Questions tagged [diy]
Questions dealing with handmade (Do It Yourself) radios and radio accessories.
159
questions
2
votes
0
answers
55
views
How can I key low voltage and still keep a tube VFO running constantly?
I'm interested in building a VFO based single tube CW transmitter.
These devices are known to have issues with frequency drift and chirp; frequency drift can apparently be mitigated by ensuring ...
0
votes
1
answer
66
views
Given that transmit "chirp" is mainly thermal related, what parts would need to be temperature regulated to limit chirp?
I'd like to build a Colpitts (or Hartley) oscillator based one-tube CW transmitter, and I'd like to use a VFO circuit rather than crystal control (in part because of the expense and limited ...
1
vote
1
answer
182
views
Need some help to design a DIY MW Radio receiver
AM Medium Wave Radio Receiver Design.
First of all, I am a hobbyist and stuff related to electronics are not very strange to me but the chapter of Radio and RF frequency , intermediate frequencies , ...
0
votes
4
answers
109
views
Wired RF connection without antenna
I’d like to build a radio system for use in underground caves. Wireless signals are nearly impossible to propagate in this environment, so I’d like to run long coaxial cable between each station. Are ...
1
vote
1
answer
110
views
Swapping crystal from HF to VHF in a QRP tranceiver
I am trying to build a short-range QRP weak signal VHF 2m CW transceiver. I found a small circuit that fit my needs, but it was made for use on 40m instead of my target frequency. The circuit included ...
1
vote
2
answers
72
views
A question about chassis mount SMPS mounting
I have couple of chassis-mount 75 W, 15 V DC Mean Well switching power supplies (the PDF datasheet is here) and I need to mount them as in a shelf of a 19" rack frame.
I have no prior experience ...
1
vote
1
answer
130
views
Why is my homebrew copper sulphate resistor behaving like a capacitor? [closed]
I brewed a CuSO4 resistor in a glass jar. I got the idea from here. This was done by creating a solution of Copper Sulphate in distilled water. The lid on the jar was provided with a BNC socket into ...
8
votes
1
answer
196
views
Is there anything special about 4.9152 MHz intermediate frequency?
I noticed that there are several QRP transceivers that use 4.9152 MHz intermediate frequency. For instance, John Dillon, WA3RNC uses it in Penntek TR-25, TR-35 and TR-45 transceivers. Also a very ...
3
votes
3
answers
129
views
Serial Inductors in Tuned Circuit - Elenco AM780K AM Radio Kit
I'm trying to understand a component of an AM radio kit that I have. (There is a document available here: https://www.elenco.com/wp-content/uploads/2017/10/AM-780K_REV-K-2.pdf describing the build ...
-1
votes
1
answer
116
views
How to build the best bang for yhe buck uhf vhf antenna or should i just buy one [closed]
Help with antenna build what makes up a great antenna what can I use for elements and would a dush network dish be good reflector and how to wire the elements like the copper to one side and the ...
2
votes
2
answers
174
views
What simple methods are available to test a homebrew SSB transceiver on transmit?
Overview
Before putting my recently completed homebrew single conversion 20m mono-bander on the air, I borrowed another radio to listen to the transmission and make sure everything was OK. It turns ...
1
vote
0
answers
69
views
How do I test if three turns are better than 4 turns?
I built a class ab amplifier kit to use with my qrp radio. 2 watts in creates 50+ out.
This was the pa 70 amplifier kit.
It is a kit with no instructions, but a whole suite of internet videos and ...
1
vote
1
answer
356
views
What is a diode for in a JFET-based audio mute circuit?
I've build the following audio mute circuit:
It works fine. However in many circuits I've seen people add an extra diode on the gate of Q1:
For instance, see "QRP Classics" page 120 / page ...
5
votes
2
answers
220
views
14dB insertion loss for bandpass filter acceptable?
I'm busy with a direct conversion receiver for the 20m band, using a VXO and a 14.060 MHz crystal.
I designed a bandpass filter with the following components, using this design calculator.
Someone ...
1
vote
1
answer
918
views
How do I wire an external mic and speaker to the Yaesu FT-250R without using their adapter?
I'm trying to wire up an external mic with PTT and a speaker to my Yaesu FT-250R to basically use as a VHF base station when I'm not mobile. Unfortunately, I can't find anywhere a description of how ...
0
votes
3
answers
123
views
How to transmit computer audio to a wireless microphone receiver? [closed]
I'm currently trying to broadcast my computer's audio output to a wireless microphone system receiver so that I can accompany my school's coming presentation with music. The frequency range is 480-598 ...
2
votes
3
answers
239
views
Motorola Microphones
Can a person use moto mic's on all their radios by rewiring the end plugs I have a few mic's and want to change the plugs to work on my Gn300's and Maxtracs and how to do this re Colors and positions ...
7
votes
1
answer
305
views
Simple circuit for acceptably clean CW in homebrew TX?
I'm working on a design for a home-brew 10 metre transmitter for CW. My oscillator is running cleanly, and I need to add a (small, probably 1/2 ~ 1 Watt) power stage to it, and I need to "...
-1
votes
1
answer
219
views
Fractal antenna shapes that work for you? [closed]
I just answered this question, and I wanted to know if any particular shape has been found to be successful for anyone.
There seems to be a lot of research on IEEE that indicates that there should be ...
8
votes
2
answers
440
views
How to reduce VFO sensitivity to the hand capacitance?
I got a little tired of Si5351 and decided to build an analog CW transceiver. It's almost done and works pretty well. However, I discovered one problem. When I reach the VFO control with my hand the ...
2
votes
1
answer
145
views
can i convert an FM coaxial antenna to just speaker wire?
I have a Sony MHC-GX450 compact mini stereo system. The connector for the FM antenna is coaxial, and is labeled 75 Ω. I'm wondering if somehow I can use speaker wire for the FM antenna.
2
votes
0
answers
101
views
IF derived AGC: how to choose the best block diagram?
I've built several transceivers in the past. I never implemented IF derived AGC, so I decided to give it a try in the next project.
I choose to build a superheterodyne receiver, which will probably ...
1
vote
2
answers
131
views
Is power output or something else to blame for my duplexer failing?
A Ham buddy of mine and I were trying to setup a UHF repeater in our area due to a lack of them. We had two Motorola CDMs, one a 1250 and one a 1550, and we purchased a $200 or so reject only duplexer ...
4
votes
4
answers
369
views
3D Printed yagi antenna
I'm trying to produce a Yagi antenna for the 2.45 GHz band using a 3D dual extruder printer. The idea is to print the antenna elements using a metal filament and encasing it all in plastic.
The ...
1
vote
1
answer
97
views
What type of omnidirectional antenna gives the most gain for a frequency of 2.4 GHz?
I have a 2.4 GHz transceiver that outputs 4.5 DBm. I wish to amplify the signal using a 15.5 DBi antenna so that the signal reaches 20 DB, the maximum legal limit. Preferably, the antenna would be of ...
3
votes
3
answers
236
views
What causes an AF amplifier to make popping sounds in a superheterodyne receiver?
Recently I've made a simple single IF superheterodyne SSB receiver for 40 meter band. The schematic is available here [PDF]. VFO and BFO are based on Si5351, the AF amplifier is LM386. It works OK but ...
4
votes
1
answer
1k
views
Looking for origins of a crystal filter schematic used in uBITX
Here is a crystal filter used in uBITX transceiver:
I've never seen such a topology in any other transceiver and decided to invest some time in exploring it. Turned out it's quite interesting. Eight ...
3
votes
2
answers
1k
views
How do you calculate the number of turns for a common mode choke?
I want to build a common mode choke for my end-fed wire antenna, using turns of coax through an FT140 or FT240 ferrite. I can find various finished products for sale, but I want to make my own. I ...
1
vote
1
answer
110
views
How do I connect a homebrew antenna using RX-8 to a Yaesu FT-70DR (SMA)?
I made an 2m / 70cm tape measure antenna using RG-8 coax. That part was quite a bit of fun and went fine. But when I tried to connect the coax to my Yaesu FT-70DR, the copper core of the RG-8 was too ...
2
votes
1
answer
178
views
Simple AM Radio Troubleshooting
I just got all the parts to make a simple AM transmitter from Scitoys. I followed the instructions from different websites and they still don't work. I don't know why it's not working. On my ...
4
votes
1
answer
166
views
Looking for criticisms on my VNA-like SWR meter I am designing
I am in the process of building a SWR meter with VNA-like features. I'd be really interested to hear from fellow hams any input, suggestions, or tips they have regarding this before I go get it mass ...
5
votes
0
answers
739
views
What is an expected IF level of SA612?
I tried to use SA612 as a frequency mixer. Since it's a Gilbert cell, it has a high input impedance. Thus I added a pair of transformers as "Experimental Methods in RF Design" book suggests:
...
4
votes
3
answers
1k
views
Is the Boom Strictly Necessary in a Vertical Dipole?
I'm planning to build a vertical dipole for 4m and a club member pointed out that my design needs to allow for a boom that should be at least a 1/4 wave long. Why does a vertical dipole need a boom ...
6
votes
0
answers
331
views
How to estimate input and output impedance of an amplifier?
I'm trying to figure out how to design power amplifiers which input and output are properly matched to 50 Ohm. My thinking was that the most bullet proofed approach would be to model an amplifier in ...
4
votes
1
answer
772
views
DIY Triplexer for HF (low), 6m (med), and 2m/440 (high)
I'm looking at picking up the TYT TH-9800, which is a Quad-Band FM radio on 10m/6m/2m and 440 (I'm lucky enough to have some 6m and 10m repeaters in the area). I know there exists quad band antennas ...
4
votes
2
answers
1k
views
How to measure quartz crystal motional parameters using a VNA?
I want to measure quartz crystal motional parameters with a VNA. Unfortunately all Google searches I've done have lead me to nothing in concrete. I know how to get an impedance curve and measure the ...
2
votes
1
answer
202
views
Can these in-band spurs from rpitx be eliminated somehow?
I'm putting together a 2m NBFM transmitter/receiver combo using rpitx and rtl-sdr. During testing my low-pass filter I discovered that rpitx is generating spurious signals within and around the band (...
10
votes
3
answers
1k
views
Why is my diplexer such a spectacular failure?
I'm trying to create a diplexer for the 2m and 70cm bands so that two antennas can share a feedline to my "shack". My radio is a Yaesu FT60 handheld, 5W max.
I have home made a j-pole for 2m, and a ...
4
votes
0
answers
169
views
Problem with theory of HF detector
I'm currently trying to build my own SWR power Meter. This design is based on the so known HT detector with schottky diode BAS70. For my understanding, and for easy purpose, I'm currently focusing on ...
0
votes
1
answer
49
views
Detect multiple broadcast on same channel
I have a number of ear guards with two way radio communication. They can only be set to send and receive on the same channel, and they have the option of dividing themselves according to the ctcss ...
2
votes
2
answers
376
views
coax switches for HF
Like many hams I have several radios and several antennas. instead of constantly connecting and disconnecting coax cables I would like to feed several antennas in to some type of switch so I can ...
1
vote
4
answers
1k
views
Indoor HF/VHF/UHF antenna, have someone an Idea?
My wife doesn't think that having tall antennas is acceptable.
Does anyone have a solution for this?
Our house is 16 meter long and 10 meter wide.
I have an antenna tuner (if it can help).
1
vote
1
answer
282
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 ...
4
votes
1
answer
110
views
no contacts with Rockmite
I finished building my Rockmite ][. It's running off of 3x 18650s, or 12v. I connected it to a MFJ-1840T and held the antenna horizontally in the air (also tried vertically) with my hand. I tried ...
3
votes
1
answer
333
views
Unknown kit from DK0TV
When my father - who became a ham years after I did - passed away, I found an unstarted project (board + components), which I only re-discovered again years later.
The board is marked DK0TV-001, and ...
5
votes
2
answers
2k
views
RF Bridge Problem - K6BEZ Antenna Analyzer
This question regards erroneous SWR measurements of K6BEZ antenna analyzer (links gone from Internet now) design from 2013 using Arduino and AD9850 DDS modules. There have been many variations of it ...
1
vote
1
answer
301
views
How to calculate VFO/IFO frequencies?
I am trying to build a simple superhet receiver for listening SSB signals.
I read several articles about SSB and got confused so I am looking for some practical explanation.
I have 2 mixers, quartz ...
0
votes
4
answers
154
views
Can I make signal transmitter without decoder?
I'm sorry if my title seems weird but I just started to learn about signal transmitting and I don't know where to start
I'm searching about simple ways to make diy radio but I can't really ...
0
votes
1
answer
119
views
Lead in wire size [closed]
I have a copper wire antenna about 100 feet long that I have relocated and now need about 75 feet of lead in wire. What type & size of wire should I use?
3
votes
1
answer
91
views
Help understanding transmission loss of trivial circuit
I was trying to DIY a VHF/UHF diplexer, and got some weird readings from the VNA.
By debugging I reached this trivial circuit:
Which has the following frequency response:
I'm trying to figure out ...