Ramsey Electronics HR30 Instruction Manual - page 17
HR30
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17
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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
SA602 audio output at the volume control, and switch in a pleasant oscillator
pitch (keying sidetone) which is amplified to listening level by LM386. The
Ramsey Electronics Universal timer kit No. UT-5 is easily adapted as a
sidetone oscillator.
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SPEAKER OPERATION
A fifty cent, two inch diameter speaker, lying naked on your workbench will give
you a fair test of the speaker output capability. Speaker quality and well-
designed enclosures have their clear purposes! A reasonable speaker in a box
delivers a pleasant listening volume. On the other hand, the LM386 indeed can
deliver more audio output punch than is developed in our HR-series kits. For
example, our FM receivers, using the same LM386 audio IC, deliver more
volume. These receivers, however, take advantage of IF amplifiers, drift-
compensation and crystal controlled oscillators built into mass production,
sophisticated FM receiver ICs. A heavier drain on the HR30’s battery by
stronger audio will quickly result in chirpy signals and oscillator drift as well as
the need for frequent battery replacement. Remember the SA602 circuits
similar to Ramsey’s generally call for sets of C or D cell batteries! For
Experienced Builders more information regarding audio output is in the general
notes.
The simple design of the audio stage of the Ramsey HR30 receiver assumes
preference for headphone or small speaker operation, low battery drain and
general economy.
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MORE AUDIO POWER - ANOTHER WAY
If you want to use your HR30 for casual band monitoring while you are busy
across the room, in the shop, or to share with a class or club, and want LOTS
more volume, try building up our very inexpensive Ramsey BN-9, 2 watt
general purpose amplifier kit. Supply DC voltage to such an amplifier
separately, using D-cells, a lantern or auto battery , or a well filtered power
supply.