Date   
Re: BITX20 Photos

Arv Evans <arvevans@...>
 

Pete

Congratulations on the very good looking BITX20 transceiver.  That LCD display is a good
addition.

Arv K7HKL
_._
On Sat, 2004-10-02 at 05:25, vdberghak wrote:
Looks good Pete!
First I searched in your directory but I found them in the main
directory.
Indeed building the circuit in some kind of box is may be the
hardest part.
I am still thinking about the best construction to make the dial
knob on the capacitor... ;-(
Best regards,
Chris.

--- In BITX20@..., "kaliediscope2004"
wrote:
> Greetings fellow BITX20 Builders. I have just uploaded some photos
> of my BITX20 in the newly completed homebrew enclosure. Still need
> to add the sides and top but the hard part is mostly done.
>
> This is one FB radio and I have had many enjoyable QSO's with the
> little radio. Am looking forward to a possible 2X QSO with another
> BITX20.
>
> 73's
> Pete W6JFR


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  • LED Frequency Display

    Mike W <mike@...>
     

    Hi folks,
    I don't know if this will interest anyone. But I have just obtained a
    fairly large quantity of minature multiplexed 7 segment LED displays.
    They have 7 numeric characters and 7 'S' meter, like leds in a
    bargraph. and fit into a standard 28 pin DIL socket.

    They would be ideal for use with an OM3CPH PIC frequency display for
    the BITX

    see picture at
    http:&#92;www.qsl.net&#92;g8nxd&#92;files&#92;LEDS.gif

    I'm a little unsure about what they are worth but if anyone would
    like one for 1.00 UKP plus postage to anywhere on Earth.
    Then please give me a shout off list.

    My BITX20 is still not finished but it will be soon. Congrats to all
    builders who have finished theirs. I hope to work you on 20m soon

    72/73 de Mike W, G8NXD qthr

    Re: Extra capacitors in your BITX...?

    Rahul Srivastava
     

    Hi!
     
    Arv,
     
    This area is indeed a new ball game all to gether.But it indeed represents a some new concepts. I hope we can have a ckt consistant with the general available components. I would be only too glad to make a board based on that for my friends.
     
    TNX once again for adding fuel to the hombrew fire. 
     
    73
     
    Rahul VU3WJM
     
     
     
     


    Arvid Evans wrote:
    Dear Rahul

    Thank you for the information on RU area transceivers.  It will take a
    while to translate and understand all this, but it is very interesting
    reading.

    Thanks,
    Arv K7HKL
    _._

    --- In BITX20@..., Rahul Srivastava wrote:
    > Dear Hans and Arv

    > Hi!

    > It is indeed pleasure to see some interest in ones post. I find this
    as a case of history repeating itself. Similar on the line of two
    different concept that evolved during development of a space suit one
    a 7 layered design and other in RU teritories almirah door type ones.

    > Hams I see you did some serious work on the hammer/ screwdriver page
    ( This is what i comprehend from the icon). At times it appeared funny
    to see something translated like the administration is done by change
    it pressure. Ultimately it boiled down to to freq control is manged by
    change in voltage, a description of PLL sections.

    > A brief lineup of RU designs would be in order for RU TRXs, UW3DI,
    Ural84, Desna, Don-M and many others with some peculiar characters.

    > Now on the topic there are another few page of these region that
    also need some looking into for hombrew projects:

    > http://ra3ggi.qrz.ru/

    > and yet another

    > http://www.qsl.net/sp3abg/index.html

    > Hope all enjoy.

    > 73

    > Rahul VU3WJM

    >
    > Hans Summers wrote:

    > BITX'ers

    > Note that if you want to see an English translation, you could try
    the Altavista "babel fish" see
    http://babelfish.altavista.com/babelfish/tr. You can type in the web
    page, and view the translated web page. It's rather neat. The
    translation is obviously not perfect but it's quite easy to follow the
    ideas. If you look at the home page http://www.cqham.ru/index.phtml
    you'll find all kind of gems. Numerous transceiver projects etc. Also
    many downloaded QST articles, and more. There is an English flag on
    the home page which provides a translation, but it does not work as
    well as the Altavista page.

    > 73 Hans G0UPL
    > http://www.HansSummers.com
    >
    > -----Original Message-----
    > From: Rahul Srivastava [mailto:vu3wjm@y...]
    > Sent: 01 October 2004 06:57
    > To: BITX20@...
    > Subject: Re: [BITX20] Extra capacitors in your BITX...?
    >
    >
    > Dear Arv,

    > From what I could make out of mechanical translations, the concept
    among RU friends was popularised with Ural 84 design. Desna was the
    more updated version probably it means dew.

    > the RU page for Desna design is here:

    > http://www.cqham.ru/desna.htm

    > The main board ckt I am posting under files section for thers to
    have a look at another way of implimenting Bi-directional concept.

    > 73

    > Rahul VU3WJM



    >
    >
    > Arv Evans wrote:
    > Rahul-VU3WJM
    >
    > I did a search (using Google) for :Ural 84" and for "Desna" and did
    find some textual mention of these units, but I did not find any web
    sites that showed equipment or schematics.  Do you have a URL that we
    might use to see schematics for this equipment?
    >
    > Thanks,
    > Arv-K7HKL
    > _._
    >
    > On Wed, 2004-09-29 at 22:17, Rahul Srivastava wrote: Hi!

    > On mention of PSK mini I also suggest looking at RU designs Ural 84
    and Desna. Similar concepts are used there while using bipolar
    transistors.

    > I am sure the coupling caps for filters can be removed.  Had I been
    and audiophile  I would  like not to have even one of them in signal path.

    > 73

    > Rahul VU3WJM


    >
    > Arvid Evans wrote: Hello
    >
    > As I sit here looking at the BITX20 schematic it 0ccured to me that
    > some of the capacitors may not be necessary:
    >
    >   1)  There is a 0.1 mf on the base of Q1, that connects to a 0.1 on
    > the collector of Q13.  These then connect via a 10 pf to the front-end
    > bandpass filter.  Would it not be acceptable to use only one 0.1 mf
    > between the collector of Q13 and the Base of Q1, and connect the base
    > of Q1 to the bandpass filter via the 10 pf cap?
    >
    >   2)  There is a 0.1 mf on the collector of Q2 that connects to the
    > crystal filter, and another 0.1 that connects the base of Q12 to the
    > same point on the crystal filter.  Would it be sufficient to use just
    > the 0.1 mf from the collector of Q2 to the crystal filter, and then
    > connect the base of Q12 directly to the same point on that filter?
    > Since crystals do not pass DC, the same amount of DC isolation would
    > be maintained.
    >
    >   3)  There is a 0.1 mf between the end of the crystal filter and the
    > base of Q3, and another 0.1 mf between that same point on the crystal
    > filter and the collector of Q11.  It seems that it would suffice to
    > have the 0.1 mf between the collector of Q11 and the base of Q3, with
    > the crystal filter simply connected to the base of Q3.  Again, the
    > crystal does not conduct DC, so there would still be the same level of
    > DC isolation.
    >
    > OK, for all you purists out there, I know that it looks more
    > symetrical with the "pairs of 0.1 mf capacitors", but are they really
    > necessary?
    >
    > What spawned this evaluation is my comparison of RV3GM's PSK-20
    > schematic with the BITX20 design by Farhan.  I was wondering if Oleg's
    > method of using one transister in bi-directional mode could also be
    > applied to the BITX20 where we are using pairs of transisters to
    > obtain bi-directionality. 
    >
    > Arv-K7HKL
    > _._
    >
    >
    >
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    request regarding asoc examination.

    fromgautam <fromgautam@...>
     

    Respected sir,
    With due respect I beg to say that I am preparing for ASOC grade-1
    and advance grade examination. Recently I was appeared in ASOC grade-
    1 and grade-2 examination, which was held on 08/09/04 in begusarai,
    bihar. I think that I should cleared grade-2 exam. I have following
    books for preparing of examination. These are as follows:-
    1. ABC of amateur Radio by Sri rajesh verma (vu2rvm) by EFY
    2. A guide to Ham Radio by Sri sandeep baruah(vu2mue ex. Vu2msy)
    by Vigyan Prasar.
    3. Scanning the world with amateur radio by Sri sandeep baruah
    (vu2mue ex. Vu2msy) by Etherial whisper group.
    4. Ham radio by prof. A.Ponnusamy(vu2aps) and Sri P.Parthiban
    (vu2ppb) by Bright Publishers.
    5. Guide to Amateur Radio in India by Sri Saad Ali (vu2st).
    6. Amateur radio made easy by Sri Manotosh Das Gupta (vu2mdg) by
    Calcutta vhf amateur radio society.

    After viewing the latest question paper of grade-1 and Advance grade
    examination I concluded that above mentioned books are not sufficient
    for part-1(Radio theory & practice) of grade-1 and advance grade
    examination.

    The latest pattern of question paper is such type that , they(WPC)
    wants that examinee knows all the electronics theory of graduate
    level and this examination is not for amateur enthusiast.
    I therefore request all of you kindly suggest me appropriate books
    for grade-1 and advance grade(satellite communication) as early as
    possible because my next examination will be tentatively held on
    feb.2005

    Thanks,
    With 73's
    De kumar gautam
    Qth :-
    S/o Sri girish chandra choudhary,
    Mohalla – Mishratola,
    P.O. + Distt.- Darbhanga,
    Bihar-846004
    E-mail :- fromgautam@...

    LED Display - More Info

    Mike W <mike@...>
     

    Hi folks,

    A little further info on the LED display I have available.

    Common Kathode .
    Size 36mm x 20mm
    7 Multiplexed numeric characters
    7 _NON _ multiplexed leds in a bargraph.

    They are ideal for use with an OM3CPH PIC frequency display. I know
    as I built one last night !. On Veroboard ( stripboard ) I managed to
    get the size down to the front area of the Display and 1/2" depth
    behind. The PIC clock can be taken direct from the CIO osc ,
    therefore eliminating any chances of mixing of PIC and other
    oscillators. Resolution to 10Hz

    see the available data that I have made available at..

    http:&#92;www.qsl.net&#92;g8nxd&#92;files&#92;ledconn.pdf

    At 1.00 UKP each plus postage costs to anywhere on Earth. They are
    going very quickly ( I have about 30 left ). I really must keep a few
    for myself !

    72/73 de Mike W, G8NXD qthr

    Re: LED Display - More Info

    Charles Darley
     

    Hi all

    Mike data is on http://www.qsl.net/g8nxd/files/ledconn.pdf

    Regards Charles G4VSZ

     

    -----Original Message-----
    From: Mike W [mailto:mike@...]
    Sent: 04 October 2004 11:16
    To: BITX20@...
    Subject: [BITX20] LED Display - More Info

    Hi folks,

    A little further info on  the LED display I have available.

    Common Kathode .
    Size 36mm x 20mm
    7 Multiplexed numeric characters
    7 _NON _ multiplexed leds in a bargraph.

    They are ideal for use with an OM3CPH PIC frequency display. I know
    as I built one last night !. On Veroboard ( stripboard ) I managed to
    get the size down to the front area of the Display and 1/2" depth
    behind. The PIC clock can be taken direct from the CIO osc ,
    therefore eliminating any chances of mixing of PIC and other
    oscillators. Resolution to 10Hz

    see the available data that I have made available at..

    http:\www.qsl.net\g8nxd\files\ledconn.pdf

    At 1.00 UKP each plus postage costs to anywhere on Earth. They are
    going very quickly ( I have about 30 left ). I really must keep a few
    for myself !

    72/73 de Mike W, G8NXD qthr


    Re: LED Display - More Info

    Hans Summers <Hans.Summers@...>
     

    Hi Mike

    I can't immediately think of an appropriate application and I tried all
    morning to resist your offer, but I have failed! I would like one to play
    with please, if there are any left ;-) What's the UK postage come to?

    73 Hans G0UPL

    -----Original Message-----
    From: Mike W [mailto:mike@...]
    Sent: 04 October 2004 11:16
    To: BITX20@...
    Subject: [BITX20] LED Display - More Info



    Hi folks,

    A little further info on the LED display I have available.

    Common Kathode .
    Size 36mm x 20mm
    7 Multiplexed numeric characters
    7 _NON _ multiplexed leds in a bargraph.

    They are ideal for use with an OM3CPH PIC frequency display. I know
    as I built one last night !. On Veroboard ( stripboard ) I managed to
    get the size down to the front area of the Display and 1/2" depth
    behind. The PIC clock can be taken direct from the CIO osc ,
    therefore eliminating any chances of mixing of PIC and other
    oscillators. Resolution to 10Hz

    see the available data that I have made available at..

    http:&#92;www.qsl.net&#92;g8nxd&#92;files&#92;ledconn.pdf

    At 1.00 UKP each plus postage costs to anywhere on Earth. They are
    going very quickly ( I have about 30 left ). I really must keep a few
    for myself !

    72/73 de Mike W, G8NXD qthr





    Yahoo! Groups Links

    Re: LED Display - More Info

    david.g3ryp <david.g3ryp@...>
     

    Hi Mike - me too please Can you let me know what the UK postage will be and I'll stick something in the post. Still at 12 Boskenna Rd?
     
    David

    ----- Original Message -----
    From: Mike W
    Sent: Monday, October 04, 2004 11:15 AM
    Subject: [BITX20] LED Display - More Info

    Hi folks,

    A little further info on  the LED display I have available.

    Common Kathode .
    Size 36mm x 20mm
    7 Multiplexed numeric characters
    7 _NON _ multiplexed leds in a bargraph.

    They are ideal for use with an OM3CPH PIC frequency display. I know
    as I built one last night !. On Veroboard ( stripboard ) I managed to
    get the size down to the front area of the Display and 1/2" depth
    behind. The PIC clock can be taken direct from the CIO osc ,
    therefore eliminating any chances of mixing of PIC and other
    oscillators. Resolution to 10Hz

    see the available data that I have made available at..

    http:\www.qsl.net\g8nxd\files\ledconn.pdf

    At 1.00 UKP each plus postage costs to anywhere on Earth. They are
    going very quickly ( I have about 30 left ). I really must keep a few
    for myself !

    72/73 de Mike W, G8NXD qthr


    Re: request regarding asoc examination.

    vu2mtq <vu_radioham@...>
     

    Dear Gautam ,
    There are few other VU specific forums for concerns
    such as the ones voiced by you in this email. Kindly use them .This
    forum solely concenttrates on Homebrewing the BITX..(No Offense
    intended)


    73's
    Manish
    VU2MTQ

    --- In BITX20@..., "fromgautam" <fromgautam@y...> wrote:

    Respected sir,
    With due respect I beg to say that I am preparing for ASOC grade-1
    and advance grade examination. Recently I was appeared in ASOC
    grade-

    Building blocks...

    Arvid Evans <arvevans@...>
     

    HI

    After building a BITX20 and a BITX40, it seems that those who are
    constructing more than one BITX transceivers might be able to increase
    efficiency by modular construction. Since there are several stages
    that are all alike regardless of the band to be covered, these could
    be pre-assembled and tested as a standard unit. Then by adding the
    frequency determining stages one could easily arrive at a transceiver
    for any particular band.

    The common stages might include:

    (1) AF Amplifier
    (2) BFO Oscillator
    (3) Crystal Filter
    (4) Microphone Amplifier
    (5) BFO Mixer
    (6) DC RX/TX Switching

    and possibly:

    (7) VOX Circuit
    (8) CW Tone Oscillator
    (9) CW Sidetone Injection
    (10) RIT DC Circuitry
    (11) USB-LSB Switching for the BFO Oscillator
    (12) Speech Sompression for the Microphone Amplifier
    (13) Detector, Amplifier, & Meter for S-Meter.
    (14) Frequency Counter & Frequency Display Circuit
    (15) Huff-Puff Frequency Stabilizer Control Circuitry
    (16) Computer Interface (for RTTY, PSK, MSK, etc.)
    (17) DDS Circuit for Digital Frequency Control

    Building multiple BITX transceivers is an alternative to trying to
    design a multi-band version. I am not sure what the cost comparison
    might be between multiple single-banders and a single multi-band
    transceiver, but the engineering effort seems to favor multiple
    single-band units. This approach would also let you customize each
    single-band unit for the operating mode you use most on any particular
    band.

    73
    Arv-K7HKL
    _._

    Re: Building blocks...

    Rahul Srivastava
     

    Hi! Arv
     
    One of the few areas that I feel it will benefit is use of High ft transistors at RF preamp and post mixer amp. This ought to bring the NF performance in tune with many modern TRX. I have used low cost cable TV transistors in past with great success ones like BFR91, 2SC2570A etc even a 2N3866 and 2N5109, or the lesser 2N5179 will add to the existing performance.
    AGC is yet another area that needs looking. The basic concept being based on the bias scheme employed I suggest a PIN diode type shall be a practical approach towards it without performance compromise. 
     
    Just few thoughts
     
    73
     
    Rahul VU3WJM
     
    PS: I feel 2N3906/06 is a still better choice for HF use
     
     
    .

    Arvid Evans wrote:

    HI

    After building a BITX20 and a BITX40, it seems that those who are
    constructing more than one BITX transceivers might be able to increase
    efficiency by modular construction.  Since there are several stages
    that are all alike regardless of the band to be covered, these could
    be pre-assembled and tested as a standard unit.  Then by adding the
    frequency determining stages one could easily arrive at a transceiver
    for any particular band.

    The common stages might include: 

         (1) AF Amplifier
         (2) BFO Oscillator
         (3) Crystal Filter
         (4) Microphone Amplifier
         (5) BFO Mixer
         (6) DC RX/TX Switching

      and possibly:

         (7) VOX Circuit
         (8) CW Tone Oscillator
         (9) CW Sidetone Injection
         (10) RIT DC Circuitry
         (11) USB-LSB Switching for the BFO Oscillator
         (12) Speech Sompression for the Microphone Amplifier
         (13) Detector, Amplifier, & Meter for S-Meter.
         (14) Frequency Counter & Frequency Display Circuit
         (15) Huff-Puff Frequency Stabilizer Control Circuitry
         (16) Computer Interface (for RTTY, PSK, MSK, etc.)
         (17) DDS Circuit for Digital Frequency Control

    Building multiple BITX transceivers is an alternative to trying to
    design a multi-band version.  I am not sure what the cost comparison
    might be between multiple single-banders and a single multi-band
    transceiver, but the engineering effort seems to favor multiple
    single-band units.  This approach would also let you customize each
    single-band unit for the operating mode you use most on any particular
    band.

    73 
    Arv-K7HKL
    _._






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    Transformer cores

    W5RCM - Ron <w5rcm@...>
     

    Can somebody familiar with the size and composition of the "used TV balun cores" have a look at http://partsandkits.com/binocular.html and tell me if any of these are suitable replacements?

    Thanks. This project looks like a lot of fun.
    --
    72, Ron - W5RCM
    w5rcm at volente dot us
    Austin TX

    Re: Transformer cores

    Arv Evans <arvevans@...>
     

    Ron W5CRN

    For both my BITX20 and BITX40 I made my own binocular cores by stacking two rows of conventional toroid cores.  You can see how to do this on page three of the PDF document at this web URL: <http://www.oselectronics.com/downloads/Broadband%20Transformers.pdf>.  It worked for me.  You might want to try it.

    Good luck,
    Arv - K7HKL
    _._
    On Wed, 2004-10-06 at 14:59, W5RCM - Ron wrote:
    Can somebody familiar with the size and composition of the "used TV
    balun cores" have a look at
    http://partsandkits.com/binocular.html and
    tell me if any of these are suitable replacements?

    Thanks.  This project looks like a lot of fun.
    --
    72, Ron - W5RCM
    w5rcm at volente dot us
    Austin TX



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  • Re: Transformer cores

    Chris van den Berg
     

    Hi Ron,
    the dimensions should not be too small, otherwise you can not make
    anough turns with some copper wire wrom transformers (or relay
    coils). I used mainly ferrite toroid cores and one balun core with
    the holes size 3,8 mm, total length 13,3 mm.
    In one of the pictures that is in the Photo's directory 'BITX17' I
    explained that you can test if it works for the wanted frequency by
    making a transformer and see if the signal pass.

    I red also the reply of Arv that he build balun cores by using
    toroid cored, I do not see the benefit of this (one core works fine
    too).
    Good luck,
    Chris.

    --- In BITX20@..., W5RCM - Ron <w5rcm@v...> wrote:
    Can somebody familiar with the size and composition of the "used
    TV
    balun cores" have a look at http://partsandkits.com/binocular.html
    and
    tell me if any of these are suitable replacements?

    Thanks. This project looks like a lot of fun.
    --
    72, Ron - W5RCM
    w5rcm at volente dot us
    Austin TX

    Inductors /Transformers ?

    vu2mtq <vu_radioham@...>
     

    Hi ,
    I was just taking a look at the inductor / transformer details
    using tap washers. The tap washer I have with me has following
    dimensions:
    OD : 15 mm
    ID: 4.5 mm

    Are my tap washers ok?

    if we consider L4 which has about 150 turns I think this is
    diffcult to achive given the dimensions of my tap washer.

    2. Next to Q9 I can see a transformer shouldnt it read T2, As both
    T1&T2 are trifilar but the ckt diagram shows this as T3.

    (Any help would be appreciated since I dont have a LC meter.)

    Many thanks,
    73's
    Manish
    vu2mtq

    Alternate cores for L4

    kaliediscope2004 <kaliediscope2004@...>
     

    For those with access to the Amidon Iron powder or Ferrite cores
    these should work for L4 the VFO coil

    Amidon T-68-2 (red core) 20 uHy = 59 Turns of #26 SWG
    Amidon t-80-2 (red core) 20 uHy = 60 Turns of #24 SWG

    The above turns and wire sizes will fill the cores.

    73's
    Pete W6JFR

    Re: BITX20 made in brasil...!!

    Chris van den Berg
     

    Any news on the subject below Arf?
    Or someone an other idea to prevent using a relay?
    Chris.

    4. The RX-TX antenna changeover circuit is presently a 20 pf
    capacitor and a pair of back-to-back 1N4148 diodes, with
    additional Rx circuit protection provided by a forward
    biased
    1N4148 to ground. There appears to be a slight signal loss
    caused by this arrangement, so I will continue to work
    toward
    something better (but it has to be simple).

    Re: Antenna transfer method...

    Arv Evans <arvevans@...>
     

    Chris

    Not much progress yet on the antenna changeover circuit, mostly due to other more important work schedules (not involving the BITX project).  On my BITX20 I did go back to using a small 5-volt relay.  Antenna transfer on the BITX40 is still a problem due to it's higher power output (22 watts) from a pair of push-pull IRF510s in Class-B running on 24 volts.  As an interim solution I am using separate transmit and receive antennas on the BITX40.

    Arv
    _._

    On Tue, 2004-10-19 at 00:43, vdberghak wrote:
    Any news on the subject below Arf?
    Or someone an other idea to prevent using a relay?
    Chris.

    >      4. The RX-TX antenna changeover circuit is presently a 20 pf
    >         capacitor and a pair of back-to-back 1N4148 diodes, with
    >         additional Rx circuit protection provided by a forward
    biased
    >         1N4148 to ground.  There appears to be a slight signal loss
    >         caused by this arrangement, so I will continue to work
    toward
    >         something better (but it has to be simple).





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  • Linear amp problem

    Hans Summers <Hans.Summers@...>
     

    Hello

    I have my BITX20 working Ok as far as the final. When I bypass the final and
    whistle loudly into the microphone, the driver puts abt 4V pk to pk into 50
    ohms which I suppose is about 300mW as it should be. I also tuned the
    longwire antenna Ok by whistling into the mic.

    Can anyone suggest what could be wrong with the IRF510 stage and how to go
    about debugging it?

    Firstly, have I connected it right? Let me run this by you - I look at the
    IRF510 with pins facing you and the printing on top. A 7805 regulator in the
    same orientation has input on the left, ground in the centre, and output on
    the right.

    Ok so the IRF510:

    Left pin: is the "drain", which is the output. It is connected to the top of
    one bifilar winding, and the bottom of the other. I have checked the
    windings to make sure I did not connect them wrongly.

    Centre pin is the "gate" which is the input, connected to the driver output
    via 0.1uF, and to the 7805 voltage regulator via 56 ohm resistor and a 2K2
    potentiometer. The diagram says 10K but I assumed the exact value wasn't
    important.

    Right pin is the "source" which is grounded.

    Have I got those connections right?

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

    Re: Linear amp problem

    Ashhar Farhan <farhan@...>
     

    Hans,

    Finally the final!!
    you got the configuration wrong. and probably you have added an IRF510
    to the Hans Collection of Fried Things.

    Ok, now the middle pin is the drain.

    Now, if you put the IRF510 flat down on the table with the markings facing up and the legs pointing down, then the gate is on the left, the drain is in the middle, and the source is on the right.

    i have uploaded the spec sheet to the files section.

    i know, i know. i have become a silent lurker on the list. i am recovering from a personal tragedy. i lost my favourite uncle who bought me my first iron, taught me to solder and made me batteries out of lime and coins. i hope to get back to the list soon.

    - farhan

    On Sat, 23 Oct 2004, Hans Summers wrote:



    Hello

    I have my BITX20 working Ok as far as the final. When I bypass the final and
    whistle loudly into the microphone, the driver puts abt 4V pk to pk into 50
    ohms which I suppose is about 300mW as it should be. I also tuned the
    longwire antenna Ok by whistling into the mic.

    Can anyone suggest what could be wrong with the IRF510 stage and how to go
    about debugging it?

    Firstly, have I connected it right? Let me run this by you - I look at the
    IRF510 with pins facing you and the printing on top. A 7805 regulator in the
    same orientation has input on the left, ground in the centre, and output on
    the right.

    Ok so the IRF510:

    Left pin: is the "drain", which is the output. It is connected to the top of
    one bifilar winding, and the bottom of the other. I have checked the
    windings to make sure I did not connect them wrongly.

    Centre pin is the "gate" which is the input, connected to the driver output
    via 0.1uF, and to the 7805 voltage regulator via 56 ohm resistor and a 2K2
    potentiometer. The diagram says 10K but I assumed the exact value wasn't
    important.

    Right pin is the "source" which is grounded.

    Have I got those connections right?

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




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