Thanks Farhan,
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I have edited the ckt. Would be uploading soon. Many wanted PCB Ver 3 unfortunately it was not possible for me to provide commercialy, mainly due to time constraints. I had few made here and those were soon whisked away by friends.
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Nice to know about the new updated version. I have yet to try the bal mod swap. Common base?AF preamp will nice touch, I have been thinking of trying a 2 transistor config as?done in Optimised ?QRP transceiver.
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Cant say much about the class A amp perhaps it may be a bit over kill TDA2003 car stereo chips may also give adequate power and decent noise figure.
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Mic amp works well but I think adding one transistor as buffer ie emitter driven bal mod may be a better match.. My request since the design has been peaked for good performance do think upon incorporating an AGC and S meter. On few of my friend signals,? speaker?cone threatens to pop out.?
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Looking forward to updated design. Will definately make a PCB for it .
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TNX & 73
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Rahul VU3WJM
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Ashhar Farhan wrote:
rahul,
do go ahead with the schematics. i have no 'property claims' on the
design. i am right now doing a bit of upgrading of the design myself. i
ill probably share this with the group as soon as i have made some
progress.
this time around, i am make a rig for my personal use. hence, i am
expending more effort on this piece as well as slightly higher cost. my
main areas of imporvment are the following:
1) high amount of shielding between stages especialy the oscillators and
the filters.
2) i am using FET based VFO for lower oscillator phase noise, tuning it
with a bank of four 1N4001 diodes with a 10 turn potentiometer for good
slow motion drive.
3) digital binary counter for low counter noise (thanks hans! ur site is a
treasure).
4) the RF front-end mixer changed to doubly balanced configuration
(one
more coil to wind).
5) the detector/modulator connections are reversed as discussed previously
in the group.
6) reworked the entire audio from detector onwards. the new audio pre-amp
is based on w7el design of a common base stage directly coupled to a
common emiiter stage. both the stages decoupled by an active decoupler.
the audio amp, though not done yet, will be a class-A amplifier with low
distortion (instead of the LM386).
7) two IRF510s in push-pull to deliver 10 watts pep (The legal limit for
qrp).
8) switching for 7MHz/14Mhz bands, making it a dual-band transceiver.
the low-sensitivity that some have complained about, according to my
analysis, is due to the mismatch between the detector and the audio
pre-amp.
hence the rework on the audio.
as an aside, are planning to attend the hamconvention in bangalore in
october? if you are, we might have an eyeball.
-
farhan
On Sat, 3 Sep 2005, Rahul Srivastava wrote:
> Dear Farhan,
>
> Hi!
>
> Many people have requested for the schematics that go with Ver3 PCB posted on the group as it incorporates many mods suggested on the group.
>
> I request your kind permission to edit the original ckt to show the Ver3 changes. Due credits to you? remain as they are.
>
> 73
>
> Rahul VU3WJM
>
>
> ---------------------------------
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