I have recently acquired my German reciprocal British Ham license, having been resident now in Germany for some 12 odd years.
I find myself at a good height above sea level (60 meters), but in an apartment house where I have no place for an antennas.
I have good contact with local repeaters 2M and 70 Cm using HB9CV home made antenna's, but hf wise I was lacking a working antenna.
I played about with long wire thrown out of the window, but that was not friendly as it hung in front of the lower floor neighbors windows.
I tried short 1/8 th wave dipoles up against the window etc. etc. With a matcher I could get a few signals but otherwise no luck, I thought ham radio was finished for me!
Then in desperation I started playing
about with a George Partridge type Joystick, United States Patent
US3274600, worked better but I still did not have room to mount it
Editor's note... The patent
for the George Partridge broadband antenna can be seen
here! (Off site)
The Joystick gave me some hope and so I did a simple crude analyses of the joystick and it just seemed to be a resonant stick, I had no lust to go into antenna technical mathematics (my brain is now too lazy for that) .
From that point I had a new idea. What happens if I pick a 20 Meter wavelength and calculate a coil that will resonate at that frequency (about 14Mhz)?
I assumed the coil would have a self capacitance of a few pF and wound a coil on a plastic tube (25 uH).
I then connected one end of the coil to a rod of about 1.5 meters long. The other end to my coax core wire (leaving the coax braid for a ground plane connection).
I then attached a length of ferrite rod to the end of another short rod and inserted this inside the coil.
I stood the contraption up against my window and powered up my receiver, tuned the coil by sliding the ferrite in and out for maximum signal and 'Hey Presto' signals from all over were now receivable!
I tried this on all the other bands and other than 28 Mhz and above (which seems to be dead at the moment of writing), I found that with tuning the ferrite, I could now receive on all bands.
I do not suppose this is a new idea, and I appreciate it is very un-scientific , but it works, and as the tuning is done with the ferrite in the antenna, it does not need an ATU.
I checked the SWR on a 1 Watt TX and it was well below 1.5!
I DO NOT have a powerful transmitter at the moment, so I do not know how the ferrite will behave with high power through the coil.
Additional construction notes:
The top rod is an aluminium rod 4mm dia. The coil is fed from the co-ax core at the bottom end, the top of the coil connects to the aluminum rod.
The top rod is more deoration than active, but I guess it picks up enough signal to resonate the coil, the length does not seem to effect the signal.
The co-ax braid I connected to a short (about 1 meter) horizontal rod which acts as a ground plane, but the effect was negligible so I left it off.
The antenna is very narrow band and with a sharp tuning point, I guess from the high Q of the ferrite tuning slug, but only needs to be adjusted when changing bands.
I have just carried out a comparison with the bottom fed joystick design on your site and the signal difference is negligible, the only difference being one does not need to go through an ATU with my version.
Because of my situation I have been trying other variants of 'Joystick' type antenna's and my general conclusion is that all of these are nothing more than a long wire compressed into a short coil with a little bit of Q, and the rods attached are pretty well inactive and add very little to the signal gain.
Being an oldy ex UK ham, I lived a couple of kilometers away from George Partridge and as nice a guy as he was, I am sure that he new it was only his ATU that was making the joystick work, and kept that a secret, as most hams desperate for an antennas would not bother to test it fully!
I am no antenna expert so I will leave the technical calculations to those that are, can only judge by the results.
When I have time, I will try another resonant coil design , perhaps better constructed and then I will give it a more scientific test. (At the moment I am slowly building up my test equipment stock again, as not being active for a few years I passed on much of my test gear to other Hams.)
Best regards and Have a good day.
Brian DB8MW Ex-Brit in Germany and I hope someone else might find this useful. 73 DB8MW
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