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HPSDR Excalibur

Excalibur Kit

Excalibur is a small accessory card for the Atlas bus that provides improved frequency stability for the HPSDR system. This card is sold as a kit, but uses the larger 1206 surface mount parts for easier manual assembly.

Excalibur has an on-board 10 MHz temperature compensated crystal oscillator (TCXO) that provides better frequency stability than the oscillators included with Penelope and Mercury. Alternatively, a BNC connector accepts an external 10 MHz source such as a GPS disciplined oscillator. A jumper selects which source is active.

The selected source is converted to a square wave and fed to the Atlas bus 10 MHz clock line C16. The square wave is also available on a two pin header that can be directly connected to the auxiliary clock input on Mercury.

A buffered 10 MHz sine wave output is available on a rear-panel BNC connector for use by other equipment.

More detailed information is available on the OpenHPSDR Wiki or in the assembly manual.


In stock now

Excalibur Warranty


This is a low volume production, experimental item. TAPR is a small, not- for-profit organization of volunteers who have helped facilitate this project because we believe it is a cool thing to have. In order for TAPR to be able to offer this board at all, we must rely on the support of all users in the HPSDR community.


Support will be provided via the HPSDR Discussion List.

Because TAPR is not staffed to provide support for Excalibur, and because the knowledge to support users resides with the developers and users on the HPSDR Discussion List, buyers should participate in that forum for support.

Firmware and software will be available for download from the HPSDR website.

Ordering Information

The price for the Excalibur Kit is:

  • $ 79 US for members of TAPR

  • $ 88 US for non-members

    + shipping/handling if applicable.
(Place Web Order)

A note regarding email addresses: When checking out please use an email address other than @earthlink.net, @hotmail.com, @live.com, @msn.com, @outlook.com. For some reason these domains reject email from tapr.org

Shipping and Handling

Shipping and Handling within the US will be by USPS Priority Mail.

International shipping costs are calculated as closely as possible. If the actual cost exceeds the estimate by more than $10.00, TAPR will contact you to get approval for the additional funds. TAPR uses insured Priority Mail International, unless the purchaser requires something else.



The Excalibur project team is:

  • Graham Haddock, KE9H, designer
  • Joe Martin, K5SO, alpha tester
  • Phil Harman, VK6APH, alpha tester
  • Graham Haddock, KE9H, alpha tester
  • Steve Niles, N5EN, kitting
  • Walter Holmes, K5WH, kitting
  • Scott Cowling, WA2DFI, parts procurement
  • Nona Jurgens, parts procurement

Other HPSDR kits

Alex Bandpass filters ... Read more.
Atlas Backplane ... Read more.
Janus Audio Converter ... Read more.
LPU Power Supply ... Read more.
Magister USB Interface ... Read more.
Mercury RX Module ... Read more.
Metis Ethernet Interface ... Read more.
Pandora Enclosure ... Read more.
PennyLane TX Module ... Read more.
PennyWhistle PA ... Read more.
Pinocchio Extender Board ... Read more.

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