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QFH Diy guide
NOTE: Please see Repository for more illustrations showing Endlift, "T" etc CLICK HERE for Repository
Right then some new developments what you've all been waiting for!
Recently a gentleman from South Africa called Angus Anderson contacted me and asked if I would like to emigrate to the South pole KIDDING I bet that made some people happy!
He offered to compile the QFH and Balun DIY guides into PDF format, well the QFH and Balun guides are now both ready please see below
I hope you all appreciate the work that Angus has done, it will save you trawling through the guide online, but I will leave the original intact for those who wish to browse through it.
For those that don't know the difference between their PDF's and MDF's then one's for DIY and one's for reading ;-)
To read the document you will need Adobe Acrobat reader, if you already have this installed on your computer then just download the Balun PDF 550KB and QFH DIY PDF 1.185KB guide you can then open it in Acrobat reader.
If you don't have Acrobat reader then I am afraid you will need to get it, where you ask?
I am good to you just click this link
Well would you believe it! we now have the Balun Guide and QFH DIY Guide as a word Doc. A big thanks to Kenneth Jones who has been very busy compiling the word docs.
And now more good news for our Spanish
speaking cousins, Pauli
Nunez has translated the Balun Guide and QFH diy Guide, a BIG Thanks Pauli
Please note Balun guide word doc updated 2nd November important changes
Balun Guide PDF 550KB
QFH DIY Guide PDF 1.185KB
Balun Guide Word Doc 106KB Zip file
QFH DIY Guide Word Doc 881KB Zip file
Spanish Balun Guide Word Doc 235KB Zip File
COMO CONSTRUIRSE UNA QFH 791KB Zip File
So you have no excuses now
If you want to start making the balun then CLICK HERE
Warning: If you intend not to use a preamp then beware that the QFH will be a dead short, if your receiver outputs 12volts DC then you may need to disable the 12 volt output either via switch or some other means.
Illustrations by Kevin Bates.
Because of the numerous enquiries about the QFH I have decided to concentrate on producing a comprehensive guide into making your own QFH.
For convenience for those not using the metric system (why not it's a lot easier) that comes from a man who learnt his apprenticeship using nothing but feet and inches, while we are on this subject why not have 10 days in a week? we could get more work done then ;-)
Please note the following conversions:
In the UK the old 1/2" copper pipe was inside diameter, metric pipe measures outside diameter, both old and new have same outside diameter so the old fittings still fit, sadly not the case with larger copper pipes.
3mm= 1/8. 4mm= 5/32. 8mm= 5/16. 10mm= 13/32. 15mm= 19/32.
22mm= 7/8. 175mm=6 7/8. 200mm= 7 7/8. 367mm= 14 7/16.
752mm= 29 5/8. 804mm= 31 5/8.
Addition 16th December 1999
I had assumed you would use Bob Thorpe's QFH calculation program which would give you a list of dimensions and perhaps a understanding of how we arrived at these figures but from the feedback I have had it would appear that some have not, so I have added below the finished sizes.
--- Half turn Quadrifilar Helix Aerial using 15mm copper tube ---
Frequency 137.50 MHz
Aspect ratio of height to diameter 1.45
Mean perimeter to wavelength ratio 1.07
Deviation of perimeter to wavelength ratio +/- 3.27%
Dimensions Inches Millimetres
Wavelength 85.83909 2180.313
Perimeter 183.69 4665.87
all measurements are to tube centres
Don't forget these are finished sizes
Diameter 14.15742 359.5985
Height 20.52825 521.4178
Length of Helix 30.26478 768.7253
Perimeter 88.8444 2256.648
Diameter 15.11462 383.9112
Height 21.91619 556.6713
Length of Helix 32.31101 820.6996
Perimeter 94.85125 2409.222
I will attempt to explain some of the technical and practical problems that you may encounter, some of my methods and conclusions may be a little controversial but at this stage I am not prepared to get involved in any debates.
I will not be quoting technical specs that I cannot prove, but I will provide images from myself and various people who have bought ready made aerials from me, because I think most readers would agree that they have on more than one occasion been taken in by some well produced advertisement quoting everything you want to see and then after purchasing the items finding that they are a disappointment.
I would encourage any one who feels confident with plumbing and safe with a blow lamp (there is an alternative to the blow lamp read on!) to have a go at making their own QFH, don't be discouraged if your first attempt fails I am sure you will get better with a little patience, the feeling of satisfaction when you complete your QFH and see the improved images is well worth all the hard work, not to mention the comments from neighbours.
I have recently developed a marine version this conforms to the British Standard 1706 for Nickel/Cobalt, this version is completely sealed with a 75cm length of RG 059 cable terminating in a 259 connector.
I will be updating this Page as I go, but in the mean time I would suggest you acquire the RIG 53 Journal and the QFH calculation software, Please go to my Favourite links page for details, go to RIG/software/QFH.
A 25cm Plant pot and some good potting compost may be useful (Kidding)
CLICK HERE Next Page: Recommended required tools and, it's that long since I wrote this bit that I have forgot what the end of the sentence was! I blame it all on all this radiation and contaminated water, not to mention senile dementia.