Reflection Technology » Ham Radio

The Flea – a minimalist CW transceiver

Giovanni — Mon, 20 Oct 2008 08:53:19 +0000

Here’s an amazingly simple 1W morse code transceiver in the tradition
of the Pixie but with much more output power and a narrower bandwidth
receiver (the oscillator crystal forms part of the receive input
filter):br /br /http://ea3fxf.googlepages.com/fleabr /br /The xtal is in the receive path so the bandwidth is quite narrow and will stop broadcast interference. A PCB layout is included. The page is just a summary – have a look at the linked .DOC file for the full article.

Why learn Morse Code?

Giovanni — Sat, 26 Apr 2008 07:52:33 +0000

Why learn morse code you may ask. Well here’s one person’s thoughts, and seeing as I’m quoting all below (excerpted from http://www.barc.org/2005/sparc_apr.pdf), he’s quoting ZL1AN, so that makes two, and I’m looking forward to when this works for me:

Morse Therapy
– Dr. Gary Bold, ZL1AN; excerpted by Eric Falkof, K1NUN
There was a magazine devoted to the preservation and glorification of Morse Code, Morsum Magnificat
(www.morsum.demon.uk).

Excerpting an excerpt from Number 41, August, 1995, I found this article that summarized my feelings about CW.

“…I know that if I go to bed now [after a stimulating period of intense thought and writing], I’ll just lie awake and the ideas I have to propound in the morning will rush madly about, echoing and muttering in my brain. My solution has always been to fire up the TS-520, limber up the Brown Brothers paddle, put on the cans and exchange CW for a while with someone on 20 metres. After a while the Morse begins to decode itself automatically, and little ASCII strings march quietly and effortlessly through my head.

My pulse-rate slows, and the network theorems and Fourier transforms of my professional life go away. I have almost become one with the radio, a bionic post-processor tacked on the end of the audio chain. CW is the purest form of communication I know, a ‘mind-to-mind’ linkage. The words appear right inside my head, words that were never spoken; uncorrupted by accents, verbal peculiarities, oddities of vocal intonation. They leave no room for other thoughts. Almost like a form of meditation. Very therapeutic. After thirty minutes of that, my metabolism has been slowed right down and I am relaxed. I can go to bed and sleep comes.”
by Gary Bold – ZL1AN.

Gary’s website http://www.physics.auckland.ac.nz/staff/geb/loads.htm has some excellent articles but the one I use most is his Morse tutoring program that, very sensibly, works most on the characters that are the least frequent and the hardest to learn and has some subtle and ingenious features that has bought me back to it year after erractic year, until I can finally copy code off the air. The program is called NZART Morse Tutor – I recommend it highly.

Giovanni – ZL2GX

My first CW contact

Giovanni — Fri, 25 Apr 2008 10:48:05 +0000

At last – I’ve finally gone on the air using CW (morse code). My first contact was with ZL2MS on 80M (3525KHz). I hadn’t intended to go on the air but the signal was strong, readable – why not I thought – got to start sometime …

Then I found out why all the tutorials on morse code contacts say “write it out first” – I hadn’t of course. Brain turned to mush but Peter was amazingly merciful. The next one will be better, but it’s a buzz anyway.

Morse code is such a simple mode but somehow, elegant.

Giovanni – ZL2GX

HF Propagation Numbers – Rules of Thumb

Giovanni — Mon, 14 Jan 2008 09:28:31 +0000

The following was sent by Bonnie VR2/KQ6XA to the HFPack Yahoo email list in reply to
a question about easily decoding HF Propagation Numbers: (quoted with approval and thanks):

A low “A index” is most important! For Low Power Portable DX openings at 10MHz to 30MHz, look for an A index LESS THAN 6.

Here is my RULE OF THUMB for How To Read Propagation Numbers:

The A index = LOW is GOOD.

1 to 6 is BEST
7 to 9 is OK
11 or more is BAD

SFI index: HIGH is GOOD.

70 NOT GOOD
80 GOOD
90 BETTER
100+ BEST

K index: LOW is GOOD.

0 or 1 is BEST
2 is OK
3 or more is BAD
5 is VERY VERY BAD

Bonnie VR2/KQ6XA
copyright 2008 Bonnie Crystal

Making Vacuum Tubes (valves) for radios at home

Giovanni — Wed, 02 Jan 2008 02:10:19 +0000

Here’s movie of someone (F2FO) making valves – the amplifying part of a radio – in a home workshop. It’s ingenious, quite clear and very clever.

The video goes from bits of metal and glass to a working radio. The subtitling is in French but that doesn’t hinder understanding, as the presentation is quite professional.

http://paillard.claude.free.fr

Inspiring …

Off-Centre-Fed (OCF) Antennas

Giovanni — Sun, 21 Oct 2007 08:45:57 +0000

I’ve now decided to use a ZS6BKW antenna as it fits better in an inverted V configuration in my garden but for Multi-band use without tuning, the off-centre fed antenna has a lot going for it (and lots of happy users), so I thought I’d put up some of the useful links I’ve found.

These links describe very clearly how it works (in summary – it’s better NOT to feed at the low impedance point like a dipole as when you double the frequency the same point is now a VERY high impedance – it’s better to accept a little mismatch and get lots of bands instead.

For more detailed explanations (with pictures :-) ) see:

* Good OCF Introduction
http://www.radioelectronicschool.net/files/downloads/ocfdipole.pdf

* Clear explanation but shows the difference using a 20% feedpoint can make -it includes 10MHz)
http://www.w8ji.com/windom_off_center_fed.htm

* A more extensive article with various shortened versions
http://www.stroobandt.com/cl-ocfd/windom/index.html

or without the frame:
http://www.stroobandt.com/cl-ocfd/windom/windom.html

OCF Antennas are sold commercially from
http://hamcall.net/7bandocf.html

and the user reviews on EHam.net do seem very positive:
http://www.eham.net/reviews/detail/5838

These are still full length antennas (e.g. 40m/130ft if you want 80M without using an ATU) but without the anti-resonance that makes a 80M dipole hard to feed on 40M (for example), and having the feedpoint at 20% or 33% can sometimes be more convenient.

Cheers
Giovanni – ZL2BOI

ZS6BKW – an Optimised G5RV multi-band wire antenna

Giovanni — Sun, 21 Oct 2007 06:10:56 +0000

I’ve been playing with aerials again (can’t be studying ALL the time) and as I usually do have come around to putting up as much wire as I can and feeding it with 300 ohm ribbon.

I tried the G5RV (in the days before I had an antenna analyser) and didn’t like it much – can’t quite remember why but (from memory) it wasn’t that easy to tune. This corresponds to what I’ve found on the net – the G5RV was never intended as an all-band antenna, however by making it just a bit shorter you can match it easily on lots of bands.

It was derived by Brian Austin ZS6BKW (now G0GSF) and will match most of the HF band excluding 10 & 21MHz.

Have a look at these two articles from Sprat (the journal of the GQRP Club – http://www.gqrp.com):

Martin G3UKV trying it out (with Antenna Analyser results):
ZS6BKW Antenna Revisited (from Sprat #129)

A more extensive article by its designer G0GSF/ZS6BKW, on the rational behind the antenna design:
ZS6BKW revisits his G5RV variant and describes its evolution

Sometime I’ll publish my measurements, but for now, these should give you something to work with …
Giovanni – ZL2BOI

A Wind Generator with high efficiency and no rotating parts

Giovanni — Mon, 15 Oct 2007 08:58:44 +0000

An amaziningly simple idea that results in a generator that really works and has about four parts – none of them rotating (so no bearings).

This is really impressive – the video really clarifies things …

or http://tinyurl.com/3yod26

Now with some powerful magnets extracted from disk drives, hmmm …

What’s a 60pf Capacitor look like?

Giovanni — Sun, 22 Jul 2007 09:18:26 +0000

### Rockmite Mods ###
This post is a response to a query on the Rockmite Yahoogroup about tweaking the frequency of a Rockmite (see .

Hi Johnathan – here’s a 60pF capacitor I’ve added to my 20m HiMite tranceiver (just like the Rockmite) so I could bring the frequency up a bit (it was around 14.058 rather than 14.060MHz).

The different capacitance trimmers are different colours: Yellow is 60pf, from memory the 20pf are green …

Cheers – Giovanni – ZL2BOI

Making printed circuit boards at home with a laser printer

Giovanni — Tue, 26 Jun 2007 10:24:53 +0000

http://www.users.on.net/~endsodds/pcb.htm

VK5JST Antenna Analyser

Giovanni — Tue, 26 Jun 2007 09:42:00 +0000

Having puddled around for ages with antennas wondering how to design and adjust them, I’d decided I needed some instrumentation.

There have been a series of articles recently in Break-In (the http://www.nzart.org.nz) and also one from Australia about antenna analysers. Having digested the maths (which is really cunning), I now understood enough to design one myself, but that was patently silly as it’s be yet another case of wheel- reinvention, so I got out the plastic and ordered the antenna analyser designed by VK5JST and now supplied by the South Coast Amateur Radio Club
http://www.scarc.org.au/projects.html.

It’s a complete kit including case for AU$140 (about US$120) and while I have a well stocked junkbox, there always seems to be one or two bits that are missing …

This is just a placeholder page – I’ll add some photos later, but here are some of the links that I want to remember:

####How is it?####

It works well (once I’d figured out that the PN2222 transistors – just to be perverse – had pinouts opposite to both the datasheet and component overlay).

I’ve installed the VK3DPM software upgrade so now it measures C & L as well as R/Z/SWR – very pleased :-)

The opposite pin-out transistors were a bit hard to find. I knew the amplifier Q11-Q12 was the problem as when I disconnected them the voltage driving them was very flat with frequency whereas when Q11-Q12 were connected the output fell off badly with increasing frequency. The puzzling bit was that the components were all correct and so were the DC voltages (more or less).

I’m really grateful to VK3PE on EHam.com for mentioning his problem with the PN2222.

Now I’m just tweaking the accuracy …

####Related Links####
VK5JST’s own page on the analyser
http://www.users.on.net/~endsodds/analsr.htm

The reviews on EHam.com – these are what convinced me to buy it, together with the fact that the project is based on the PicAxe microcontroller which is programmed in Basic so there are lots of user contributed software updates.

**Mods to increase frequency range and accuracy:**
http://members.optusnet.com.au/dpmilne/Amateur_files/AntennaAnalyser/HW_Mods/VK3XPW/VK3XPW.htm

A Russian page (no idea what it’s about but there’s lots of words and following discussion – included for completeness):
http://www.cqham.ru/aa_VK5JST.htm

Software Defined Radio (SDR) – and DSP – a Great Introduction

Giovanni — Mon, 18 Jun 2007 10:03:44 +0000

I’ve just found a great introduction to Digital Modulation Systems from Agilent (was HP) at http://cp.literature.agilent.com/litweb/pdf/5965-7160E.pdf as used in the growing are of Software Defined Radio.

It was mentioned on the SoftRock 40 mailing list at http://groups.yahoo.com/group/softrock40 – the SoftRock40 is an amazingly simple (and cheap) multimode transceiver (CW, SSB, PSK31 …) as all the modulation/demodulation uses your PC and its soundcard. It’s only about US$33 including international postage.

EchoLink Install Hangs

Giovanni — Sat, 23 Dec 2006 09:19:37 +0000

Today I was shown how EchoLink works – it’s an amalgam of Amateur Radio and the Internet – see www.echolink.org for details, really neat if you can’t put up an antenna or the band conditions are horrible. It’s closely related to IRLP but enables you to access remote repeaters without a radio at your end.

Anyway, I came home and tried to install EchoLink on a recently received box with Windows XP SP2 and found the installer would start up and then just fails, it terminates with no message, no event in the Event Log, nothing …

Searching around I found the note about the InstallShield 16 bit installer not being happy with the %Temp% and %tmp% folders having names like C:\Documents and Settings\Fred\local settings\temp (or whatever it is – I just made that up but it doesn’t like having spaces in the name.

I went to the Control Panel/System/Advanced/Environment Variables and changed both tmp and temp for both “User Variables” and “System Variables” to be c:/tmpfiles and problem fixed … Any name less than eight characters is probably ok.

There was also a problem with MusicMatch V7.5 not installing (same symptoms) but this was related to Internet Explorer V7 – deinstalling that and it was happy too.

This is a new PC and I’m discovering just how much software is (was) installed and how little I use on a daily basis :-(

Securing Toroids – what’s best?

Giovanni — Mon, 06 Feb 2006 05:47:16 +0000

Just found a link on the GQRP mailing list http://www.gqrp.com about the optimal way of securing toroids for VFOs – what effect differing glues and coatings have on inductance and Q. see http://www.qrp.pops.net/w7el.htm

HiMite – a tiny morse code transceiver

Giovanni — Wed, 01 Feb 2006 10:23:45 +0000

Well I’ve gone and ordered one – enough thinking

Here’s what someone with style has done with theirs WB9LPU Richard Meiss Website

WB9LPU Rock-Mite 40M transceiver
with cool new blue lucite base paddle

The base isn’t just for the morse key – it contains the complete transceiver.

The thought of a complete rig with decent performance that can cover the whole of New Zealand (hopefully) without needing a power point, doesn’t need a ISP, or Cellphone plan to run really appeals. For more on the Rockmite see http://www.smallwonderlabs.com