to the recieve side of a Bitx in a altoids tin. That
was easy, the knobs are always a problem. Seriously, the real problem was
keeping the BFO from swamping the RF amp from being so close. Shielding was
the required item to solve that. It's also
needed so that the Xtal filter can do it's work rather than blow by. I also
found SMT parts very handy.

The VFO is a problem. Heat, or rather heat transfer from other parts will
have to be attended to or the drift will be tough to manage. Any case flex
or the lid moving also caused frequency shifts. I
had enough heat from the audio too induce drift. You may wish to consider a
VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz). A
higher freq VXO will tune more.

You can use FT25-43 toroids or BN43-2402 binocular cores for the
transformers as they are small. The turns ratio is all you need for those as
8-10 turns will be enough. Consider using TUF1 DBMs as they are very small
and would save space over a core and diodes for the modulator and mixer.
You'll have to use shielded cans (maybe IF transformers rewound) for the
bandpass filter. The crystals used for the filter and BFO consider the hc49
size or smaller.

The transmit chain will have to scale back. The size of the parts and the
current they need to handle presesnts limits for thermal and
RF isolation with conventionally available parts. Running without the
IRF510 can get you about 300MW with a good transistor and the right output
match.

You will have to use electronic TR switching, space for relays is scarce.
Antenna, Mic and earphone jacks must be small too.

It can be done but a lot of care will me needed to render a useful radio.

Oh, I do have a larger Altoids tin it's nearly 3x the size
of the usual one. That would be easy.

Currently I'm building a BITx for 6M in a computer AB switch box measuring
of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy. the 5.25"x2" pannel
space is cramped for space to accomodate
tuning, audio gain, mic and headphone jacks and S meter.

Allison
KB1GMX

--- In BITX20@..., Jim Strohm <jstrohm@e...> wrote:

On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:

Unfortunately I do not get Altiods here in Lucknow so a rough
dimension will be helpful this looks like a neat challenge.

2.25 x 3.75 in.

Whoops, 5.7 x 9.5 cm

0.75 in deep (2 cm)





Yahoo! Groups Links

Re: Altoids tin? go small???

Arv Evans K7HKL <arvevans@...>
 

Miniature BITX builders:

Using a brass-screw type PTO also makes the VFO section much more compact, without compromising slow and precise tuning, but like Hans says, you will then need some sort of frequency counter to determine where you are in the band.

You can use very small low-voltage type capacitors (5 Volt rated units) for the emitter bypass caps because the operating voltage will not exceed that amount. Same applies to some other caps if you check the maximum voltage that they might be exposed to.

Chip type resistors and capacitors are actually not too bad to work with in ugly-construction method, and they will save additional space.

With GI (galvanized iron roof flashing) material or double-sided PCB as the sub-strata you can build on both sides of the board. This also saves significant space.

If you use earphones only, or an external AF amp & speaker (PC speakers work well) you can eliminate the space required for the LM386 or other high power AF amplifier circuit.

The whole microphone amplifier section (including VOX) might be built inside the microphone instead of inside your miniature BITX chassis.

An IC socket on the rear panel might provide all the external connections. Use a IC-type header plug to make connections to the rig.

Hans' G0UPL has a "FAST H&P Design" <http://www.hanssummers.com/radio/huffpuff/minimalist/fast/> that incorporates both VFO and stabilizer into a two-chip layout. This makes the VFO rather compact and still includes step-locked tuning for very good stability. You can further decrease the size of Hans design by making the VFO tuning a PTO where a brass screw tunes the VFO/PTO and eliminates the need for a large pot to adjust the frequency.

Relay based T/R switching can be replaced with solid-state switching methods that are probably more compact than even miniature relay units. This will also conserve power by elimination of current required by the relay coil.

Arv K7HKL
_._

On Mon, 12 Sep 2005 08:32:40 -0600, Hans Summers <Hans.Summers@...> wrote:


I like that kind of challenge too, though I have yet to even finish my
conventionally sized BITX :-(

If you look in your component catalogues you will find very small
alternatives to large conventional items such as potentiometers. One example
is a kind of preset trimmer which has an 11 x 11mm footprint nd is 10mm
high. See Farnell part number 452853 or this link:
http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=452853 (I hope the
link works for you). Despite only being a trimmer potentiometer, is actually
has a tiny knob instead of just a screwdriver hole. The little knob can be
turned between thumb and finger, though obviously not as easily as a real
full size knob.

Other ideas:

The VFO course and fine tune could be replaced by a single multiturn
ultraminiature preset potentiometer, these come with a small protruding
metal shaft to take a flat-headed screwdriver. You can glue a small PCB disk
onto the shaft in order to turn it. This idea replaces the two separate
controls for course and fine tuning, but it does mean that you won't have
any idea where on the band you are tuned to. Unless you 1) count turns, 2)
miniature frequency counter such as
http://www.hanssummers.com/radio/sfreq/index.htm (could be made even smaller
using Surface Mount Devices) 3) meter the tuning voltage somehow.

You can get very tiny switches too, as well as other miniature components
for things like headphone sockets etc.

PCB: you can get board which has half the thickness of the usual stuff.
Might not sound like much difference, but volume consumed by the PCB is
wasted volume!

With "ugly" construction you can be VERY compact, provided you don't mind
double- or tripple-deckering your components!

73 Hans G0UPL

-----Original Message-----
From: Allison Parent [mailto:kb1gmx@...]
Sent: 11 September 2005 04:34
To: BITX20@...
Subject: [BITX20] Re: Altoids tin? go small???


Go for it, thats a real challenge.

I've put what amounts to the recieve side of a Bitx in a altoids tin. That
was easy, the knobs are always a problem. Seriously, the real problem was
keeping the BFO from swamping the RF amp from being so close. Shielding was
the required item to solve that. It's also
needed so that the Xtal filter can do it's work rather than blow by. I also
found SMT parts very handy.

The VFO is a problem. Heat, or rather heat transfer from other parts will
have to be attended to or the drift will be tough to manage. Any case flex
or the lid moving also caused frequency shifts. I
had enough heat from the audio too induce drift. You may wish to consider a
VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz). A
higher freq VXO will tune more.

You can use FT25-43 toroids or BN43-2402 binocular cores for the
transformers as they are small. The turns ratio is all you need for those as
8-10 turns will be enough. Consider using TUF1 DBMs as they are very small
and would save space over a core and diodes for the modulator and mixer.
You'll have to use shielded cans (maybe IF transformers rewound) for the
bandpass filter. The crystals used for the filter and BFO consider the hc49
size or smaller.

The transmit chain will have to scale back. The size of the parts and the
current they need to handle presesnts limits for thermal and
RF isolation with conventionally available parts. Running without the
IRF510 can get you about 300MW with a good transistor and the right output
match.

You will have to use electronic TR switching, space for relays is scarce.
Antenna, Mic and earphone jacks must be small too.

It can be done but a lot of care will me needed to render a useful radio.

Oh, I do have a larger Altoids tin it's nearly 3x the size
of the usual one. That would be easy.

Currently I'm building a BITx for 6M in a computer AB switch box measuring
of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy. the 5.25"x2" pannel
space is cramped for space to accomodate
tuning, audio gain, mic and headphone jacks and S meter.

Allison
KB1GMX

--- In BITX20@..., Jim Strohm <jstrohm@e...> wrote:

On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:

Unfortunately I do not get Altiods here in Lucknow so a rough
dimension will be helpful this looks like a neat challenge.

2.25 x 3.75 in.

Whoops, 5.7 x 9.5 cm

0.75 in deep (2 cm)





Yahoo! Groups Links








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Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

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--
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Re: Altoids tin? go small???

Rahul Srivastava
 

--- In BITX20@..., "Allison Parent" <kb1gmx@a...> wrote:
Hello,

One material I found years ago or chassis and finished boxes is
Aluminum extrusions in square or rectangular shape. I found some
peices 5ft long measuring 2.5"x5" and 3"x4". Very handy for
making
a box 2.5x5x7 or other lengths.

Hi!

Dont know how I missed on this one. I have made many SWR bridges in
these extrusions. Thanks will try squeezing one into it.

Plans are as follows:

Bi-directional amplifiers using 1/8w resistors and chip caps on
copper clad laminate.

Miniature Xtals.

7mm coils from defunt cordless phones.

Super VXO with switched xtals.

PA will be mounted to extrusion. Will still have to work on
isolation.

Some homebrewing for upcoming Pooja (Festival) Holidays.

73

Rahul VU3WJM

Re: Altoids tin? go small???

Allison Parent <kb1gmx@...>
 

Hello,

You've never seen my junkbox. I've been collecting and building for
over 40 years as a result it's a large collection. Materials like
tin plate, GI, Sheet copper, sheet brass, aluminum, and other forms
like bar, rod and tube are part of my stock of materials I keep for
building.

One material I found years ago or chassis and finished boxes is
Aluminum extrusions in square or rectangular shape. I found some
peices 5ft long measuring 2.5"x5" and 3"x4". Very handy for making
a box 2.5x5x7 or other lengths.

Old (US) CB radios are not only good for parts but the cases can be
rather nice.

I personally have built in Altoids tins but the box is more novelty
than useful. Most gear I've built tends to live long lives and gets
used in the field so strong cases are a good thing.

Allison
KB1GMX


--- In BITX20@..., Rahul Srivastava <vu3wjm@y...> wrote:
Hi!

Allison and others,

Practicaly the galvanised iron is simply known as GI sheet here. It
is very common in all sort of gauges as it is effectively used in
manufacture of Desert coolers in large scale.

It will not be dificult to have one bent in proportions of Altoid tin.

As far as salvage is concerned there are lot of feed thru to be
slavaged from defunt BW TV tuners.

73

Raahul VU3WJM

Allison Parent <kb1gmx@a...> wrote:
Hi,

Strips of PCB mounted edgewise was how I solved the space and
shielding problem. Still required some feedthrough caps to pass
DC and control voltages.

Allison
KB1GMX

--- In BITX20@..., Rahul Srivastava <vu3wjm@y...> wrote:
Hi!

Thanks for the tips and suggestion. Idea of Altoid tin reminds me of
the excellent Qptimised QRP transceiver. BITX though is full blown
design.

I would try assenbling stages on .7 inches pcb strips and secure
them verticaly ie just solder the bottom edge to box , extra peice
between stages can provide shielding.

PA I would like to redo somethind on the lines of ATS sprint , low
power and better efficiency.

Let me arrange a tin for now of this size.

73

Rahul VU3WJM

Allison Parent <kb1gmx@a...> wrote:
Go for it, thats a real challenge.

I've put what amounts to the recieve side of a Bitx in a altoids tin.
That was easy, the knobs are always a problem. Seriously, the real
problem was keeping the BFO from swamping the RF amp from being so
close. Shielding was the required item to solve that. It's also
needed so that the Xtal filter can do it's work rather than blow by.
I also found SMT parts very handy.

The VFO is a problem. Heat, or rather heat transfer from other parts
will have to be attended to or the drift will be tough to manage.
Any case flex or the lid moving also caused frequency shifts. I
had enough heat from the audio too induce drift. You may wish to
consider a VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz). A
higher freq VXO will tune more.

You can use FT25-43 toroids or BN43-2402 binocular cores for the
transformers as they are small. The turns ratio is all you need for
those as 8-10 turns will be enough. Consider using TUF1 DBMs as they
are very small and would save space over a core and diodes for the
modulator and mixer. You'll have to use shielded cans (maybe IF
transformers rewound) for the bandpass filter. The crystals
used for the filter and BFO consider the hc49 size or smaller.

The transmit chain will have to scale back. The size of the parts and
the current they need to handle presesnts limits for thermal and
RF isolation with conventionally available parts. Running without
the IRF510 can get you about 300MW with a good transistor and the
right output match.

You will have to use electronic TR switching, space for relays is
scarce. Antenna, Mic and earphone jacks must be small too.

It can be done but a lot of care will me needed to render a useful
radio.

Oh, I do have a larger Altoids tin it's nearly 3x the size
of the usual one. That would be easy.

Currently I'm building a BITx for 6M in a computer AB switch box
measuring of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy.
the 5.25"x2" pannel space is cramped for space to accomodate
tuning, audio gain, mic and headphone jacks and S meter.

Allison
KB1GMX

--- In BITX20@..., Jim Strohm <jstrohm@e...> wrote:

On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:

Unfortunately I do not get Altiods here in Lucknow so a rough
dimension will be helpful this looks like a neat challenge.

2.25 x 3.75 in.

Whoops, 5.7 x 9.5 cm

0.75 in deep (2 cm)



SPONSORED LINKS
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Ham radio store

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Re: Suggestions for group administration

Jim Strohm <jstrohm@...>
 

On Sep 11, 2005, at 12:19 PM, Rahul Srivastava wrote:

Bitx involves a lot of design implementation from grass root level and some unique ideas. There would be lot of queries. Be prepared for it.
Voice of experience from somebody who moderates a couple of electronics groups ... Rahul is right. You see 10 times the back- channel traffic sometimes. I'm not sure if Bill K0ZL is here to vouch for that, but he'll tell ya the same thing.

Jim N6OTQ

Re: Altoids tin? go small???

Rahul Srivastava
 

Hi!
 
Allison and others,
 
Practicaly the galvanised iron is simply known as GI sheet here. It is very common in all sort of gauges as it is effectively used in manufacture of Desert coolers in large scale.
 
It will not be dificult to have one bent in proportions of Altoid tin.
 
As far as salvage is concerned there are lot of feed thru to be slavaged from defunt BW TV tuners.
 
73
 
Raahul VU3WJM

Allison Parent wrote:
Hi,

Strips of PCB mounted edgewise was how I solved the space and
shielding problem.  Still required some feedthrough caps to pass
DC and control voltages.

Allison
KB1GMX

--- In BITX20@..., Rahul Srivastava wrote:
> Hi!

> Thanks for the tips and suggestion. Idea of Altoid tin reminds me of
the excellent Qptimised QRP transceiver. BITX though is full blown design.

> I would try assenbling stages on .7 inches pcb strips and secure
them verticaly ie just solder the bottom edge to box , extra peice
between stages can provide shielding.

> PA I would like to redo somethind on the lines of ATS sprint , low
power and better efficiency.

> Let me arrange a tin for now of this size.

> 73

> Rahul VU3WJM
>
> Allison Parent wrote:
> Go for it, thats a real challenge.
>
> I've put what amounts to the recieve side of a Bitx in a altoids tin.
> That was easy, the knobs are always a problem.  Seriously, the real
> problem was keeping the BFO from swamping the RF amp from being so
> close. Shielding was the required item to solve that.  It's also
> needed so that the Xtal filter can do it's work rather than blow by.
> I also found SMT parts very handy.
>
> The VFO is a problem. Heat, or rather heat transfer from other parts
> will have to be attended to or the drift will be tough to manage.
> Any case flex or the lid moving also caused frequency shifts. I
> had enough heat from the audio too induce drift. You may wish to
> consider a VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz).  A
> higher freq VXO will tune more.
>
> You can use FT25-43 toroids or BN43-2402 binocular cores for the
> transformers as they are small. The turns ratio is all you need for
> those as 8-10 turns will be enough. Consider using TUF1 DBMs as they
> are very small and would save space over a core and diodes for the
> modulator and mixer.  You'll have to use shielded cans (maybe IF
> transformers rewound) for the bandpass filter.  The crystals
> used for the filter and BFO consider the hc49 size or smaller.
>
> The transmit chain will have to scale back. The size of the parts and
> the current they need to handle presesnts limits for thermal and
> RF isolation with conventionally available parts.  Running without
> the IRF510 can get you about 300MW with a good transistor and the
> right output match.
>
> You will have to use electronic TR switching, space for relays is
> scarce.  Antenna, Mic and earphone jacks must be small too.
>
> It can be done but a lot of care will me needed to render a useful
> radio.
>
> Oh, I do have a larger Altoids tin it's nearly 3x the size
> of the usual one.  That would be easy.
>
> Currently I'm building a BITx for 6M in a computer AB switch box
> measuring of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy.
> the 5.25"x2" pannel space is cramped for space to accomodate
> tuning, audio gain, mic and headphone jacks and S meter.
>
> Allison
> KB1GMX
>
> --- In BITX20@..., Jim Strohm wrote:
> >
> > On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:
> >
> > > Unfortunately I do not get Altiods here in Lucknow so a rough 
> > > dimension will be helpful this looks like a neat challenge.
> > >
> >
> >
> > 2.25 x 3.75 in.
> >
> > Whoops, 5.7 x 9.5 cm
> >
> > 0.75 in deep (2 cm)
>
>
>
>
> SPONSORED LINKS
> Ham radio antenna Ham radio Ham radio sales Asian tsunami disaster
Ham radio store
>
> ---------------------------------
> YAHOO! GROUPS LINKS
>
>
>     Visit your group "BITX20" on the web.
>  
>     To unsubscribe from this group, send an email to:
>  BITX20-unsubscribe@...
>  
>     Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.
>
>
> ---------------------------------
>
>
>
>            
> ---------------------------------
> To help you stay safe and secure online, we've developed the all new
Yahoo! Security Centre.




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Re: Suggestions for group administration

Rahul Srivastava
 

Hi!
 
Bitx involves a lot of design implementation from grass root level and some unique ideas. There would be lot of queries. Be prepared for it.
 
73
 
Rahul VU3WJM
 
 
 
 
 

Arv Evans K7HKL wrote:
Farhan

I do not mind helping with admin duties if needed.
From work on other forum groups, it seems that admin activities mostly 
involve the verification and authorization of new members (and very 
infrequently the removal of a spammer).  That I can handle, but the 
acknowledged technical expert will still be Farhan VU3ICQ.

Opening the forum up for read-only access by non-members might increase 
the number of lurkers, but it may also stimulate some of them to join the 
group so they can insert their comments.  Allowing Read-only access will 
also allow hams with web sites to include links to the BITX20 forum and 
thus drive more interest to our group.

It is interesting to see the different directions that the BITX has taken:
   1) Other bands than the original 20 Meters.
   2) Band-switched models.
   3) Transverter versions
   4) VHF versions of the BITX.
   5) Very compact designs (i.e. Altoids box chassis).
   6) Digital VFOs, VXOs, PTOs, Huff & Puff VFOs, etc.
   7) QRPP to QRO models.
   8) SSB plus CW, plus PSK/MSK, etc.
   9) both ugly construction and PCB based layouts.
  10) and all the circuit improvements(?) to the original design.

It will be very interesting to follow the future evolution of this fun 
radio.  We owe a lot to Farhan for starting this project and for making 
the design available to the rest of us.  Thanks O.M.

Arv K7HKL
_._

On Sat, 10 Sep 2005 22:44:47 -0600, Ashhar Farhan  
wrote:

>
> i have a couple of suggestions for administeration of this group.
> at the moment, hans (the silent lurker, the original bitx procastinator,
> the real-soon-now soldering iron maniac) and i 'manage' the group. our
> work: we okay every membership application. that apart, there are no
> resitrctions on postings, file uploads etc.
>
> however, our group policy is that casual surfers cannot see what we are
> upto unless they become members. i am proposing that we allow 'read-only'
> access to non-members. the good part is that we will be able to attract
> many more builders who land up on our site while surfing. the bad part
> will be that many may choose not to be members as they can get 
> information
> to get byfrom the group without signing up, so we will lose count of how
> many eye-balls we have (as if that matters).
>
> i also propose to add arv as an admin of the group (arv, i know, i didnt
> ask your permission on this one. hehe).
>
> comments?
>
> - farhan
>
>
> SPONSORED LINKS
> Ham radio antenna  Ham radio  Ham radio sales
> Asian tsunami disaster  Ham radio store
>
> YAHOO! GROUPS LINKS
>
> Visit your group "BITX20" on the web.
>
> To unsubscribe from this group, send an email to:
> BITX20-unsubscribe@...
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
>
>



--
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Re: Suggestions for group administration

Hans Summers <Hans.Summers@...>
 

I support this change Farhan, I think it's a good idea. I also welcome the
OM Arv on board as moderator!

In case members are worried: I believe that non-members who are reading the
postings cannot view email addresses. Therefore making this change should
not put posting members at risk of spam.

My BIX20 still languishes in a state of 95% completion; but it competes with
many other radio projects, and almost non-existent radio hobby time right
now :-(

73 Hans G0UPL
http://www.HansSummers.com

-----Original Message-----
From: Ashhar Farhan [mailto:farhan@...]
Sent: 11 September 2005 05:45
To: BITX20@...
Subject: [BITX20] Suggestions for group administration



i have a couple of suggestions for administeration of this group. at the
moment, hans (the silent lurker, the original bitx procastinator,
the real-soon-now soldering iron maniac) and i 'manage' the group. our
work: we okay every membership application. that apart, there are no
resitrctions on postings, file uploads etc.

however, our group policy is that casual surfers cannot see what we are
upto unless they become members. i am proposing that we allow 'read-only'
access to non-members. the good part is that we will be able to attract
many more builders who land up on our site while surfing. the bad part
will be that many may choose not to be members as they can get information
to get byfrom the group without signing up, so we will lose count of how
many eye-balls we have (as if that matters).

i also propose to add arv as an admin of the group (arv, i know, i didnt
ask your permission on this one. hehe).

comments?

- farhan




Yahoo! Groups Links

Re: Suggestions for group administration

Mike W <mike@...>
 

On 11 Sep 2005 at 2:23, Arv Evans K7HKL wrote:

Opening the forum up for read-only access by non-members might increase
the number of lurkers, but it may also stimulate some of them to join the
group so they can insert their comments. Allowing Read-only access will also
allow hams with web sites to include links to the BITX20 forum and thus drive
more interest to our group
Pro's and Con's. If It were up to me I would at least give 'read-only' access
a trial, assuming that it can be revoked should it be necessary.
JMO, Mike G8NXD
--

Re: Altoids tin? go small???

Allison Parent <kb1gmx@...>
 

Hi,

Strips of PCB mounted edgewise was how I solved the space and
shielding problem. Still required some feedthrough caps to pass
DC and control voltages.

Allison
KB1GMX

--- In BITX20@..., Rahul Srivastava <vu3wjm@y...> wrote:
Hi!

Thanks for the tips and suggestion. Idea of Altoid tin reminds me of
the excellent Qptimised QRP transceiver. BITX though is full blown design.

I would try assenbling stages on .7 inches pcb strips and secure
them verticaly ie just solder the bottom edge to box , extra peice
between stages can provide shielding.

PA I would like to redo somethind on the lines of ATS sprint , low
power and better efficiency.

Let me arrange a tin for now of this size.

73

Rahul VU3WJM

Allison Parent <kb1gmx@a...> wrote:
Go for it, thats a real challenge.

I've put what amounts to the recieve side of a Bitx in a altoids tin.
That was easy, the knobs are always a problem. Seriously, the real
problem was keeping the BFO from swamping the RF amp from being so
close. Shielding was the required item to solve that. It's also
needed so that the Xtal filter can do it's work rather than blow by.
I also found SMT parts very handy.

The VFO is a problem. Heat, or rather heat transfer from other parts
will have to be attended to or the drift will be tough to manage.
Any case flex or the lid moving also caused frequency shifts. I
had enough heat from the audio too induce drift. You may wish to
consider a VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz). A
higher freq VXO will tune more.

You can use FT25-43 toroids or BN43-2402 binocular cores for the
transformers as they are small. The turns ratio is all you need for
those as 8-10 turns will be enough. Consider using TUF1 DBMs as they
are very small and would save space over a core and diodes for the
modulator and mixer. You'll have to use shielded cans (maybe IF
transformers rewound) for the bandpass filter. The crystals
used for the filter and BFO consider the hc49 size or smaller.

The transmit chain will have to scale back. The size of the parts and
the current they need to handle presesnts limits for thermal and
RF isolation with conventionally available parts. Running without
the IRF510 can get you about 300MW with a good transistor and the
right output match.

You will have to use electronic TR switching, space for relays is
scarce. Antenna, Mic and earphone jacks must be small too.

It can be done but a lot of care will me needed to render a useful
radio.

Oh, I do have a larger Altoids tin it's nearly 3x the size
of the usual one. That would be easy.

Currently I'm building a BITx for 6M in a computer AB switch box
measuring of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy.
the 5.25"x2" pannel space is cramped for space to accomodate
tuning, audio gain, mic and headphone jacks and S meter.

Allison
KB1GMX

--- In BITX20@..., Jim Strohm <jstrohm@e...> wrote:

On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:

Unfortunately I do not get Altiods here in Lucknow so a rough
dimension will be helpful this looks like a neat challenge.

2.25 x 3.75 in.

Whoops, 5.7 x 9.5 cm

0.75 in deep (2 cm)



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Re: Altoids tin? go small???

Arv Evans K7HKL <arvevans@...>
 

FYI

Here is an idea that Hans G0UPL and myself have been discussing on another forum:

Thin galvanized iron sheet used for roof flashing may be available in your local DIY (Do It Yourself) hardware store. This material takes solder quite readily and is usually less expensive than PCB stock. It has an added advantage over PCB material in that being iron it also provides magnetic sheilding, where the PCB just blocks electro-static radiation.

Roof flashing material is a bit flexible, but that may be an advantage because it can be bent into chassis and sheilding sections without special tools. Now you can build your own custom Altoids Tins!

Arv K7HKL
_._

On Sun, 11 Sep 2005 07:37:03 -0600, Allison Parent <kb1gmx@...> wrote:

Hi,

Strips of PCB mounted edgewise was how I solved the space and
shielding problem. Still required some feedthrough caps to pass
DC and control voltages.

Allison
KB1GMX

--- In BITX20@..., Rahul Srivastava <vu3wjm@y...> wrote:
Hi!

Thanks for the tips and suggestion. Idea of Altoid tin reminds me of
the excellent Qptimised QRP transceiver. BITX though is full blown design.

I would try assenbling stages on .7 inches pcb strips and secure
them verticaly ie just solder the bottom edge to box , extra peice
between stages can provide shielding.

PA I would like to redo somethind on the lines of ATS sprint , low
power and better efficiency.

Let me arrange a tin for now of this size.

73

Rahul VU3WJM

Allison Parent <kb1gmx@a...> wrote:
Go for it, thats a real challenge.

I've put what amounts to the recieve side of a Bitx in a altoids tin.
That was easy, the knobs are always a problem. Seriously, the real
problem was keeping the BFO from swamping the RF amp from being so
close. Shielding was the required item to solve that. It's also
needed so that the Xtal filter can do it's work rather than blow by.
I also found SMT parts very handy.

The VFO is a problem. Heat, or rather heat transfer from other parts
will have to be attended to or the drift will be tough to manage.
Any case flex or the lid moving also caused frequency shifts. I
had enough heat from the audio too induce drift. You may wish to
consider a VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz). A
higher freq VXO will tune more.

You can use FT25-43 toroids or BN43-2402 binocular cores for the
transformers as they are small. The turns ratio is all you need for
those as 8-10 turns will be enough. Consider using TUF1 DBMs as they
are very small and would save space over a core and diodes for the
modulator and mixer. You'll have to use shielded cans (maybe IF
transformers rewound) for the bandpass filter. The crystals
used for the filter and BFO consider the hc49 size or smaller.

The transmit chain will have to scale back. The size of the parts and
the current they need to handle presesnts limits for thermal and
RF isolation with conventionally available parts. Running without
the IRF510 can get you about 300MW with a good transistor and the
right output match.

You will have to use electronic TR switching, space for relays is
scarce. Antenna, Mic and earphone jacks must be small too.

It can be done but a lot of care will me needed to render a useful
radio.

Oh, I do have a larger Altoids tin it's nearly 3x the size
of the usual one. That would be easy.

Currently I'm building a BITx for 6M in a computer AB switch box
measuring of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy.
the 5.25"x2" pannel space is cramped for space to accomodate
tuning, audio gain, mic and headphone jacks and S meter.

Allison
KB1GMX

--- In BITX20@..., Jim Strohm <jstrohm@e...> wrote:

On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:

Unfortunately I do not get Altiods here in Lucknow so a rough
dimension will be helpful this looks like a neat challenge.

2.25 x 3.75 in.

Whoops, 5.7 x 9.5 cm

0.75 in deep (2 cm)



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Ham radio store

---------------------------------
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Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.


---------------------------------




---------------------------------
To help you stay safe and secure online, we've developed the all new
Yahoo! Security Centre.




YAHOO! GROUPS LINKS

Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

--
Life is too short to be serious. 8-)

Re: Suggestions for group administration

Arv Evans K7HKL <arvevans@...>
 

Farhan

I do not mind helping with admin duties if needed.
From work on other forum groups, it seems that admin activities mostly involve the verification and authorization of new members (and very infrequently the removal of a spammer). That I can handle, but the acknowledged technical expert will still be Farhan VU3ICQ.

Opening the forum up for read-only access by non-members might increase the number of lurkers, but it may also stimulate some of them to join the group so they can insert their comments. Allowing Read-only access will also allow hams with web sites to include links to the BITX20 forum and thus drive more interest to our group.

It is interesting to see the different directions that the BITX has taken:
1) Other bands than the original 20 Meters.
2) Band-switched models.
3) Transverter versions
4) VHF versions of the BITX.
5) Very compact designs (i.e. Altoids box chassis).
6) Digital VFOs, VXOs, PTOs, Huff & Puff VFOs, etc.
7) QRPP to QRO models.
8) SSB plus CW, plus PSK/MSK, etc.
9) both ugly construction and PCB based layouts.
10) and all the circuit improvements(?) to the original design.

It will be very interesting to follow the future evolution of this fun radio. We owe a lot to Farhan for starting this project and for making the design available to the rest of us. Thanks O.M.

Arv K7HKL
_._

On Sat, 10 Sep 2005 22:44:47 -0600, Ashhar Farhan <farhan@...> wrote:


i have a couple of suggestions for administeration of this group.
at the moment, hans (the silent lurker, the original bitx procastinator,
the real-soon-now soldering iron maniac) and i 'manage' the group. our
work: we okay every membership application. that apart, there are no
resitrctions on postings, file uploads etc.

however, our group policy is that casual surfers cannot see what we are
upto unless they become members. i am proposing that we allow 'read-only'
access to non-members. the good part is that we will be able to attract
many more builders who land up on our site while surfing. the bad part
will be that many may choose not to be members as they can get information
to get byfrom the group without signing up, so we will lose count of how
many eye-balls we have (as if that matters).

i also propose to add arv as an admin of the group (arv, i know, i didnt
ask your permission on this one. hehe).

comments?

- farhan


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YAHOO! GROUPS LINKS

Visit your group "BITX20" on the web.

To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

--
Life is too short to be serious. 8-)

Suggestions for group administration

Ashhar Farhan <farhan@...>
 

i have a couple of suggestions for administeration of this group.
at the moment, hans (the silent lurker, the original bitx procastinator, the real-soon-now soldering iron maniac) and i 'manage' the group. our work: we okay every membership application. that apart, there are no resitrctions on postings, file uploads etc.

however, our group policy is that casual surfers cannot see what we are upto unless they become members. i am proposing that we allow 'read-only' access to non-members. the good part is that we will be able to attract many more builders who land up on our site while surfing. the bad part will be that many may choose not to be members as they can get information to get byfrom the group without signing up, so we will lose count of how many eye-balls we have (as if that matters).

i also propose to add arv as an admin of the group (arv, i know, i didnt ask your permission on this one. hehe).

comments?

- farhan

Re: 13 trifilar turns

Ashhar Farhan <farhan@...>
 

these are broad-band transformers. their inductance not very critical at all. as long as you have about 200 ohms reactance at the lowest frequency of operation (which is 4MHz: the VFO, in this case).

i have made transformers with 10 as well as 25 turns. they worked as well.
The problem with too many turns will be that the stray capacitances between successive turns of the wires will lead to self-resonance somewhere in HF range and lead to bad karma (narrow-band operation). This is the reason why i didnt use the infamous tap-washers for broad-band work.

Interestingly, the PA output transformer is not on TV balun. this is because the stray capacitances across it's windings become a part of the half-wave filter that follows the output transformer (a trick i saw on a VHF boot in 1974 Handbook).

Let me suggest an experiment to determine when turns are enough.
Wire up a transformer with ten turns in the primary and ten in teh secondry.

Next, take a signal source (like a crystal oscillator) with a 50 ohms ouput (just add a 6 db pad to the output of the oscillator). and measure the output with a 50 ohm resistor connected to it.

Next, instead of the 50 ohms resistor, connect one side of the primary and connect the 50 ohms resistor on the secondary side. Measure if you have about the same amount of RF energy on the other side too.

If you have, then 10 turns are enough. If the output is low, add more turns. If the output is higher with steep peaks ('ringing') then maybe the turns are too many and you can do with less.

Central to our endeavours is that we (amateurs) progress not through theoretical designing but experimental verification and rough and ready measurements. design of these transformers is a case in point.

- farhan

On Sat, 10 Sep 2005, Jim Strohm wrote:

Was this turns count number determined experimentally,
calculationally, by cut-and-try, or by "that's how many fit"?

Just wondering ... I found some tiny tiny binocular cores.

Jim N6OTQ




Yahoo! Groups Links





Re: Altoids tin? go small???

Rahul Srivastava
 

Hi!
 
Thanks for the tips and suggestion. Idea of Altoid tin reminds me of the excellent Qptimised QRP transceiver. BITX though is full blown design.
 
I would try assenbling stages on .7 inches pcb strips and secure them verticaly ie just solder the bottom edge to box , extra peice between stages can provide shielding.
 
PA I would like to redo somethind on the lines of ATS sprint , low power and better efficiency.
 
Let me arrange a tin for now of this size.
 
73
 
Rahul VU3WJM

Allison Parent wrote:
Go for it, thats a real challenge.

I've put what amounts to the recieve side of a Bitx in a altoids tin.
That was easy, the knobs are always a problem.  Seriously, the real
problem was keeping the BFO from swamping the RF amp from being so
close. Shielding was the required item to solve that.  It's also
needed so that the Xtal filter can do it's work rather than blow by.
I also found SMT parts very handy.

The VFO is a problem. Heat, or rather heat transfer from other parts
will have to be attended to or the drift will be tough to manage.
Any case flex or the lid moving also caused frequency shifts. I
had enough heat from the audio too induce drift. You may wish to
consider a VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz).  A
higher freq VXO will tune more.

You can use FT25-43 toroids or BN43-2402 binocular cores for the
transformers as they are small. The turns ratio is all you need for
those as 8-10 turns will be enough. Consider using TUF1 DBMs as they
are very small and would save space over a core and diodes for the
modulator and mixer.  You'll have to use shielded cans (maybe IF
transformers rewound) for the bandpass filter.  The crystals
used for the filter and BFO consider the hc49 size or smaller.

The transmit chain will have to scale back. The size of the parts and
the current they need to handle presesnts limits for thermal and
RF isolation with conventionally available parts.  Running without
the IRF510 can get you about 300MW with a good transistor and the
right output match.

You will have to use electronic TR switching, space for relays is
scarce.  Antenna, Mic and earphone jacks must be small too.

It can be done but a lot of care will me needed to render a useful
radio.

Oh, I do have a larger Altoids tin it's nearly 3x the size
of the usual one.  That would be easy.

Currently I'm building a BITx for 6M in a computer AB switch box
measuring of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy.
the 5.25"x2" pannel space is cramped for space to accomodate
tuning, audio gain, mic and headphone jacks and S meter.

Allison
KB1GMX

--- In BITX20@..., Jim Strohm wrote:
>
> On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:
>
> > Unfortunately I do not get Altiods here in Lucknow so a rough 
> > dimension will be helpful this looks like a neat challenge.
> >
>
>
> 2.25 x 3.75 in.
>
> Whoops, 5.7 x 9.5 cm
>
> 0.75 in deep (2 cm)



To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre.

Re: BITX in Texas

Allison Parent <kb1gmx@...>
 

Hello,

Some comments inserted in line.

--- In BITX20@..., "Dave WardenDurkee" <dwarden2@c...> wrote:

Hi Jim,
I live in Leander, Texas.
I've built one BITX 20 (20 Meter band) so far using all through hole
parts.
I used a PCB and I never finished the transmitter because of a spur
in the output that is at 12Mhz.
One of the things to watch for is tuning to the third harmonic of the
VFO or the mixer having bad balance(excessive VFO feedthrough). Insure
the bandpass filter is really tuned to 14mhz as it's easy to tune
low and get excessive 12mhz output. I found making the Mixer doubly
balanced and matching the diodes for forward voltage at 2ma gave
improvement. Also watch the L-C ratio of the bandpass filter if you
deveate from the published values excessively the filter will have
very wide skirts and the output will have too much 12mhz and possibly
10mhz. Like all filters layout is important.

Allison
KB1GMX



I redesigned some of the circuits and a new PCB using about half surface
mount parts. I hope to get a cleaner signal with my second BITX.

How far are you into building the BITX?

Dave

Re: Altoids tin? go small???

Allison Parent <kb1gmx@...>
 

Go for it, thats a real challenge.

I've put what amounts to the recieve side of a Bitx in a altoids tin.
That was easy, the knobs are always a problem. Seriously, the real
problem was keeping the BFO from swamping the RF amp from being so
close. Shielding was the required item to solve that. It's also
needed so that the Xtal filter can do it's work rather than blow by.
I also found SMT parts very handy.

The VFO is a problem. Heat, or rather heat transfer from other parts
will have to be attended to or the drift will be tough to manage.
Any case flex or the lid moving also caused frequency shifts. I
had enough heat from the audio too induce drift. You may wish to
consider a VXO at 24mhz (20m, IF at 10mhz and LO at 24mhz). A
higher freq VXO will tune more.

You can use FT25-43 toroids or BN43-2402 binocular cores for the
transformers as they are small. The turns ratio is all you need for
those as 8-10 turns will be enough. Consider using TUF1 DBMs as they
are very small and would save space over a core and diodes for the
modulator and mixer. You'll have to use shielded cans (maybe IF
transformers rewound) for the bandpass filter. The crystals
used for the filter and BFO consider the hc49 size or smaller.

The transmit chain will have to scale back. The size of the parts and
the current they need to handle presesnts limits for thermal and
RF isolation with conventionally available parts. Running without
the IRF510 can get you about 300MW with a good transistor and the
right output match.

You will have to use electronic TR switching, space for relays is
scarce. Antenna, Mic and earphone jacks must be small too.

It can be done but a lot of care will me needed to render a useful
radio.

Oh, I do have a larger Altoids tin it's nearly 3x the size
of the usual one. That would be easy.

Currently I'm building a BITx for 6M in a computer AB switch box
measuring of 7.25"Dx5.25"Wx2"H and I'm finding that fairly roomy.
the 5.25"x2" pannel space is cramped for space to accomodate
tuning, audio gain, mic and headphone jacks and S meter.

Allison
KB1GMX

--- In BITX20@..., Jim Strohm <jstrohm@e...> wrote:

On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:

Unfortunately I do not get Altiods here in Lucknow so a rough
dimension will be helpful this looks like a neat challenge.

2.25 x 3.75 in.

Whoops, 5.7 x 9.5 cm

0.75 in deep (2 cm)

BITX in Texas

Dave WardenDurkee <dwarden2@...>
 

Hi Jim,
I live in Leander, Texas.
I've built one BITX 20 (20 Meter band) so far using all through hole parts.
I used a PCB and I never finished the transmitter because of a spur in the
output that is at 12Mhz.

I redesigned some of the circuits and a new PCB using about half surface
mount parts. I hope to get a cleaner signal with my second BITX.

How far are you into building the BITX?

Dave

13 trifilar turns

Jim Strohm <jstrohm@...>
 

Was this turns count number determined experimentally, calculationally, by cut-and-try, or by "that's how many fit"?

Just wondering ... I found some tiny tiny binocular cores.

Jim N6OTQ

Re: Altoids tin? go small???

Jim Strohm <jstrohm@...>
 

On Sep 10, 2005, at 1:37 PM, Rahul Srivastava wrote:

Unfortunately I do not get Altiods here in Lucknow so a rough dimension will be helpful this looks like a neat challenge.

2.25 x 3.75 in.

Whoops, 5.7 x 9.5 cm

0.75 in deep (2 cm)