Ham Radio

From HackPittsburgh Wiki
Jump to: navigation, search

THIS CLUB HAS DISBANDED AND IS NO LONGER ACTIVE



Resources for Ham Radio:

Member Tim wrote to the list: (Dates are 2010)

  • I spoke with Joe Sciulli (ka3tdq@verizon.net) regarding the classes I took at the Salvation Army Disaster Center and when they would be scheduled again. He mentioned that he and a few adjuncts would be there October 13,14,20,21,27,28 (Wednesdays and Thursdays for October) from 7-9PM and that he would post more details on the arrl.org site when he gets around to it.


Links

HackPgh Hams

Place any links to information you've found here if they don't go in any of the following sections.

Antennas

Antennas Delta and Gamma Matching

Amateur Radio Satellites

Live Tracking Websites

JTrack - from NASA

N2YO - Uses Google maps

Frequency and Status

AMSAT's Operational List

Satellites We Care About

These are the ones that have FM repeaters or Linear Transponders on them. We should add easy links to some of the pass calculators here

Satellites We Might Want To Track

These are the ones that are downlink only, usually CW or packet telemetry data. Add pass calculators

  • AO-7 "OSCAR 7" ( Linear transponder, sort of works, but its been up there for nearly 40 years so why stop trying now ) (N2YO Pass list - click 'Show All')
  • bloo
  • blah

Resources

Find your grid square - the shop is FN00AK - Foxtrot November Zero Zero Alpha Kilo

ARRL Homebrew Challenge Information

The ARRL has completed two Homebrew Challenges so far and a third has begun. These contests produce some great designs that HackPGH might be interested in building as a group kit or just for fun. The reason you'd build one of these designs instead of some random one off the internet is that the ARRL has tested the designs to show that they meet a rigorous level of performance (selectivity, stability, harmonic output, etc).

Unfortunately, the ARRL changed their website around in 2010 and it is hard to find information about the contests and their results. Also the circuits and instructions for the winning entries are scattered throughout various issues of QST spanning several years. We have many years worth of QST in the shop, but we need to find out when the different designs were published and if any updates to the designs are available online. Of course there is a Yahoo group too. :/

First Homebrew Challenge - 40 meter QRP CW and SSB transceiver

  • Initial Announcement
  • Announcement of Winners
  • Information on designs
    • NM0S
    • N3ZI
    • WA2EUJ
    • KD1JV

Second Homebrew Challenge - 40 meter power amplifier

Third Homebrew Challenge - 10m and/or 6m CW and SSB transceiver

  • Initial Announcement
  • Announcement of Winners - TBA Nov 2011 D:
  • Information on designs - TBA a zilliondy years from now D:

Ham Radio Kit Links

DDS Kits

A HackPGH 10 meter radio Kit

A neat radio that would be useful to Technician and General class license holders is an all-mode 10 meter radio. Techs get a very good swath of spectrum available with both CW/Data and Voice portions. We are currently at the very beginning of the 11-year sunspot cycle. As time goes by, the propagation conditions for 10 meters will only increase. So with every passing month, your 10 meter rig will become more and more useful.

Even without sunspots to produce the correct space weather to allow for transcontinental communication, the 10 meters band is still a viable "local" channel.

10 meters is also a true "HF" band, meaning that Tech class license holders can get a taste of what they're missing on the lower frequency bands and learn useful operating procedures.

Feature Set

  • 10 meter transmit and receive
  • digital read-out of operating frequency
  • USB (Upper Side Band)
    • CW possible using Audio CW
    • digital modes possible using software such as FLDigi
    • Voice using external microphone
  • 20 Watts RF output
  • adjustable filtering ( audio )
  • crystal IF filter (for good selectivity)
  • adjustable RF gain
  • adjustable output (speaker / to sound card ) and input (microphone / from sound card) volume
  • AGC - (software based using on board microcontroller)
  • simple connections to computer for digital ("soundcard") modes
    • Isolation transformers built in
    • volume controls (see above)
    • Audio based keying circuit built in (could also operate as VOX) see this circuit
  • SWR meter
  • received signal meter ("S-meter") (software based using on board microcontroller)

Extraneous Features

New operators won't typically need any of these features, though some of them "come for free" when using a Direct Digital Synthesizer (DDS):

  • RIT
  • IF shift (though this can be a good way to get adjustable filtering)
  • frequency memories ( "free" )
  • selectable attenuator
  • selectable preamp

Design

As of Friday Oct 22 2010, Ed has come up with the following (sorry for the ASCII art):

Transmitter

Mic -> Mic Amp -> Mixer -> Xtal Filter -> IF Amp -> Mixer -> BandPass -> Power Amp -> Antenna Match/Bandpass -> SWR Meter -> Antenna
                    ^                                 ^
                    \-- Fixed LO                      \-- DDS <-- Microprocessor --> Frequency Display

Receiver

Speaker <- Spkr Amp <- Audio Low Pass <- Mixer <- IF Amp <- Xtal Filter <- Mixer <- Band Pass <- Preamp <- Antenna
                                           ^                                 ^
                                           \-- Fixed LO                      \-- DDS --> Microprocessor --> Frequency Display

Astute readers will notice many common blocks in the RX and TX diagrams. Many of these blocks are used in both with relays or PIN diode switching to re-route signals appropriately.

This design only will do a single sideband voice signal, but this shouldn't be a problem because CW can be done by inserting an audio signal. This is how FLDigi does CW. AM would be more troublesome.

Complexity of the build could be reduced by using integrated circuits, like the Chinese KN-Q7/8.

Features to still add:

  • AGC on the receiver; A circuit that monitors the amplitude of the audio being output at the Speaker Amplifier and increases or decreases the gain of the Intermediate Frequency (IF) Amplifier to adjust total receiver gain. It is also used on some radios as a signal strength meter. Perhaps this could be done using the microcontroller to measure an analog signal off the audio output and generate a DC control voltage for the IF Amp.
  • switching LO frequency; I think we'll need to adjust the LO frequency between transmit and receive to account for the fact that we're generating a USB signal using up-conversion but receiving the signal via down-conversion.
  • some twiddly knobs for things like Microphone Gain and Speaker Volume
  • switches to bypass things like a receiver preamp, control the Direct Digital Synthesizer (DDS), etc
  • the obvious relays or PIN diode switching; although the transceiver could be built as two stand alone units, a receiver and a transmitter

Influences on Design

Hams have been making radios from scratch for over a century. There are some great designs already floating around. Here is a list of a few that influenced this design.

  • Bitx20 and Bitx20+
  • Yaesu FT-77
  • Yaesu FT-817
  • Icom IC-817
  • Chinese KN-Q7 and KN-Q8 HF Radio Kits
  • Henry SM0VPO (not a single radio design, but many many good radio circuits)

Radio Circuit Design Links

Here are some tools to help you design radio circuits.