HR20
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16
USING YOUR RECEIVER:
In your first tests, you might feel that tuning in CW and SSB stations by turning
the control shaft seems tricky. Don't despair! The addition of a simple knob to
the final version of your kit will result in more comfortable tuning right away.
Also, the larger the knob, the easier tuning is. Even smoother control can be
accomplished by a vernier dial, which will also provide calibration marks.
Finally, if you intend to use this receiver only for monitoring or working a very
specific frequency range, you can add a resistor in series with the tuning
control to achieve the bandspread you want for your own application. For
details, please see the upcoming section, Notes to Experienced QRP
Builders.
We want you to enjoy this economical receiver, whether you use it for portable
listening or as a base for easy experimentation. Isn’t it amazing the
performance that can be achieved with just two IC chips?
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TUNING SSB SIGNALS
As you know, the protocol for the 160 - 80 - 40 Meter Bands is Lower
Sideband (LSB), with Upper Sideband (USB) used for 20 - 18 - 15 - 12 - 10
Meter SSB. To check or ‘scan’ a given band for SSB signals, tune your HR20
up from the low end for USB signals and down from the high end for LSB.
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CW OPERATION
A direct-conversion receiver lets you hear equal ‘sidebands’ on either side of
the zero-beat ‘null’ of the exact frequency of the signal to which you are
listening. Therefore, when adjusting the frequency of your companion Ramsey
QRP transmitter, be certain that you have in fact tuned to the other station’s
lower sideband. The two stations will actually be several KHz apart. Because
this receiver’s oscillator is not shared with a transmitter, as in transceivers,
there is no need for separate RIT (receiver incremental tuning).
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ON THE AIR TRANS-RECEIVING
Let’s assume that you plan to use this receiver together with a Ramsey QRP
transmitter, which provides an RF protected receiver antenna jack. While the
receiver will be protected from RF damage from the transmitter, do not expect
to monitor your own signal on this receiver while transmitting unless you are a
QRP design expert and do not care about future factory service from Ramsey.
Even with the circuit protection, the RF signal is just too much for the SA602.
The transmitter signal overpowers the SA602, disrupting the internal oscillator.
However, the receiver can handle the output of a crystal oscillator or VFO for
frequency spotting purposes.
A better operating arrangement will consist of a T-R switch, either a manual
switch or break-in delay relay circuit. This switching circuit can disconnect the
Summary of Contents for HR20
Page 9: ...HR20 9...
Page 10: ...HR20 10 HR20 PARTS LAYOUT DIAGRAM...
Page 25: ...HR20 25 CONSTRUCTION NOTES...
