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Questions tagged [diy]

Questions dealing with handmade (Do It Yourself) radios and radio accessories.

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A first homebrew design: Band, antenna, and short distance ground wave propagation

I'm working on a very simple homebrew transceiver and request review of our selected band, antenna, and power. Background: A child got very interested in ham radio, as an incentive for to earn his ...
SRobertJames's user avatar
0 votes
2 answers
85 views

How is the length of an inverted V affected by being too close to the ground?

In the near future, I'm planning to build an indoor inverted V dipole. However, I won't be able to raise the ends significantly above the floor. I understand that this will adversely affect ...
Someone's user avatar
  • 604
2 votes
1 answer
85 views

How can i convert a modulated DSB-SC signal to a SSB-SC signal?

I am designing a simple transmitter using an SI5351A to generate the carrier, then modulating it with a diode ring modulator to generate a dsb-sc signal, then somehow converting it to ssb modulated ...
I_like_python's user avatar
2 votes
0 answers
66 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 ...
Zeiss Ikon's user avatar
  • 4,107
0 votes
1 answer
70 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 ...
Zeiss Ikon's user avatar
  • 4,107
1 vote
1 answer
498 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 , ...
CoderBittu's user avatar
0 votes
4 answers
146 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 ...
Elliott B's user avatar
  • 101
1 vote
1 answer
146 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 ...
Jayanta Pandit's user avatar
1 vote
2 answers
77 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 ...
GNZ's user avatar
  • 111
1 vote
1 answer
142 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 ...
VU2NHW's user avatar
  • 2,834
8 votes
1 answer
234 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 ...
Aleksander Alekseev - R2AUK's user avatar
3 votes
3 answers
154 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 ...
Jared's user avatar
  • 201
-1 votes
1 answer
165 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 ...
vanny tran's user avatar
2 votes
2 answers
234 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 ...
Buck8pe's user avatar
  • 989
1 vote
0 answers
118 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 ...
Jeffrey Edward Messikian's user avatar
1 vote
1 answer
506 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 ...
Aleksander Alekseev - R2AUK's user avatar
5 votes
2 answers
333 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 ...
Hans Fong's user avatar
2 votes
1 answer
1k 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 ...
byl's user avatar
  • 131
0 votes
3 answers
134 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 ...
user21397's user avatar
2 votes
3 answers
404 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 ...
Allan B's user avatar
  • 41
7 votes
1 answer
394 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 "...
Toby Eggitt's user avatar
-1 votes
1 answer
260 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 ...
MicroservicesOnDDD's user avatar
8 votes
2 answers
475 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 ...
Aleksander Alekseev - R2AUK's user avatar
2 votes
1 answer
179 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.
Brittany Russell's user avatar
2 votes
0 answers
113 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 ...
Aleksander Alekseev - R2AUK's user avatar
1 vote
2 answers
158 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 ...
Caleb Krajnak's user avatar
4 votes
4 answers
431 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 ...
PHOLAN's user avatar
  • 73
1 vote
1 answer
130 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 ...
Elias Jonsson's user avatar
3 votes
3 answers
267 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 ...
Aleksander Alekseev - R2AUK's user avatar
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 ...
Aleksander Alekseev - R2AUK's user avatar
3 votes
2 answers
2k 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 ...
Joel Clark's user avatar
1 vote
1 answer
113 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 ...
David Wiley's user avatar
2 votes
1 answer
189 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 ...
Derpy's user avatar
  • 95
4 votes
1 answer
175 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 ...
Jeffrey Phillips Freeman's user avatar
5 votes
0 answers
916 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: ...
Aleksander Alekseev - R2AUK's user avatar
4 votes
3 answers
2k 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 ...
Buck8pe's user avatar
  • 989
6 votes
0 answers
400 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 ...
Aleksander Alekseev - R2AUK's user avatar
4 votes
1 answer
970 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 ...
Michael KC1MJP's user avatar
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 ...
S.s.'s user avatar
  • 153
2 votes
1 answer
214 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 (...
user9103's user avatar
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 ...
user avatar
4 votes
0 answers
186 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 ...
F4BJH's user avatar
  • 61
0 votes
1 answer
51 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 ...
Sodori's user avatar
  • 3
2 votes
2 answers
514 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 ...
Jim's user avatar
  • 1,698
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).
OZ5JKM's user avatar
  • 11
1 vote
1 answer
310 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 ...
Charles's user avatar
  • 11
4 votes
1 answer
115 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 ...
mh00h's user avatar
  • 143
3 votes
1 answer
390 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 ...
jcoppens's user avatar
  • 699
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 ...
Peter Buxton's user avatar
1 vote
1 answer
348 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 ...
k1zmt's user avatar
  • 337