Questions tagged [equipment-design]

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2
votes
1answer
258 views

Influence of bending and asymetric ground wire on monopole antenna

I'm currently building a rc radio system using the 433mhz RFM69W transceiver, so far everything works fine, but i am not sure about the way i laid out my antenna and how the layout cripples the ...
2
votes
1answer
158 views

How is impedance matching related to balance and common-mode currents?

Does a good impedance match imply good balance and lack of common-mode currents? Does a poor impedance match imply poor balance and excessive common-mode currenst?
2
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1answer
1k views

Receiver using a NE602 oscillator-mixer not working

I built a CW receiver using NE602 for the 20m band. Unfortunately, I do not receive any CW or SSB signals, only some noise and sometimes broadcast stations. The schematic here shows the circuit that ...
2
votes
1answer
211 views

Basic Signal Detector using MOSFETs

I am trying to design and build a basic signal detector using MOSFETs because they are more compact than resistors, capacitors, and inductors. I was wondering if anyone here has any suggestions on how ...
2
votes
1answer
98 views

voltage rating for RF filter components

I want to design a PCB for a diplexer for Satellite operations. I want to use SMD capacitors and possible inductors to get some experience with soldering SMD components. What should the voltage rating ...
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3answers
387 views

What replaces the T/R switch in modern transceiver

I have been watching and reading about the time when receiver/transmitter were separated and T/R switches were used. Current transceivers are still sharing a single antenna to transmit and receive. ...
1
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3answers
483 views

Weird Harmonic Issue on Raspberry PI FM Transmitter

So I talked to my neighbor about my Raspberry PI, harmonics and his emergency radio. He told me to fire it up, as we saw the FCC sticker on it, meaning it is in compliance with Part 15. I started my ...
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2answers
168 views

What are Smart Antennas?

What are smart antennas? How are they used in amateur radio, and how might they better than conventional antennas?
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2answers
100 views

Toroid Coupling Issue in Common-base Amplifier

I'm working on an old school VFO for the 15 meter band based on a JFET Hartley oscillator. The plan is to follow the oscillator section with a JFET buffer, then a CB amplifier (for increased reverse ...
1
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2answers
107 views

RF PCB Design Difference Between Controlled Impedance Track and Impedance Matching Circuit

Im new on RF circuit designing. Im designing an circuit with GSM and GPS capabilities. I know when using high frequency signals the RF traces must be impedance matched. Now what I understand is, I can ...
1
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3answers
385 views

What kind of ham radio license should I get?

I have an interest in studying and researching how radio technology can be used in other fields of electronics. What kind of license should I look into so I can carry out some experiments or research? ...
1
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2answers
285 views

Benefits of AGC?

I note that many popular kit and QRP radios do not include any AGC capability. Thus it must be possible to operate successfully without AGC. Are there difficulties involved in manual gain control? ...
1
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2answers
1k views

How to convert a crystal controlled tranceiver to VFO (aka Unbinding from the Rock)?

If you look at the circuit diagram for a Colpitts crystal oscillator, it's pretty simple -- a crystal, load resistor, and capacitive voltage divider, with the positive supply feeding the control ...
1
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1answer
490 views

Raspberry Pi rpitx for SSB with filter?

Using rpitx, we can transmit SSB using a single GPIO port from the Raspberry Pi. This of course uses square waves so creates a lot of harmonics. If I were to use a ...
1
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1answer
48 views

multiple pcb trace antennas in the same design. Bad idea?

Since time is money and my PCB home making skills are not the sharpest, I would rather fit my PCB design with two unbalanced antennas (no balun, just impedance matching parts, for 315 / 433 MHz) for ...
1
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1answer
80 views

Need way to indicate when rotary inductor reached its limit switches on a remote homebrew motorized hf tuner

I have a homebrew motorized hf tuner which is controlled by coupling dc from the shack through two BiasTs - one topside, the other in the shack. As I reverse polarity to adjust tuner, will two LEDs, ...
1
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1answer
157 views

Crystal Oscillator Output Impedance and Output Voltage

I am working on a project designing a 40 MHz radio transmitter, but I need some clarifications. I need to know how to calculate its output impedance. I know how to calculate common collector's output ...
1
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1answer
62 views

CW speaker and volume control

I'm building a kit for the LNR precision mountaintopper 3 band qrp radio. I'm having problems wiring a panel mounted volume knob and speaker to hear the cw output. I'm new to home brew electronics ...
1
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1answer
93 views

PSR500/Pro106/WS1040 Phase II Upgrade?

I want to know if one can upgrade the hardware chips/ the CPU/DSP inside police scanners to do Phase II. I know they cannot do Phase II due to hardware/software limits but if whistler can upgrade ...
1
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1answer
64 views

Can the transmit and receive functions of a boat anchor transceiver share the tank circuit?

I'm starting design work on a two-tube (two-valve, for those who prefer that term) reflex-regen receiver that I hope will cover AM broadcast through 160m-10m -- both amateur bands and those "in ...
1
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1answer
337 views

Old Yaesu FT-470 HT audio feedback with external speaker mic

I have a generic external speaker mic with the two-pin connection (1x 3.5mm, 1x 2.5mm mono jack), which doesn't work with my FT-470 (no real surprise, figured I'd just mod it.) I've started the mod, ...
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0answers
167 views

LA1185 FM downconverter shows weird behavior

I've built FM CCIR/OIRT downconverter based on Sanyo LA1185 IC. I've used most famous schematics for it with slight modification (added DC blocking capacitor 1 nF rated on the output) Coils L1 and L2 ...
0
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3answers
80 views

How can the waterfall still be displayed during transmission

I noticed that on some higher-end transceivers, the panadapter/waterwall is still being displayed during transmission. How is this possible? If the panadapter is part of the receiver, it should be ...
0
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2answers
116 views

Imaging with radio Frequency

Is it possible to image bones and tissues with radio waves (2.7GHz-5GHz) with a tiny radio frequency source and on one side and a receiver on other side which can image the data through a PC mediated ...
0
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1answer
68 views

Circuit for RF Splitter [closed]

Does anyone know of any resources which describe how to design a circuit with one RF input and multiple (at least 6) RF outputs, whereby the signal strength of each output matches (does not exceed and ...
0
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1answer
130 views

How to compute/simulate signal propagation latency?

I need to transmit small amounts of data (~5kb/s) in the fastest way possible over the distance around 2500 km. What is the the best way to carry out such transmission? How could I estimate or ...
0
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0answers
42 views

Simple minimum component RF Amplifier Design

Looking for advice/assistance in Retrofitting sans Cabinet Antique 2 and 3 Dialer 1920's TRF tube radios to operate with low safe Plate voltages.Both Hollow State and Solid State. The plan is to ...
-1
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2answers
174 views

At what watt level is it safe to use metal strips for modulated signals?

In my working design, I have a transceiver TX on low power; Then boost it in a preamp phase in the back. The way I'm sending the signals (RX and TX) through the radio is by a network of 1/8 to 1/4 ...

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