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

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

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