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fanatical mega-loopstick question
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Hi Garry,
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I had been thinking about spider coils also for an ultralight. How large of a coil form do you think would be needed to compete with a hot rodded ferrite loop? Also, do you envision concentric coils on the form separated by a distance or one continuous coil with tap points as needed? Guy Atkins Puyallup, WA USA www.perseus-sdr.blogspot.com Sent via BlackBerry from T-Mobile -----Original Message-----
From: "sloshatron" <wa1gwh@...> Date: Sat, 05 Apr 2008 22:58:16 To:ultralightdx@... Subject: [ultralightdx] fanatical mega-loopstick question Hi Gary; When you measure the recycled coils on the LCR meter, are you checking only the L or are you somehow taking into account any C differences between the original and tranplant coils (either on or off the ferrite bars)? This would be the distributed capacity of the coils. If this is working with just L measurements that would be great and much easier for folks to duplicate. Also, I'm still thinking about air core coils (small loop antenna style) to replace the original ferrite loopstick. I realized that if spider web construction was used it would be much easier to take off turns and portions of turns and if necessary to add them back on if the best spot was missed in the iterative alignment process. A spider web coil form could be cut out of plastic with one spoke extending way out to mount the form to the radio in the same way as your ruler idea. TNX, Garry Nichols near Syracuse, NY |
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Garry and Guy,
All of the mega-loopsticks (7", 14" and 21") have
been constructed using an LCR meter to measure inductance only, to ensure that
the recycled coils (mostly salvaged from the vintage long ferrite bars) match
the SRF-39 stock coils in inductance. The alignment procedure, in
which the small coil is slid along the ferrite bar to peak a low-band (usually
600 kHz) signal, optimizes the match between the recycled coils and the
SRF-39 circuitry, making it unnecessary to measure capacitance and resistance
during the construction process. As long as the inductances match, and the
600 kHz peak is sharp, the newly recylced coils are perfect for DX
reception in the SRF-59.
As for comparison of the ferrite mega-loopsticks
and spider coils, I'm sorry that I have never experimented with spider
coils, or air-core loops. The ferrite mega-loopsticks seem to be great for
DX, relatively cheap, and still quite portable. The only drawback is that
you inevitably make longer and longer ones, as you fanatically strive for
the highest sensitivity level. Eventually you need to face the reality
that doorways are only 30" wide.
Guy, if you wish to make some spider coils and
compare them to the mega-loopsticks, you can borrow them at any time (Guy and I
live in the same city). As of today, all of them will still fit through a
doorway :>)
73, Gary
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sloshatron <wa1gwh@...>
Hi Gary;
When you measure the recycled coils on the LCR meter, are you checking only the L or are you somehow taking into account any C differences between the original and tranplant coils (either on or off the ferrite bars)? This would be the distributed capacity of the coils. If this is working with just L measurements that would be great and much easier for folks to duplicate. Also, I'm still thinking about air core coils (small loop antenna style) to replace the original ferrite loopstick. I realized that if spider web construction was used it would be much easier to take off turns and portions of turns and if necessary to add them back on if the best spot was missed in the iterative alignment process. A spider web coil form could be cut out of plastic with one spoke extending way out to mount the form to the radio in the same way as your ruler idea. TNX, Garry Nichols near Syracuse, NY |
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