Shack Board
The Shack Board provides power for PreampA and PreampB as well as
interface from each of their outputs. Power is the input 10-16
VDC passed up to PreampA and also regulated with an adjustable LDO to
produce 8V at both Preamp &B, after any voltage drop in the
intervening cables.
The Shack Board can also provides LPF and HPF filtering for PreampA
and HPF filtering for PreampB, respectively, to create the hybrid
antenna system.
Besides functioning to combine Preamps A&B by way of a diplexer,
it may also be used for initial testing of each Preamp, Junction Box
and cables.
Testing
For flexibility in use and testing, there are three switches on the
PCB, two to bypass the respective filters and one to interconnect the
output SMAs.
Since assembled PCBs must be ordered with minimum quantity = 2 ,
this makes a good arrangement for testing. Bypassing the filters and
using each of two PCBs as a simple 50 Ohm <==> 100
balanced line adapter lets transmission through a length cable be
measured. Similarly one board may have temporary short wires
connected to either Preamp input while the a second board receive and
power that preamp. This provides end-end 50 Ohm SMA connectons to
measure a Preamp's performance. Applying power to either of the
interconnected boards also allows checking power function of each
board.
DC tests can be performed with a multimeter for power supplies. For
RF testing a broadband measurement using a scalar or network analyzer
is a very good method. This may be done with a TinySA
or nanoVNA. Loss through each
transformer during a two-Shack board test should be no more than about
2 dB. Typically CAT5 cable loss should be about 3 dB/100' at 30 MHz.
Use
In addition to its main function of supplying power to Preamps and receiving differential RF over CAT5 cable and delivering the filtered/combined results to a receiver, this board also has a switch to disconnect the 12V supply from the input circuits of a probe preamplifier while leaving output stages operative. This allows identifying common mode and other unwanted noise ingress apart from the intended balanced antenna. A better method is to simply short the dipole elements but this is not always possible or convenient so simply disabling the input high impedance OpAmps is useful to verify a system.
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Item Description |
Provider |
Source Code |
Notes |
Approximate Material Cost(excludes setup fees and shipping) |
Assembled ShackPCB PCB |
Download ShackPCB Kit Files |
Download ShackPCB Source Files |
Added Preamp12V Switch/LED |
US$ |
38x88x100mm Clam Shell Enclosure |
eBay |
Other sources possible. Enclosure needs to accept 84mm wide PCB. | US$12 |
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38x88mm ShackPCB Front Panel |
Download ShackPCB Front Panel Kit Files |
Download ShackPCB Front Panel Source Files |
US$1 | |
38x88mm ShackPCB Rear Panel |
Download ShackPCB Rear Panel Kit Files |
Download ShackPCB Rear Panel Source Files |
US$1 | |
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