Hi gang,
Thanx for all the great info, going to try a new self wound rfchoke
today. This time i´m going to wind it on a keramic form and not on a
teflon one.
I was told that this will also give a better result.
73´s Jan, ON6ZG.
KD7QAE wrote:
>Here are my results after building an RFC for my 2xGS35B amp:
>Progress on testing the choke:
>
>2 series resonance dips in the 30MHz spectrum. 1st dip at 7.1MHz and
>second at 14.3MHz, clean above and below. Tested on grounded Al plate
>with coils normal (vertical) to the plate. Removed Form 2 Coil 1.
>Reduced L to 274uH and moved resonances up 1+ MHz. Success!
>
>Reactance at 1.8MHz = 3099 Ohms
>
>Tomm, KD7QAE
>
>
>
>KD7QAE wrote:
>
>All,
>
>I just finished sacrificing 12" of Teflon bar stock to the 2xGS35b
>project this evening. The result is a 320uH inductor in 2 sections. I
>will sweep the unit tomorrow at work and report back with the resonance
>story. The basics are as follows:
>
>Wire: 24AWG
>OD of coils: approx. 39mm
>Form 1: Coil 1: 25mm
>Form 1: Coil 2: 27mm
>Form 1: Coil 3: 49mm
>
>Form 2: Coil 1: 26.5mm
>Form 2: Coil 2: 24mm
>Form 2: Coil 3: 18mm
>Form 2: Coil 4: 27mm
>
>The coils are parallel (against conventional wisdom) Center to Center
>separation: 85mm. It certainly looks cool. I plan on adding a HV
>capacitor and relay at the connection point if necessary to switch out
>~1/2 of the inductance if necessary.
>
>Tomm, KD7QAE
>
>
>k7fm wrote:
>
>
>
>>It has been stated that winding two solenoids rf chokes end-to-end will in
>>effect make one rf choke, so that they must be at right angles.
>>
>>That statement is only true if the rf chokes couple. But, it is possible
>>for them not to couple. How? Wind them in opposite directions. Then,
>>coupling will be minimal.
>>
>>I just wound two solenoid rf chokes in line, separated by about 1/4".
>>Measured the resonance of the first rf choke before winding the second.
>>Then, wound the second with more turns, so I could look for a different
>>resonant frequency. The resonant frequency of the first was unaffected by
>>the additional solenoid wound end-to-end. Then checked the resonant
>>frequency of the second coil. It was right where it was supposed to be.
>>
>>I then measured the inductance and they added.
>>
>>So, it is possible to make rf chokes on one form for the purpose of avoiding
>>resonant frequencies.
>>
>>The problem with resonant rf chokes is that the hi Q creates fireworks.
>>There may be another solution, and that is to use resistance wire for the rf
>>choke. It is common to install a glitch resistor in the high voltage line.
>>If you wind an rf choke with the correct resistance wire so that the desired
>>resistance is equalled by the wound rf choke, then you can eliminate the
>>resistor. Whether the choke Q would be low enough to not worry about
>>resonances I am not sure.
>>
>>That is a project for another day, to wind such a choke and get the Q meter
>>out - but I do not have neough desk space to do that at the moment.
>>
>>73, Colin K7FM
>>
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>>
>>
>>
>>
>
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