Microwave air variable capacitors
More informations
The concept of air coaxial giga trimmer is not new, even Philips in the 60's built very good variable coaxial capacitors used in the first hybrid RX/TX mobile stations (transistors and vacuum tubes in the TX final stage) for professional version and consumer version for TV tuners.
Gigatrimmers are used in RF in particulary critical situations, for example in crystal high stability oscillators tuning, on filters or high Q resonant circuits or even for quite high powers, the main features are:
- A high Q given by air dielectric and by the particular mechanical design that reduces parasitic parameters.
- An insulation voltage between 250 and 500 work voltage and better thermal stability (almost all are NPO).
- High RF power especially for 500 work voltage ultra-miniature sapphire types.
- High self-resonant frequency, between 1 and 12 GHz (depends on type and capacity).
- Slow regulation due to a multi turn variation and so better repeatability in tuning.
| GIGATRIMMER TYPE CVG-N1 | AIR GIGATRIMMER | |
 |
 |
 A = STATOR B = PORCELAIN BODY C = ROTOR |
|
APPLICATIONS |
MOBILE PART(ROTOR) by rotating the rotor it enters in the stator changing the capacity, the concentric circles are needed to reach the desired capacity |
MECHANICAL PRECISION |
| Classification of gigatrimmer depending on the type of mounting | |||
| Universal mounting |
Air or PCB mounting |
Chassis (or panel) mounting |
PCB Mounting |
| They have leads for pcb or air mount but also the nut for chassis mount | They have leads for pcb or air mount | They have no leads so they can be mounted only on chassis or panel | CVG-W… types SMD mount |
example:  |
 example of vertical mount: |
 example provided of cap and nut: |
 |
 example of horizontal mount: |
 cheap version because it has no thread, it has to be soldered directly to the panel: |
||
| pcb mount holes (in this example 3 leads) |  |
protection cap (if provided) |  |
| leads | chassis mount nut (if provided) |
Microelectronics Ltd. MAV01E05
Sprague-Goodman GDT10026
Sprague-Goodman JFD DC434Y
Airtronic 5801
Johanson 8051
Microelectronics Ltd. MAV01E05
Temex AT5553
Sprague-Goodman GDT10026
AFM Microelectronics Inc MPT51101A
Sprague-Goodman VC20GY
-
0.8 pF
-
12 pF
-
750 V
-
> 500 @ 20 MHz
-
glass
-
horizontal
-
chassis, PCB
Sprague-Goodman JFD DC434Y
- N
-
2.5 pF
-
12 pF
-
250 V
-
glass
-
horizontal
-
PCB
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