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Author Topic: 6M RX?  (Read 1777 times)
KG6FUT
Member

Posts: 16




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« on: April 30, 2001, 08:23:27 PM »

Has anyone made a 6m recever for cw? Xtal controled prefered. Also do you use a 2 pole 2 throw swich for tx and rx swiching or 1 pole 2 throw?
73 de KG6FUT
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WB6BYU
Member

Posts: 13242




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« Reply #1 on: May 01, 2001, 11:50:58 AM »

Most of the common receiver circuits can be used on 6m with some
changes to the VFO and input tuning.  Direct conversion with an
NE602 and LM386 should work fine, but you probably will want a
preamp to improve the noise figure.  If you have an existing receiver
for the HF bands, you can add a converter to allow it to tune 6m.
I've seen some which use only an NE602 chip, but, again, this is
not high performance, and a preamp may be useful.

I have been considering designing a small xcvr (like the Pixie) for
crystal control on 6m as a club project, since any licensed ham
(at least in the US) has access to the band.  This would be a good
opportunity for groups to get on the air and practice CW together.
Crystals in the 16.67 - 17 MHz range operating on the third
overtone are probably the simplest to use, as it doesn't require a
separate multiplier stage.  You could also try a 10 MHz crystal on
the 5th overtone, which may put it just inside the band edge (due
to the difference between overtone and harmonic frequencies.)
But if you look through the stock crystal frequecies available from
Digi-Key or any of the surplus distributors, you should find a
number of combinations that will put you somewhere in the band.

Beyond that, receiver design will depend on your intended uses.
Do you need high sensitivity for weak-signal work?  Do you just
want to practice CW with another ham down the street?  Do you
have a specific frequency you want to monitor?  Is a narrow or
wide bandwidth required?  These are the sorts of questions which
will determine what type of receiver circuit will meet your needs.
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KG6FUT
Member

Posts: 16




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« Reply #2 on: May 01, 2001, 06:30:34 PM »

I jest need to rx a net or two and discribe how radios work to my class so cw sounded good and I am going to set up a pre aranged qso to show what ham radio is all about ( will bring my ht to explane repeters too).
73 -.. . .-. --. -.... ...-. ..- - .-.-.-
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WB6BYU
Member

Posts: 13242




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« Reply #3 on: May 02, 2001, 12:36:36 PM »

If you are doing a demo, you need know that there will be some 6m
activity at the right time.  In general, I'd guess that 40m might be
more reliable for having signals present.

For a scheduled CW QSO, 6m would work well because the
antennas are reasonably sized.  You will need to make sure that
your receiver has enough audio output (or add an external audio
amplifier) so the whole room can hear the QSO.

Probably the simplest receiver to build would be a crystal
controlled direct-conversion.  Here are some places to look for
ideas:
http://www.alphalink.com.au/~parkerp/project.htm
http://www.intio.or.jp/jf10zl/
http://www.qrp.pops.net/

Also, if you just want to demonstrate a CQ QSO, you can do that
by running an audio oscillator into your 2M HT.  It demos best if the
station you are talking to is using an oscillator at a different audio
frequency,so the class can tell the difference between what you are
sending and receiving.


good luck ! - Dale WB6BYU
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WB2WIK
Member

Posts: 20595




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« Reply #4 on: May 02, 2001, 03:03:57 PM »

You're teaching a ham class and need to know if a TX/RX antenna switch should be single pole or dual pole?

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WB6BYU
Member

Posts: 13242




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« Reply #5 on: May 03, 2001, 11:39:27 AM »

Now, Steve, give him a break...  Not everyone remembers the days
of separate transmitters and receivers that we connected up
ourselves.  I suspect a lot of hams currently licensed have only
ever used transceivers, and haven't dealt with antenna changeover
switches.  I think he should be acknowledged for (1) teaching a
class, and (2) asking for help on the stuff he isn't clear on, instead
of dispensing garbage (which, unfortunately, is too often the case.)

To answer the question, . . . well, it depends. . . .

If you are just switching coax antenna leads, then a single pole
switch or relay will work.  The old-fashioned knife switches were
usually double pole because they were used in balanced feedline,
and had to switch both wires.  Sometimes an extra set of contacts
is used to short the receiver input to ground in transmit mode, to
protect the input ciruitry even more.  And there are times when a
single switch handles not only the antennas, but also the DC power
and other circuits in the transmitter and receiver.  (For example, to
turn on the oscillator in the transmitter if only an amplifier stage is
keyed.)

With a simple (low power) transmitter and receiver, I would use a
double pole switch, with one pole switching the inner conductor
of the coax and the other switching the power to the transmitter
(and perhaps the receiver, if turn-on drift isn't a problem.)
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