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A 1-amp, 12 Volt, well filtered and regulated power supply should be used with the receiver. If the voltage drops below 10.5 volts, some of the IR switching may not work. If a 13.8 Volt power supply is used, use three 2 amp rectifier diodes in series to drop the voltage to ~11.5 Volts to the receiver. Cathode side (Black band) goes to the receiver, anode side to power supply. The receiver works best with a supply voltage of between 11.5 and 12 Volts. Total current draw of the receiver with no signal is about 1 amp, but the audio amplifier (TDA2002) can draw instantaneous peaks of up to 700 mA. The first indication of a weak power supply will be distortion in the audio amplifier. Wall warts (plug-in wall transformers/power supplies) are not filtered enough and will cause hum in the audio. A 1 amp wall wart will work, but be aware that most of them will cause hum in the audio and need additional filtering. Several wall warts were tested with the receiver and we never found one that did not cause hum in the audio. |
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The receiver is designed for use with Hamstick antennas on the inside of a condo/townhouse window. The RF amplifier and lots of mixer gain helps the receiver work in areas with poor reception. A 17 meter ham stick will bring in all the bands of the receiver with equal gain. Hamsticks for the other bands, when used as a general purpose antenna, will show marked differences between the bands. For example, a 20 meter Hamstick will bring in 20 meters with a bang, but be poor on 40 meters. There is a 50 ohm pad at the output of the RF amplifier that can be changed to fit the receiver to your antenna farm. A 3dB 50 ohm pad comes stock with the receiver, but it can be increased to 6 dB, or even 12 dB, to reduce overloading the receiver when using very good outside antennas. See Circuit Details, RF Amplifier, "Adjusting Gain". If you need more gain, the 50 ohm pad can be bypassed for more gain from the RF Amplifier. To remove the 50 ohm pad, remove the two .01 capacitors that go to and from the pad, and then insert one .01 capacitor in the two unmarked holes just to the right of the pad. That jumpers the output of the bifilar coil directly to the relays. |
Tuning the ReceiverThe bands are chosen with the DDS VFO by pushing Button 3 and turning the DDS VFO knob within one second. The DDS VFO will scroll through the bands until it reaches the one you want and quit turning the knob. The bands on the DDS VFO are 160/80/60/40/30/20/17/15/12/10. The next band is 200kHz, which does not have the offset programmed and is a signal generator that outputs the exact frequency it is showing. It is used to determine the center frequency of the crystal filters so it can be programmed into the offset frequency if the crystal filter frequency is changed. To use this function, tune the 200kHz band near the frequency of the Crystal Filter frequency and peak the output at the S-Meter. Use the 100 Hz or 10 Hz tuning digit to find the peak. The peak frequency is then the offset frequency put into the programming for the bands. The next band shows 0 and is a general coverage band that has the offset programmed (plus 3.546 MHz) and can be used to go to any frequency between the limits of the Bandpass Filters, below 60 to 10 Meters. The Band numbers showing on the display go from 1 to 9, 1.800 to 24.890 (160 to 12 Meters). On 10 Meters it shows :, on General Coverage band 0, it shows ;, and on 200 kHz, it shows >. I guess the original programming didn't go above a one digit number. This will probably be fixed in a future release, but it doesn't effect operation. The BLT does not have a Bandpass Filter for 160, so it can't be used unless one is added. Information on 60 Meters is below: Amateurs are permitted to operate on five frequency channels, each having an effective bandwidth of 2.8 kHz. Channel 1: 5330.5 kHz The effective radiated power permitted is 100 Watts. CW operation takes place at the center of the chosen channel: The channel center frequencies are: Channel 1: 5332.0 kHz BFO TuningA positive offset is used on all the bands, so Lower and Upper sidebands are on opposite sides of the BFO tuning label. LSB is to the left of zero beat, and USB is to the right of zero beat. It is best to tune in a SSB signal at it's strongest level and then tune the BFO for proper reception. |
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There is so much difference in hearing sensitivities between individuals that being able to set the audio gain to different levels was considered very important in the design of this receiver. There is a black PC mount potentiometer labeled "Gain Adjust" at the BFO amplifier directly above the MOSFET. This pot varies the injection level to the product detector. The injection level is indicated by the LED brightness at the BFO amplifier. For minimum noise from the audio amplifier, this pot is usually run with the LED barely on. Increasing the injection level will raise the audio level a noticeable amount. For quiet ham shack locations, this pot will give all the variation you will need in audio levels. |
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Some features on receivers that are not included are the following: Noise Blanker Notch Filter/Q-Multiplier Audio Filter |
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The output of the Key box at the back of the DDS VFO and amplifier chain is ~12 Volts and is grounded to key the output of approximately 200 mW. To set the transmit frequency, the DDS VFO knob is pushed in (the switch in the encoder is attached to Button 3), and then the key is tapped with either a dit or dah. Release the Knob switch or Button 3, tap the key again and the transmit frequency is displayed with Xmtr displayed with the transmit frequency. You can move the receive frequency by turning the encoder (RIT), Rcvr will be displayed, but the transmit frequency will stay the same until the key and Button 3 (or encoder switch) are pressed on a different frequency. Every time the key is pressed (while transmitting), the display will show Xmtr. Information on attaching a transmitter can be found at Transmitter to Interface with the BLT Currently, the page is thrown together to help one get a transmitter working with the BLT. It will be simplified and improved as more time is put into the page. |
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Check out the article in the September/October 2002 QEX, "The DX Prowess of HF Receivers", and the design features of what he considers best for DX hunting. Most of those features are incorporated into this receiver. Some of them are the following, taken from the article, page 38: >Only single or double conversion is used instead of a chain of several mixers commonly used by other makers.>A relatively low first IF that allows installation of narrow SSB/CW crystal filters with good shape factors to greatly attenuate out-of-band IF signals just at the front of the IF amplifier. >The main IF selectivity of the crystal filters is very close to the receiver front end, which helps substantially to obtain high Blocking Dynamic Range (BDR) and good IMD DR even for closely spaced strong signals. >Ham-band-only pre-selector filters that substantially suppress strong signals outside of the ham bands and prevent receiver front-end overload and IMD. >Narrow double-tuned preselector filters are switched by relays, so the receiver front end offers much better IMD response then when diode switching is used. >A switchable HF pre-amplifier and switchable attenuator increase the range of receiver sensitivity adjustments, which allow the operator to adjust the receiver to particular propagation conditions and the receiving antenna in use. Note: This concept is implemented in the Blue Lightning Transceiver receiver with the 50 ohm pad at the tail end of the RF amplifier. >AGC is derived from the IF signal. >A sharp IF crystal filter is close to the mixer and because of the relatively low IF, the crystal filter greatly attenuates out-of-IF signals. That helps to prevent receiver overloading by strong signals from outside the IF-filter pass-band. Check out the article and compare! |
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You are welcome to send an image of your completed project. Any comments you have, be sure to email. Enjoy and Have Fun! |
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