TX/RX on 108kHz need a lot of help.

  • Thread starter Thread starter Arctic Fox
  • Start date Start date
Click For Summary

Discussion Overview

The discussion revolves around the challenges and considerations involved in building a transmitter for 108 kHz, with plans for a receiver in the future. Participants explore the technical requirements for designing the transmitter, including the need for a custom crystal and the concept of load capacitance. The conversation also touches on the motivations behind the project, which include long-distance communication experiments and testing antenna designs.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the load capacitance required for a custom 108 kHz crystal, indicating a lack of circuit design knowledge.
  • Another participant points out the difficulty of transmitting at such a low frequency and questions the necessity of using 108 kHz.
  • Some participants suggest that the original poster should design the circuit first to determine the load capacitance before ordering the crystal.
  • There are discussions about the cost and time involved in obtaining a custom crystal, with one participant stating that a quote of $104.58 is acceptable for their purposes.
  • Participants mention the importance of education and suggest resources such as books and joining a ham radio club for further learning.
  • One participant expresses skepticism about ham radio operators and their regulations, indicating a desire to experiment without bureaucratic constraints.
  • There is a discussion about modulation methods, with one participant considering using CW and exploring the possibility of AM and SSB, while questioning the feasibility of FM at this frequency.
  • Another participant inquires about the type of information intended for transmission, emphasizing the need to choose modulation based on that information.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement. While some suggest educational resources and emphasize the importance of understanding regulations, others challenge the necessity of such constraints and express a desire for creative experimentation. The discussion on modulation methods also reflects differing opinions on the best approach for the project.

Contextual Notes

Participants note the complexity of designing a transmitter at 108 kHz and the potential challenges associated with obtaining the necessary components. There is an acknowledgment of the need for a solid understanding of radio design principles before proceeding with the project.

Arctic Fox
Messages
176
Reaction score
0
I’m wanting to first build a transmitter for 108kHz (later a reciever). I started by asking for a quote from a company for a custom made 108kHz crystal. Now they meantion that I need to give them the “load capacitance” before they cut it.

So in one single request, I’ve already gotten way over my head - I’ve no idea what to do now. I don’t know what they’re talking about, or what numbers I can give without actually having a TX curcuit design in mind.

Searching 108kHz on google brings up nothing about actually transmitting/recieving on that frequency... is there anyone here who could help me design these?
 
Engineering news on Phys.org
By transmit, I assume you mean transmit via radio. 108 kHz is going to be very difficult to transmit, as it's extremely low. Why do you want to transmit on 108 kHz?

The load capacitance is the capacitance of whatever circuit is connected to the crystal. You'd need to either estimate the value of whatever circuitry you're going to connect to it, or you need to pick a nominal value and then design the circuitry to approximate that nominal value.

Getting a crystal custom-cut is an expensive business. Why are you doing this?

- Warren
 
chroot said:
By transmit, I assume you mean transmit via radio. 108 kHz is going to be very difficult to transmit, as it's extremely low. Why do you want to transmit on 108 kHz?
Yes TX/RX via CW only (due to low frequency).

The load capacitance is the capacitance of whatever circuit is connected to the crystal. You'd need to either estimate the value of whatever circuitry you're going to connect to it, or you need to pick a nominal value and then design the circuitry to approximate that nominal value.
So, as I thought, I’'ll need to design the circuit first and find out its capacitance before ordering the crystal?

Getting a crystal custom-cut is an expensive business. Why are you doing this?
The price I was quoted was $104.58 and production time of six weeks. This is acceptable to me.

I’m doing this as an extremely-long-distance communication experiment. Also wanting to test out different modified antenna designs for this frequency.
 
What kind of transmitter design have you worked out so far? Maybe we can help you refine it.

A $100 crystal... yikes.

- Warren
 
Well, since this was to be my first attempt at a transmitter, I was going to try something simple... something even I could understand from start:
http://www.scitoys.com/scitoys/scitoys/radio/computer/computer_controlled_transmitter.html

In fact, I’m quite embarassed on just how simple this example is, but I’m hoping to learn quick. An RF amplifier is also in my thoughts, but will come much later.
 
Last edited by a moderator:
Arctic Fox:

I suggest you spend some more time educating yourself before attempting to build anything, particularly at 108 kHz. Radio Shack offers a number of good books for beginners.

- Warren
 
chroot said:
Arctic Fox:

I suggest you spend some more time educating yourself before attempting to build anything, particularly at 108 kHz. Radio Shack offers a number of good books for beginners.

- Warren

LOL! That’s why i’m posting here - to learn more. :D

I am familiar with the employees and products of RatShak - I’ve no interest in them.

What’s wrong with building something at 108kHz?
 
As I've already said, RadioShack sells a couple of decent books on radio design. They are worth buying, even though the average Radio Shack employee doesn't know how to spell 'radio.'

You should really look into joining a ham radio club in your area. The ARRL offers a number of fine books on beginner radio design, also.

- Warren
 
I agree with chroot.
Particuarly on joining a ham radio club.

The club could help you avoid a visit from the MIB (in this case the FCC) should your project actually work :smile:
 
  • #10
I’ll have a look at RatShak again - maybe there’s something different I haven’t seen there (I used to work at one years ago).

I hate to sound mean, but HAM operators have always been a problem for me. I’ve yet to find one who isn’t full of himself or self-righteous. I’ve also yet to find one who can think outside the box. If I was to meantion to them that I need to build a transmitter for 108kHz, like vomit they’d spew out every rule and regulation on the FCC and insist on my taking years out of my life to get (probably) a general-class permit before anything else. (read: blah blah, blah blah blah...)

Who’s to say this transmitter is to be used in the US? As far as I’m concerned, the FCC, DOT, FBI, USSS, ABC, XYZ... have no bearing on this project. It’s a free experiment that will be done outside any red-taped borders. :)

*calming down*
Chroot, I will take a look at any ARRL books I find, as well as checking out RS. I feel it would be a lot easier to learn from people here as apposed to having to go out and search for info or learn from scratch...
 
  • #11
You're always within some government's borders -- unless you're in Antarctica, I guess -- so you are always obliged to obey that government's regulations. I wasn't really concerned with the legality of it.

For the record, I got my general class license after studying Morse for approximately a week.

So you just want to use CW? Just encoding information with the presence or absence of a carrier?

- Warren
 
  • #12
chroot said:
You're always within some government's borders -- unless you're in Antarctica, I guess -- so you are always obliged to obey that government's regulations. I wasn't really concerned with the legality of it.

LOL! You've got it - TX at the magnetic north pole with RX at the magnetic south. :biggrin:


So you just want to use CW? Just encoding information with the presence or absence of a carrier?
- Warren

I thought about trying both - carrier on AM and no carrier on SSB. Is FM possible on this low of a frequency?
 
  • #13
Arctic Fox said:
LOL! You've got it - TX at the magnetic north pole with RX at the magnetic south. :biggrin:
I hope you're not serious. :frown:
I thought about trying both - carrier on AM and no carrier on SSB. Is FM possible on this low of a frequency?
What kind of information are you planning on transmitting? You should pick your modulation based on that.

- Warren
 
  • #14
chroot said:
I hope you're not serious. :frown:

I am. I’m wanting to see if the magnetic fields, Van Allen belts, or Auroras have any positive or negative effects on these frequencies and what effects they might be.



What kind of information are you planning on transmitting? You should pick your modulation based on that.

- Warren

I was thinking of just CW for person-to-person communications, but I’d be curious to see data through at that frequency; maybe start at 300baud and see how high it can go before complete failure.
 

Similar threads

Undergrad Sound transmission underwater -- looking for equations TX --> Rx
  • · Replies 18 ·
Replies
18
Views
3K
Antenna gain reciprocity violation of conservation of energy?
  • · Replies 37 ·
2
Replies
37
Views
6K
High School Delayed choice experiment and FTL communication
  • · Replies 15 ·
Replies
15
Views
4K
Help designing/finding a vendor for this magnetic field
  • · Replies 12 ·
Replies
12
Views
3K
Engineering Advice of pursing two MS degrees given my situation
  • · Replies 2 ·
Replies
2
Views
2K
Stress Analysis of Lifting Plate With Bail
  • · Replies 1 ·
Replies
1
Views
2K
How can I improve the range of my AM transmitter?
  • · Replies 10 ·
Replies
10
Views
5K
How are pseudo ranges obtained?
  • · Replies 15 ·
Replies
15
Views
4K
Need help deciding between physics and engineering
  • · Replies 2 ·
Replies
2
Views
2K
Circuit designs with crystals and layout of digital clock lines
  • · Replies 2 ·
Replies
2
Views
6K